BY4-June 2013

Question 1

Suggest a reason for the slower speed of response by jellyfish.

Answer 1

Only have a nerve net/no CNS.
Nerve fibres non-myelinated.
Narrower axons.

Question 2

Name the substance that plants use to detect day and night length.

Answer 2

Phytochrome.

Question 3

Suggest two density I dependant factors, which might prevent numbers of red kites to continue to rise.

Answer 3

Nesting sites.
Source of food.
Mates.
Disease.

Question 4

Suggest on density independent factor that might cause the population of the red kite in Wales to crash in the future.

Answer 4

Deforestation.

Question 5

Explain how carbon dioxide is used in the production of glycerate-3-phosphate.

Answer 5

RuBP and carbon dioxide are fixed together.
RuBP carboxylase (RUBISCO) catalysed the reaction.
Unstable 6C compound formed, splits into two 3C.

Question 6

State the general role of muscles and glands in simple reflexes.

Answer 6

Effectors carry out the response/react to stimulus.

Question 7

Describe how glycerate-3-phosphate is converted to triode phosphate.

Answer 7

Glycerate 3 phosphate reduced using reduced NADP.
ATP also required to supply energy.
Reduced NADP and ATP from light dependant reactions.

Question 8

State why only some of the triode phosphate produced by the Calvin Cycle can be used to produce the hexose phosphate.

Answer 8

Some triode phosphate needed to regenerate RuBP.

Question 9

Suggest how many times the Calvin cycle must occur to produce one molecule of glucose.

Answer 9

Six times.

Question 10

Suggest two reasons for the the use of a sparser in fermenters.

Answer 10

Improves aeration.
Helps to mix the contents.
Improves contact with nutrients.

Question 11

Suggest why the pH probe is needed.

Answer 11

Monitor pH.

Used to determine whether acid or alkaline must be added to maintain optimum pH for growth.

Question 12

State one waste gas that will need to be removed if the microorganism is an obligate aerobe.

Answer 12

Carbon dioxide.

Question 13

Suggest why its necessary to warm contents at start and cool towards end.

Answer 13

Heated at the start to speed up enzyme reactions/growth.

Removal of heat produced by respiration/more microbes at the end so more respiration and heat.

Question 14

Suggest reasons for preventing the fermenter becoming contaminated with other microorganism.

Answer 14

Competition for nutrients.
Lower yield.
Toxic products.
Contamination of product.

Question 15

Explain the reasons for reduced NAD being required to maintain a proton gradient.

Answer 15

Reduced NAD supplies protons.
And brings high energy electrons.
Electrons supply energy for proton pumping.

Question 16

Outline the pathway for the production of triose phosphate in glycolysis.

Answer 16

Glucose is phosphorylated by ATP.
Two phosphorylations/production of hexose biphosphate.
Hexose biphosphate is split from 6C to 3C.

Question 17

Explain the biomechanical reasons for carrying out the reaction, despite the fact that lactate is toxic in high concentrations.

Answer 17

Allows reduced NAD to be converted back into NAD without oxygen.
Allows for ATP production without oxygen.
Allows glycolysis/substrate level phosphorylation to continue.
No O2 to act as final hydrogen acceptor, must use pyruvate.

Question 18

Explain in terms of movement of ions, what causes the rise in membrane potential.

Answer 18

(Voltage gated) sodium channels open.

Sodium ions rush in/sudden influx.

Question 19

State the name given to the rapid fall in membrane potential.

Answer 19

Repolarisation.

Question 20

Suggest how cardiac muscle fibres would respond when the voltage across the membrane rises.

Answer 20

Contraction.

Question 21

Consider the ethics of killing a frog to obtain cardiac muscle fibres by giving one argument in favour and one against.

Answer 21

Frog has right to life, causes suffering and distress to frog.
Benefits to medicine/health of heart research.

Question 22

Name the vessel that brings blood to the kidney.

Answer 22

Renal artery.

Question 23

Describe two structural features of glomeruli that allow ultrafiltration to occur.

Answer 23

Many gaps in the endothelium.
Basement membrane with pores, acting as molecular sieve.
Efferent arteriole has smaller diameter than afferent.

Question 24

Using your knowledge of processes occurring in the nephron, explain the difference in glucose concentration between glomerular filtrate and urine.

Answer 24

All glucose selectively reabsorbed.
Reabsorption in the proximal convoluted tubule.
Reabsorption by active transport.

Question 25

Describe the role of the nephron an collecting duct in achieving this increase in concentration.

Answer 25

Water reabsorbed from filtrate.
Less urea reabsorbed.
Sodium ions reabsorbed in proximal convoluted tubule.
Therefore water reabsorbed by osmosis in proximal convoluted tubule.
Active transport of sodium ions in the ascending limb of loop of Henle.
Descending limb permeable, ascending limb impermeable.
Hypertonic conditions in the medulla.
Therefore water reabsorbed in the collecting duct.

Question 26

Suggest an advantage to mammals of excreting urine with a high concentration.

Answer 26

Less water lost in urine.

Reduces risk of dehydration.

Question 27

The concentration of sodium ions in the urine of a person varies. The concentration is affected by the level of a hormone. Name this hormone and explain how it affects the concentration of sodium ions in the urine.

Answer 27

ADH.
Increases reabsorption of water as increases the permeability of the collecting duct to water so increases the ion concentration.