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Biology Year 13 > Respiration > Flashcards

Respiration Flashcards

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1
Q

Describe glycolysis

A

Occurs in cytoplasm of cell

1.glucose is phosphorylated to hexose bisphodphate by two ATP molecules, this destabilises glucose molecule so they can’t leave and easier to breakdown

  1. Hexose bisphodphate splits into 2 molecules of triose phosphate
  2. TP is phosphorylated (by free inorganic phosphate rather then ATP)
  3. The 2 TP molecules lose H atoms (dehydrogenation, forming reduced NAD) and phosphate (enabling ATP formation) to produce two molecules of pyruvate
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2
Q

What is the overall net gain of ATP in glycolysis

A

+2

1 glucose, 2 pyruvate, 4 ATP, 2 reduced NAD, 2 ATP used

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3
Q

Explain why one glucose molecule yields two molecules of ATP from glycolysis (3 marks)

A

2 ATP used to convert glucose to hexose 1,6-bisphodphate

4 ATP produced in converting TP to pyruvate

Net of 2 ATP produced

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4
Q

Describe the role of phosphorylation in glycolysis (4 marks)

A

ATP phosphorylates glucose

To prepare it for subsequent reactions/ to be broken down

TP is phosphorylated

By inorganic phosphate

ADP is phosphorylated when TP is converted to pyruvate

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5
Q

Describe the link reaction

A

Occurs in matrix of mitochondria, requires pyruvate to move from cytoplasm into mitochondria through active transport

Pyruvate loses hydrogen (degydrogenation), which produces reduced NAD

Pyruvate loses carbon (decarboxylation), which produces CO2 and a 2-C group called acetyl

Acetyl group binds to coenzyme A, which produces Acetyl coenzyme A (Acetyl coA)

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6
Q

What is the role of coenzyme A in the link reaction

A

Deliver the Acetyl group to the Krebs cycle

Pyruvate + coenzyme A——-> Acetyl coenzyme A + CO2

(NAD—-> reduced NAD)

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7
Q

What is used and produced in the link reaction

A

Used: 2 pyruvate molecules

Produced: 2CO2, 2 reduced NAD, 2 Acetyl coA

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8
Q

Describe the structure of a mitochondrion

A

Outer mitochondrial membrane (separates contents of mitochondrion from rest of the cell)

Inner mitochondrial membrane (contains ETC chains and ATP synthase)

Cristae (projections of inner membrane which increase SA available for oxidative phosphorylation)

Matrix (contains enzymes for Krebs cycle and link reaction and mitochondrial DNA)

Inter membrane space (proteins pumped into space by ETC, the space is small so concentration builds up quickly)

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9
Q

Describe what happens to pyruvate after it has been produced in glycolysis (4 marks)

A

Enters mitochondria

(Through) active transport

Converted to Acetyl groups

Decarboxylated

Dehydrogenated

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10
Q

Explain what happens to CO2 produced by link reaction in plant species (2 marks)

A

Leaves the plant through stomata

Used in photosynthesis

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11
Q

Suggest why pyruvate is transported into mitochondria after it is produced in glycolysis (2 marks)

A

Subsequent stages of aerobic respiration take place in mitochondria

Enzymes in Krebs cycle are located in mitochondrial matrix

ETC are located on inner mitochondrial membrane

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12
Q

Describe the Krebs cycle

A
  1. Acetyl CoA delivers an acetyl group
  2. Acetyl (2C) reacts with oxaloacetate (4C) to produce citrate (6C)
  3. Citrate undergoes dehydrogenation forming reduced NAD and decarboxylation forming CO2. This results in a 5C being produced
  4. The 5C compound is decarboxylated and dehydrogenated further, regenerating oxaloacetate, which is free to react with another Acetyl CoA
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13
Q

What is being used and produced in the Krebs cycle

A

Used: 2 Acetyl-CoA

Produced:
4CO2,
6 reduced NAD (which are used in ETC)
2 reduced FAD (which are used in ETC)
2 ATP (through substrate level phosphorylation)

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14
Q

How many original 6C atoms in a glucose molecule are released as CO2 during the Krebs cycle (1 mark)

A

4

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15
Q

Suggest why oxaloacetate is present in cells at very low concentrations (2 marks)

A

/idea/ of rapid turnover/ constantly reacting

Reacts with Acetyl CoA to form citrate

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16
Q

What is the purpose of the electron transport chain

A

Located in inner mitochondrial membrane

Chain uses energy from electrons to pump H+ ions into inter membrane space. A proton gradient is established, which enables chemiosmosis to occur through ATP synthase

17
Q

Describe what happens in the electron transport chain

A

1.High energy electrons are passed from NADH and FADH2 to electron Carriers in ETC

  1. Electrons are passed between carriers in a series of redox reactions
  2. Energy is released from each reaction
  3. The energy is used to pump H+ ions from matrix into inter membrane space
  4. H+ ions diffuse through ATP synthase (chemiosmosis) back into matrix, which produce ATP
  5. H+ ions and electrons react with O2 to produce water
18
Q

What many ATP are produced per molecule for each stage of respiration

A

Glycolysis:
Substrate level phosphorylation-2
2 NADH- 3-5

Link reaction:
2NADH-5

Krebs cycle:
Substrate level phosphorylation-2
6NADH-15
2FADH2-3

Total-32

19
Q

Explain how structure of mitochondrial Cristae maintains a high rate of oxidative phosphorylation (2 marks)

A

Cristae are folds of inner membrane

Which increase SA available for oxidative phosphorylation

20
Q

Explain why oxygen is called the final
Electron acceptor in respiration (3 marks)

A

Oxygen accepts electrons that have passed through the ETC

Forming water

When combined with H+ ions

21
Q

The theoretical max yield of ATP from aerobic respiration may not always be achieved, suggest why (2 marks)

A

Some ATP is used for active transport of pyruvate (from the cytoplasm)

ETC is inefficient/ some energy is released as heat (and is not used to transport H+ ions)

Some reduced coenzymes may be used in other processes (not the ETC)

22
Q

How does anaerobic generate ATP

A

Generates small amounts of ATP through substrate-level phosphorylation in glycolysis.

Link reaction, Krebs cycle and ETC stop working in absence of oxygen

23
Q

Define fermentation and what is its function

A

Breakdown of pyruvate into lactate or ethanol

To oxidize NADH, thereby generating NAD. This enables glycolysis to continue, glycolysis stops without fermentation because supplies of NAD would run out and TP would no longer be converted to pyruvate

24
Q

State the equation of fermentation in animals

A

Pyruvate + reduced NAD—-> lactate + NAD

25
Q

State the equation of fermentation in yeast and in plants

A

Pyruvat—-> ethanal + CO2

26
Q

Explain why mammals use anaerobic respiration only for short periods of time (2 marks)

A

Relatively small amounts of ATP are generated

Insufficient chemical energy to sustain the functions of mammalian bodies

27
Q

Suggest why the absence of oxygen stops
A) chemiosmosis and ETC (2 marks)
B) Krebs cycle (2 marks)

A

A: idea of no terminal electron acceptor to accept electrons from the final electron carrier protein complex

Proton gradient is disrupted because O2 is not present to remove H+ ions diffusing through ATP synthase

B: NAD is not regenerated because the ETC stops

Reactions needed to convert citrate back to oxaloacetate cannot occur

28
Q

Which stage of respiration does amino acids enter and what molecules it It used to form

A

Link reaction or Krebs cycle

Depends on amino acid EG. Glycine—->pyruvate
Isoleucine—-> Acetyl CoA
Aspartate—-> oxaloacetate

29
Q

What stage does triglycerides (glycerol and fatty acids) enter respiration and what molecule is it used to form

A

Glycerol: glycolysis, triose phosphate

Fatty acids: Krebs cycle, Acetyl CoA

30
Q

What stage does lactate enter respiration and what molecules are formed from it

A

Link reaction

Pyruvate

31
Q

What must be removed from all amino acids before they can be metabolized as respiratory substrates? State the name of this process (2 marks)

A

Amine group

Deamination

32
Q

Some respiratory molecules are easier than others to form from an amino acid. Suggest the likely respiratory molecules formed from following amino acids. Explain your answer

A: asparagine (C4H8N2O3)
B: alanine (C3H7NO2)

A

A: oxaloacetate
Both have 4C

B: pyruvate
Both have 3C atoms

Biology Year 13 (5 decks)

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