Metabolic pathways and ATP production II Flashcards Preview

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Flashcards in Metabolic pathways and ATP production II Deck (39)
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1
Q

What are the products of one turn of the TCA cycle?

A

3 x NADH 1 x FADH2 1 x GTP 2 x CO2

2
Q

Where are the Krebs’ Cycle enzymes found?

A

Mitochondrial Matrix

3
Q

Which Krebs’ Cycle enzyme is not found in this location?

A

Succinate Dehydrogenase

4
Q

What happens in Transamination?

A

An amine group is transferred between an amino acid and a keto acid to generate a new amino acid and keto acid (the basis of the malate-aspartate shuttle) EXAMPLE: alanine + alpha-ketoglutarate  pyruvate + glutamate (enzyme = alanine aminotransferase)

5
Q

What are the two ways of electrons from NADH entering the mitochondrial matrix? Where are these two transport mechanisms found?

A

Glycerol Phosphate Shuttle – skeletal muscle, brain Malata-Aspartate Shuttle – liver, kidney, heart

6
Q

Describe the glycerol phosphate shuttle.

A

Cytoplasmic glycerol-3-phosphate dehydrogenase transfers electrons from NADH to dihydroxyacetone phosphate converting it to glycerol-3-phosphate Glycerol-3-phosphate is converted by mitochondrial glycerol-3-phosphate back into Dihydroxyacetone phosphate and the electrons are passed via FAD to coenzyme Q

7
Q

What different types of reactions are NADPH and NADH involved in?

A

NADPH = Anabolic NADH = Catabolic

anabolic is building up

catabolic is breaking down

8
Q

What are the components involved in the malate-aspartate shuttle?

A

Malate (in) Alpha-ketoglutarate (out) Oxaloacetate (converted from malate) Glutamate (in) Aspartate (out)

9
Q

what are the 6 types of metabolic reaction? explain ones i dont know

A
  • reduction and oxidation - ligation requiring ATP cleavage (Formation of covalent bonds) - Isomerisation (Rearrangement of atoms to form isomers) - Group Transfer (transfer of the functional group from one molecule to another) - Hydrolytic (cleavage of bonds by the addition of water) - Addition or removal of functional groups (this is the formation or removal of double bonds)
10
Q

how is acetyl CoA made from pyruvate?

A

pyruvate + Hs - CoA ——> acetyl CoA + CO2 this happens in the mitochondria and then moves into the krebs cycle

11
Q

what is a description of the TCA cycle?

A

A continuous cycle of eight reactions, starting with 2 carbon atoms from acetyl CoA being condensed with the 4 carbon unit of oxaloacetate to give a 6 carbon unit, citrate

12
Q

what is reaction 1?

A
  1. : Oxaloacetate (4C) + ——> Citrate (6C) the enzyme is citrate synthase 2C acetyl group from acetyl CoA is transferred to the 4C oxaloacetate to form 6C citrate
13
Q

what is reaction 2?

A

Citrate (6C)———–> Isocitrate (6C) - Citrate is isomerised to give isocitrate Enzyme = Aconitase

14
Q

what is reaction 3?

A

Isocitrate (6C) —————> a- ketoglutarate (4C) Isocitrate is OXIDISED to form a-ketoglutarate changing from 6C to 5C - the enzyme is isocitrate dehydrogenase

15
Q

what is reaction 4?

A

a-ketoglutarate ———–> succinyl-CoA - Similar to reaction catalysed by Pyruvate Dehydrogenase Complex - changes from 5C - 4C - Enzyme = a-ketoglutarate dehydrogenase complex

16
Q

what is reaction 5?

A

succinyl-CoA ————-> Succinate both 4 C - CoA is displaced by phosphate molecule which is transferred to GTP - Enzyme = succinyl CoA synthetase - GDP + Pi —> GTP

17
Q

how does GTP / GDP work?

A

GTP + ADP —> GDP + ATP

using enzyme nucleoside diphosphokinase

18
Q

what is reaction 6?

A

Succinate (4C) ———-> Fumarate (4C) - Succinate is OXIDISED and some FADH2 is generated from FAD - Enzyme = succinate dehydrogenase

19
Q

what is reaction 7?

A

Fumarate————-> Malate - Addition of water molecule breaks a double bond - enzyme = fumarate

20
Q

what is reaction 8?

A

Malate ———> Oxaloacetate Dehydrogenation of malate to give oxaloacetate -Enzyme = malate dehydrogenase

21
Q

what does one turn of the krebs cycle give?

A

• 3 x NADH • 1 x GTP • 1 x FADH2 • 2 x CO2 - 2 x ATP

22
Q

where are most of the krebs cycle enzymes? what is the exception?

A

soluble proteins located in mitochondrial matrix space. SUCCINATE DEHYDROGENASE - this is an integral membrane protein which is attached to the inner surface of inner mitochondrial membrane

23
Q

what conditions does the krebs cycle work under?

A

operates under AEROBIC CONDITIONS because of NAD+ and FAD being regenerated

24
Q

how much ATP does the reoxidation of co factors via oxidative phosphorylation make?

A
  • 1 NADH –> 3ATP - 1FADH2 –> 2ATP - 1GTP –> 1 ATP therefore one acetyl CoA (3x NADH) + (1x FADH) + ( 1x GTP)
25
Q

what is the theoretical maximum yield of ATP?

A
26
Q

what is the general strategy of degradation of amino acids?

A
  • Amino Acid group is removed (eventually excreted as urea)
  • Carbon skeleton is either funnelled into production of glucose or fed into krebs’ cycle.
27
Q
A
28
Q

what does the degradation of all 20 amino acids give rise to?

A
  • pyruvate
  • acetyl CoA
  • Acetoacetyl CoA
  • a-ketoglutarate
  • Succinyl CoA
  • fumarate
  • oxaloacetate
29
Q

what is a transamination reaction?

A
  • a reaction in which an amine group is transferred from one amino acid to a keto acid thereby forming a new pair of amino and keto acids.
30
Q

where does transamination come into role in cell metabolism?

A
  • Alanine undergoes transamination by the action of enzyme Alanine Aminotransferase
  • Pyruvate can enter the TCA cycle
  • Glutamate is converted back to a-ketoglutarate by Glutamate Dehydrogenase, this also makes NH4+ which is converted back to urea
31
Q

what do high levels of alanine aminotransferase suggest?

A

hepatic disorders … eg Hep C

32
Q

why does the NADH need to be moved from glycolysis to be used in oxidative phosphorylation?

A
  • to regenerate NAD+
  • There is only a finite amount of NAD+ so unless it’s regenerated, glycolysis will stop
33
Q

how does the NADH cross the cytosol?

A
  • The NADH cross the cytosol into the matrix of the mitochondrion by:
    • Glycerol Phosphate Shuttle - skeletal muscle, brain
    • Malate-Aspartate Shuttle - liver, kidney, heart
34
Q

how does the glycerol phosphate shuttle work?

A

Electrons from NADH, rather than NADH itself are carried across the mitochondrial membrane via a shuttle.

Cytosolic glycerol-3-phosphate dehydrogenase transfers electrons to Dihdroxyacetone phosphate to form glycerol 3-phosphate

A membrane bound form of the same enzyme transfers the electrons to FAD. The electrons then get transferred to co-enzyme Q, part of the electron transport chain

35
Q

how does the malate-aspartate shuttle work?

A

Uses 2 membrane carriers + 4 enzymes.

  1. Hydride Ion (H-) is transferred from cytoplasmic NADH to oxaloacetate to give malate (catalysed by cytosolic malate dehydrogenase (MDH)).
  2. Malate is transported into mitochondria where it is rapidly re-oxidised by NAD+ to give oxaloacetate and NADH (catalysed by mitochondrial MDH).
36
Q

are NADPH and NADH anabolic or catabolic?

A

NADPH = anabolic

NADH - catabolic

37
Q

why is NADPH important in cholesterol synthesis?

A
  • NADPH helps catalyse the final reaction of many, that leads to cholesterol synthesis
  • The C=C double bond is reduced by the transfer of a hydride ion
38
Q

what is NADP+ ?

A

NADP+ is similar to NAD+, the only differing by a phosphate group attached to one of the ribose rings.

Like NAD+, NADP+ can pick up two high-energy electrons and a proton collectively known as a hydride ion (H-).

NADP is an electron carrier

the phosphate group does not participate but it has a different structure so it can bind to different enzymes than NAD+

39
Q
A