Unit two - Metabolism and survival

Question 1

Describe the difference between a reversible and an irreversible step

Answer 1

With a reversible step the product can react to form the original substrate. in am irreversible step the reactants form the product which cannot be reversed.

Question 2

explain what is meant by an alternative route in a metabolic pathway

Answer 2

when a substrate is acted upon by a different enzyme and follows a different pathway to the end product

Question 3

name an enzyme which is embedded in the inner mitochondrial membrane

Answer 3

ATP synthase

Question 4

describe the role of protein pumps embedded in the inner mitochondrial membrane

Answer 4

the use of energy to pump hydrogen ions across the inner mitochondrial membrane

Question 5

Describe the role of genes in the control of metabolic pathways

Answer 5

each step in a metabolic pathway is controlled by a specific enzyme, each enzyme is coded for by a gene, the order of bases in the gene determine the order of the amino acids, which determines the structure of the protein.

Question 6

describe the role of the active site of an enzyme during a reaction

Answer 6

The active site has a slightly high affinity for the substrate molecule and a low affinity for the products. this lowers the activation energy of the chemical reaction

Question 7

Describe the mechanism of induced fit

Answer 7

the enzyme is flexible and so the active site can change shape, the substrate induces the active site to change shape, and the active site can orientate the position of the substrate molecules so they fit better.

Question 8

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

Answer 8

increase in substrate concentration drives the chemical reaction in the direction of the end product and increases the rate of reaction

Question 9

Explain how enzymes speed up the rate of reaction in metabolic pathways

Answer 9

The active site can alter the position of the substrate molecules so that they fit more closely, and the activation energy is lowered when an enzyme is involved

Question 10

describe the effect of substrate concentration and end- product concentration on a reversible metabolic reaction

Answer 10

increase substrate concentration drives the chemical reaction in the direction of the end product, increase in the end product concentration drive the chemical reaction in the direction of the substrate.

Question 11

describe the effect of increasing concentration on the rate of reaction in the presence of a competitive inhibitor

Answer 11

reaction rate increases with the substrate concentration, but as substrate concentration increases further there is no further effect on the rate of reaction

Question 12

describe the effect of increasing substrate concentration on the rate of reaction in the presence of non-competitive inhibitors

Answer 12

inhibitors reduce the rates of reaction nearly to 0 increasing substrate concentration makes no difference.

Question 13

explain the advantages of end-product inhibition to a cell

Answer 13

stops the production of too much end product

Question 14

explain the difference between a competitive and a non-competitive inhibitor

Answer 14

competitive inhibitors binds reversibly at the active site, and non-competitive inhibitors binds irreversibly at another binding site.

Question 15

explain the effect of a competitive inhibitor on the rate of reaction

Answer 15

the rate of the enzyme reaction decreases, and competitive inhibitors have a similar shape to the substrate molecule and attaches at the active site of the enzyme

Question 16

explain the effect of a non-competitive inhibitor on the rate of reaction

Answer 16

the rate of reaction is reduced to nearly zero and inhibitors cause a change in the shape of the active site so that the substrate cannot bind

Question 17

Explain why the phosphorylation of intermediates in glycolysis is referred tp as an energy investment stage

Answer 17

Two ATP molecules are used to phosphorylate the intermediates in the energy investment stage, and four ATP molecules are gained in the pay-off stage

Question 18

Describe the role of the dehydrogenase enzymes in glycolysis and the citric acid cycle

Answer 18

Dehydrogenase enzymes remove hydrogen ions and electrons

Question 19

Explain the role of ATP during glycolysis

Answer 19

In glycolysis, ATP is used in the phosphorylation of glucose and intermediates

Question 20

Explain why the ATP produced in glycolysis is referred to as an energy pay-off

Answer 20

Four ATP molecules are produced in the pay-off stage, this gives a net gain of 2 ATP

Question 21

Describe the role of the co-enzyme NAD

Answer 21

It transports hydrogen ions and electrons to the electron transport chain

Question 22

Describe how hydrogen ions caused the synthesis of ATP during respiration

Answer 22

ATP is regenerated as the hydrogen ions flow back through the ATP synthase

Question 23

describe how the role of the electrons that pass down the electron transport chain

Answer 23

it releases energy to pump the hydrogen ions across the inner membrane of the mitochondria

Question 24

describe the role of proteins in the electron transport chain

Answer 24

the electrons cascade down the chain of proteins releasing energy and to pump the hydrogen ions across the inner membrane of the mitochondria

Question 25

describe the role played by oxygen in the electron transport chain

Answer 25

Acts as the final electron acceptor combines with hydrogen ions and electrons to form water

Question 26

Compare the products of fermentation in animal and yeast cells

Answer 26

Fermentation in animal cells produces lactate but in yeast cells produces ethanol and CO2, fermentation in animals is reversible but in yeast cells it is irreversible

Question 27

describe the role of ATP in cell metabolism

Answer 27

ATP is used to transfer the energy from cellular respiration to cellular process which requires energy

Question 28

name to cellular processes which are anabolic

Answer 28

protein synthesis transcription translation DNA replication

Question 29

Describe to measurements which can be used in determining the metabolic rate os an organism

Answer 29

oxygen consumed in a given period of time and carbon dioxide produced in a given period of time and the energy released as heat in a given period of time

Question 30

Explain why the structure of a mammalian heart makes it more efficient than the heart of a fish

Answer 30

Mammals have four chambered heart this helps deliver oxygen at higher blood pressure to tissues

Question 31

Explain why organisms with a high metabolic rate require an efficient delivery of oxygen to their cells

Answer 31

More oxygen so more aerobic respiration and more ATP needed to maintain high metabolic rate.

Question 32

Explain how the heart of a mammal is better adapted than the heart of an amphibian to allow high metabolic rates in the cells that it supplies with blood

Answer 32

in mammals, fully oxygenated blood can be delivered to the muscles because heart has two ventricles, and amphibians incompletely oxygenated blood is delivered to the muscles because the heart has only one ventricle where blood can mix

Question 33

Explain why the circulatory system of mammals needs to be more efficient than those of the other vertebrates shown

Answer 33

Mammals have higher metabolic rates and they require more efficient delivery of oxygen to cells

Question 34

Explain how a named abiotic factor can affect the ability of an organism to maintain it metabolic rate

Answer 34

Temperature affects the enzyme activity

Question 35

Explain why conformers have low metabolic costs

Answer 35

They do not use physiological mechanisms to control their metabolic rate, however this requires energy

Question 36

Explain why conformers usually have a narrow ecological niche

Answer 36

conformers lack the ability to tolerate environmental change should it occur

Question 37

Explain why regulators can occupy a wide range of ecological niches

Answer 37

Because they can maintain their internal environment in a wide range of conditions using their metabolism

Question 38

Explain why regulators have high metabolic costs

Answer 38

the use energy to maintain homeostasis

Question 39

Describe the response of a mammal to an increase in body temperature

Answer 39

increased sweat productions vasodilation of blood vessels hair erector muscles relaxed

Question 40

Explain the advantage of a mammal vasoconstriction of its blood vessels when skin temperature drops from 20 to 5 degrees

Answer 40

Reduces the volume of blood flow to skin surface this reduces heat loss by radiation

Question 41

Describe the role of negative feedback control in thermoregulation

Answer 41

Ensures that when the body temperature returns to normal the corrective mechanisms are switched off.

Question 42

Explain why regulating body temperature is important to the metabolism of mammals

Answer 42

Mammals maintain the optimum temperature for enzyme activity so can maintain a high metabolic rate, rates of diffusion of substances such as oxygen and carbon dioxide are faster, which helps to maintain a high metabolic rate.

Question 43

Explain the importance of thermoregulation to mammals

Answer 43

Mammals can maintain the optimum temperature for enzyme activity so can maintain a high metabolic rate, rates of diffusion of substances such as oxygen and carbon dioxide which helps maintain a high metabolic rate.

Question 44

Describe the difference between consequential and predictive dormancy

Answer 44

Predicitive dormancy is when an organism becomes dormant before onset of the adverse conditions, Consequential dormancy is when an organism becomes dormant after the onset of adverse conditions.

Question 45

Explain the benefit to some animals of being able to undergo daily torpor

Answer 45

It increases an organisms chances of survival by reducing the energy required to maintain a high metabolic rate

Question 46

Explain the survival role fo aestivation

Answer 46

Aestivation allows survival in periods of high temperature when there would be a lack of food and water.

Question 47

Explain the survival role of hibernation in some mammals

Answer 47

Hibernation allows survival in periods of low temperature when organisms would not able to meet its metabolic costs

Question 48

Explain the benefit to some animals of being able to migrate

Answer 48

Adverse conditions are avoided by migrating

Question 49

Describe a technique which could be used to track species which undertake long-distance migration

Answer 49

Transmitters and receivers

Question 50

In culturing bacteria it is important to control the pH of the culture medium. Explain why the pH of a culture medium should be controlled.

Answer 50

pH is a factor which affects rates of enzyme activity, in fermenters buffers can be added to maintain optimum pH conditions for enzyme activity.