textbook to work on

Question 1

describe what is meant by a metabolic pathway.

Answer 1

Sequence of chemical reactions controlled by enzymes.

Question 2

State two differences between anabolic and catabolic pathways

Answer 2

Anabolic pathways are biosynthetic processes / involve the buildup of complex molecules from simpler substances and catabolic pathways involve the breakdown of complex molecules into simpler molecules.

Anabolic Require energy and catabolic release energy.

Question 3

Give two roles of proteins embedded in phospholipid membranes.

Answer 3

Pores; pumps ; enzymes

Question 4

Give two examples of organelles bounded by double membranes.

Answer 4

Mitochondria ; chloroplasts ; nucleus

Question 5

Explain the advantage of membrane bound compartments in cells.

Answer 5

Localise the metabolic activity of the cell
Provide more favourable conditions for reactions to take place
Membrane folds in organelles provide a large surface area for metabolic reactions to take place.
The large surface area to volume ratio of small compartments allow high concentrations of reactants to occur.
High reaction rates possible.

Question 6

Extended Response - Write notes on metabolic pathways

Answer 6

A metabolic pathway is a sequence of chemical reactions controlled by enzymes. Chemical reactions are anabolic and catabolic. Anabolic pathways are biosynthetic processes / involve the building up of complex molecules from simpler molecules. ANabolic pathways require the input of energy. Catabolic pathways involve the breakdown of complex molecules into simpler molecules. Catabolic releases energy.

Question 7

Extended Response - Write notes on the functions of membranes.

Answer 7

Membrane separates the internal contents of the cell from its surrounding environment. Membranes can form compartments to localise the metabolic activity of the cell. Compartments provide more favourable conditions for reactions to take place. Membrane folds in organelles provide a large surface area for metabolic reactions to take place. Large surface to volume ratio of small compartments in organelles allow high concentrations of reactants to occur/ higher reaction rates. Channel forming proteins/ pores allow diffusion of small molecules. Carrier proteins / pumps involved in active transport. Some proteins act as enzymes.

Question 8

Describe the role of genes in the control of metabolic pathways

Answer 8

Each step in a metabolic pathway is controlled by a specific enzyme. Each enzyme is coded for by a gene. Order of bases in the gene determines the order of amino acids , which determines structure, shape and function of the protein/ enzyme.

Question 9

Describe the effect of an increase in substrate concentration on the direction and rate of an enzyme reaction.

Answer 9

Increase in substrate concentration drives the chemical reaction in the direction of the end product. Increases the rate of reaction.

Question 10

Explain how enzymes speed up the rate of directions in metabolic pathways.

Answer 10

Active site can alter the position of/ orientate the substrate molecules so that they fit more closely. Activation energy is lowered when an enzyme is involved.

Question 11

Extended response - Give an account of enzyme action and the effects of competitive and non competitive inhibition.

Answer 11

Enzyme activity depends on the flexible / dynamic shape of enzyme molecules. Substrate has an affinity for the active site. Induced fit ; active site orientates the reactants; enzymes lower the activation energy. Products have a low affinity for the active site. Substrate and product concentration affects the direction and rate of reactions or increasing the substrate concentration increases/ speeds up the rate of reaction. Enzymes act in groups / multi enzyme complex. In competitive inhibition the inhibitor resembles the substance molecule. Inhibition is reduced by increase in substrate concentration. In non competitive inhibition the shape of the active site is changed.

Question 12

Describe the role of the coenzyme NAD.

Answer 12

NAD transport H+ and high energy electrons to the electron transport chain.

Question 13

Name the enzyme embedded in the inner membrane of a mitochondria responsible for the regeneration of ATP.

Answer 13

ATP synthase.

Question 14

Name 2 alternative respiratory substrates

Answer 14

Other sugars, glycogen, starch, fats, amino acids, fatty acids, gylcerol.

Question 15

Extended Response - Give an account of glycolysis and the citric acid cycle in respiration.

Answer 15

Glycolysis is the breakdown of glucose to pyruvate. 2 ATP molecules are used to phosphorylate intermediates in glycolysis. An energy investment stage. 4 ATP molecules are produced / made in a pay off stage. H carried away by NAD.
If oxygen is available / in aerobic conditions pyruvate progresses to the citric acid cycle. Pyruvate is broken down to an acetyl group which then combines with coenzyme A forming Acetyl coenzyme A. Acetyl coenzyme A combines with oxaloacetate to form citrate. Citric acid cycle involves dehydrogenases. ATP produced at substrate level in the citric acid cycle. Oxaloacetate is regenerated. NAD /NADH transports electrons / hydrogen ions to the electron transport chain.

Question 16

Extended Response - Give an account of the electron transport chain and the transfer of energy by ATP.

Answer 16

Electron transport chain on the inner membrane of the mitochondria. Electron transport chain is a collection of proteins attached to a membrane. NADH release the high energy electrons to the electron transport chain on the inner mitochondrial membrane. Electrons pass down the chain of electron acceptors, releasing their energy. Energy is used to pump hydrogen ions across the inner mitochondrial membrane. Return flow of the hydrogen ions back into the matrix drive the enzyme ATP synthase. Synthesis of ATP from ADP + Pi. This stage produces most of the ATP generated by cellular respiration. Final electron acceptor is oxygen. Oxygen combines with hydrogen ions and electrons to form water.
ATP is used to transfer the energy from cellular respiration to synthetic pathways.

Question 17

State what is meant by an organism’s metabolic rate.

Answer 17

Metabolic rate of an organism is the amount of energy consumed in a given time period.

Question 18

Describe 2 methods of measuring the metabolic rate of an organism.

Answer 18

Can be measured in terms of the oxygen consumed in a given period of time, carbon dioxide produced in a given period of time, the energy released as heat in a given period of time.

Question 19

Describe how the gas exchange system of birds is adapted to enable them to maintain their very high metabolic rates.

Answer 19

Have a system of large air sacs associated with their lungs. Air flows through the lungs in one direction / does not go in and out by the same route.

Question 20

Describe one physiological adaptation for low oxygen niches.

Answer 20

Humans respond to high altitude by increasing their number of red blood cells. Diving mammals for example slow their heart rate down to conserve oxygen or collapse their lungs to reduce buoyancy, allowing them to sink quickly and save energy.

Question 21

Explain the term VO2 max and why it can be used as a measure of fitness in humans.

Answer 21

V02 max is the maximum volume of oxygen that the body can take up and use. The oxygen can be used in respiration to release energy for exercise.

Question 22

Extended response - Compare and contrast the heart structure and circulation of fish, amphibians and mammals.

Answer 22

Fish circulation and heart structure - Single circulatory system / heart to gills to body ro heart. Heart with 1 atrium and a ventricle. Loss of pressure is a problem.
Amphibian circulation and heart structure - incomplete double circulatory system, heart with right and left atrium and one ventricle. Pressure maintained. Tissue blood is incompletely oxygenated.
Mammal circulation and heart structure - complete double circulatory system. Heart has two atria and two ventricles. Pressure maintained. Tissue blood completely oxygenated. No mixing of blood.

Question 23

The corrective mechanism in response to a decrease in body temperature includes (vasoconstriction/vasodilation) which (increases/decreases) blood flow in the skin.

Answer 23

Vasoconstriction and decreases.

Question 24

Describe how the messages from the temperature monitoring centre are relayed to the effectors in the skin.

Answer 24

Nerve impulses

Question 25

State 2 reasons why body temperature in humans is important to metabolic processes.

Answer 25

Enzymes controlling the metabolism are maintained at their optimum temperature. Affects rates of diffusion.

Question 26

Give 2 abiotic factors that affect the ability of an organism to maintain its metabolic rate.

Answer 26

Temperature, salinity, PH

Question 27

Give the name of the control system used by regulators to maintain a relatively stable internal environment.

Answer 27

Homeostasis is the maintenance of a steady state/ a constant internal environment with an organism.

Question 28

Extended Response - Give an account of the mechanisms of thermoregulation in mammals.

Answer 28

Temperature monitoring centre. Thermorwceptors are located in the hypothalamus. Informations about temperature detected by hypothalamus. Mammals derive most of their body heat from respiration / metabolism / chemical reactions. Nerve impulse sent to skin/ effectors. Vasodilation / widening of blood vessels to skin in response to increased temperature. Vascoconstriction -narrowing of blood vessels in response to decreased temperature. Temperature regulation is an example of negative feedback.

Question 29

Extended Response - Give an account of metabolism in conformers in relation to their ecological niches.

Answer 29

Ability of an organism to maintain its metabolic rate is effected by external abiotic factors such as temperature, salinity, PH. Conformers internal environment is dependent upon its external environment. Conformers cannot alter their metabolic rate using physiological means. Conformers usually have a narrow ecological niche. Conformers lack the ability to tolerate change should it occur. Conformers live in stable environments. Conformers do not use energy requiring physiological mechanisms to alter their metabolic rate. Conformers have low metabolic costs. MANY CONFORMERS MANAGE TO MAINTAIN THEIR OPTIMUM METABOLIC RATE BY EMPLOYING CERTAIN BEHAVIOURAL RESPONSES.

Question 30

Give the meanings of innate and learned behaviour in bird migration.

Answer 30

Innate means that it is inherited. Migratory behaviour is also influenced by learning which is gained by experience.

Question 31

Give 2 methods of tracking migratory animals.

Answer 31

Ringing, tagging, transmitters.

Question 32

Extended Response - Give an account of the adaptations of organisms to surviving and avoiding adverse environmental conditions.

Answer 32

The extremes of conditions do not allow the normal metabolism of the organism present. Variation in conditions can be cyclical or unpredictable. Metabolic rates can be reduced when conditions would make the cost of metabolic activity too high. Dormancy may be predictive or consequential. Examples from hibernation or aestivation. Daily torpor is a period of reduced activity.
Avoiding adverse conditions - migration avoids metabolic adversity by relocation.

Question 33

Extended Response - Give an account of Extremophiles

Answer 33

Thrive in an environment that would be lethal to almost all other species. Eg hot springs, seabed vents, saline lakes. Have tolerant enzymes or have heat tolerant DNA polymerase.

Question 34

Describe 2 features of microorganisms that make them useful for a variety of research and industrial uses.

Answer 34

Use a wide range of substrates for metabolism. Produce a wide range of products from their metabolic pathways. Ease of cultivation. Speed of growth.

Question 35

Give 2 complex compounds that are sometimes added to culture media to enable certain microorganisms to grow.

Answer 35

Vitamins, fatty acids, beef extract.

Question 36

Explain why temperature, pH and oxygen levels must be monitored and controlled during the culture of microorganisms.

Answer 36

Optimum temperature and PH for microorganism enzymes, oxygen for aerobic respiration for microorganisms.

Question 37

Name 2 types of substance that may need to be added to some fermentations to control the metabolism of microorganisms so that the desired product is obtained.

Answer 37

Precursors, inducers, inhibitors

Question 38

Describe what happens during the primary metabolism of a microorganism in culture.

Answer 38

Substrates are broken down to obtain energy. Produces primary metabolites used for the biosynthesis of substances such as proteins/ nucleic acids.

Question 39

Explain why substances produced during secondary metabolism might give an ecological advantage to a microorganism.

Answer 39

Results in the production of secondary metabolites such as antibiotics; inhibit the growth of bacteria and so reduce competition of the available resources.

Question 40

Extended Response - Give an account of the different culture conditions required for the growth of microorganisms.

Answer 40

Require an energy source, energy is derived from substances such as carbohydrates/ light in the case of photosynthetic microorganisms. Supply of raw materials for the biosynthesis of proteins. Many microorganisms only require simple chemical compounds in growth media. Other microorganisms require specific complex compounds e.g vitamins / fatty acids. Growth media can contain complex ingredients such as beef extract. Sterility to eliminate any effects of contaminating microorganisms. Control of temperature / PH / oxygen. Control of oxygen levels by aeration. Control of PH by buffers or the addition of acid or alkali.

Question 41

Extended Response - Give an account of the phases of growth of microorganisms cultured in a fermenter.

Answer 41

Growth is recorded by measuring the increase in cell number in a given period of time. The time it takes for a unicellular organism to divide into two is called the doubling or generation time. The lag phase of growth is where the microorganisms induce the production of enzymes that metabolise the substrates. No cell division occurs at this stage.
Log or exponential phase of growth is where the culture medium becomes depleted / nutrients or oxygen start to run out. Stationary phase is reached when the rate of production of new cells is equal to the death rate of the older cells. Death phase occurs due to the lack of substrate / toxic accumulation of metabolites. More cells die than are being produced.

Question 42

Give 2 reasons for the transfer of gene sequences to microorganisms other than for the production of plant and animal proteins.

Answer 42

Genes that remove inhibitory controls to increase the yield of a desired protein. Genes that amplify specific metabolic steps to increase the yield of a desired protein. Genes preventing the survival of the microorganism in an external environment.

Question 43

Explain why animal DNA that has been transferred to bacteria might produce proteins that are not functional. ii) Suggest how this problem might be overcome.

Answer 43

Production of polypeptides that are folded incorrectly. Production of polypeptides that lack posttranslational modifications.

Question 44

Give 2 reasons for the transfer of gene sequences to microorganisms other than for the production of a desired protein.

Answer 44

Marker genes, genes which prevent survival in an external environment.

Question 45

Extended Response - Give an account of the production of protein by recombinant DNA technology.

Answer 45

Recombinant DNA technology involves the joining together of DNA molecules from two different species. Plant or animal gene sequences can be transferred to microorganisms to produce plant or animal proteins. Genes that remove inhibitory controls/ amplify specific metabolic steps in a pathway can be introduced to increase the yield of a desired protein. Genes to prevent the survival of the microorganism in an external environment can be introduced as a safety mechanism. Recombinant plasmids or artificial chromosomes act as vectors. Vector carries the DNA from the donor organism into the host cell. Vectors must contain restriction sites/ marker genes/ genes for self replication and regulatory sequences. Restriction endonucleases cut target sequences of DNA, leaving sticky ends. Treatment of vectors with the same restriction endonuclease. Complementary sticky ends are then combined using DNA ligase to form recombinant DNA.