C1 - Respiration

Question 1

What bonds are broken in respiration?

Answer 1

C-C

C-H

C-OH

And then lower energy bonds are formed.

Question 2

Does ATP produce energy?

Answer 2

NO

It releases it when hydrolysed.

Question 3

What are the 4 main stages of aerobic respiration?

Answer 3

Glycolysis

Link reaction

Kreb’s cycle

Electron Transport Chain

Question 4

Why does glycolysis happen in the cytoplasm?

Answer 4

Glucose can’t pass through the mitochondrial membranes.

+

Even if it could, enzymes for its breakdown aren’t present in the mitochondria anyway.

Question 5

What is the result of the phosphorylated glucose - Glucose diphosphate?

Answer 5

Polar = less likely to diff. out of cell.

More reactive = less activation energy is required for the enzyme-controlled reactions.

Question 6

Define dehydrogenation

Answer 6

Removal of 1 or more H atoms from a mol.

Question 7

Define carboxylation

Answer 7

Removal of a carboxyl group from a mol. in which CO2 is released.

Question 8

What is the link reaction?

Answer 8

Linking glycolysis to the Kreb’s cycle:

Pyruvate diff. from cytoplasm into mitochondrial matrix.

Pyruvate is dehydrogenated + decarboxylated to form an (2C) acetyl group each.

Both are picked up by CoA to then become AcCoA (2C)

Question 9

What can happen to pyruvate if O2 is present during the Kreb’s cycle?

Answer 9

Some of the chemical potential energy in the pyruvate can be released.

Question 10

What equation can be used to summarise the link reaction?

Answer 10

Pyruvate + NAD + CoA —- AcCoA + red. NAD + CO2.

Question 11

Where does the link reaction and Krebs cycle take place?

Answer 11

Mitochondrial matrix

Question 12

What is the function of red. NAD + red. FAD from the Krebs cycle?

Answer 12

Deliver H atoms to ETC on inner mitochondrial membrane.

Question 13

What are the 2 significant types of reactions in the Kreb’s cycle?

Answer 13

DECARBOXYLATION (happens twice). 6C acid – 5C acid – 4C acid

DEHYDROGENATION (4 times). to give 3 mol. of red. NAD + 1 mol. of red. FAD.

Question 14

What happens to the acetate group from the original glucose molecule by the end of the Krebs cycle?

Answer 14

Entirely broken down to CO2 + H20.

Question 15

What is the energy in the bonds of the glucose mol. carried by?

Answer 15

By e- in the H atoms in red. NAD + red. FAD.

Question 16

How many times does the Krebs cycle have to turn for each glucose molecule and why??

Answer 16

Twice for each glucose mol.

Because each glucose mol. makes 2 mol. of pyruvate so 2 mol. of AcCoA.

Question 17

How many of each products is made per glucose put through glycolysis, the link reaction + the Krebs cycle?

Answer 17

CO2 = 6

Red. NAD = 10

Red. FAD = 2

ATP = 4

Question 18

38 ATP is produced during aerobic respiration but only 4 in glycolysis, the link reaction + the Krebs cycle from one glucose molecule. Where does the rest come from?

Answer 18

For every red. NAD you get 3 ATP in the E.T.C = 30 ATP

For every red. FAD you get 2 ATP in the E.T.C = 4 ATP

Question 19

Where is the electron transport chain located?

Answer 19

Cristae in the inner mitochondrial membranes.

Question 20

What are cytochromes?

Answer 20

Proteins conjugated to iron or copper.

These metal ions are oxidised + reduced by e- transport.

The reactions they catalyse release energy which is carried by ATP.

Question 21

How are H atoms carried into the E.T.C?

Answer 21

By coenzymes NAD + FAD.

NAD earlier than FAD.

Question 22

What happens to the pyruvate produced during glycolysis if O2 is absent?

Answer 22

Converted to lactate.

• Necessary to reoxidise reduced NAD so that glycolysis can continue.

Question 23

When does fermentation happen?

Answer 23

2nd stage of anaerobic respiration after glycolysis

Question 24

What does the shortage of O2 in the cells mean for anaerobic respiration?

Answer 24

Must find another way to convert reduced NAD back into NAD.

== Fermentation

Question 25

Lactate fermentation

Answer 25

Each pyruvate mol. produced takes up 2 H mol. (from red. NAD in glycolysis) to form lactate. NAD can then be recycled.

Question 26

Where can the lactate be taken away from cells to?

Answer 26

Liver to be converted into glycogen through the Cori cycle.

Question 27

What is the gross production of ATP by substrate level phosphorylation in glycolysis

Answer 27

4 ATP

Question 28

What is the purpose of the ETC?

Answer 28

To produce ATP through chemiosmosis by carrying out oxidative phosphorylation

Question 29

How many proton pumps are involved in the ETC?

Answer 29

3 1 Red. NAD is able to produce 3 ATP due to it passing through all 3 pumps. 1 Red. FAD is able to produce 2 ATP due to only passing through 2nd + 3rd pump.

Question 30

Describe the ETC

Answer 30

Red. NAD is oxidised at 1st P pump by losing 2H. Then split -- 2e- + 2H+. High energy e- fuel the 1st P pump to pump 2H+ from MATRIX --- inter membranous space. 2 e- then passed to mobile e- carrier in membrane which takes e-'s to 2nd P pump. Energy is used to pump 2 P across membrane into IM Space. Repeat stage 3 at 3rd P pump. 2e-'s then passed to O2 (final e- acceptor) to combine w. 2H+ ---- H20. ==== P Pumps create a P gradient between IM space + matrix. == P diff ⬇️ conc. grad. through ATPsynthase. Energy released is used to ADP+Pi-- ATP

Question 31

Where would cyanide bond in the ETC?

Answer 31

On the 3rd proton pump and would have the same effect as if there was no O2 present.

Question 32

What is the theoretical max. no. of ATP mol. that can be produced from 1 glucose? Why doesn't this actually happen?

Answer 32

38 ATP Doesn't happen because: - ATP is used to move PYRUVATE, ADP + RED. NAD across inner mit. memb. - Proton leakage across inner memb. rather than passing through ATP synthase.

Question 33

How many ATP are produced by substrate-level phosphorylation and oxidative phosphorylation?

Answer 33

Substrate-level = 4 Oxidative = 34

Question 34

If 1 mole of glucose is combusted in O2, it produces 2880kJ. The energy required to make a molecule of aTP is 30.6kJ/mol. Calculate the efficiency of aerobic respiration

Answer 34

(38 ATP x 30.6 ) / 2800 x 100 = 40.4%

Question 35

Mechanism B = If cytoplasmic levels of red. NAD are low, then an alternative pathway is used whereby reduced NAD passes its electrons to FAD in the inner mitochondrial membrane. Explain why the ATP yield per glucose mol. will be decreased if mechanism B is used.

Answer 35

Red. FAD only uses the 2nd + 3rd proton pump. Only 2 ATP mol. are produced per Red. FAD.

Question 36

Describe the production of nitrogenous waste and state where this take place when proteins are broken down to use as a respiratory substrate

Answer 36

Deamination results in a keto acid/ammonia being left. Amino group + CO2 --- urea In the liver

Question 37

Suggest what might happen to the energy from the break down of glucose which isn't transferred to ATP

Answer 37

Lost as heat

Question 38

Why is ATP better than glucose as an immediate energy source for cell metabolism

Answer 38

Releases in smaller amounts In 1 reaction by single enzyme - ATPase Energy is available quicker

Question 39

List uses of ATP in a liver cell

Answer 39

Active Transport Phagocytosis Synthesis of glycogen Bile production Cell division

Question 40

If a pond freezes over during winter, goldfish can remain alive in the water under the ice. Explain why they use CHO stores in their bodies much faster in these conditions.

Answer 40

CHO as they're respiring anaerobically. Less efficient as it requires more glucose for the same amount of ATP so more is needed to be carried out.

Question 41

Why do lipids produce more ATP than CHO.

Answer 41

1 x 2C fragment produces 12 ATP.

Question 42

Does glycolysis occur for alternative respiratory substrates (not glucose)?

Answer 42

NO

Question 43

Describe briefly what happens to a mol. of CO2 removed by decarboxylation

Answer 43

Diff. out of mit. into blood. Carried as H carbonate ions Breathed out

Question 44

Suggest why the substrate level phosphorylation is referred to as the 'simplest and oldest way to make ATP'.

Answer 44

Doesn't involve a complex series of carriers + pumps. Doesn't require ATP synthase. Doesn't need an electrochemical gradients Doesn't require O2.

Question 45

Where does fermentation occur

Answer 45

Cytoplasm

Question 46

Cyanide inhibits the enzyme cytochrome oxidase and prevents the reg. of NAD. Explain why cyanide could be used to confirm which sample contained resuspended mitochondria.

Answer 46

Cyanide would only affect mit. as cytochrome oxidase is part of the ETC. No NAD would be available to act as H acceptor = Krebs cycle would stop = no CO2 would be produced.

Question 47

Explain why the rate calculated from a graph for the 1st 30 secs would be lower than the initial rate

Answer 47

Less glucose available as reaction progresses. All active sites are occupied at the start.

Question 48

Name 2 body fluids that could be analysed using a glucose biosensor

Answer 48

Blood + urine

Question 49

Name substances for which there would be a net movement into the mitochondria

Answer 49

ADP Red. NAD Pi O2 Pyruvate

Question 50

Name substances for which there would be a net movement out of the mitochondria

Answer 50

CO2 H20 ATP NAD

Question 51

Glucose is oxidised to pyruvate during the process of glycolysis. Explain why glycolysis is said to involve oxidation

Answer 51

Because oxidation involves the removal of H+