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IMMS > Important Cycles > Flashcards

Important Cycles Flashcards

1
Q

Where does Glycolysis occur

A

Cytosol under anaerobic conditions

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2
Q

Why does glycolysis occur

A

Emergency energy producing pathway when oxygen is limiting

Generates precursors for biosynthesis

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3
Q

What is produced overall as a result of glycolysis

A

2 x pyruvate (C3H4O3)
2 x NADH + H+
2x ATP (two used in previous steps)

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4
Q

What is the order of molecules in glycolysis

A

Glucose

Glucose-6-phosphate

Fructose-6-phosphate

Fructose-1,6-biphsophate

Dihydroxyacetone phosphate/glyceraldehyde-3-phopshate

2x 1,3-bisphosphoglycerate

2x 3-phosphoglycerate

2x 2-phosphoglycerate

2x phosphoenolpyruvate

2x pyruvate

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5
Q

Glycolysis Summary

A

Glucose + 2NAD+ + Pi + 2ADP

=

2 pyruvate + 2NADH + 2H+ + 2ATP + 2H2O

-22kcal = not readily reversible

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6
Q

What are the 3 enzyme regulators of glycolysis

A

Hexokinase
Phosphofructokinase-1
Pyruvate kinase

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7
Q

What are the regulations of glycolysis

A

Allosteric
- Binds to a non-catalytic site
- Conformational change
- Increase/decrease affinity for the substrate

Hormonal (insulin and glucagon)
- increases/decreases gene expression of the enzyme
- indirect route - through affecting regulatory molecules (usually kinases or phosphatases)
- increase or decrease enzyme activity

Glycolytic enzymes are sensitive to the cell’s energy levels

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8
Q

What is the activator and inhibitor for phosphofuctokinase-1

A

Activator AMP

Inhibitor ATP, citrate, F2,6 BP

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9
Q

What happens to pyruvate in anaerobic conditions

A

Lactate formation catalysed by lactate dehydrogenase

Regeneration on NAD+

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10
Q

What happens to pyruvate in aerobic conditions

A

Enters mitochondria converted to Acetyl CoA and CO2 by pyruvate dehydrogenase

Acetyl CoA can enter TCA cycle for more energy production

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11
Q

What is the equation for lactate in anaerobic conditions

A

Glucose + 2ADP + 2Pi

=

2 lactate + 2 ATP + 2H2O + 2H+

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12
Q

What is the reaction of pyruvate in aerobic conditions

A

Irreversible reaction

pyruvate + CoA + NAD+

=

acetyl-CoA + CO2 + NADH + H+

Enzyme - pyruvate dehydrogenase (multienzyme complex within the mitochondrial matrix)

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13
Q

What is the aerobic conditions to produce acetyl-CoA

inhibited
inactivated
activate

by

A

Inhibited - high concentrations acetyl-CoA and NADH

Inactivated - phosphorylation

Activated - phosphate removal

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14
Q

What is the Kreb’s cycle also named as

A

Citric acid cycle
Tricarboxylic acid (TCA) cycle

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15
Q

Where does the kreb’s cycle occur

A

Mitochondrial matrix - aerobic conditions

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16
Q

Why does the krebs cycle occur

A

Generates LOTS of energy - ATP

Provides final common pathway for oxidation of carbohydrates, fat and protein via acetyl CoA

Produces intermediates for other metabolic pathways

17
Q

What is the overall reaction of the krebs cycle

A

Acetyl-CoA + 3NAD+ + FAD + GDP + Pi + 2H2O

=

2CO2 + 3NADH + FADH2 + GTP + 3H+ + CoA

18
Q

What is the general overview of the krebs cycle

A

Acetyl CoA condenses oxaloacetate and acetate

Oxaloacetate regenerated in the Krebs’ cycle

19
Q

What is the activator and inhibitor for citrate synthase

A

Activator - ADP

Inhibitor - ATP, NADH, citrate

20
Q

What is the activator and inhibitor for isocitrate dehydrogenase

A

Activator - ADP

Inhibitor - ATP, NADH

21
Q

What is the activator and inhibitor for a-ketoglutarate dehydrogenase

A

Activator - Ca2+

Inhibitor - ATP, NADH, Succinyl CoA, GTP

22
Q

Where does oxidative phosphorylation occur

A

In the inner mitochondrial membranes, aerobic conditions

23
Q

Why does oxidative phosphorylation occur

A

Releases the majority of energy during cellular respiration

Reduced NADH or FADH2 from glycolysis and krebs cycle are oxidised and their electrons passed to components of the electron transport chain (ETC). There is a series of carriers embedded in the inner mitochondrial membrane. The final electron acceptor is O2

Energy released is trapped to generate ATP

24
Q

What is the energy gain of the Kreb’s cycle

A

6 NADH
2 FADH
2 ATP

25
Q

Overview of oxidative phosphorylation

A

Components of ETC accept electrons (reduced) and pass them on (oxidised)

Electrons transfer to their final electron acceptor = oxygen

ATP produced a protons flux on through ATP synthase

26
Q

What is the equation of oxidative phosphorylation

A

NADH = NAD+ + H+ + 2e-

Free energy - drop as electrons are passed down the ETC

27
Q

What precursors for biosynthesis does glycolysis produce

A

G-6-P converted to robse-5-P and G-1-P for glycogen synthesis

Pyruvate
- transaminated to alanine
- Substrate for fatty acid synthesis

Glycerol-3-P is backbone of triglycerides

28
Q

What are the phases of glycolysis

A

Preparative phase
- Glucose to fructose 1,6-biphosphate
- Energy investment
- Uses 2x ATP

ATP generating phase
- 2 triose phosphates to 2 pyruvate
- Energy production phase
- 2 NADH and 4 ATP produced

Net production of ATP = 2

29
Q

Why is the pathways regulated

A

Produce the amount of energy needed - to increase or decrease the pathways where needed

30
Q

When is glycolysis activated

A

When energy levels in the cell is low

31
Q

What is ATP in glycolysis

A

Inhibitor of PFK-1

32
Q

What is AMP in glycolysis

A

Activator of PFK-1

When ATP is used up, ADP accumulates and is converted to AMP by adenylate kinase reaction to generate ATP

2ADP = ATP + AMP

33
Q

In glycolysis what does increasing levels of AMP do

A

Relieves inhibition of PFK-1 by ATP

34
Q

What is the role of citrate in regulation of glycolysis

A

First product of glycolysis

Acts allosterically inhibit PFK-1

Increase in citrate levels is a single that the cycle does not need more fuel

35
Q

What is the role of fructose-2,6-biposphate in regulation of glycolysis

A

Generated from frutose-6-phosphate

Most important allosteric activator of PFK-1

Mediates effects of insulin and glucagon

36
Q

What are the enzymes that regulate kreb’s cycle

A

Pyruvate dehydrogenase
Citrate synthase
Isocitrate dehydrogenase
a-ketoglutarate dehydrogenase

37
Q

Define metabolism

A

The sum of the physical and chemical processes by which living organized substance is built up and maintained (anabolism), and by which large molecules are broken down into smaller molecules to make energy available to the organism (catabolism).

IMMS (16 decks)

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