booklet 17 mark scheme answers

Question 1

in which part of the mitochondrion does the Krebs cycle take place

Answer 1

matrix

Question 2

name two substances for which there would be net movement into the mitochondrion

Answer 2

pyruvate and ADP

Question 3

Apart from respiration give three uses of ATP in a liver cell

Answer 3

-cell division
-synthesis of lipids
-bile production

Question 4

Describe what happens to pyruvate in anaerobic conditions and explain why anaerobic respiration is advantageous to human skeletal muscle

Answer 4

-forms lactate
-use of reduced NAD
-regenerates NAD
-NAD can be re-used to oxidise more repository substrate
-can still release energy/ form ATP
-when oxygen is in short supply

Question 5

suggest one reason why it was important that the student left the apparatus for one hour after the yeast culture reached a constant temperature

Answer 5

so the oxygen is used/ absorbed/ respired

Question 6

aerobic respiration produces more ATP per molecule than anaerobic respiration. Explain why

Answer 6

-oxygen is the final electron acceptor
-aerobic respiration has oxidative phosphorylisation
-ananerobic respiration only glycolysis occurs

Question 7

many yeast cells die during the death phase, suggest one reason why

Answer 7

no glucose
increase in ethanol/ carbon

Question 8

explain why the concentration of oxygen and amount of ADP fell during the investigation

Answer 8

ADP and phosphate forms ATP
oxygen used to form water

Question 9

if aerobic respiration had been investigated rather than anaerobic respiration, how would you expect the volumes of gas collected at 30 to differ from these results? explain your answer

Answer 9

volume less as C02 evolved and 02 taken in

Question 10

the scientist measured the uptake of oxygen by the mitochondria during the investigation. The uptake of oxygen decreased when malonate was added. Explain why

Answer 10

Krebs cycle inhabited as NAD less reduced
hydrogen not passed to electron carrier therefore 02 not used as final electron acceptor

Question 11

describe how acetyl coenzyme a is formed in the link reaction

Answer 11

oxidation of hydrogen removed from pyruvate and carbon dioxide released. Addition of coenzyme A

Question 12

Explain why converting pyruvate to lactate allows continued production of ATP during anaerobic respiration

Answer 12

regenerates/ produces NAD/ oxidises reduced NAD in glycolysis

Question 13

Describe how ATP is made in mitochondria

Answer 13

-substrate level phosphorylation/ ATP produced in Krebs cycle
-Krebs cycle/ link reaction produces reduced coenzyme / reduced NAD/ reduced FAD
-electrons released from reduced/ coenzymes/ NAD/ FAD
electrons passed along carriers through electron transport chain through serious of redox reactions
-energy released
-ADP
-protons move into inter membrane space
-ATP synthase

Question 14

Explain why it is important for plants to produce ATP during respiration in addition to during photosynthesis

Answer 14

-in the dark no ATP production in photosynthesis
-some tissues unable to photosynthesise
-ATP cannot be moved from cell to cell
-plant uses more ATP than produced in photosynthesis
-ATP for active transport

Question 15

suggest three reasons why the apparatus was left for 10mins

Answer 15

-equilibrium reached
-allow expansion
-allow respiration rate off seeds to stabilise

Question 16

what measurements would the scientists have made in order to calculate the rate of carbon dioxide production?

Answer 16

-volume of carbon dioxide given off
-area
-in a known set time

Question 17

suggest how the rise in the mean rate of photosynthesis could lead to the rise in the mean rate of respiration in soil under trees

Answer 17

photosynthesis produces sugars
-sugars move to roots
-sugars are required for respiration