Respiration Flashcards
1
Q
Describe the order of events in glycolysis.
A
- Glucose is phosphorylated, 2 ATP molecules release a phosphate group each, these bind to glucose to form hexose bisphosphate.
- Lysis occurs and hexose bisphosphate splits into 2 triose phosphate molecules.
- A free inorganic phosphate group is added to both TP molecules, forming triose bisphosphate.
- Each TBP has 2 phosphate groups removed, which forms 2 ATP molecules per pyruvate. Each also has a H removed, which reduces NAD+.
2
Q
What are the products of glycolysis?
A
- 4 ATP (net gain of 2), 2 reduced NAD, 2 pyruvate.
3
Q
What is substrate level phosphorylation?
A
- The production of ATP without the use of the electron transport chain.
4
Q
What is the other name for the link reaction? Why?
A
- Oxidative decarboxylation.
- Pyruvate is decarboxylated (CO2) removed and oxidised (H removed).
5
Q
Is glycolysis aerobic or anaerobic?
A
- anaerobic.
6
Q
Describe the steps of the link reaction.
A
- Pyruvate is decarboxylated (CO2 removed) and oxidised (H removed to form reduced NAD).
- Acetyl group formed, which combines with coenzyme A to form acetylcoenzyme A (acetyl CoA).
7
Q
Where does glycolysis occur?
A
- Cytoplasm/cytosol.
8
Q
How does Pyruvate get into the mitochondrial matrix?
A
- Active transport via specific carrier proteins.
9
Q
How does Pyruvate get into the mitochondrial matrix?
A
- Active transport.
10
Q
Where does the link reaction occur?
A
- Mitochondrial matrix.
11
Q
How is the NADH produced by the link reaction used?
A
- It is used in oxidative phosphorylation later on.
12
Q
What happens to the CO2 produced by the link reaction?
A
- It will diffuse away and be removed as metabolic waste or, in autotrophic organisms, it may be used as a raw material in photosynthesis.
13
Q
Where does the Krebs cycle take place?
A
- the mitochondrial matrix.
14
Q
What are the products of the Krebs cycle?
A
- 3 reduced NAD
- 1 reduced FAD (FADH2)
- Oxaloactetae (which is recombined with a new acetyl group)
- 2 CO2
- 1 ATP
15
Q
What is the purpose of the reduced NAD and FAD produced by Krebs?
A
- They are used in the electron transport chain and for oxidative phosphorylation.
16
Q
Describe the steps of the Krebs cycle.
A
- Acetyl CoA delivers an acetyl group to the Krebs cycle. The 2C acetyl group combines with 4C oxaloacetate to form 6C citrate.
- Citrate undergoes dehydrogenation and decarboxylation, producing 1 reduced NAD and CO2. a-Ketoglutarate (5C) is formed.
- a-Ketoglutarate (5C) undergoes further decarb and dehydro. This forms a Succinyl CoA (4C), and releases 1 CO2 and 1 reduced NAD.
- This Succinyl CoA (4C) reacts further to produce Succinate (4C). In the process ADP is phosphorylated to produce ATP.
- Succinate (4C) reacts to form fumarate (this produces FADH2 from FAD).
- Fumarate (4C) is then converted into Malate (4C).
- Malate is then converted into Oxaloacetate (this produces NADH from NAD+). Oxaloacetate is combined with a new acetyl group.
Steps 4-7 can be summarised as ‘the 4 carbon molecule undergoes further decarb and dehydro before OAA is eventually regenerated.
17
Q
State the differences between FAD and NAD.
A
- NAD+ is reduced in all steps of respiration, FAD is only reduced in Krebs.
- NAD is responsible for the synthesis of 3 ATP, FAD for 2.
18
Q
Where does oxidative phosphorylation occur?
A
- Inner mitochondrial membrane.
19
Q
How many ATP molecules are produced total? How many in ETC?
A
- 38, 34.
20
Q
What is the final electron acceptor in ETC?
A
- Oxygen.
21
Q
What is the role of electrons in the ETC?
A
- They reduce protein complexes, releasing energy which allows for the active transport of H+ ions into the inter-membrane space.
22
Q
How is ATP generated by the ETC/OP?
A
- H+ ions diffuse back across the mitochondrial inner membrane by chemiosmosis along the proton gradient. They go through ATP synthase which transfers the energy from the electronchemical proton gradient to ADP and Pi to make ATP.
23
Q
What are obligate anaerobes?
A
- They cannot survive in the presence of oxygen.
- Almost exclusively prokaryotes, some fungi.
24
Q
What are faculatative anaerobes?
A
- Synthesise ATP by aerobic when possible, can also use anaerobic.
- E.g yeast
25
What are obligate aerobes?
- Can only synthesise ATP in the presence of oxygen.
- E.g mammals
- Some cells in them can be described as facultative anaerobes as they can generate ATP by anaerobic resp, but this is for short periods of time and the products are broken down when oxygen becomes available again.
26
What is fermentation?
- A form of anaerobic resp.
- The process by which complex organic compounds are broken down into simpler compounds without oxygen or an electron transport chain.
27
How is ATP produced in anaerobic resp?
- Substrate-level phosphorylation
28
What are the two types of fermentation? Where do they occur?
- Alcoholic fermentation, occurs in yeast and some plant root cells. Produces ethanol and CO2.
- Lactate fermentation, occurs in animal cells. Allows NAD to be regenerated for glycolysis.
29
Describe the process of lactate fermentation in mammals
- Pyruvate can act as a H acceptor, taking H from reduced NAD. This is catalysed by the enzyme lactate dehydrogenase.
- The pyruvate is converted into lactate and NAD is regenerated.
- This regenerated NAD can be reused in glycolysis to produce a small amount of ATP.
30
How is creatine phosphate used in anaerobic resp?
- Acts a backup source of phosphates in glycolysis.
31
How many molecules of ATP does fermentation produce?
- Net gain of 2.
32
How many molecules of ATP are produced in aerobic respiration?
- 38.
- 34 from ETC
33
Why can lactate fermentation not occur indefinitely?
- Reduced quantity of ATP produced, not enough to maintain vital processes.
- Lactic acid accumulation causes a fall in pH leading to proteins denaturing. Respiratory enzymes and muscle filament will cease to function at low pH.
34
Describe the process of alcoholic fermentation in yeast (and many plants)?
- Alocohlic fermentation is not a reversible process, unlike lactate fermentation.
- Pyruvate is converted into ethanal, catalysed by the enzyme pyruvate decarboxylase.
- Ethanal can then accept a hydrogen atom from reduced NAD, becoming ethanol.
- NAD is regnerated and can be reused in glycolysis.
35
What are the differences between alcoholic and and lactate fermentation?
- Alcoholic can continue indefinitely, but is irreversible.
36
How can triglycerides be used in respiration?
- Triglycerides from adipose tissue are hydrolysed.
- Fatty acids undergo beta oxidation to make acetyl CoA.
- Glycerol is first converted to pyruvate, the it undergoes oxidative decarboxylation, producing an acetyl group, then acetyl CoA.
- Acetyl CoA can then enter Krebs.
37
Do lipids or carbs store and release more energy?
- Lipids store and release about twice as much energy.
38
How can proteins be used in respiration?
- Hydrolysed to AAs.
- AAs are deaminated.
- Enter respiratory pathway, usually via pyruvater.
- These steps require ATP, reducing net ATP gain.
39
What are ketone bodies? How do they enter respiration?
- Proteins found in the brain.
- Metabolised and enter respiratory pathway via acetyl group (in acetyl CoA).
40
How do you calculate RQ?
CO2 produced/O2 consumed
41
What is the RQ of each molecule?
- Carbs: 1
- Protein: 0.9
- Lipids: 0.7
42
What is the RQ during normal activity?
- Range between 0.8 - 0.9
- This shows that carbs and lipids (and probably some proteins) are being used as substrates.
43
What is the RQ during anaerobic resp?
The RQ increases above 1
44
