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A-level Biology > Respiration > Flashcards

Respiration Flashcards

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1
Q

What is respiration?

A

The process that occurs in living cells and releases energy which is immediately used to synthesise ATP molecules

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2
Q

What is the structure of a mitochondrion?

A

Outer membrane:
Contains proteins to allow passage of molecules into the mitochondrion

Inner membrane:
Less permeable to H+ than outer
Cristae (folding of inner membrane) increasing SA
ATPsynthase channels

Inter membranal space

Matrix

Ribosomes

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3
Q

What are the stages of aerobic respiration?

A

Glycolysis

Link reaction

Krebs cycle

Electron transport chain

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4
Q

Where does glycolysis take place? And what are the products of glycolysis?

A

Happens in the cytoplasm

Products:

2x ATP
2x Red. NADH
2x Pyruvate

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5
Q

What happens during glycolysis?

A
  1. Glucose is phosphorylated by the hydrolysis of ATP donating a Pi group to the glucose molecule creating glucose phosphate
  2. Another Pi group is added by the hydrolysis of another ATP molecule creating Hexose Bisphosphate
  3. This molecule is then split into 2x triose phosphate molecules
  4. Each of the triose phosphate molecules can be oxidised to pyruvate, and the electrons are accepted by 2 molecules of NAD forming NADH. This step forms 4 molecules of ATP
  5. This leads to overall production of 2x (ATP, NADH and Pyruvate molecules)
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6
Q

What happens during the link reaction?

A

After glycolysis Pyruvate gets transported into the matrix via a Pyruvate - H+ sympatric protein

From 1 glucose molecule:

2x Pyruvate +2NAD + 2CoA ——> 2CO2 + 2NADH + 2AcetylCoA

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7
Q

What are the products of the link reaction?

A

2x NADH
2x CO2
2x AcetylCoA

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8
Q

What happens during Krebs cycle?

A
  1. Acetyl CoA (2 Carbon) binds with oxaloacetate (4 carbon) producing citrate (6 carbon)
  2. This is then turned into a 5 carbon intermediate releasing CO2 and one molecule of NAD becomes reduced to NADH
  3. This is then turned into a 4 carbon intermediate releasing another CO2 molecule and forming another NADH molecule
  4. This 4 carbon intermediate may undergo substrate level phosphorylation producing one molecule of ATP
  5. The 4 carbon intermediate is rearrange releasing 2 H+ ions which combine with FAD to form FADH2
  6. This rearrange 4 carbon intermediate is rearranged again to releasing another H+ ions which reduces a molecule of NAD forming NADH
  7. This newly arrange 4 carbon molecule has reformed oxaloacetate and the cycle repeats for the next acetylCoA molecule
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9
Q

What are the products from the Krebs cycle?

A

6x NADH

2x FADH2

4x CO2

2x ATP

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10
Q

What happens during the electron transport chain?

A
  1. Electron hungry acceptors accept an electron from NADH or FADH2 to reduce them
  2. The electron is passed from one electron acceptor to the next (eg cytochrome oxidase) each electron acceptor has an iron ion
  3. The acceptance or donation of the electrons along the electron transport chain causes a series of redox reactions as the next acceptor is reduced and current acceptor becomes oxidised
  4. Once electron reaches the final acceptor oxygen accepted the electron to drive the ETC
  5. Along with the electrons oxygen also accepts H+ ions in order to produce water molecules
  6. The energy from the redox reactions enables proton pumps which pump H+ ions into the intermembranal space.
  7. This creates a chemiosmotic gradient as the concentration of H+ is higher in the intermembranal space than the matrix
  8. The H+ ions diffuse back into the matrix through ARPsynthase proteins which catalyse the reaction between ADP + Pi to form ATP
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11
Q

What is the net production of ATP from the electron transport chain?

A

NAD produces 3x ATP
FAD produces 2x ATP

Total NADH molecules= 10 and therefore produces 30 ATP in ETC

Total FADH2 molecules = 2 and therefore produces 4 ATP in ETC

Total ATP from ETC = 34

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12
Q

What is the total ATP yield from respiration?

A

Unsure so ranged from 32-38 ATP molecules

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13
Q

What happens if there is no oxygen to drive the ETC?

A

Anaerobic means no oxygen present

So there is no final electron acceptor driving the ETC

  1. H+ and electrons cannot combine with O2 to form H2O
  2. The chemiosmotic gradient gets disrupted so there is a higher concentration of H+ in the matrix
  3. Oxidative phosphorylation ceases
  4. Red NADH and Red FADH2 unable to offload H+ atoms and cannot be re- oxidised
  5. Krebs cycle and link reaction will stop

Must now respire anaerobically

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14
Q

How do organisms respire anaerobically?

A

Glycolysis still functions without the presence of Oxygen

In animals:
Pyruvate can be converted to lactate (via lactate dehydrogenase) which can then be recycle to glycogen or glucose.
Otherwise lactate would lower pH

In yeast and some plants:
Pyruvate is converted to ethanal and then ethanol

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15
Q

How good is anaerobic respiration?

A

Glycolysis happens quickly and can therefore quickly produce ATP molecules

However

The yield per glucose molecule is very small and therefore cannot be sustained for a long period of time, and there is also a build up of lactate which is toxic

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16
Q

How do you calculate the respiratory quotient?

A

RQ= CO2 produces / O2 consumed

17
Q

What are the main respiratory substrates?

A

Glucose and other carbohydrates

Lipids

Proteins

18
Q

What is a respiratory substrate?

A

A substance which can be oxidised by cells to release energy without being converted to carbohydrates

19
Q

How are lipids used as respiratory substrates?

A

Lipids can be hydrolysed to glycerol and fatty acids. Glycerol is able to be converted to triose phosphate which can enter glycolysis to provide ATP

20
Q

How are proteins used as respiratory substrates?

A

Proteins are hydrolysed to their amino acids. The amino acids can then be converted to keto acid and ammonia via deamination (amine group removed) and these substances can enter the respiratory pathway to provide energy.

21
Q

Explain why converting Pyruvate to lactate during anaerobic respiration allows for the continued production of ATP

A

Oxidised reduces NAD producing NAD which can then be reused in glycolysis allowing for the continued production of ATP

A-level Biology (23 decks)

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