Carbohydrates 3 Flashcards

1
Q

Define glycolysis

A

A series of cellular reactions, not requirin oxygen, that splits glucose, glycogen or other carbohydrates into pyruvic or lactic acid while storing energy in ATP molecules.

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2
Q

Why is glycolysis important?

A

Its the only way ATP can be made when lacking oxygen (e.g. during strenuous exercise) or in cells lacking mitochondria (RBCs)

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3
Q

How many stages/steps are involed in glycolysis?

A

2 stages
The preparatory phase has 5 steps
The payoff phase has 5 steps

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4
Q

Why cant glycolysis be easily reversed?

A

It has an overall -delta G making it spontaneous and thermodynamically impossible to reverse. This applies mainly to 3 steps that are very spontaneous.

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5
Q

What happens overall in the preparatory phase?

A

Glucose is converted to two Glucose-3-phosphates at the cost of 2 ATP

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6
Q

What occurs in step one of the preparatory phase?

A

Glc is converted to G-6-P by hexokinase at the cost of 1 ATP

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7
Q

What occurs in step 3 of the preparatory phase?

A

F-6-P is phosphorylated to F-1,6-bisP by phosphofructokinase-1 (PFK-1) at the cost of 1 ATP

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8
Q

Why is Step 3 of the preparatory phase especially importnat?

A

It is the first commited step of glycoslysis because it has a very -deltaG so is irreversible.

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9
Q

What happens overall in the payoff phase?

A

Two G-3-P molecules are converted to two pyruvates. This produces 4 ATP and 2 NADH.

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10
Q

What occurs at step 6 of glycolysis (step one of payoff phase)?

A

Two G-3-P are converted to 1,3-Bisphosphoglycerate (1,3-bisPG) producing two NADH

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11
Q

What happens in step 7?

A

Phosphate is transfered form the two 1,3-bisPG molecules to ADP to form two ATP and 3-phosphoglycerate

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12
Q

What occurs in step 10?

A

Phosphate transferred from two PEP to ADP to form two ATP and two Pyruvate.

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13
Q

What is different between substrate level and respiration-linked phosphorylation?

A

Substrate level phosphorylation needs soluble enzymes and chemical intermediates
Respiration linked phosphorylation requires membrane bound enzymes, oxygen and gradients of protons.

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14
Q

How is NAD+ replenished?

A

By converting pyruvate to Lactace (or other intermediates e.g. ethanol & CO2) which has a by-product of using up NADH.

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15
Q

What term is used to describe the constant use and replenishment of NAD+?

A

A redox Balance

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16
Q

How is pyruvate converted to Lactate?

A

By Fermentation involving oxidation of NADH using Lactate Dehydrogenase

17
Q

What is the Cori Cycle?

A

The cori cycle is the process for the conversion of glucose to lactate durin glycolysis and back again. I.e. the liver is repaying the muscles oxygen debt,

18
Q

Where does the Cori cycle occur?

A

In the muscle and liver

19
Q

What two pathways make up the Cori Cycle?

A

Glycolysis and Gluconeogenisis

20
Q

When happens to pyruvate under aerobic conditions?

A

It is converted to Acetyl-CoA and fed into the Citric acid cycle (CAC)

21
Q

How is pyruvate converted to Acetyl-CoA?

A

It is moved to the mitochondria and is reacted with CoA-SH to form Acetyl-CoA and CO2. This also involves the reduction of NAD+.

22
Q

What enzyme catalyses the conversion of pyruvate to acetyl-CoA?

A

Pyruvate dehydrogenase.