Photosynthesis is the process used by plants to synthesise (make) many of the chemicals they need. Most of the substance of a plant (except the water) was made by photosynthesis. The process is therefore vital for the survival of all the organisms on this planet, including humans which grow plants to eat and to feed to animals. Many chemicals are made by photosynthesis, but the main one we will look at is glucose, which is the main food source for the plant to provide it with energy.
Glucose is made from Carbon, Hydrogen and Oxygen (C6H12O6). Complicated substances like glucose need to be built by an organism, which is why we say that they are organic. If you went to the moon or Venus you would not find any complicated substances like this. You would only find simple substances like Carbon dioxide (CO2) and water (H2O). Plants use the Carbon and Oxygen from CO2 and the Hydrogen from H2O to synthesize molecules of glucose. The Oxygen from the H2O is not needed, so is given off as a waste gas. A lot of energy is needed to convert simple substances into more complicated ones. Plants get this energy from sunlight. This is why glucose (a kind of sugar) contains so much stored chemical energy.
We can summarise photosynthesis with the following word equation (you don?t need to know the chemical equation):
Carbon dioxide + Water + Sunlight 輯font> Glucose + Oxygen
Sunlight is absorbed by a chemical in plants called chlorophyll. Chlorophyll is green, and it is what gives plants their distinctive colour. The reason it is green is because green light cannot be used for photosynthesis (only the red and blue wavelengths of light can be used), so it is reflected.
Like all chemical reactions, photosynthesis works faster in warm conditions than in cold conditions. It also works faster if there is more Carbon dioxide and sunlight and plenty of water. This is why plants grow so quickly in El Salvador in the wet season. If any of these factors is in short supply the rate of photosynthesis will be less and the plant will not grow as fast. Farmers sometimes use greenhouses to increase the temperature, or grow plants on slopes that face the sun, or even pump extra CO2 into their greenhouses to increase the rate of photosynthesis.
Conversely, a lot of photosynthesis can affect the environment, such as aquatic environments and the atmosphere. Most of the Oxygen in the air has come from photosynthesis. The more photosynthesis that takes place, the more Oxygen is produced and the less CO2 remains.
Most photosynthesis takes place in leaves, which are specially designed for the job they do. The flat shape provides a big surface to allow more sunlight to be trapped, but is thin enough to allow CO2 to diffuse in and O2 to diffuse out. The leaves need to have an outer layer of wax, called cuticle, to prevent them from drying out. This is made by the outer protective layer of cells called the epidermis. These cells do not take part in photosynthesis. The water is transported from the roots to the leaves in the xylem vessels, which are found in the veins of the leaf. The veins also contain phloem to transport the glucose (and other products of photosynthesis) to the rest of the plant.
Near the surface of the leaf lie the palisade cells which have large numbers of chloroplasts containing chlorophyll to trap sunlight. The underside of the leaf has small holes called stomata. This is where CO2 and O2 diffuses in and out. The size of the hole can be altered by the guard cells on each side of the stoma. This means that the stomata can be closed to prevent drying out in dry conditions. The diffusion of these gasses around the inside of the leaf is made easier because the spongy mesophyll cells in the lower half of the leaf have air pockets between them to increase the movement of air.
You may remember back to topic 2 where we looked at osmosis. If a cell has lots of dissolved solutes it will tend to absorb more water and could eventually burst. For this reason plants cannot store very much glucose, so they convert it into starch before they store it. Starch is made from about a thousand glucose molecules joined together into a complex chain. The size of the starch molecules means that they cannot dissolve very easily, so they do not cause very much osmosis, which makes them ideal for storage.
You need to remember how to perform starch tests on leaves.
1. Boil leaf in water for one minute to kill the cells.
2. Place the leaf in a boiling tube of alcohol and boil the leaf for 10 minutes (do not use a flame, but place the tube of alcohol in a beaker of boiling water). This removes the chlorophyll and makes the leaf white so that you can see the results of the Iodine test.
3. Dip the leaf in water to soften it.
4. Lay the leaf on a flat surface and add a few drops of Iodine.
5. The presence of a blue/black colour indicates the presence of starch.
We saw how Carbon, Hydrogen and Oxygen are used in photosynthesis to make glucose and other organic substances. Many of these other substances contain other important elements such as Nitrogen. Nitrogen is particularly important to make proteins. However, plants cannot take Nitrogen directly from the air. It first needs to be in the form of nitrate (NO3-) ions. These (and other important ions) are found in the soil, dissolved in the water. When the plant absorbs water through the roots it also takes in the nitrates.
Monday, October 27, 2008
Cell Respiration
2.7.1. Define cell respiration.
Cell respiration is the controlled release of energy in the form of ATP from organic compounds in cells.
2.7.2. State that in cell respiration, glucose in the cytoplasm is broken down into pyruvate with a small yield of ATP.
In cell respiration, glucose in the cytoplasm is broken down into pyruvate with a small yield of ATP.
2.7.3. Explain that in anaerobic cell respiration, pyruvate is converted into lactate or ethanol and carbon dioxide in the cytoplasm, with no further yield of ATP.
In anaerobic cell respiration, pyruvate is converted into either lactate by lactic acid fermentation or ethanol and carbon dioxide during alcohol fermentation. This produces no further yield of ATP. The ethanol and carbon dioxide are produced in yeast whereas lactate is produced in humans.
2.7.4. Explain that in aerobic cell respiration, pyruvate is broken down in the mitochondrion into carbon dioxide and water with a large yield of ATP.
In aerobic respiration, each pyruvate enters the Krebs cycle, a series of chemical reactions within the mitochondria. Just before this cycle, the pyruvate is decarboxylated, which produces the carbon dioxide, and the remaining two-carbon molecule reacts with a reduced Coenzyme A, and at the same time one NADH+H+ is formed. The pyruvate then enters the cycle, with the end result being the production of 3 NADH, 3 H+, 3 carbon dioxide molecules,and one ATP. The NADH and H+ molecules will be used in the electron transport chain (ETC), where the H+ will react with oxygen to produce water. The result of the ETC is a large yield of ATP.
Cell respiration is the controlled release of energy in the form of ATP from organic compounds in cells.
2.7.2. State that in cell respiration, glucose in the cytoplasm is broken down into pyruvate with a small yield of ATP.
In cell respiration, glucose in the cytoplasm is broken down into pyruvate with a small yield of ATP.
2.7.3. Explain that in anaerobic cell respiration, pyruvate is converted into lactate or ethanol and carbon dioxide in the cytoplasm, with no further yield of ATP.
In anaerobic cell respiration, pyruvate is converted into either lactate by lactic acid fermentation or ethanol and carbon dioxide during alcohol fermentation. This produces no further yield of ATP. The ethanol and carbon dioxide are produced in yeast whereas lactate is produced in humans.
2.7.4. Explain that in aerobic cell respiration, pyruvate is broken down in the mitochondrion into carbon dioxide and water with a large yield of ATP.
In aerobic respiration, each pyruvate enters the Krebs cycle, a series of chemical reactions within the mitochondria. Just before this cycle, the pyruvate is decarboxylated, which produces the carbon dioxide, and the remaining two-carbon molecule reacts with a reduced Coenzyme A, and at the same time one NADH+H+ is formed. The pyruvate then enters the cycle, with the end result being the production of 3 NADH, 3 H+, 3 carbon dioxide molecules,and one ATP. The NADH and H+ molecules will be used in the electron transport chain (ETC), where the H+ will react with oxygen to produce water. The result of the ETC is a large yield of ATP.
Transcription and Translation
2.6.1. Compare the structure of RNA and DNA.
RNA has the ribose sugar while the DNA has the deoxyribose sugar in its structure. RNA is only one single strand while DNA has a double helix with two strands. Also, the thymine nucleotide of DNA is replaced by uracil in RNA (uracil, like thymine, attaches to adenine by hydrogen bonds).
2.6.2. Outline the DNA transcription in terms of the formation of an RNA strand complementary to the DNA strand by RNA polymerase.
The synthesis of RNA uses DNA as a template. First, the two strands of DNA are separated in a specific place. Then, with the help of RNA polymerase, RNA nucleotides attach to thier complimentary bases on one side of the exposed DNA strand. This creates a single strand of complimentary nucleotide bases. After this is done, the RNA molecule separates from the DNA.
2.6.3. Describe the genetic code in terms of codons composed of triplets of bases.
The genetic code for an amino acid is contained in DNA as a series of three nitrogenous bases. Each of these triplets (codons) code for a particular amino acid.
2.6.4. Explain the process of translation, leading to peptide linkage formation.
After transcriptions, the mRNA moves out of the nucleus into the cytoplasm where the mRNA attaches ro a ribosome. In the cytoplasm there are transfer RNA (tRNA) molecules. These molecules are composed of a short RNA molecule folded into a specific shape. Each tRNA molecule is shaped so that it bonds to a certain amino acid. Each tRNA moelcule also has an anticodon which compliments a certain mRNA codon. Once the mRNA attaches to a ribosome, it acts as a sort of conveyor belt. The tRNA molecules attach to the mRNA according to the complimentary nature of their bases. For example, a tRNA molecule with the anitcodon ACC will carry the amino acid tryptophan. This tRNA molecule will attach to the codon UGG on the mRNA because UGG compliments ACC. After two tRNA molecules are attached to the mRNA, they bond and the first tRNA molecule is released. Then another tRNA molecule connects to the mRNA etc, and the polypeptide is created.
2.6.5. Define the terms degenerate and universal as they relate to the genetic code.
Degenerate means that multiple triplets code for the same amino acid. For example, UUU and UUC both code for phenylalanine. Univeral refers to the fact that this genetic code occurs in all living organisms.
2.6.6. Explain the relationship between one gene and one polypeptide.
One gene corresponds to one polypeptide. It does not, however, always code for a protein, because many proteins consists of more than one polypetide
RNA has the ribose sugar while the DNA has the deoxyribose sugar in its structure. RNA is only one single strand while DNA has a double helix with two strands. Also, the thymine nucleotide of DNA is replaced by uracil in RNA (uracil, like thymine, attaches to adenine by hydrogen bonds).
2.6.2. Outline the DNA transcription in terms of the formation of an RNA strand complementary to the DNA strand by RNA polymerase.
The synthesis of RNA uses DNA as a template. First, the two strands of DNA are separated in a specific place. Then, with the help of RNA polymerase, RNA nucleotides attach to thier complimentary bases on one side of the exposed DNA strand. This creates a single strand of complimentary nucleotide bases. After this is done, the RNA molecule separates from the DNA.
2.6.3. Describe the genetic code in terms of codons composed of triplets of bases.
The genetic code for an amino acid is contained in DNA as a series of three nitrogenous bases. Each of these triplets (codons) code for a particular amino acid.
2.6.4. Explain the process of translation, leading to peptide linkage formation.
After transcriptions, the mRNA moves out of the nucleus into the cytoplasm where the mRNA attaches ro a ribosome. In the cytoplasm there are transfer RNA (tRNA) molecules. These molecules are composed of a short RNA molecule folded into a specific shape. Each tRNA molecule is shaped so that it bonds to a certain amino acid. Each tRNA moelcule also has an anticodon which compliments a certain mRNA codon. Once the mRNA attaches to a ribosome, it acts as a sort of conveyor belt. The tRNA molecules attach to the mRNA according to the complimentary nature of their bases. For example, a tRNA molecule with the anitcodon ACC will carry the amino acid tryptophan. This tRNA molecule will attach to the codon UGG on the mRNA because UGG compliments ACC. After two tRNA molecules are attached to the mRNA, they bond and the first tRNA molecule is released. Then another tRNA molecule connects to the mRNA etc, and the polypeptide is created.
2.6.5. Define the terms degenerate and universal as they relate to the genetic code.
Degenerate means that multiple triplets code for the same amino acid. For example, UUU and UUC both code for phenylalanine. Univeral refers to the fact that this genetic code occurs in all living organisms.
2.6.6. Explain the relationship between one gene and one polypeptide.
One gene corresponds to one polypeptide. It does not, however, always code for a protein, because many proteins consists of more than one polypetide
DNA Replication
2.5.1. State that DNA replication is semi-conservative.
DNA is semi-conservative.
2.5.2. Explain DNA replication in terms of unwinding of the double helix and separation of the strands by helicase, followed by formation of the new complementary strands by DNA polymerase.
When replication takes place, the enzyme helicase first unwinds the double helix . Next the two DNA strands are split apart at hundreds, sometimes thousands, of points along the strand. Each splitting point is an area where replication is occuring, called a replication bubble. In each replication bubble, new DNA is made by attaching free nucleotides to the original strand (called the template) by base-pairing rules with the help of the enzyme DNA polymerase. The process results in two identical DNA strands produced from one.
2.5.3. Explain the significance of complementary base pairing in the conservation of the base sequence of DNA.
Because the nitrogenous bases that compose DNA can only pair with complementary bases, any two linked strands of DNA are necessarily complementary to one another. The fact that only complementary base pairs can join together means that in replication the newly formed strands must be complementary to the old strands, thus conserving the same base sequence as previously existed.
DNA is semi-conservative.
2.5.2. Explain DNA replication in terms of unwinding of the double helix and separation of the strands by helicase, followed by formation of the new complementary strands by DNA polymerase.
When replication takes place, the enzyme helicase first unwinds the double helix . Next the two DNA strands are split apart at hundreds, sometimes thousands, of points along the strand. Each splitting point is an area where replication is occuring, called a replication bubble. In each replication bubble, new DNA is made by attaching free nucleotides to the original strand (called the template) by base-pairing rules with the help of the enzyme DNA polymerase. The process results in two identical DNA strands produced from one.
2.5.3. Explain the significance of complementary base pairing in the conservation of the base sequence of DNA.
Because the nitrogenous bases that compose DNA can only pair with complementary bases, any two linked strands of DNA are necessarily complementary to one another. The fact that only complementary base pairs can join together means that in replication the newly formed strands must be complementary to the old strands, thus conserving the same base sequence as previously existed.
DNA Structure
Outline DNA nucleotide structure in terms of sugar (deoxyribose), base and phosphate.
A DNA nucleotide is composed of deoxyribose, a phosphate group and a nitrogenous base (adenine, guanine, thymine, or cytosine). The phosphate group is covalently bonded to the carbon of the deoxyribose, and the nitrogenous base is attached to the deoxyribose on the opposite side.
A DNA nucleotide is composed of deoxyribose, a phosphate group and a nitrogenous base (adenine, guanine, thymine, or cytosine). The phosphate group is covalently bonded to the carbon of the deoxyribose, and the nitrogenous base is attached to the deoxyribose on the opposite side.
2.4.2. State the names of the four bases of DNA.
Adenine, Guanine, Thymine, and Cytosine.
Adenine, Guanine, Thymine, and Cytosine.
2.4.3. Outline how the DNA nucleotides are linked together by covalent bonds into a single strand.
given
given
2.4.4. Explain how a DNA double helix is formed using complimentary base pairing and hydrogen bonds.
Each sugar of the backbone (sides of the "ladder") is covalently bonded to a nitrogenous base. Each of these bases forms hydrogen bonds with its complimentary nitrogenous base, forming the '"rungs" of the "ladder". The sides of the ladder are composed of alternating sugar and phosphate groups. The rungs are each composed of two nucleotides which are attached to the sugars of opposite sides of the DNA ladder and are attatched to eachother by hydrogen bonds.
Each sugar of the backbone (sides of the "ladder") is covalently bonded to a nitrogenous base. Each of these bases forms hydrogen bonds with its complimentary nitrogenous base, forming the '"rungs" of the "ladder". The sides of the ladder are composed of alternating sugar and phosphate groups. The rungs are each composed of two nucleotides which are attached to the sugars of opposite sides of the DNA ladder and are attatched to eachother by hydrogen bonds.
2.4.5. Draw a simple diagram of the molecular structure of D
Enzymes
2.3.1 Define enzyme and active site.
An enzyme is a globular protein functioning as a biological catalyst. An active site is the site on the surface of an enzyme to which substrate or substrates bind.
An enzyme is a globular protein functioning as a biological catalyst. An active site is the site on the surface of an enzyme to which substrate or substrates bind.
2.3.2 Explain enzyme-substrate specificity.
An enzyme has an active site that fits with one specific substrate, like a lock and key.
An enzyme has an active site that fits with one specific substrate, like a lock and key.
2.3.3 Explain the effects of temperature, pH and substrate concentration on enzyme activity.
For all enzymes, there is an optimum temperature at which the maximum amount of collisions occur in the active sites. As the temperature decreases, there is less movement and fewer collisions, so enzyme activity decreases. There is a limit to which the enzyme activity can increase because at a certain temperature the enzymes denature. This means that the enzyme changes shape and no longer fits with its substrate. Also, as the substrate concentration increases, so does the enzyme activity, but there is also a limit to the increase in enzyme activity because there is a limit to how quickly the enzymes can catalyze each reaction. There is a specific pH at which the enzyme will denature, and so pH also plays a part in enzymatic activity.
For all enzymes, there is an optimum temperature at which the maximum amount of collisions occur in the active sites. As the temperature decreases, there is less movement and fewer collisions, so enzyme activity decreases. There is a limit to which the enzyme activity can increase because at a certain temperature the enzymes denature. This means that the enzyme changes shape and no longer fits with its substrate. Also, as the substrate concentration increases, so does the enzyme activity, but there is also a limit to the increase in enzyme activity because there is a limit to how quickly the enzymes can catalyze each reaction. There is a specific pH at which the enzyme will denature, and so pH also plays a part in enzymatic activity.
2.3.4 Define denaturation.
Denaturation is a structural change in a protein that results in a loss of its biological properties.
Denaturation is a structural change in a protein that results in a loss of its biological properties.
2.3.5 Explain the use of pectinase in fruit juice production, and one other commercial applicatoin of enzymes in biotechnology.
Pectinase is used in fruit juice production to break down the acidity of the juices. Also, during oil spills, oil-digesting bacteria are used to clean up the spills since these bacteria have enzymes that can break down oil.
Pectinase is used in fruit juice production to break down the acidity of the juices. Also, during oil spills, oil-digesting bacteria are used to clean up the spills since these bacteria have enzymes that can break down oil.
Carbohydrates, Lipids and Proteins
Define organic.
Compounds containing carbon that are found in living organisms, except hydrogencarbonates, carbonates and oxides, are organic.2.2.2 Draw the basic structure of a generalized amino acid.
2.2.3 Draw the ring structure of glucose and ribose.
2.2.3 Draw the ring structure of glucose and ribose.
Ribose - given
Glucose - given
Glucose - given
2.2.4 Draw the structure of glycerol and a generalized fatty acid.
2.2.5 Outline the role of condensation and hydrolysis in the relationships between monosaccharides, disaccharides, and polysaccharides; fatty acids, glycerol and glycerides; amino acids, dipeptides and polypeptides.
For monosaccharides, fatty acids, and amino acids to become disaccharides, glycerol, and didpeptides, a condensation reaction needs to occur. When these monomers covalently bond, a water molecule is released; this is a condesation reaction. When many monomers join together through condensation reactions, polymers result. In a hydrolysis reaction, the addition of a water molecule breaks down the covalent bonds and polymers break down into monomers.
2.2.6 Draw the structure of a generalized dipeptide, showing the peptide linkage.
Drawing will be inserted at a later date.
Drawing will be inserted at a later date.
2.2.7 List two examples for each of monosaccharides, disaccharides and polysaccharides.
Two examples of monosaccharides are glucose and fructose. Two examples of disaccharides are maltose and lactose. Two examples of polysaccharides are starch and cellulose.
Two examples of monosaccharides are glucose and fructose. Two examples of disaccharides are maltose and lactose. Two examples of polysaccharides are starch and cellulose.
2.2.8 State one function of a monosaccharide and one function of a polysaccharide.
One function of a monosaccharide is that they are major nutrients for the cell. One function of a polysaccharide is that provide structural support for the cell.
One function of a monosaccharide is that they are major nutrients for the cell. One function of a polysaccharide is that provide structural support for the cell.
2.2.9 State three functions of lipids.
One function of lipids is that they are great insulators. Also, some lipids function as hormones. In addition, lipids are used for long term energy storage.
2.2.10 Discuss the use of carbohydrates and lipids in energy storage.
The use of carbohydrates in energy storage is through its sugar polymers, glycogen in animals and starch in plants. These sugars are released when the demand for sugar increases. Animals use lipids, mainly fats, for long-term energy storage.
The use of carbohydrates in energy storage is through its sugar polymers, glycogen in animals and starch in plants. These sugars are released when the demand for sugar increases. Animals use lipids, mainly fats, for long-term energy storage.
Chemical Elements and Water in body
2.1.1 State that the most frequently occurring chemical elements in living things are carbon, hydrogen and oxygen.
The most frequently occurring chemical elements in living things are carbon, hydrogen and oxygen.
2.1.2 State that a variety of other elements are needed by living organisms including nitrogen, calcium, phosphorus, iron and sodium.
A variety of other elements are needed by living organisms including nitrogen, calcium, phosphorus, iron and sodium.
2.1.3 State one role for each of the elements mentioned in 2.1.2.
Nitrogen is a major element of proteins and nucleic acid (for DNA and RNA). Calcium is neccesary for bone and tooth formation, blood clotting, and nerve impulse transmission. Phosphorus is also used for bone and tooth formation, and to balance acid and base concetrations in the body. Iron is a part of hemoglobin, a molecule needed to carry oxygen in the blood. Sodium balances both water in the body and acid/base concentration. It also functions in nerve function.
2.1.4 Outline the difference between an atom and an ion.
An atom has the same amount of protons as electrons, so it is neutral in charge. An ion has either a positive or negative charge because there are unequal numbers of electrons and protons. A positive ion is called a cation, while a negative ion is called an anion.
2.1.5 Outline the properties of water that are significant to living organisms including transparency, cohesion, solvent properties and thermal properties. Refer to the polarity of water molecules and hydrogen bonding where relevant.
Water is transparent which allows light to filter into the oceans. This allows for aquatic plants to absorb light and perform photosynthesis. Since the ancestor of all plants originated in the ocean, the transparency of water has had a immeasurable influence on life as we know it.
Water is also cohesive, that is it binds to itself, due to the polarity of the water molecule. The positive, hydrogen side of the molecule binds to the negative, oxygen side of another water molecule. This bond is called a hydrogen bond Thus, a glass of water could be considered one giant molecule, because all of the water molecules inside of it are bonded to one another. This property allows for transport of water against gravity in plants.
Water is the universal solvent because it is capable of dissolving many organic and inorganic particles. All the reactions in cells must take place in aqueous solution.
Water's polarity also inhibits movement of its molecules. Since all the molecules are connected, they cannot freely move about as other, nonpolar molecules do. Heat, the kinetic energy of molecules, is thus restricted and so water has a high specific heat (it must absorb large amounts of energy in order to change states). This means that water can serve as a temperature insulator, and does so in organisms of all kinds.
2.1.6 Explain the significance to organisms of water as a coolant, transport medium and habitat, in terms of its properties.
Water's high specific heat allows it to absorb large amounts of energy and act as an insulator for all living things. For example, our bodies use water in the for of sweat to lower body temperature. The sweat absorbs a large amount of heat, and then evaporates carryiing that heat away from the body.
The most frequently occurring chemical elements in living things are carbon, hydrogen and oxygen.
2.1.2 State that a variety of other elements are needed by living organisms including nitrogen, calcium, phosphorus, iron and sodium.
A variety of other elements are needed by living organisms including nitrogen, calcium, phosphorus, iron and sodium.
2.1.3 State one role for each of the elements mentioned in 2.1.2.
Nitrogen is a major element of proteins and nucleic acid (for DNA and RNA). Calcium is neccesary for bone and tooth formation, blood clotting, and nerve impulse transmission. Phosphorus is also used for bone and tooth formation, and to balance acid and base concetrations in the body. Iron is a part of hemoglobin, a molecule needed to carry oxygen in the blood. Sodium balances both water in the body and acid/base concentration. It also functions in nerve function.
2.1.4 Outline the difference between an atom and an ion.
An atom has the same amount of protons as electrons, so it is neutral in charge. An ion has either a positive or negative charge because there are unequal numbers of electrons and protons. A positive ion is called a cation, while a negative ion is called an anion.
2.1.5 Outline the properties of water that are significant to living organisms including transparency, cohesion, solvent properties and thermal properties. Refer to the polarity of water molecules and hydrogen bonding where relevant.
Water is transparent which allows light to filter into the oceans. This allows for aquatic plants to absorb light and perform photosynthesis. Since the ancestor of all plants originated in the ocean, the transparency of water has had a immeasurable influence on life as we know it.
Water is also cohesive, that is it binds to itself, due to the polarity of the water molecule. The positive, hydrogen side of the molecule binds to the negative, oxygen side of another water molecule. This bond is called a hydrogen bond Thus, a glass of water could be considered one giant molecule, because all of the water molecules inside of it are bonded to one another. This property allows for transport of water against gravity in plants.
Water is the universal solvent because it is capable of dissolving many organic and inorganic particles. All the reactions in cells must take place in aqueous solution.
Water's polarity also inhibits movement of its molecules. Since all the molecules are connected, they cannot freely move about as other, nonpolar molecules do. Heat, the kinetic energy of molecules, is thus restricted and so water has a high specific heat (it must absorb large amounts of energy in order to change states). This means that water can serve as a temperature insulator, and does so in organisms of all kinds.
2.1.6 Explain the significance to organisms of water as a coolant, transport medium and habitat, in terms of its properties.
Water's high specific heat allows it to absorb large amounts of energy and act as an insulator for all living things. For example, our bodies use water in the for of sweat to lower body temperature. The sweat absorbs a large amount of heat, and then evaporates carryiing that heat away from the body.
Cell Division
1.5.1 State that the cell-division cycle involves interphase, mitosis and cytokinesis.
The cell-division cycle involves interphase, mitosis and cytokinesis.
The cell-division cycle involves interphase, mitosis and cytokinesis.
1.5.2 State that interphase is an active period in the life of a cell when many biochemical reactions occur, as well as DNA transcription and DNA replication.
Interphase is an active period in the life of a cell when many biochemical reactions occur, as well as DNA transcription and DNA replication.
Interphase is an active period in the life of a cell when many biochemical reactions occur, as well as DNA transcription and DNA replication.
1.5.3 Describe the events that occur in the four phases of mitosis (prophase, metaphase, anaphase and telophase).
Mitosis contains four phases which are prophase, metaphase, anaphase, and telophase. During mitosis, chromatin fibers become tightly coiled and can be seen as chrmosomes. The chromosomes appear as two identical sister chromatids joined at the centromere. The mitotic spindle begins to from in the cytoplasm. Some of the microtubules that make up the spindle attach to the chromosomes. In metaphase the chromosomes line up on the cell equator, with each sister chromatid facing a different pole of the cell. During anaphase, the centromere replicates and the sister chromatids separate. These news chromosomes move to opposite poles, so that each pole of the cell contains a complete set of chromosomes. During telophase, the microtubules elongate the cell, further separating the two poles. Then the parent cell's nuclear encelope is broken down and fragments are used to form new nuclear envelopes.
Mitosis contains four phases which are prophase, metaphase, anaphase, and telophase. During mitosis, chromatin fibers become tightly coiled and can be seen as chrmosomes. The chromosomes appear as two identical sister chromatids joined at the centromere. The mitotic spindle begins to from in the cytoplasm. Some of the microtubules that make up the spindle attach to the chromosomes. In metaphase the chromosomes line up on the cell equator, with each sister chromatid facing a different pole of the cell. During anaphase, the centromere replicates and the sister chromatids separate. These news chromosomes move to opposite poles, so that each pole of the cell contains a complete set of chromosomes. During telophase, the microtubules elongate the cell, further separating the two poles. Then the parent cell's nuclear encelope is broken down and fragments are used to form new nuclear envelopes.
1.5.4 Explain how mitosis produces two genetically identical nuclei.
During mitosis, pairs of two identical chromosomes are pulled to opposite ends of the cell. These identical chromosomes contain the same genetic information as the chromosomes of the parent cell, so they are genetically identical. The two identical sets of chromsomes become the nuclei of the two daughter cells.
During mitosis, pairs of two identical chromosomes are pulled to opposite ends of the cell. These identical chromosomes contain the same genetic information as the chromosomes of the parent cell, so they are genetically identical. The two identical sets of chromsomes become the nuclei of the two daughter cells.
1.5.5 Outline the differences in mitosis and cytokinesis between animal and plant cells.
The differences in plant and animal cell mitosis exist because the plant cell has a cell wall. Mitosis in plant cells involves the formation of a cell plate that separates the two daughter cells, while animal cells use a cleavage furrow to separate the two new cells. Also, plant cells lack the centrioles involved in animal cell mitosis.
The differences in plant and animal cell mitosis exist because the plant cell has a cell wall. Mitosis in plant cells involves the formation of a cell plate that separates the two daughter cells, while animal cells use a cleavage furrow to separate the two new cells. Also, plant cells lack the centrioles involved in animal cell mitosis.
1.5.6 State that growth, tissue repair and asexual reproduction involve mitosis.
Growth, tissue repair and asexual reproduction involve mitosis.
Growth, tissue repair and asexual reproduction involve mitosis.
1.5.7 State that tumours (cancers) are the result of uncontrolled cell division and that these can occur in any organ.
Tumours (cancers) are the result of uncontrolled cell division and these can occur in any organ
Tumours (cancers) are the result of uncontrolled cell division and these can occur in any organ
Membranes
Draw a diagram to show the fluid mosaic model of a biological membrane.
1.4.2 Explain how the hydrophobic and hydrophilic properties of phospholipids help to maintain the structure of the cell membrane.
The head of the phospholipid is polar and hydrophilic (water-loving), and these heads make up the outside of the phospholipid bilayer. The tail of the phospholipid that is located inside the membrane is nonpolar and hydrophobic(water-fearing). Because one end of the phospholipid is hydrophobic and the other is hydrophilic, phospholipids naturally form bilayers in which the heads are facing outward (toward the water), and the tails are facing inward (away from the water). Therefore, the characteristics of phospholipids enable the phospholipids to form a stable structure.
1.4.3 List the functions of membrane proteins including hormone binding sites, enzymes, electron carriers, channels for passive transport and pumps for active transport.
Membrane proteins perform many taks which help the cell with its functions. They act as hormone binding sites, enzymes, electron carriers, channels for passive transport and pumps for active transport.
Membrane proteins perform many taks which help the cell with its functions. They act as hormone binding sites, enzymes, electron carriers, channels for passive transport and pumps for active transport.
1.4.4 Define diffusion and osmosis.
Diffusion is the total movement of particles from a region of higher concentration of that particle to a region of lower concentration of that particle. The difference in concentration that drives diffusion is called a concentration gradient. Osmosis is the passive movement of water molecules, across a partially permeable membrane, from a region of lower solute concentration to a region of higher solute concentration.
Diffusion is the total movement of particles from a region of higher concentration of that particle to a region of lower concentration of that particle. The difference in concentration that drives diffusion is called a concentration gradient. Osmosis is the passive movement of water molecules, across a partially permeable membrane, from a region of lower solute concentration to a region of higher solute concentration.
1.4.5 Explain passive transport across membranes in terms of diffusion.
Passive transport happens naturally (it requires no energy from the cell) if there is a concentration gradient between one side of the membrane and the other. This concentration gradient drives diffusion across the membrane.
Passive transport happens naturally (it requires no energy from the cell) if there is a concentration gradient between one side of the membrane and the other. This concentration gradient drives diffusion across the membrane.
1.4.6 Explain the role of protein pumps and ATP in active transport across membranes.
During active transport across membranes, the substance being transported goes against the gradient (it is going from where there is a lesser concentration to a greater concentration), and so energy is required to transport it in the form of ATP. Proton pumps in the cell membrane function in transporting particles across a membrane against concentration membranes with energy from ATP.
During active transport across membranes, the substance being transported goes against the gradient (it is going from where there is a lesser concentration to a greater concentration), and so energy is required to transport it in the form of ATP. Proton pumps in the cell membrane function in transporting particles across a membrane against concentration membranes with energy from ATP.
1.4.7 Explain how vesicles are used to transport materials within a cell between the rough endoplasmic reticulum, Golgi apparatus and plasma membrane.
Vesicles are membranous sacs in which materials are stored and transported throughout the cell. In order for the materials within a vesicle to go through a membrane (the membranes of organelles, or the cell's plasma membrane), the membranous vesicle becomes part of the organell's membrane or the plasma membrane, releasing the materials inside. The materials that were inside the vesicle are now free on the opposite side of the membrane.
Vesicles are membranous sacs in which materials are stored and transported throughout the cell. In order for the materials within a vesicle to go through a membrane (the membranes of organelles, or the cell's plasma membrane), the membranous vesicle becomes part of the organell's membrane or the plasma membrane, releasing the materials inside. The materials that were inside the vesicle are now free on the opposite side of the membrane.
1.4.8 Describe how the fluidity of the membrane allows it to change shape, break and reform during endocytosis and exocytosis.
Endocytosis is the movement of material into a cell by a process in which the plasma membrane engulfs extracellular material, forming membrane-bound sacs that enter the cytoplasm. Exocytosis is the movement of material out of a cell by a process in which intracellular material is enclosed within a vesicle that moves to the plasma membrae and fuses with it, releasing the material outside the cell.
The cell membrane is fluid in that it is constantly in motion. The movement of the phospholipids changes the membrane's shape, and allows for temporary holes in the membrane that let materials flow in and out of the cell. If the membrane were not fluid in nature, it would not be able to fuse with vesicles in endocytosis and
Eukaryotic Cells
1.3.1 Draw a diagram to show the ultrastructure of a generalized animal cell as seen in electron micrographs.
1.3.2 State one function of each of these organelles: ribosomes, rough endoplasmic reticulum, lysosome, Golgi apparatus, mitochondion and nucleus.
The ribosomes are the main site for protein synthesis. The proteins made by ribosomes can be used inside the cell, or be sent out of the cell. One function of the rough endoplasmic reticulum is the portion of the endoplasmic reticulum that is studded with ribosomes. The proteins made in these ribosomes are packaged in the rough ER and are usually sent outside of the cell. A lysosome uses hydrolytic enzymes to digest macromolecules. The Golgi apparatus recieves many of the products of the rough endoplasmic reticulum and it modifies them. Later these proteins are transported to other destinations in packages of membrane. A mitochondrion is the site of cellular respiration. The nucleus contains the DNA which controls and contains the genotype for the cell.
The ribosomes are the main site for protein synthesis. The proteins made by ribosomes can be used inside the cell, or be sent out of the cell. One function of the rough endoplasmic reticulum is the portion of the endoplasmic reticulum that is studded with ribosomes. The proteins made in these ribosomes are packaged in the rough ER and are usually sent outside of the cell. A lysosome uses hydrolytic enzymes to digest macromolecules. The Golgi apparatus recieves many of the products of the rough endoplasmic reticulum and it modifies them. Later these proteins are transported to other destinations in packages of membrane. A mitochondrion is the site of cellular respiration. The nucleus contains the DNA which controls and contains the genotype for the cell.
1.3.3 Compare prokaryotic and eukaryotic cells.
Both prokaryotic and eukaryotic cells have cell membranes and both carry out functions of cells (metabolic functions, reproduction etc).
In contrast to eukaryotes, prokaryotic cells have no organelles (no nucleus, no mitochondria, etc.). Prokaryotes have one circular loop of DNA that is located in the cytoplasm, whereas eukaryotic DNA is arranged in a very complex manner with many proteins and is located inside a nuclear envelope. Because the prokaryotic DNA is associated with very little protein, it is considered naked. Also, eukaryotic cells are much larger than prokaryotic cells. In addition, the ribosomes in prokaryotes and eukaryotes are structurally different. Prokaryotes have 70S ribosomes, whereas eukaryotes have 80S ribosomes.
Both prokaryotic and eukaryotic cells have cell membranes and both carry out functions of cells (metabolic functions, reproduction etc).
In contrast to eukaryotes, prokaryotic cells have no organelles (no nucleus, no mitochondria, etc.). Prokaryotes have one circular loop of DNA that is located in the cytoplasm, whereas eukaryotic DNA is arranged in a very complex manner with many proteins and is located inside a nuclear envelope. Because the prokaryotic DNA is associated with very little protein, it is considered naked. Also, eukaryotic cells are much larger than prokaryotic cells. In addition, the ribosomes in prokaryotes and eukaryotes are structurally different. Prokaryotes have 70S ribosomes, whereas eukaryotes have 80S ribosomes.
1.3.4 Describe three differences between plant and animal cells.
Plant cells contain a cell wall while animal cells do not.
Plant cells have chloroplasts while animal cells do not. Animal cells contain mitochondria and plant cells do not.
Most animal cells do not contain large central vacuoles while most plant cells do.
Plant cells contain a cell wall while animal cells do not.
Plant cells have chloroplasts while animal cells do not. Animal cells contain mitochondria and plant cells do not.
Most animal cells do not contain large central vacuoles while most plant cells do.
1.3.5 State the composition and function of the plant cell wall.
The plant cell wall contains cellulose microfibrils which help to maintain the cell's shape.
The plant cell wall contains cellulose microfibrils which help to maintain the cell's shape.
Prokaryotic Cells
1.2.1 Draw a generalized prokaryotic cell as seen in electron micrographs.
Drawing will be inserted at a later date
1.2.2 State one function for each of the following: cell wall, plasma membrane, mesosome, cytoplasm, ribosomes and naked DNA.
One function of the cell wall is that it maintains the shape of the cell. The plasma membrane acts as a selective membrane that lets sufficient amounts of oxygen and other nutrients to enter and leave the cell as needed. A mesosome increases the cell's surface area for metabolic reactions to occur. The cytoplasm holds and suspends the organelles of specialized function. Ribosomes are the main site for protein synthesis and naked DNA contain genes which controll the cell and contain its genotype.
1.2.3 State that prokaryotes show a wide range of metabolic activity including fermentation, photosynthesis and nitrogen fixation.
Prokaryotes show a wide range of metabolic activity including fermentation, photosynthesis and nitrogen fixation.
Drawing will be inserted at a later date
1.2.2 State one function for each of the following: cell wall, plasma membrane, mesosome, cytoplasm, ribosomes and naked DNA.
One function of the cell wall is that it maintains the shape of the cell. The plasma membrane acts as a selective membrane that lets sufficient amounts of oxygen and other nutrients to enter and leave the cell as needed. A mesosome increases the cell's surface area for metabolic reactions to occur. The cytoplasm holds and suspends the organelles of specialized function. Ribosomes are the main site for protein synthesis and naked DNA contain genes which controll the cell and contain its genotype.
1.2.3 State that prokaryotes show a wide range of metabolic activity including fermentation, photosynthesis and nitrogen fixation.
Prokaryotes show a wide range of metabolic activity including fermentation, photosynthesis and nitrogen fixation.
Cell Theory
1.1.1 Discuss the theory that living organisms are composed of cells.
All living things are made of cells, and that cells arise from other cells.
It is important to note that all "rules" have exceptions. Skeletal muscles and some fungal hyphae are not divided into cells but have a multinucleate cytoplasm. Some biologists consider unicellular organisms to be acellular.
1.1.2 State that a virus is a non-cellular structure consisting of DNA or RNA surrounded by a protein coat.
A virus is a non-cellular structure consisting of DNA or RNA surrounded by a protein coat. 1.1.3 State that all cells are formed from other cells.
All cells are formed from other cells.
1.1.4 Explain three advantages of using light microscropes.
Advantages of using a light microscope include: color images instead of monochrome images (one color), easily prepared sample material, the possibilty of observing living material and movement, and a larger field of view.
Advantages of using a light microscope include: color images instead of monochrome images (one color), easily prepared sample material, the possibilty of observing living material and movement, and a larger field of view.
1.1.5 Outline the advantages of using electron microscopes.
Since the resolution is higher in an electron microscope than a light microscope, one can see more seperate particles and have a clearer picture of those particles. Also, an electron microscope has a higher magnifaction than a light microscope, so one would be able to see smaller objects.
Since the resolution is higher in an electron microscope than a light microscope, one can see more seperate particles and have a clearer picture of those particles. Also, an electron microscope has a higher magnifaction than a light microscope, so one would be able to see smaller objects.
1.1.6 Define organelle.
An organelle is a discrete structure within a cell that has a specific function, it also needs to be covered by its own membrane.
An organelle is a discrete structure within a cell that has a specific function, it also needs to be covered by its own membrane.
1.1.7 Compare the relative sizes of molecules, cell membrane thickness, viruses, bacteria, organelles and cells, using appropriate SI units.
1000 nm(nanometer) = 1 um, 1000 um = 1mm
Molecules are 1 nm while the thickness of a membrane is 10 nm. Viruses are 100 nm, bacteria are 1 um, organelles can be up to 10 um, and most cells can be up to 100 um. The cell is much larger than all these when taken into consideration the three-dimensional shape.
1000 nm(nanometer) = 1 um, 1000 um = 1mm
Molecules are 1 nm while the thickness of a membrane is 10 nm. Viruses are 100 nm, bacteria are 1 um, organelles can be up to 10 um, and most cells can be up to 100 um. The cell is much larger than all these when taken into consideration the three-dimensional shape.
1.1.8 Calculate linear magnification of drawings.
(drawings will be inserted at a later date)
(drawings will be inserted at a later date)
1.1.9 Explain the importance of the surface area to volume ratio as a factor limiting cell size.
When a cell grows, the volume increases at a faster rate than the surface area. Thus, as the cell grows the surface to volume ratio dereases. A cell needs surface area in order to carry out metabolic functions (chemical reactions need a surface), and as a cell grows it needs to carry out more and more reactions. Therefore, since a cell must maintain a certain surface area to volume ratio, its size is limited.
When a cell grows, the volume increases at a faster rate than the surface area. Thus, as the cell grows the surface to volume ratio dereases. A cell needs surface area in order to carry out metabolic functions (chemical reactions need a surface), and as a cell grows it needs to carry out more and more reactions. Therefore, since a cell must maintain a certain surface area to volume ratio, its size is limited.
1.1.10 State that unicellular organisms carry out all the functions of life.
Unicellular organisms carry out all the functions of life.
Unicellular organisms carry out all the functions of life.
1.1.11 Explain that cells in multicellular organisms differentiate to carry out specialized functions by expressing some of their genes but not others.
In multicellular organisms, all the cells contain all the genes, but they do not use all of them. The cells of a multicellular organism differentiate to carry out specialized funcions by only expressing some of thier genes.
In multicellular organisms, all the cells contain all the genes, but they do not use all of them. The cells of a multicellular organism differentiate to carry out specialized funcions by only expressing some of thier genes.
1.1.12 Define tissue, organ, and organ system.
A tissue is an integrated group of cells that have a common stucture and function. An organ is a center of body function specialized for that one function that is composed of several different types of tissue. An organ system is a group of organs that specialize in a certain function together.
A tissue is an integrated group of cells that have a common stucture and function. An organ is a center of body function specialized for that one function that is composed of several different types of tissue. An organ system is a group of organs that specialize in a certain function together.
Wednesday, October 8, 2008
modified cells
1. Root hair cells- are modified for the absorption of water and minerals. These are elongated cells and have more surface area for the absorption of water
2. Xylem vessels-they are fine tubes to help the conduction of waterThey have lignified walls for support they have no cross walls, no cytoplasm and no nuclei for the transport of water and minerals
Muscle cells- rare modified cells to carry out contraction and movement .it have lots of mitochondria for the production of energy to carry out the functions They have stored food (glycogen) for the release of energy
Red blood cells – they are bi concave disc like cells and this shape provides more surface area to carry oxygen
Ciliated cells –have tiny hair that move from side to side it helps to keep trachea clear of dust
Nerve cell – are long cells with many connecting side branches. It transmit messages
2. Xylem vessels-they are fine tubes to help the conduction of waterThey have lignified walls for support they have no cross walls, no cytoplasm and no nuclei for the transport of water and minerals
Muscle cells- rare modified cells to carry out contraction and movement .it have lots of mitochondria for the production of energy to carry out the functions They have stored food (glycogen) for the release of energy
Red blood cells – they are bi concave disc like cells and this shape provides more surface area to carry oxygen
Ciliated cells –have tiny hair that move from side to side it helps to keep trachea clear of dust
Nerve cell – are long cells with many connecting side branches. It transmit messages
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