A-level biology OCR > respiration > Flashcards

respiration Flashcards

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1
Q

Where does glycolysis occur?

A

In the cytoplasm.

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2
Q

What happens during glycolysis?

A

Glucose (6C) is split into 2 pyruvate (3C), producing a small amount of ATP and NADH.

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3
Q

What are the products of glycolysis per glucose?

A

2 pyruvate, 2 ATP (net), 2 NADH.

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4
Q

Where does the Link Reaction occur?

A

In the mitochondrial matrix.

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5
Q

What happens during the Link Reaction?

A

Pyruvate (3C) is converted into acetyl-CoA (2C), producing CO2 and NADH.

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6
Q

What are the products of the Link Reaction per pyruvate?

A

1 acetyl-CoA, 1 CO2, 1 NADH.

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7
Q

Where does the Krebs cycle occur?

A

Mitochondrial matrix.

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8
Q

What happens during the Krebs cycle?

A

Acetyl-CoA is oxidized, producing CO2, ATP, NADH and FADH2.

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9
Q

What are the products of the Krebs cycle per acetyl-CoA?

A

3 NADH, 1 FADH2, 1 ATP, 2 CO2.

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10
Q

Where does oxidative phosphorylation occur?

A

Inner mitochondrial membrane.

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11
Q

What happens during oxidative phosphorylation?

A

Electrons from NADH and FADH2 pass along the electron transport chain, creating a proton gradient that drives ATP synthesis. Oxygen is the final electron acceptor, forming water.

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12
Q

Why is oxygen essential for aerobic respiration?

A

It acts as the final electron acceptor in the electron transport chain.

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13
Q

How much ATP is produced per glucose molecule in aerobic respiration ?

A

Approximately 30–32 ATP per glucose.

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14
Q

Products of oxidative phosphorylation

A

many molecules of ATP, production of water from oxygen

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15
Q

Where does oxidative phosphorylation take place?

A

At the inner mitochondrial membrane.

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16
Q

What is the final stage of aerobic respiration called?

A

Oxidative phosphorylation.

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17
Q

What are the main products of oxidative phosphorylation?

A

Many molecules of ATP and water.

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18
Q

What theory explains oxidative phosphorylation?

A

The chemiosmotic theory.

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19
Q

What is the role of the electron transport chain in oxidative phosphorylation?

A

It passes electrons through proteins to pump protons into the intermembrane space.

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20
Q

How are protons (H⁺ ions) transported during oxidative phosphorylation?

A

They are pumped from the matrix to the intermembrane space using energy from electrons.

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21
Q

How do protons return to the mitochondrial matrix?

A

Via facilitated diffusion through ATP synthase.

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22
Q

What enzyme is responsible for synthesizing ATP in oxidative phosphorylation?

A

ATP synthase.

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23
Q

How is the energy for ATP synthesis generated in oxidative phosphorylation?

A

From protons moving down their concentration gradient through ATP synthase.

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24
Q

Which molecules donate hydrogen atoms to the electron transport chain?

A

Reduced NAD (NADH) and reduced FAD (FADH₂).

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25
What happens to the hydrogen atoms donated by NADH and FADH₂?
They split into protons (H⁺) and electrons (e⁻).
26
What happens to electrons in the electron transport chain?
They move through electron carriers, releasing energy.
27
What is the energy released by electrons used for?
To pump protons across the inner mitochondrial membrane into the intermembrane space.
28
What creates the proton concentration gradient in oxidative phosphorylation?
Pumping of protons from the matrix to the intermembrane space.
29
What provides the energy to synthesize ATP from ADP?
The movement of protons down their concentration gradient through ATP synthase.
30
What is the role of oxygen in oxidative phosphorylation?
It acts as the final electron acceptor and forms water with electrons and protons.
31
What is formed when oxygen combines with electrons and protons at the end of the electron transport chain?
Water (H₂O).
32
What is the electron transport chain composed of?
A series of membrane proteins or electron carriers.
33
Why are the electron carriers positioned close together in the inner membrane?
To allow electrons to pass efficiently from one carrier to the next.
34
Why is the inner mitochondrial membrane impermeable to hydrogen ions?
To maintain the proton gradient required for ATP synthesis.
35
What is the first stage of respiration?
Glycolysis.
36
Where does glycolysis take place?
In the cytoplasm of the cell.
37
What are the key events of glycolysis?
Phosphorylation of glucose, splitting glucose, oxidation of triose phosphate, and ATP production.
38
What is the net yield of ATP from glycolysis?
2 ATP.
39
How many molecules of pyruvate are produced in glycolysis?
2 pyruvate molecules.
40
How many reduced NAD molecules are produced in glycolysis?
2 reduced NAD.
41
What happens in the phosphorylation step of glycolysis?
Glucose is phosphorylated by 2 ATP to form hexose bisphosphate.
42
What is the chemical equation for the phosphorylation of glucose?
Glucose + 2ATP → Hexose bisphosphate.
43
What happens during the lysis step of glycolysis?
Hexose bisphosphate splits into two triose phosphate molecules.
44
What is the product of lysis in glycolysis?
2 triose phosphate molecules.
45
What happens in the oxidation step of glycolysis?
Hydrogen is removed from triose phosphate and transferred to NAD, forming reduced NAD.
46
What is the chemical equation for the oxidation step?
4H + 2NAD → 2NADH + 2H⁺.
47
What happens during dephosphorylation in glycolysis?
Phosphate groups are transferred to ADP to form ATP via substrate-level phosphorylation.
48
What is the chemical equation for ATP production in dephosphorylation?
4Pi + 4ADP → 4ATP.
49
What is the final product of glycolysis?
Pyruvate (3C).
50
What can pyruvate be used for after glycolysis?
It enters the next stage of respiration.
51
What is hexose bisphosphate sometimes also called?
Fructose bisphosphate.
52
What is the purpose of phosphorylating glucose in glycolysis?
To trap glucose in the cell and make it more reactive.
53
How many ATP molecules are used in the phosphorylation step of glycolysis?
2 ATP molecules.
54
How many ATP molecules are produced in total during glycolysis?
4 ATP molecules (net gain of 2 ATP).
55
What is the end product of glycolysis?
Pyruvate.
56
Why is pyruvate important in respiration?
It contains chemical energy that can be further used to produce ATP.
57
What happens to pyruvate when oxygen is available?
It enters the mitochondrial matrix and aerobic respiration continues.
58
How does pyruvate enter the mitochondrial matrix?
By active transport using a transport protein and a small amount of ATP.
59
From where does pyruvate enter the mitochondria?
From the cytosol (cytoplasm).
60
What is the purpose of the link reaction?
To link glycolysis to the Krebs cycle.
61
Where does the link reaction occur?
In the mitochondrial matrix.
62
What are the steps of the link reaction?
Oxidation of pyruvate to acetate and CO₂, and combination with coenzyme A to form acetyl CoA.
63
What are the products of the link reaction?
Acetyl CoA, carbon dioxide (CO₂), and reduced NAD (NADH).
64
What is the overall equation for the link reaction?
Pyruvate + NAD + CoA → Acetyl CoA + CO₂ + NADH.
65
What happens to pyruvate during the link reaction?
It is oxidised and decarboxylated to form acetate and CO₂.
66
What coenzyme is reduced during the link reaction?
NAD is reduced to NADH.
67
What molecule combines with acetate to form acetyl CoA?
Coenzyme A (CoA).
68
What is the function of coenzyme A in the link reaction?
It binds to the acetyl group to form acetyl CoA and delivers it to the Krebs cycle.
69
What is a coenzyme?
A molecule that helps an enzyme function but is not used up in the reaction.
70
What is coenzyme A made of?
A nucleoside (ribose and adenine) and a vitamin.
71
How does coenzyme A link glycolysis to the Krebs cycle?
It transports the acetyl group from pyruvate into the Krebs cycle.
72
Which types of molecules can be used in the link reaction besides carbohydrates?
Lipids and amino acids.
73
Why is the link reaction called a ‘link’?
Because it connects glycolysis in the cytoplasm to the Krebs cycle in the mitochondria.
74
What type of reactions occur during the link reaction?
Dehydrogenation and decarboxylation.
75
What is another name for the Krebs cycle?
The citric acid cycle.
76
Where does the Krebs cycle take place?
In the matrix of the mitochondria.
77
What type of reactions make up the Krebs cycle?
A series of enzyme-controlled reactions.
78
What molecule enters the Krebs cycle from the link reaction?
Acetyl CoA (2C).
79
Which molecules other than glucose can enter the Krebs cycle?
Acetyl CoA formed from fatty acids and amino acids.
80
What molecule does acetyl CoA combine with to begin the Krebs cycle?
Oxaloacetate (4C).
81
What is formed when oxaloacetate and acetyl CoA combine?
Citrate (6C).
82
What happens to coenzyme A when citrate is formed?
It is released.
83
What happens to citrate during the Krebs cycle?
It is converted back to oxaloacetate through a series of redox reactions.
84
What is regenerated during the Krebs cycle to allow it to continue?
Oxaloacetate.
85
What waste gas is produced during the Krebs cycle?
Carbon dioxide (CO₂).
86
How many molecules of carbon dioxide are released during one turn of the Krebs cycle?
2 CO₂ molecules.
87
What coenzymes are reduced during the Krebs cycle?
NAD and FAD.
88
What is the equation for the reduction of coenzymes in the Krebs cycle?
8H + 3NAD + FAD → 3NADH + 3H⁺ + FADH₂.
89
What type of phosphorylation occurs in the Krebs cycle?
Substrate-level phosphorylation.
90
How is ATP produced in the Krebs cycle?
By transferring a phosphate group from an intermediate to ADP.
91
How many ATP molecules are produced per turn of the Krebs cycle?
1 ATP.
92
What is the main purpose of the Krebs cycle?
To produce reduced coenzymes (NADH and FADH₂) for oxidative phosphorylation.
93
Which two types of reactions are central to the Krebs cycle?
Decarboxylation and dehydrogenation (oxidation).
94
What is a coenzyme?
A molecule that helps an enzyme function but is not used up in the reaction.
95
What does coenzyme A consist of?
A nucleoside (ribose and adenine) and a vitamin.
96
What is the role of coenzyme A in the link reaction?
It binds to the acetyl group from pyruvate to form acetyl CoA.
97
What is the role of acetyl CoA in the Krebs cycle?
It supplies the acetyl group to the cycle for further aerobic respiration.
98
What does coenzyme A help link?
It links glycolysis in the cytoplasm to the Krebs cycle in the mitochondria.
99
What are NAD and FAD?
Coenzymes that act as hydrogen carriers in aerobic respiration.
100
When are NAD and FAD reduced?
When they accept hydrogen atoms (H⁺ and electrons).
101
What does OIL RIG stand for?
Oxidation Is Loss, Reduction Is Gain.
102
What happens when NAD or FAD gain hydrogen?
They become reduced (NADH or FADH₂).
103
What happens when hydrogen is removed from NADH or FADH₂?
They are oxidised (return to NAD or FAD).
104
Where do NADH and FADH₂ transport hydrogen atoms?
To the electron transport chain on the inner mitochondrial membrane.
105
What do hydrogen atoms consist of?
Hydrogen ions (H⁺) and electrons (e⁻).
106
What happens to the electrons from reduced NAD and FAD?
They enter the electron transport chain.
107
What happens to the hydrogen ions from reduced NAD and FAD?
They are released and pumped into the intermembrane space to create a proton gradient.
108
What is the role of the proton gradient in respiration?
It drives ATP synthesis as protons move back into the matrix.
109
Where is the electron transport chain located?
On the inner mitochondrial membrane.
110
How many reduced NAD molecules are produced from glycolysis?
2 NADH.
111
How many reduced NAD molecules are produced from the link reaction?
2 NADH.
112
How many reduced NAD molecules are produced from the Krebs cycle?
6 NADH.
113
How many reduced FAD molecules are produced from the Krebs cycle?
2 FADH₂.
114
How many total reduced NAD molecules are produced per glucose molecule in aerobic respiration?
10 NADH.
115
How many total reduced FAD molecules are produced per glucose molecule in aerobic respiration?
2 FADH₂.
116
What happens when there is no oxygen available for respiration?
The electron transport chain stops functioning because there is no final electron acceptor (oxygen).
117
What is the final electron acceptor in aerobic respiration?
Oxygen.
118
What happens to oxidative phosphorylation without oxygen?
It stops, and no more ATP is produced by this pathway.
119
What happens to reduced NAD and FAD when oxygen is not available?
They cannot be oxidised by the electron transport chain.
120
What is the consequence of reduced NAD and FAD not being oxidised?
No oxidised coenzymes are available for the Krebs cycle, so it stops.
121
How can cells still produce ATP in low oxygen conditions?
Through anaerobic respiration, which allows glycolysis to continue.
122
How is reduced NAD recycled during anaerobic respiration?
It transfers its hydrogen to another molecule to become oxidised again.
123
Why is the recycling of NAD important in anaerobic respiration?
It allows glycolysis to continue, producing small amounts of ATP.
124
What are the two main anaerobic pathways?
Ethanol fermentation and lactate fermentation.
125
Which organisms use ethanol fermentation?
Yeast and some microorganisms.
126
What is the first step in ethanol fermentation?
Pyruvate is decarboxylated to ethanal, producing CO₂.
127
What happens to ethanal in ethanol fermentation?
It is reduced to ethanol by accepting hydrogen from reduced NAD.
128
What enzyme reduces ethanal to ethanol?
Alcohol dehydrogenase.
129
What is the hydrogen acceptor in ethanol fermentation?
Ethanal.
130
Is ethanol further metabolised?
No, it is a waste product.
131
Which organisms use lactate fermentation?
Some microorganisms and mammalian muscle cells.
132
What happens to pyruvate in lactate fermentation?
It is reduced to lactate by accepting hydrogen from reduced NAD.
133
What enzyme catalyses the reduction of pyruvate to lactate?
Lactate dehydrogenase.
134
What is the hydrogen acceptor in lactate fermentation?
Pyruvate.
135
Can lactate be further metabolised?
Yes, it can be converted back to pyruvate or into glycogen.
136
What are the two fates of lactate after fermentation?
Oxidised back to pyruvate for the Krebs cycle or stored as glycogen in the liver.
137
What is required to oxidise lactate back to pyruvate?
Extra oxygen.
138
What is the term for the extra oxygen needed to remove lactate?
Oxygen debt.
139
Why do animals breathe faster and deeper after exercise?
To repay the oxygen debt and oxidise lactate.
140
Which type of respiration yields more energy: aerobic or anaerobic?
Aerobic respiration.
141
Why does aerobic respiration yield more energy than anaerobic?
Because glucose is fully oxidised, allowing much more ATP to be produced.
142
How many ATP molecules are produced from glycolysis in anaerobic respiration?
Approximately 2 ATP.
143
How many ATP molecules are produced from aerobic respiration in total?
Approximately 38 ATP (usually cited as ~36 net ATP).
144
Which stages of respiration occur in anaerobic conditions?
Only glycolysis.
145
Which stages of respiration occur in aerobic conditions?
Glycolysis, link reaction, Krebs cycle, and oxidative phosphorylation.
146
Why can't the mitochondria function in anaerobic respiration?
Because oxygen is not available to act as the final electron acceptor in the electron transport chain.
147
Why is glucose only partially oxidised in anaerobic respiration?
Because the mitochondria-dependent stages of respiration do not occur, so only a small portion of glucose’s energy is released.
148
What is the final electron acceptor in aerobic respiration?
Oxygen.
149
Why is oxygen essential for ATP production in mitochondria?
It accepts electrons at the end of the electron transport chain, allowing oxidative phosphorylation to continue.
150
Which type of respiration is more efficient?
Aerobic respiration.
151
How many ATP are typically produced by the stages within the mitochondria?
About 34–36 ATP (from link reaction, Krebs cycle, and oxidative phosphorylation).
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