Important Cycles Flashcards by Amber Dabill

Where does Glycolysis occur

Cytosol under anaerobic conditions

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Why does glycolysis occur

Emergency energy producing pathway when oxygen is limiting

Generates precursors for biosynthesis

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What is produced overall as a result of glycolysis

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

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What is the order of molecules in glycolysis

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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Glycolysis Summary

Glucose + 2NAD+ + Pi + 2ADP

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

-22kcal = not readily reversible

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What are the 3 enzyme regulators of glycolysis

Hexokinase
Phosphofructokinase-1
Pyruvate kinase

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What are the regulations of glycolysis

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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What is the activator and inhibitor for phosphofuctokinase-1

Activator AMP

Inhibitor ATP, citrate, F2,6 BP

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What happens to pyruvate in anaerobic conditions

Lactate formation catalysed by lactate dehydrogenase

Regeneration on NAD+

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What happens to pyruvate in aerobic conditions

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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What is the equation for lactate in anaerobic conditions

Glucose + 2ADP + 2Pi

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

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What is the reaction of pyruvate in aerobic conditions

Irreversible reaction

pyruvate + CoA + NAD+

acetyl-CoA + CO2 + NADH + H+

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

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What is the aerobic conditions to produce acetyl-CoA

inhibited
inactivated
activate

Inhibited - high concentrations acetyl-CoA and NADH

Inactivated - phosphorylation

Activated - phosphate removal

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What is the Kreb’s cycle also named as

Citric acid cycle
Tricarboxylic acid (TCA) cycle

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Where does the kreb’s cycle occur

Mitochondrial matrix - aerobic conditions

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Why does the krebs cycle occur

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

What is the overall reaction of the krebs cycle

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

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

What is the general overview of the krebs cycle

Acetyl CoA condenses oxaloacetate and acetate

Oxaloacetate regenerated in the Krebs’ cycle

What is the activator and inhibitor for citrate synthase

Activator - ADP

Inhibitor - ATP, NADH, citrate

What is the activator and inhibitor for isocitrate dehydrogenase

Activator - ADP

Inhibitor - ATP, NADH

What is the activator and inhibitor for a-ketoglutarate dehydrogenase

Activator - Ca2+

Inhibitor - ATP, NADH, Succinyl CoA, GTP

Where does oxidative phosphorylation occur

In the inner mitochondrial membranes, aerobic conditions

Why does oxidative phosphorylation occur

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

What is the energy gain of the Kreb’s cycle

6 NADH
2 FADH
2 ATP

Overview of oxidative phosphorylation

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

What is the equation of oxidative phosphorylation

NADH = NAD+ + H+ + 2e- Free energy - drop as electrons are passed down the ETC

What precursors for biosynthesis does glycolysis produce

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

What are the phases of glycolysis

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

Why is the pathways regulated

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

When is glycolysis activated

When energy levels in the cell is low

What is ATP in glycolysis

Inhibitor of PFK-1

What is AMP in glycolysis

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

In glycolysis what does increasing levels of AMP do

Relieves inhibition of PFK-1 by ATP

What is the role of citrate in regulation of glycolysis

First product of glycolysis Acts allosterically inhibit PFK-1 Increase in citrate levels is a single that the cycle does not need more fuel

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

Generated from frutose-6-phosphate Most important allosteric activator of PFK-1 Mediates effects of insulin and glucagon

What are the enzymes that regulate kreb's cycle

Pyruvate dehydrogenase Citrate synthase Isocitrate dehydrogenase a-ketoglutarate dehydrogenase

Define metabolism

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).