5.7 Respiration Flashcards
1
Q
What process converts light energy into chemical energy
A
Photosynthesis
2
Q
What types of energy are stored in organic molecules
A
Chemical energy and Potential energy
3
Q
What is adenosine triphosphate (ATP) comprised of
A
- 1 adenine nucleotide base
- 1 ribose sugar (5C)
- 3 phosphate groups
4
Q
How is energy released
A
Through the hydrolysis of ATP to ADP and Pi
5
Q
What is the mitochondria surrounded by
A
The mitochondrial envelope
6
Q
How many membranes make up the mitochondrial envelope
A
2
7
Q
What are the two membranes surrounding the mitochondria
A
- inner membrane
- outer membrane
8
Q
What is between the inner and outer mitochondrial membranes
A
Intermembrane space
9
Q
What is the name given to the highly folded inner mitochondrial membrane
A
Cristae
10
Q
What is enclosed by the inner mitochondrial membrane
A
Mitochondrial matrix
11
Q
What proteins are embedded in the cristae
A
- ATP synthase enzymes
- electron carriers
12
Q
What is the cofactor that each electron carrier protein has
A
A haem group with an iron ion
13
Q
What is the use of iron ions in the electron transport proteins
A
They are reduced and then oxidised to carry the excited electron from one protein to the next in the electron transport chain
14
Q
What are the 4 stages in the aerobic respiration of glucose
A
-glycolysis
-link reaction
-krebs cycles
oxidative phophorylation
15
Q
Which 3 coenzymes are involved in anaerobic respiration
A
- NAD
- FAD
- Coenzyme A
16
Q
What is the first stage of aerobic respiration
A
Glycolysis
17
Q
Where does glycolysis occur
A
The cytoplasm of the cell
18
Q
What is the primary purpose of glycolysis
A
To convert a molecule of glucose (6C) into 2 molecules of pyruvate (3C)
19
Q
What are the 3 sub-stages within glycolysis
A
- phosphorylation of glucose
- splitting of hexose biphosphate
- oxidation of triose phosphate
20
Q
Describe the phosphorylation of glucose in glycolysis
A
- 2 molecules of ATP are hydrolysed and the resulting 2 phosphate groups are used to phosphorylate the 1C and 6C ends of the glucose to become hexose biphosphate
- This has to happen as glucose is unreactive on its own
21
Q
Describe the splitting of hexose biphosphate in glycolysis
A
-the hexose biphosphate molecule is unstable so it splits into 2 triose phosphate molecules (3C)
22
Q
Describe the oxidation of triose phosphate in glycolysis
A
- a dehydrogenase enzyme removes a hydrogen atom from each triose phosphate molecule
- the hydrogen atom is accepted by the coenzyme NAD to become reduced NAD
- the triose phosphate molecules have been oxidised and become pyruvate molecules (3C)
- 4 ATP molecules (per glucose) are produced in this process
23
Q
What is the ‘net gain’ of ATP in glycolysis
A
2 ATP
as 4 are produced in the oxidation of triose phosphate but 2 are used of in the phosphorylation of glucose
24
Q
What are the products of glycolysis
A
- 2 ATP
- 2 reduced NAD
- 2 pyruvate (3C)
25
How is pyruvate transported across the mitochondrial membranes into the mitochondria
Specific transporter proteins (this process requires energy)
26
What is the second stage of aerobic respiration
Link reaction
27
Where does the link reaction occur
The mitochondrial matrix
28
Describe the stages in the link reaction
- each pyruvate is decarboxylated and has a carboxyl group removed this releases carbon dioxide
- each pyruvate is then oxidised by pyruvate dehydrogenase enzymes and NAD accepts the hydrogen to become reduced NAD
- the pyruvate has now become an acetyl group (2C)
- the acetyl group then combines with coenzyme A to become acetyl coenzyme A
- the acetyl coenzyme A then carries on to the next stage of aerobic respiration
29
What are the products of the link reaction
- 2 reduced NAD
- 2 CO2
- 2 acetyl coenzyme A
30
What is the 3rd stage in aerobic respiration
Krebs Cycle
31
Where does the krebs cycle take place
The mitochondrial matrix
32
What has to happen before the krebs cycle starts
The acetyl coenzyme A releases the acetyl group
33
Describe the stages in the krebs cycle
- the acetyl group binds to oxaloacetate (4C) to form citrate (6C)
- the citrate molecule is decarboxylated and oxidised twice. Two NAD accept the hydrogens to become reduced and two CO2 are released. A 4C compound forms
- the 4C compound temporarily binds to coenzyme A to undergo substrate level phosphorylation. This produces one ATP
- the 4C compound is oxidised twice more and the hydrogens are accepted by NAD and FAD forming reduced NAD and reduced FAD
- the resulting compound is oxaloacetate (4C) so the krebs cycle can continue
34
How many turns of the krebs cycle are there per glucose molecule
2
35
What are the products of the krebs cycle per glucose molecule
- 6 reduced NAD
- 2 reduced FAD
- 2 ATP
- 4 CO2
36
What compound forms when an acetyl group binds with oxaloacetate
Citrate
37
How many carbon atoms are in a molecule of citrate
6
38
What is the final stage of aerobic respiration
Oxidative phosphorylation
39
Where does oxidative phosphorylation occur
The cristae
40
What is the primary function of oxidative phosphorylation
To synthesize ATP using energy released from the electron transport chain.
41
Describe chemiosmosis
The flow of protons down their concentration gradient across a membrane through an ATP synthase enzyme. This phosphorylates ADP to synthesize ATP
42
Why does the flow of protons through ATP synthase allow phosphorylation to occur
There is a conformational change in the structure of the ATP synthase protein
43
What is the first stage in oxidative phosphorylation
When reduced NAD and FAD are oxidised when delivering the hydrogen atoms to the electron transport chain in the cristae.
44
What happens to the hydrogen atoms when they are released by the FAD and NAD coenzymes in oxdidative phosphorylation
They split into H+ protons and electrons
45
What happens to the electrons that split from the hydrogen atoms in oxdidative phosphorylation
The electrons pass along one protein to the next in the electron transport chain. The iron ion in the protein is reduced and then reoxidised to pass along the electron down the chain
46
Where in the mitochondria is the electron transport chain in oxdidative phosphorylation
The cristae
47
What is released as electrons pass down the ETC in oxdidative phosphorylation
Energy
48
What is the energy from the ETC used for in oxdidative phosphorylation
To pump the H+ protons into the intermembrane space
49
What happens once the H+ protons have accumulated in the intermembrane space
A proton concentration gradient forms
50
What is generated by the proton concentration gradient
Chemiosmotic potential (aka Proton Motive Force)
51
Is the inner mitochondrial membrane permeable to protons
No
52
What does the proton concentration gradient allow the protons to do in oxdidative phosphorylation
Diffuse down the concentration gradient
53
What happens as the protons diffuse down the concentration gradient in oxdidative phosphorylation
Chemiosmosis
54
What is the final electron acceptor in the electron transport chain in oxdidative phosphorylation
Oxygen
55
What happens to the H+ protons after they pass through ATP synthase in oxidative phosphorylation
The H+ combine with the electrons and the oxygen (as the final electron acceptor) to produce a molecule of water
56
What is the theoretical yield of ATP from oxidative phosphorylation (per glucose molecule)
28
57
What are the products of oxidative phosphorylation
- ATP
- Water
- the oxidised NAD and FAD
58
What is the theoretical total ATP yield from all of aerobic respiration
32
59
Give 3 reasons why the theoretical yield of ATP is rarely reached in aerobic respiration
- some ATP is used to actively transport pyruvate into the mitochondria
- some protons may leak out of the intermembrane space through the outer membrane to reduce the chemiosmotic potential
- some ATP is used to transport reduced NAD from glycolysis into the mitochondria
60
What are respiratory substrates?
Organic molecules that can be oxidised in respiration to produce ATP
61
What are the 3 main categories of respiratory substrates
- carbohydrates
- lipids
- proteins
62
What determines how much oxygen is used in respiration (per molecule of substrate) and why
The amount of of hydrogen atoms in the molecule. This is because the more Hs there are, the more H+ protons there will be in oxidative phosphorylation. Therefore there will need to be more oxygen molecules to react with the H+ protons.
63
What determines how much energy is released in respiration and why
The amount of hydrogen atoms in the substrate. This is because there will be more H+ protons available for chemiosmosis.
64
Which group of respiratory substrates have the most H atoms and therefore the highest energy value
Lipids
65
Which group of respiratory substrates have the second most H atoms and therefore the second highest energy value
Proteins
66
Which group of respiratory substrates have the third most H atoms and therefore the third highest energy value
Carbohydrates
67
Briefly describe how lipids enter the respiratory pathway
Lipids are hydrolysed by lipase to produce glycerol and fatty acids. The glycerol can be converted to triose phosphate which can enter the glycolysis stage. The fatty acids can join with coenzyme A and join the start of the krebs cycle`
68
Briefly describe how proteins enter the respiratory pathway
Proteins are hydrolysed to amino acids. The excess amino acids are deaminated and converted to urea in the liver. The remaining keto acids can enter the respiratory pathway as pyruvate, acetlyl COA or an oxaloacetic acid in the krebs cycle
69
What is the respiratory quotient
The ratio of volume of CO2 produced to O2 used in the same time
70
How is the respiratory substrate calculated
Volume of CO2 produced / Volume of O2 used
71
What is the respiratory quotient of lipids (the fatty acids)
0.7
72
What is the respiratory quotient of proteins (the amino acids)
0.8-0.9
73
What is the respiratory substrate of carbohydrates (e.g gluocse)
1
74
What is the respiratory substrate of anaerobic respiration
greater than 1
75
Which stages of respiration can not happen when oxygen is absent and why
Oxidative phosphorylation, krebs cycle and link reaction.
There is no oxygen to be the final electron acceptor in oxidative phosphorylation so less energy is released from the ETC so less protons are pumped into the intermembrane space. Therefore oxidative phosphorylation stops. Therefore NADH and FADH+ cant unload their hydrogen atoms. Therefore they cant be reused in the link reaction and the krebs cycle so they also stop
76
Which stage of respiration can still happen in anaerobic conditions.
Glycolysis
77
Why can glycolysis still occur in anaerobic conditions
The NADH from the oxidation of TP to pyruvate is able to be oxidised in other ways so that it can be reused
78
What are the 2 anaerobic pathways in which NADH can be reoxidised
- Lactate fermentation pathway
| - Ethanol fermentation pathway
79
Which organisms use the ethanol fermentation pathway in anaerobic respiration
Plants, Fungi and Yeast
80
Which organisms use the lactate fermentation pathway in anaerobic respiration
Mammals
81
When and where does anaerobic respiration occur in mammals
In muscle tissue during exercise (when there is oxygen debt)
82
Describe the lactate fermentation pathway
The pyruvate accepts the H from the NADH to be reduced to lactate (catalysed by the enzyme lactate dehydrogenase) so that the NADH can be reoxidised. The NAD can then be reused in the oxdiation of triosephosphate. This glycolysis will give a net yield of 2 ATP so that muscle contraction can be maintained in the short term.
83
What happens to the lactate after anaerobic respiration
It is transported in the blood to the liver where it can be converted into pyruvate or glucose. The lactate is dangerous in the muscle cells as it forms lactic acid which lowers the pH
84
Describe the ethanol fermentation pathway
The pyruvate is decarboxylated to ethanal (via pyruvate decarboxylase). The ethanal then accepts the H from NADH to be reduced to ethanol (in order to allow the NAD to be reused).
