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Flashcards in Metabolic Pathways and ATP Production Deck (19):
1

What are the three stages of cellular metabolism converting food to waste products?

1. Glycolysis- generates ATP + NADH in cytosol of the cell.
2. TCA Cycle- Oxidisies products formed from glycolysis in mitochondira, generating ATP, NADH, FADH2, waste products.
3. Oxidative phosphorylation- generation of ATP in mitochondria using products of of TCA Cycle by reducing oxygen to water.

2

Explain the metabolism of glucose during glycolysis: key pathways

1 Glucose-> 2 Pyruvate + 2 ATP
Essentially anaerobic
2 concepts:
-Forming high energy compound: investing ATP
- Splitting High energy compounds: releasing ATP

10 STEPS:
1ST HALF---
1. Glucose --> Glucose 6-phosphate
- Hexokinase


3

Explain the metabolism of glucose during glycolysis: key pathways

1 Glucose-> 2 Pyruvate + 2 ATP
Essentially anaerobic
2 concepts:
-Forming high energy compound: investing ATP
- Splitting High energy compounds: releasing ATP

10 STEPS:
1ST HALF---
1. Glucose --> Glucose 6-phosphate
- Hexokinase
- ATP--> ADP
2. Glucose 6-Phosphate--> Fructose 6-phosphate
- phosphoglucose Isomerase
3. Fructose 6-Phosphate --> fructose 1,6-Bisphosphate
- phosphofructokinase
- ATP --> ADP
4. Fructose- 1,6-bisphosphate --> glyceraldehyde 3-phosphate + dihydroxyacetone phosphate
5. Dihydroxyacetone phosphate --> Glyceraldehyde 3-phosphate
- triose phosphate isomerase
2ND HALF----
6. 2x Glyceraldehyde 3-Phosphate --> 1,3-bisphosphoglycerate
-glyceraldehyde 3-phosphate dehydrogenase
- NADH generated to produce ATP in oxidative phosph.
7. 1,3-bisphosphoglycerate --> 3-phosphoglycerate
-phosphoglycerate kinase
- ADP--> ATP
8. 3-phosphoglycerate --> 2-phosphoglycerate
- phosphoglycerate mutase
9. 2-phosphoglycerate --> phosphoenolpyruvate
- Enolase in Dehydration reaction
10. phosphoenolpyruvate--> pyruvate
- pyruvate kinase
- ADP--> ATP

4

Explain metabolism of glucose during gluconeogenisis: key pathways

Glucose is produced by gluconeogensis, only energy source used by brain. Like glycolysis but in reverse.

5

Distinguish between aerobic and anaerobic metabolism of glucose

Pyruvate has 3 fates:

1. Alcoholic fementation:
yeast
Pyruvate--> acetaldehyde
- pyruvate decarboxylase
Acetaldehyde --> ethanol
- alcohol dehydrogenase
- NADH +H+ --> NAD+

2. Generate lactate

Pyruvate -->lactate
lactate dehydrogenase
- NADH + H+ --> NAD+
Regeneration of NAD+ needed to continue glycolysis.
These two fates serve as methods for this

3. Generation of Acetyl CoA in Link Reaction

Pyruvate + HS-CoA --> Acetyl CoA + CO2
- Pyruvate dehydrogenase complex
- NAD+ --> NADH
- occurs in mitochondria

6

What is the definition of substrate level phosphorylation

production of ATP throuhg direct tranfer of a high energy phosphate group to an intermediate substrate in a biochemical pathway, to ADP, e.g. in glycolysis

7

What does lactate dehydrogenase do and what is it used for?

LDH catalyses interconversionbetween pyruvate and lactate, the level of LDH used as a diagnostic tool for:
- Stroke
- Heart Attack
- Pulmonary infarction
- Muscle Injury
- Muscular dystrophy
- Liver Disease

8

What is creatine phosphate and what can it be used for?

It is a large resevoir of phosphate, used to phosphorylate ADP to ATP.
In muscle damage, creatine phosphate leaks into the bloodstream.
Elevated levels can be used to diagnose
- myocardial infaction
-Determine extent of muscular disease
-Evaluate cause of chest pain
- discover carriers of muscular dystrophy

9

What process turns glucose into products that can enter the tricarboxylic cycle (TCA/Krebs cycle)

glycolysis, then link reaction

10

What is creatine phosphate?

It is a large resevoir of phosphate, used to phosphorylate ADP to ATP.

11

What process turns amino acids into products that enter the TCA Cycle?

Degradation of amino acids
- Amino group removed + excreted as urea
- Cabon skeleton funnelled into production of glucose/ fed into krebs cycle
- Requires transamination reactions (Amine grp from amino acid to keto acid therefore forming new amino and keto acids.

- Degradation of all 20 amino acid gives only 7 molecules:
- Pyruvate
- Acetyl CoA
- Acetoacetyl CoA
a-Ketoglutarate
-Succinyl CoA
-Fumarate
-Oxaloacetate

12

Explain the oxidation of acetyl-CoA, with the formation of NADH and FADH2 by the TCA Cycle.

CONTINUOUS CYCLE OF 8 REACTIONS:

1. Oxaloacetate (4C) --> Citrate (6C)
- Acetyl CoA has Acetyl added to oxaloacetate, and thus turns into HS-CoA + H+
- Citrate synthase
2. Citrate --> Isocitrate
- aconitase
3. Isocitrate (6C) --> a-ketoglutarate (5C)
- NAD+ --> NADH + CO2 + H+
- Isocitrate dehydrogenase
4. a-Ketoglutarate (5C) --> Succinyl-CoA (4C)
- a-ketogluarate dehydrogenase complex
- HS-CoA + NAD+ --> NADH + H+ + CO2
5. Succinyl CoA --> Succinate
- GDP + Pi + H2O --> GTP + HS-CoA
- Succinyl CoA synthetase
(In bacteria and plants ATP is formed instead)
6. Succinate --> Fumarate
- FAD --> FADH2
- Succinate dehydrogenase
- Succinate is oxidised
7. Fumarate --> Malate
- Addition of H2O, breaks double bond
- Fumerase
8. Malate--> Oxaloacetate
- NAD+--> NADH + H+
- Malate dehydrogenase
- dehydrogenation of malate

SO:
1 Cycle produces:
- 3x NADH
- 1x GTP
- 1x FADH2
- 2x CO2

13

What is the glycerol phosphate shuttle and why is it required?

Transports NADH formed in glycolysis accross the cytosol into mitochondrial matrix.
In Skeletal muscle and brain.

14

What is the malate-aspartate shuttle and why is it required?

Transports NADH formed in glycolysis accross the cytosol into mitochondrial matrix.
In Liver, kidney, heart

15

What are the 5 co-factors involved in pyruvate dehydrogenase?

- Thiamine Pyrophosphate (TPP)
derivative of Vit B
loses proton, resulting carbanion attack pyruvate --> hydroxyethyl TPP
- Lipoamide
undergoes oxidation and reduction
-FAD
accepts and donates two electrons and 2 protons
FAD + 2e- + 2H+ --> FADH2
-CoA
-NAD+
the prosthetic groups e.g.. TPP, lipoamide are permanent in the complex, others bind reversibly to enzymes.

16

Why is Acetyl Coenzyme A readily hydrolysed and what does this help it do?

As it has a thioester bond which is a high energy linkage, and this allows Acetyl CoA to donate Acetate (2C) to other molecules

17

Where are the Krebs cycle enzymes located?

Mitochondrial matrix space APART FROM SUCCINATE DEHYDROGENASE- on inner surface of inner mitochondrial membrane

18

Why does the krebs cycle only occur in aerobic conditions?

Because NAD+ and FAD are needed and these are only regenerated via the transfer of electrons to O2 during oxidative phosphorylation

19

What is yielded in Oxidative phosphorylation?

Reoxidation of reduced cofactors yields:
- 1 NADH --> 3 ATP
- 1 FADH2 --> 2 ATP
THEREFORE oxidation od 1 Acetyl CoA gives
3 x NADH + 1 x FADH2 + 1 x GTP = 12 ATP
SO MAX YIELD IN AEROBIC RESP = 38 ATP per 1 glucose.