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AQA A-level Biology > Topic 5: Respiration > Flashcards

Topic 5: Respiration Flashcards

1
Q

What is the word equation for respiration?

A

Glucose + oxygen -> carbon dioxide + water

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2
Q

What is oxidation?

A

The loss of electrons/ hydrogen atoms
The release of energy

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3
Q

What is reduction?

A

Gain of electrons/ hydrogen atoms
Energy is required

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4
Q

The process of respiration is a series of what kind of reactions?

A

A series of chemical reactions but they are oxidation reactions
Glucose is oxidised into carbon dioxide and water, releasing stored energy & making it available for use by the organism

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5
Q

Name the stages of respiration

A
  1. Glycolysis
  2. Link reaction
  3. Krebs cycle
  4. The electron transfer chain
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6
Q

Where does glycolysis occur?

A

In the cytoplasm

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7
Q

Where does the link reaction occur?

A

In the mitochondrial matrix

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8
Q

where does the Krebs cycle occur?

A

In the mitochondrial matrix

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9
Q

Where does the electron transfer chain?

A

In the Cristae of the mitochondrion

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10
Q

Which reactions in respiration produce ATP and how much?

A

Glycolysis: 2 ATP
Krebs cycle: 2 ATP
ETC:32 ATP

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11
Q

Which stage of respiration doesn’t release ATP?

A

The link reaction

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12
Q

Summarise what Glycolysis is

A

When Glucose (6-carbon) is oxidised by the removal of hydrogen producing 2 pyruvate molecules (3C)

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13
Q

What type of respiration does glycolysis occur in and why?

A

It is common to both aerobic and anaerobic because it doesnt require oxygen

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14
Q

What catalyses glycolysis?

A

Enzymes

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15
Q

Explain how in glycolysis the 6-carbon compound glucose is inverted to 2 molecules of triose phosphate

A
  • glucose is phosphorylated to from golucse phosphate
  • done by 2 phosphate molecules being added from the hydrolysis of 2 ATP
  • means it is more chemically reactive so can be split into 2
    Each phosphorylated glucose is split into 2 molecules of triose phosphate (3C)
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16
Q

How does triose phosphate form pyruvate and what is the role of NAD in this process?

A
  • each triose phosphate (3C) is oxidised to form a pyruvate (3C)
  • a hydrogen is removed in oxidation, from the triose phosphate and transferred to NAD so it forms reduced NAD or NADP
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17
Q

True or false: NAD is an enzyme

A

False, it is a coenzyme

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18
Q

What is the total ATP made in glycolysis?

A

4

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19
Q

Why is the net yield of ATP in glycolysis not 4- which is the total produced?

A
  • when each Triose phosphate is converted to pyruvate, 2 ATP are produced. Hence the total of 4
  • however 2 ATP are hydrolysed in the phosphorylation of glucose
  • so net yield is 2
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20
Q

What is a coenzyme?

A

A molecule that aids the function on an enzyme by transferring a chemical group from one group to another

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21
Q

Name the co-enzymes in respiration

A
  • NAD
  • Coenzyme A
    -FAD
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22
Q

How are the coenzymes NAD & FAD used in respiration?

A

They transfer hydrogen from one molecule to another, they reduce or oxidise a molecule (give or remove hydrogen

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23
Q

Give one reason that NAD, a coenzyme is not an enzyme

A

It is a non protein and enzymes are proteins
It does still need to be present in order for the enzyme to work

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24
Q

How does phosphorylation occur?

A

Any molecule can be phosphorylated by the addition of an inorganic phosphate (Pi) from the hydrolysis of ATP

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25
Q

What does phosphorylation do to a molecule?

A

The addition of Pi makes molecules more chemically reactive

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26
Q

What is substrate level phosphorylation?

A

The direct phosphorylation of ADP via enzymes, using energy from a coupled reaction

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27
Q

What happens to energy in a coupled reaction?

A

Energy is moved from one side of the reaction to the other via an intermediate molecule

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28
Q

Use glycolysis as an example of substrate level phosphorylation

A

The chemical energy from glucose is used to phosphorylate ADP to form ATP
Glucose phosphate is the intermediate molecule

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29
Q

Compare substrate-level phosphorylation and oxidative phosphorylation

A
  • substrate level phosphorylation is the direct phosphorylation of ADP using the energy from a coupled reaction
    Oxidative phosphorylation is the phosphorylation of ADP from oxidised NADH & FADH2 by the transfer of electrons/redox reactions and pumping of protons
30
Q

What is decarboxylation?

A

A chemical reaction that removes a carboxyl group and releases CO2

31
Q

What is dehydrogenation?

A

Process by which hydrogen is removed from an organic compound to form a new chemical

32
Q

What does the link reaction do?

A

Connects glycolysis and the Krebs cycle

33
Q

What product of glycolysis is moved from cytoplasm into the mitochondrion?

A

Pyruvate

34
Q

How does pyruvate move from the cytoplasm to the mitochondrial matrix where the link reaction occurs?

A

It is actively transported

35
Q

What happens to pyruvate in the link reaction and what is the end result?

A

-pyruvate is oxidised to form acetate (2C) which then combines with coenzyme A and forms acetyl-coenzyme A

36
Q

What is the chemical equation for the link reaction?

A

Pyruvate (3C) + NAD + Coenzyme A -> Acetyl CoA (2C) + reduced NAD + CO2

37
Q

What happens in the Krebs cycle?

A
  • Acetylcoenzyme A reacts with a 4C compound to form a 6C compound
  • The 6C compound is oxidised to release hydrogen
38
Q

What are the products of the Krebs cycle?

A
  • reduced NAD and reduced FAD: the hydrogen released is accepted by them forming the reduced versions
  • carbon dioxide is released
  • small amount of ATP is generated
39
Q

What part of the Krebs Cycle makes it a cycle?

A

The fact that the 6C compound is reformed to a 4C compound so it can be reused to react with Acetyl-coenzyme A

40
Q

Why is the Krebs cycle important?

A
  • produces hydrogen atoms that are carried to the electron transfer chain by NAD and FAD. The energy transferred into the production of ATP in oxidative phosphorylation
  • it breaks down larger molecules into smaller ones. E.g pyruvate into CO2
  • 4C molecule accepting acetlyCoA is recycled
  • intermediate molecules are produced which are used in the production of other substances
41
Q

Intermediate molecules produced in the Krebs cycle are used in the production of substances.
Give examples of the substances

A

Chlorophyll
Fatty acids
Amino acids

42
Q

What is the electron transfer chain also known as?

A

Oxidative phosphorylation

43
Q

Summarise the electron transfer chain

A
  • reduced NAD & FAD that are produced in glycolysis and the Krebs cycle reduce the first protein in a series of electron carriers
    -The hydrogen from NAD/FAD gives an electron or proton (H+)
  • they pass electrons down the carriers which releases energy
44
Q

how are electrons passed down the carriers in the Electron transfer chain?

A

Through a series of redox reactions

45
Q

Explain how the movement of hydrogen ions because of the energy released in the electron transfer chain, results in the production of ATP

A
  • energy is used to transport hydrogen ions through the inner membrane into the intermembrane space
  • the hydrogen ions build up
  • there is a greater concentration of hydrogen ions in the intermembrane space than the matrix
  • hydrogen ions then enter the matrix by diffusion down an electrochemical gradient, and across the ATP synthase enzyme in the inner membrane
  • this results in the phosphorylation of ADP to ATP
46
Q

What is the terminal electron acceptor in the electron transfer chain?

A

Oxygen

47
Q

how does the terminal electron acceptor in the electron transfer chain result in one of the products of respiration?

A

Oxygen combines with protons (H+) and electrons to form water

48
Q

Where in the stages of respiration are the products released?

A

Carbon dioxide-released in the Krebs Cycle
Water-the end of the electron transfer chain when oxygen combines with protons and electrons

49
Q

Why is the final stage of aerobic respiration also known as oxidative phosphorylation?

A

In the presence of oxygen, energy is released to allow the phosphorylation of ADP

50
Q

Define chemiosmosis

A

The term used to describe the movement of ions across a selectively permeable membrane, down an electrochemical gradient

51
Q

Where does chemiosmosis occur in respiration?

A

When ATP is synthesised by the movement of hydrogen ions across the mitochondrial membrane, via ATP synthase

52
Q

What happens if more energy is produced in one stage of respiration than normal?

A

More will be lost as heat
Means less is available for other purposes like the formation of ATP

53
Q

How is an energy gradient created in the Electron transfer chain and how is it used ?

A
  • when energy is released by the transfer of electrons from reduced NAD/FAD along the ETC, each carrier molecule is at a slightly lower energy level than the one before
    The energy is released down an energy gradient so it can be released more gradually
54
Q

What is the first common stage in both anaerobic and aerobic respiration?

A

Glycolysis

55
Q

In the absence of oxygen (anaerobic respiration) what stages of respiration cannot occur?

A

The Krebs cycle and the electron transfer chain

56
Q

If both the Krebs cycle and the Electron transfer chain cannot occur is ATP still produced? How much?

A

Yes- only glycolysis will occur as the source of ATP
2 ATP

57
Q

What must happen for glycolysis to occur?

A

It’s products pyruvate and hydrogen must be removed
The removal of hydrogen must be removed from reduced NAD in order to regenerate NAD

58
Q

Why is it important to regenerate NAD from reduced NAD for glycolysis?

A

If the supplies of NAD run out, glycolysis stops
This is because there is no more NAD to accept hydrogen as glucose is oxidised

59
Q

When is NAD regenerated?

A

When pyruvate accepts hydrogen

60
Q

What happens to pyruvate in animals?

A

It is converted to lactate
- when oxygen is available the lactate can be converted back into pyruvate which can then be oxidised or converted to glycogen in the liver

61
Q

What happens to pyruvate in plants & microbes?

A

Pyruvate is converted into ethanol and CO2

62
Q

Compare the energy yields of aerobic and anaerobic respiration

A
  • the energy yield of anaerobic respiration is very low in comparison with aerobic
  • one molecule of glucose yields a net gain of 36 molecules of ATP in anaerobic respiration but only 2 in anaerobic respiration
63
Q

Why is the energy yield lower in anaerobic respiration?

A

Glycolysis is the only source of ATP production- whereas ATP is produced in the Krebs cycle and ETC in aerobic
- these 2 stages can only occur in the presence of oxygen

64
Q

Which stage of respiration results in the production of the most ATP?

A

The electron transfer chain 32 ATP

65
Q

How efficient is respiration?

A

40% efficient
60% is lost as heat

66
Q

How are other substances used in respiration?

A

Conversion to glycolysis or Krebs intermediate molecules

67
Q

How are lipids used in respiration?

A
  • they are hydrolysed into glycerol & long chain fatty acids
  • glycerol is phosphorylated into triose phoshate, which enters glycolysis
  • fatty acids are broken down to produce a series of 2 carbon compounds which are converted to AcetlylCoA
68
Q

How are proteins used in respiration?

A

-They are hydrolysed to amino acids which can be deaminated (removing amino group)
-the acid residues enter the respiratory pathway at different points depending on the amount of carbons they contain:
-3C compounds are converted to pyruvate
- 4 & 5 carbon compounds enter the Krebs cycle

69
Q

What is/was DNP?

A

-It is a chemical that acts as an uncoupling agent
- it makes the inner mitochondrial membrane leaky to protons
- was used as a weight loss drug until 1938

70
Q

How would DNP affect the amount of ATP produced in cellular respiration?

A
  • DNP allows protons to travel down their gradient and back into the mitochondrial matrix without passing through ATP synthase
  • thus reducing ATP production in cellular respiration
  • the energy of the gradient dissipated in the form of heat which raises the body temperature
71
Q

Why was DNP removed from the market?

A
  • it caused deaths due to hyperthermia ( severely elevated body temperatures)
  • also because it was linked to cataracts and vision loss

AQA A-level Biology (25 decks)

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