Module 5.7

Question 1

Why is cellular respiration needed

Answer 1

active transport
endo/exocytosis
DNA replication
cell division
activation of chemicals
movement e.g. flagella

Question 2

components of the mitochondria

Answer 2

inner membrane
outer membrane
cristae
matrix
mitochondrial DNA

Question 3

role of the matrix

Answer 3

where the link reaction and krebs cycle take place
contains enzymes for these reactions
contains the mitochondrial DNA to code for enzymes and other proteins
mitochondrial ribosomes assemble these proteins

Question 4

role of the outer membrane

Answer 4

contains proteins which form channels or carriers for the passage of molecules e.g. pyruvate

Question 5

role of the inner membrane

Answer 5

folded into cristae for increased surface area for oxidative phosphorylation
less permeable to small ions like hydrogen
has proteins embedded in it e.g. electron carriers and ATP synthase

Question 6

role of the intermembrane space

Answer 6

involved in oxidative phosphorylation
inner membrane is in close contact with the matrix so reduced NAD and FAD can easily deliver hydrogens to the electron transport chain

Question 7

where does glycolysis occur

Answer 7

cytoplasm

Question 8

what are the 3 stages of glycolysis

Answer 8

phosphorylation of glucose
splitting of hexose bisphosphate
oxidations of triose phosphate

Question 9

what is phosphorylation of glucose - glycolysis

Answer 9

ATP is hydrolysed and 2 phosphoryl groups are added to the glucose to for hexose bisphosphate
the energy from the hydrolysed ATP molecules activates the hexose sugar and prevents it from being transported out of the cell

Question 10

what is splitting of hexose bisphosphate - glycolysis

Answer 10

each molecule of hexose bisphosphate is split into 2 3C molecules of triose phosphate

Question 11

what is oxidation of triose phosphate - glycolysis

Answer 11

dehydrogenase enzymes aided by coenzyme NAD remove hydrogens from triose phosphate
2 molecules of NAD accept the hydrogens and become reduced
4 molecules of ATP are made for every 2 triose phosphate molecules undergoing oxidation
pyruvate is produced

Question 12

products of glycolysis

Answer 12

for every molecule of glucose
2 molecule of ATP
2 molecules of reduced NAD
2 molecules of pyruvate

Question 13

where does the link reaction occur

Answer 13

matrix

Question 14

how is the acetyl group produced in the link reaction

Answer 14

pyruvate is decarboxylated (produces carbon dioxide) and dehydrogenated (reduces NAD)
to produce the acetyl group

Question 15

how is reduced NAD produced in the link reaction

Answer 15

the hydrogen removed from pyruvate combines with NAD to produce reduced NAD

Question 16

how is acetyl coenzyme A produced int he link reaction

Answer 16

coenzyme A combines with the acetyl group to become acetyl coenzyme A

Question 17

products of the link reaction

Answer 17

glycolysis produces 2 pyruvate molecules so
2 reduced NAD
2 acetyl coenzyme A
2 carbon dioxide

Question 18

where does the krebs cycle occur

Answer 18

matrix

Question 19

how does acetyl co enzyme A enter the krebs cycle

Answer 19

co enzyme a is removed from acetyl coenzyme A and the acetyl group enters the krebs cycle

Question 20

how is citrate formed in the krebs cycle

Answer 20

the acetyl group (2C) from acetyl coenzyme A combines with oxaloacetate (4C) to produce citrate (6C)

Question 21

how is citrate converted to a 4C compound

Answer 21

citrate is decarboxylated and dehydrogenated to a 5C compound then dehydrogenated and decarboxylate again to a 4C compound
the decarboxylation produced CO2 and the dehydrogenation produces hydrogen to reduce NAD

Question 22

how is ATP produced in the krebs cycle

Answer 22

the 4C compound temporarily combines with and is then released from coenzyme A
at this stage substrate level phosphorylation occurs producing one molecule of ATP

Question 23

how is the 4C compound converted to oxaloacetate in the krebs cycle

Answer 23

the 4C compound is dehydrogenated to a different 4C compound and reduced FAD is produced
further dehydrogenation produces oxaloacetate and reduced NAD

Question 24

products of the krebs cycle

Answer 24

for every molecule of glucose there are two turns of the krebs cycle
6 reduced NAD
2 reduced FAD
4 carbon dioxide
2 ATP

Question 25

where does oxidative phosphorylation occur

Answer 25

the cristae/ inner membrane and the intermembrane space

Question 26

what happens to reduced NAD and FAD in oxidative phosphorylation

Answer 26

they are reoxidised when they deliver their hydrogen atom to the electron transport chain

Question 27

what happens to the hydrogen atoms delivered from reduced NAD and FAD

Answer 27

the hydrogen atoms split into protons and electrons the protons go into solution in the matrix and the electrons go to the electron transport chain

Question 28

how does the electron transport chain work

Answer 28

electron carriers are proteins embedded in the cristae each electron has an iron ion at its core the iron ions can gain electrons becoming reduced and then become reoxidised donating the electron to the iron ion in the next electron carrier

Question 29

role of the electron transport chain

Answer 29

as electrons pass along the chain some of their energy is used to pump protons across the inner mitochondrial membrane into the intermembrane space to create a proton gradient

Question 30

role of the proton gradient and chemiosmosis

Answer 30

the proton gradient generate a chemiosmotic potential that is a source of potential energy the protons diffuse through protein channels associated with ATP synthase the flow of protons causes a conformational change in the enzyme which allows ADP and Pi to combine to form ATP

Question 31

role of oxygen in oxidative phosphorylation

Answer 31

oxygen is the final electron acceptor it combines with the electrons coming off the electron transport chain and with protons diffusing through the ATP synthase channel forming water

Question 32

products of oxidative phosphorylation

Answer 32

theoretically 28 molecules of ATP per molecule of glucose

Question 33

what is the total theoretical yield of ATP during aerobic respiration

Answer 33

32

Question 34

why is the theoretical yield of aerobic respiration rarely achieved

Answer 34

some ATP is used to actively transport pyruvate into the mitochondria some ATP is used to transport reduced NAD from glycolysis into the mitochondria some protons may leak out through the outer mitochondrial membrane

Question 35

respiration in the absence of oxygen

Answer 35

oxygen cant act as the final electron acceptor combining electron and protons with oxygen to form water proton gradient reduced so oxidative phosphorylation stops reduced NAD and FAD cannot unload their hydrogen atoms and become reoxidised krebs cycle and link reaction stop glycolysis can take place but the reduced NAD had to be reoxidised for glycolysis to continue

Question 36

what are the two pathways used to reoxidise the reduced NAD in anaerobic respiration

Answer 36

ethanol fermentation (fungi and plants) lactate fermentation (mammals)

Question 37

how is reduced NAD reoxidised in the ethanol fermentation pathway

Answer 37

each molecule of pyruvate produced in glycolysis is decarboxylate by pyruvate decarboxylase producing ethanal ethanal accepts hydrogen atoms from reduced NAD becoming ethanol catalysed by ethanol dehydrogenase this reoxidises the NAD so it can accept more hydrogen atoms from triose phosphate for glycolysis to continue

Question 38

how is reduced NAD reoxidised in the lactate fermentation pathways

Answer 38

pyruvate from glycolysis accepts hydrogen atoms from the reduced NAD producing lactate catalysed by lactate dehydrogenase and reoxidising the NAD

Question 39

benefits of anaerobic respiration

Answer 39

faster than aerobic respiration provides energy when oxygen supply is insufficient e.g. intense exercise glucose is only partly broken down so more molecule can undergo glycolysis per minute making overall yield of ATP quite large

Question 40

why does anaerobic respiration produce a lower ATP yield than aerobic respiration

Answer 40

allows glycolysis to continue so the net gain of 2 ATP molecules is still obtained for each molecule of glucose only 2 ATP molecules are produced compared to the 32 in aerobic respiration

Question 41

how can yeast cells be used to investigate respiration

Answer 41

if oxygen is available yeast respires aerobically if oxygen is lacking the yeast respires anaerobically to divide by mitosis yeast requires ATP and rate of reproduction depends o amount of ATP available - faster reproduction under aerobic condition yeast can also oxidise ethanol under aerobic conditions so alcohol content will decrease in aerobic conditions or increase in anaerobic conditions

Question 42

energy value of carbohydrates

Answer 42

15.8

Question 43

energy value of lipids

Answer 43

39.4

Question 44

energy value of protein

Answer 44

17

Question 45

how is respiratory quotient calculated

Answer 45

CO2 produced divided by O2 consumed

Question 46

RQ value of glucose

Answer 46

1

Question 47

RQ value of fatty acids

Answer 47

0.7

Question 48

RQ value of amino acids

Answer 48

0.8-0.9

Question 49

what does and RQ value greater than 1 mean

Answer 49

some anaerobic respiration is taking place as more carbon dioxide is being produced than oxygen is being consumed