p1 - set b

Question 1

Explain how the chromosome number is halved during meiosis.

Answer 1

• homologous chromosomes pair up
• one of each pairs goes to opposite poles

Question 2

Crossing over greatly increases genetic diversity in this species of moss. Describe the process of crossing over and explain how it increases genetic diversity.

Answer 2

• homologous pairs of chromosomes associate
• chiasmata forms
• equal lengths of alleles are exchanged
• producing new combinations of alleles

Question 3

Compare and contrast the molecular structures of globular and fibrous proteins.

Answer 3

similarities -
- they both are a chain of amino acids joined together by peptide bonds
- they both contain hydrogen bonds

differences -
- globular has hydrophillic group on the outside and fibrous has hydrophobic group on the outside
- globular is folded into a compact shape whereas fibrous have long chains
- globular has tertiary or quartenary structure whereas fibrous has little to no tertiary structure

Question 4

Describe the roles of transcription and translation in the synthesis of a globular protein by a muscle cell.

Answer 4

• the gene for the globular protein is transcribed
• the rna and dna nucleotides pair via complementary base pairing producing mrna
• the mrna leaves the nucleus and attaches to the ribosome
• the codon on the mrna pairs with the anticodon on the trna
• the trna provides specific amino acids
• the sequence of codons determines the structure of the protein

Question 5

The adult damselfly uses a tracheal system for gas exchange. Explain three ways in which an insect’s tracheal system is adapted for efficient gas exchange.

Answer 5

• tracheoles have a thin wall so short diffusion distance
• has large number of tracheoles so short diffusion pathway
• has a large number of tracheoles so large surface area
• trachea provides tubes full of air

Question 6

The damselfly larva is a carnivore that actively hunts prey. It has gills to obtain oxygen from water. Some other species of insect have larvae that are a similar size and shape to damselfly larvae and also live in water. These larvae do not actively hunt prey and do not have gills. Explain how the presence of gills adapts the damselfly to its way of life.

Answer 6

• the damesfly has a higher metabolic rate and so uses more oyxgen

Question 7

Describe the role of glucagon in gluconeogenesis. Do not include in your answer details on the second messenger model of glucagon action.

Answer 7

• activates enzymes
• allowing the conversion of glycerol/amino acids/fatty acids into glucose

Question 8

Explain how increasing a cell’s sensitivity to insulin will lower the blood glucose concentration.

Answer 8

• more insulin binds to receptors
• this stimulates more uptake of glucose by transport proteins
• alternatively we could say, activates enzymes which convert glucose to glycogen

Question 9

Explain how inhibiting adenylate cyclase may help to lower the blood glucose concentration.

Answer 9

• less atp is converted to cyclic amp
• less kinase activated
• less glycogen converted into glucose

Question 10

In the trachea,bronchi,bronchioles and alveoli can the following structures be found; cartilage, elastic fibres and goblet cells

Answer 10

• trachea, cartillage, elastic fibres, and goblet cells
• bronchi, cartillage, elastic fibres, and goblet cells
• bronchiole, elastic fibres
• alveoli, elastic fibres

Question 11

Name the apparatus used to measure and record air movements

Answer 11

• spirometer

Question 12

Compare and contrast expiration at normal levels and when a subject is told to breathe out fully

Answer 12

normal expiration -
- passive
- diaphragm relaxes and external intercostal muscles relax
- diaphragm moves up
- ribs move down and in
- thorax volume reduced
- pressure inside thorax increased
- pressure inside thorax is greater than atmospheric pressure

forced expiration -
- active so requires energy
- internal intercostal muscles contract
- ribs pulled down and hard
- abdominal muscles contract forcing diaphragm up

Question 13

Describe the sequence of actions that occur once adenylyl cyclase is activated in the target liver cells.

Answer 13

• more atp is converted into cyclic amp
• cyclic amp activates enzymes that convert glycogen into glucose

Question 14

The response in Fig. 20.1 also occurs when a person is subjected to stress. However, the body does not need to respond physically to the stimulus and so, for example, the bronchioles do not dilate. From the information given and your own knowledge, suggest the long term adverse effects of continued exposure to stress on body function.

Answer 14

• high blood pressure can cause cardiovascular problems
• a suppressed immune system can cause disease

Question 15

What is the role of compound pyruvate in anaerobic respiration?

Answer 15

• is a hydrogen acceptor

Question 16

Why is it important that compound NAD is formed during the reaction in which compound pyruvate is converted into compound lactate in anaerobic respiration?

Answer 16

• for glycolysis to take place
• there is a limited amount of NAD
• for some ATP formation

Question 17

Compound lactate is toxic and is removed from the muscle cell. It is transported to an organ in the body. Which organ is compound lactate transported to and how does it reach this organ?

Answer 17

• to the liver in the blood

Question 18

Athletic sprinters require large amounts of energy in short periods of time. Many elite sprinters can run 100 metre races in under 10 seconds. Under normal conditions, exercise requires an increased rate of breathing. It has been observed that some of the best sprinters only take one breath at the start of the race and do not inhale again until the end of the race. Suggest how these sprinters can expend so much energy without needing to carry out aerobic respiration.

Answer 18

• they have high phosphopcreatine stores
• use of stored atp
• cells are able to tolerate high levels of lactate