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biology > Respiration > Flashcards

Respiration Flashcards

1
Q

Types of respiration?

A
  1. Aerobic
  2. Anaerobic
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2
Q

What are the 4 stages of aerobic respiration?

A
  1. Glycolysis : Each glucose is broken down into 2 molecules of the compound pyruvate
  2. Link reaction : Pyruvate is oxidised to form acetyl CoA
  3. Krebs cycle : Acetyl CoA is decomposed to form CO2, NADH and H+ (reduced NAD) or FADH2 (electron carriers)
  4. Oxidative phosphorylation : Reduced NAD or FADH2, transfer electrons to electron transport chain (ETC). The chem energy is converted to drive chemiosmosis.
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3
Q

What is the overall equation for respiration?

A

C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP (energy)
(glucose + oxygen -> carbon dioxide + water).

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4
Q

What is ATP?

A

Adenosine triphosphate is the main source of chemical energy for cell metabolism

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5
Q

What is the structure of ATP?

A

Nucleotide consisting of adenine, a ribose sugar and 3 phosphate groups condensed tgt

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6
Q

When is ATP formed?

A
  1. Substrate-level phosphorylation
  2. Oxidative phosphorylation
  3. Photophosphorylation <photosynthesis></photosynthesis>
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7
Q

What are the significance of ATP?

(4)

A
  • It is a universal energy carrier
  • It is a mobile energy carrier
  • It can be easily formed
  • It is the source of energy for many energy -requiring processes
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8
Q

What is the equation for synthesis and hydrolysis of ATP?

A

Hydrolysis : ATP+H2O→ADP+Pi+ energy

Synthesis : ADP + Pi+ energy→ATP+H2O

Pi = inorganic phosphate

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9
Q

When does ATP form during substrate level phosphorylation?

A
  1. Glycolysis (in the cytoplasm)
  2. Krebs cycle (in the mitochondrial matrix)

*only a small amount of ATP is generated

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10
Q

Where does respiration takes place?

A

Mitochondrion

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11
Q

Outline the process of glycolysis

(3 steps)

A
  1. Phosphorylation of glucose (6C)
    - 2 ATP is used
    * energy level of the molecule is raised so that useful energy can be extracted later
    glucose ——-> fructose 1,6 biphosphate
    kinase
  2. Splitting of fructose-1,6-biphosphate (6C) into 2 triose phosphate/ glyceraldehyde-3-phosphate (GALP) (3C)
    fructose-1,6-biphosphate ————-> 2 GALP
    aldolase
  3. Oxidation of 2 GALP (3C) to 2 pyruvate (3C)
    - 4 ATP formed
    - NAD+ reduced to NADH + H+
    2 GALP ——————————> 2 pyruvate
    dehydrogenase & kinase
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12
Q

What are the products of glycolysis?

A
  • Net 2 ATP
  • 2 reduced NAD
  • 2 pyruvate
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13
Q

What happens to pyruvate after glycolysis?

A

It depends on the presence of oxygen.

  1. Aerobic resp : complete oxidation of pyruvate via LR, KC and OP, releasing a lot of energy
  2. Anaerobic resp : incomplete oxidation of pyruvate, no energy released, regenerate NAD+ only
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14
Q

Outline the process of Link Reaction.

(3 main steps)

A
  1. Oxidative decarboxylation of pyruvate
    - CO2 removed
  2. Oxidation of pyruvate to form reduced NAD
  3. Coenzyme A added to form acetyl CoA (2C)

pyruvate dehydrogenase = enzyme that oxidize pyruvate to acetyl coA NOT coenzymeA

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15
Q

What are the products formed after Link Reaction?

A
  • 2 CO2
  • 2 reduced NAD
  • 2 Acetyl CoA
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16
Q

Where does glycolysis occurs?

A

Cytoplasm

17
Q

Where does Link Reaction occurs?

A

Mitochondrial matrix

18
Q

Outline Krebs cycle.

(Owen’s Cat Asked Susan For Milk)
(6 steps hehe)

A
  1. Acetyl CoA (2C) combines with oxaloacetate (4C) to form citrate (6C).
  2. Citrate (6C) breaks down to form ketoglutarate (5C).
    -Citrate (6C) undergoes oxidative decarboxylation, releasing CO2.
    -H atoms released (oxidation) are picked up by e- carriers NAD+ to form reduced NAD.
  3. Ketoglutarate (5C) breaks down to succinate (4C).
    -Ketoglutarate (5C) undergoes oxidative decarboxylation, releasing CO2.
    -H atoms released are picked up by e- carriers NAD+ to form reduced NAD.
    -ATP is produced via substrate-level phosphorylation.
  4. Succinate (4C) to fumarate (4C)
    -H atoms released are picked up by carriers FAD to form reduced FAD
  5. Fumarate (4C) to malate (4C)
  6. Malate (4C) to oxaloacetate (4C)
    - H atoms released taken up by NAD+ to form reduced NAD
19
Q

What are the products formed from Krebs Cycle?

A
  • 4 CO2
  • 6 reduced NAD
  • 2 reduced FAD
  • 2 ATP

*KC occurs twice coz of 2 Acetyl CoA needed to be oxidised

20
Q

Where does Krebs cycle occur?

A

Mitochondrial matrix

21
Q

Outline the process of oxidative phosphorylation.

(Process 1 first -> 4 steps)

A

2 main processes : Electron Transport Chain (ETC) and Chemiosmosis

ETC:
1. High energy electrons in reduced NAD are transferred to the first e- carrier of the ETC, reducing the first e-carrier while NAD+ is regenerated…

Similarly, high-energy e- in reduced FAD are transferred to and e-carrier in the ETC resulting in regeneration of FAD…

  1. The high energy e-s migrates from one e- carrier to another in a series of redox reactions until they are finally accepted by the final electron and proton acceptor, O2. Protons from the mitochondrial matrix and e-s from the ETC are taken up by O2 to form H2O.

1/2 O2 + 2H+ → H2O

  1. The e- carriers in the ETC are each at a progressively lower energy, when high-energy e-s are transferred down the chain, energy is released by the e-s. The e- carriers use this energy to pump H+ from the matrix into the intermembrane space.
  2. Inner membrane is impermeable to H+, H+ accumulates in the intermembrane space, forming a proton reservoir. *Proton gradient is set up across the inner membrane!

<3+4 helps in chemiosmosis!!>

22
Q

Outline chemiosmosis in photosynthesis.

A

ATP synthase on the mitochondrial cristae allow H+ to pass though via facilitated diffusion.

  1. When H+ flow down their proton gradient back into the matrix via ATP synthase, ATP synthase uses this energy from the proton motive force to synthesize ATP.
  2. Each reduced NAD has sufficient energy to form 3 ATP / 2.5 ATP while each reduced FAD yields 2 ATP / 1.5 ATP per molecule.
23
Q

Define chemiosmosis

A

It is an energy-coupling mechanism that uses energy stored in the form of a H+ gradient across a membrane to drive cellular work, such as the synthesis of ATP.

24
Q

What is the products formed during OP?

A

ATP synthesized by chemiosmosis : 34

25
Q

What is the total number of ATP produced from 1 glucose molecule during respiration?

A

38

substrate level phosphorylation : 4
oxidative phosphorylation : 34

26
Q

What happens to the pyruvate in anaerobic conditions in yeast?

(2 steps)

A
  1. Pyruvate (3C) breaks down to ethanal (2C) + CO2
    - undergoes decarboxylation w enzyme pyruvate decarboxylase
  2. Ethanal to ethanol and NAD+
    - reduced NAD loses e- to form back NAD+ w enzyme ethanol dehydrogenase
27
Q

Explain the production of small yield of ATP from respiration in anaerobic conditions in yeast and in mammalian muscle cell

A

In absence of O2, LR, KC and OP cannot take place. Hence only glycolysis continue so 1 molecule of glucose is partially broken down to 2 molecules of pyruvate, net yield of 2 ATP, and 2 reduced NAD

28
Q

Explain the significance of the formation of ethanol in yeast in the regeneration of NAD.

A

Pyruvate accepts the H atom from reduced NAD and is reduced to ethanol , hence regenerating NAD+, to allow glycolysis to continue.

29
Q

Explain the significance of the formation of lactate in mammals in the regeneration of NAD.

A

Pyruvate is oxidised to lactate, regenerating NAD+ in the process to allow glycolysis to continue

30
Q

What happens to the electron carriers during anaerobic conditions?

A

In absence of oxygen, there is no O2 to be the final proton and electron acceptor in the ETC. Since e-s are not passed down the ETC, e- carriers remain reduced. NAD+ is not regenerated.

31
Q

Why must there be regeneration of NAD+ in anaerobic respiration?

A

Under anaerobic conditions, glycolysis needs to continue to synthesis some ATP. Hence, there must be constant regeneration of NAD+ which is achieved by regenerating NAD+ from reduced NAD produced from glycolysis.

32
Q

What happens to pyruvate in anaerobic conditions in mammals?

A
  1. Pyruvate + reduced NAD converts reversibly to lactate and NAD+ via enzyme lactate dehydrogenase.
33
Q

What does accumulation of lactate cause?

A

Lowers pH -> affect enzyme activity -> muscle cramp and fatigue

accumulate O2 debt

34
Q

What happens to lactate when O2 level is restored?

A

Some lactate oxidised back to pyruvate which enters the LR, KC, OP.

The rest of the lactate is converted to glucose and then to glycogen for storage in the muscles and liver.

35
Q

What other biomolecules are used as respiratory substrates?

A
  1. Fats - to glycerol and fatty acids
    - glycerol -> GALP
  2. Proteins - to amino acids

Monomers of these molecules enter glycolysis or KC at various points.

36
Q

Why is anaerobic respiration much less efficient than aerobic respiration?

A

Glucose is completely oxidised in aerobic respiration but lactate (mammals) and ethanol (yeast) is produced at the end of anaerobic respiration since glucose is oxidised partially. Hence, a lot of energy is stored in lactate and lactate.

biology (20 decks)

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