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The liver and regulation of metabolism > Roles of ATP in living cells > Flashcards

Roles of ATP in living cells Flashcards

1
Q

What is anabolism?

A

synthesis of complex molecules from simpler ones (necessary energy usually derived from ATP)

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2
Q

What is catabolism?

A

breakdown of energy- rich molecules to simpler ones (CO2 H2O and NH3)

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3
Q

What is energy used for?

A

Motion (muscle contraction)
Transport (of ions/molecules across membranes)
Biosynthesis of essential metabolites
Thermoregulation

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4
Q

Why are storage forms required?

A

Because feeding times and usage times do not coincide all the time

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5
Q

Where is free energy gained from?

A

Food

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6
Q

What is gibbs free energy?

A

Energy capable of doing work at constant temperature and pressure
The energy derived from the oxidation of dietary fuels

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7
Q

When does entropy increase?

A

Breakdown

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8
Q

When does enthalpy increase?

A

When energy is put into the system

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9
Q

What is an exergonic reaction?

A

One which releases energy

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10
Q

When is free energy negative?

A

When the reaction releases energy

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11
Q

When is free energy positive?

A

When reaction is endergonic and require energy to begin

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12
Q

Give an example of an exergonic reaction?

A

Catabolism

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13
Q

Give an example of endergonic reactions

A

Anabolism

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14
Q

Describe coupling of reactions

A

An endergonic reaction can be driven in the forward direction by coupling it to an exergonic reaction through a common intermediate

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15
Q

When is phosphate group transfer used?

A

When ATP is used

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16
Q

What can magnesium deficiency do?

A

Interfere with metabolism

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17
Q

Describe substrate level phosphorylation

A

Formation of ATP by phosphoryl group transfer from a substrate to ADP

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18
Q

Respiration-linked phosphorylation involve…

A

Membrane-bound enzymes and transmembrane gradients of protons and require oxygen

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19
Q

How do enzymes interfere with gibbs free energy?

A

They do not

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20
Q

What are coenzymes derived from?

A

Vitamins

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21
Q

What is a prosthetic group?

A

Non-protein cofactor that is covalently bound to the enzyme

Acts as a temporary store for e- or intermediates

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22
Q

What is NAD formed from?

A

Niacin

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23
Q

What is FAD formed from?

A

B2 Riboflavin

24
Q

In each redox case how many electrons and protons are transferred?

A

2 electrons

Various protons

25
Q

What is NAD+ reduced to?

A

NADH

26
Q

What is FAD reduced to?

A

FADH2

27
Q

What is the functional group of NAD+

A

Nicotinamide

28
Q

What are priming reactions?

A

Where ATP is put into the reaction to begin it

29
Q

Where does glycolysis occur in the cell?

A

Cytoplasm

30
Q

What continues to the next stage of the glycolysis reaction

A

G3P

31
Q

How many times do the payoff reactions occur per molecule of glucose?

A

Twice

32
Q

What is the product of glycolysis?

A

Pyruvate

33
Q

What is the priming stage?

A

investment of ATP at the hexokinase and PFK-1 reactions

34
Q

What is the payoff stage?

A

recovery of ATP by SLP using the 1,3 - bisphosphate kinase and pyruvate kinase reactions

35
Q

What are the two possible fates of pyruvate?

A

Under aerobic conditions, oxidation and complete degradation
In hypoxic conditions, it can be reduced to lactate

36
Q

Under aerobic conditions where does pyruvate get degredated?

A

Mitochondria

37
Q

Describe how pyruvate is transported into the mitochondria?

A

Occurs via by specific carrier protein embedded in the mitochondrial membrane

38
Q

How does pyruvate form acetyl CoA?

A

Pyruvate undergoes oxidative decarboxylation by the pyruvate dehydrogenase complex to form Acetyl CoA:

39
Q

Describe the structure of the pyruvate dehydrogenase complex?

A

Three different enzymes

Five different coenzymes

40
Q

List the vitamins essential for the pyruvate dehydrogenase complex

A

Thiamine (in TPP)
Riboflavin (in FAD)
Niacin (in NAD)
Pantothenate (in CoA)

41
Q

What is the TCA cycle?

A

Krebs cycle/Tricarboxylic acid cycle/Citric acid cycle
Final common pathway for the oxidation of fuel molecules
In 8 steps, acetyl residues (CH3-CO-) are oxidised to CO2

42
Q

What does 1 turn of the TCA cycle produce?

A

3 NADH
FADH2
GTP
2 CO2

43
Q

Describe the 3 ways TCA cycle is regulated

A

Entry of acetyl-CoA into the TCA cycle (citrate synthase reaction)
Conversion of pyruvate to acetyl-CoA (PDH reaction)
Also regulated at isocitrate dehydrogenase and -ketoglutarate dehydrogenase reactions

44
Q

Name some other sources of Acetyl coA

A

Fatty acids

Amino acids

45
Q

How are the TCA intermediates replenished?

A

By anaplerotic reactions

46
Q

What happens to the NADH and FADH2 after the TCA and glycolysis? State the problem here

A

Oxidised by the mitochondrial ETC
The inner mitochondrial membrane is impermeable to NADH!
There is no carrier in the membrane to transport it across

47
Q

Describe how NADH is transported?

A

It is not!

The shuttles transport the electrons across the membrane

48
Q

Describe the two shuttles stating where they are prevalent and what they do

A

The glycerol-3-phosphate shuttle, especially prevalent in brain and muscle
The malate-aspartate shuttle, in liver and heart
Both shuttles act to regenerate NAD+ and make 1.5 or 2.5 moles of ATP

49
Q

Describe the action of the glycerol-3-phosphate shuttle

A

NADH reduces dihydroxyacetone-P (DHAP) to glycerol-3-phosphate (G-3-P)

Catalysed by G-3-P dehydrogenase

G-3-phosphate diffuses into the intramembrane space

A mitochondrial G-3-P dehydrogenase (called flavoprotein dehydrogenase) uses FAD to oxidise it to DHAP

FADH2 carries electrons to ubiquinone in the electron transport chain eventually producing 1.5 ATP

50
Q

Describe the action of the malate aspartate shuttle

A

Electrons of cytosolic NADH transfer to cytosolic oxaloacetate yielding malate

Malate is transported into the matrix via an exchanger protein that transports α-KG in the opposite direction

In the matrix, malate is oxidised back to oxaloacetate

NADH formed transfers its reducing power to the electron transport chain producing 2.5 ATP

Oxaloacetate is converted to aspartate

Aspartate is transported to the cytosol via an exchanger protein that transports glutamate into the matrix

Cytosolic aspartate is transaminated to oxaloacetate

51
Q

Describe the electron transport chain

A

Comprises four large multi-unit proteins intrinsic to the inner mitochondrial membrane

52
Q

State the reaction the electron transport chain catalyses

A

NADH + H+ + 1/2O2 = NAD+ + H2O

Energy released from this reaction not released as heat but tightly coupled to the production of ATP

53
Q

The 4 complexes are linked by 2 soluble proteins. What are they?

A

Ubiquinone (coenzyme Q) – a lipid soluble benzoquinone with a long isoprenoid tail
Cytochrome C - These are free to move in the membrane by diffusion (they are not part of the complexes)

54
Q

Which complex does NADH pass its electrons to in the electron transport chain?

A

Complex 1

55
Q

Which complexes move protons in the electron transport chain?

A

1,3,4

The liver and regulation of metabolism (15 decks)

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