Important Cycles Flashcards
Where does Glycolysis occur
Cytosol under anaerobic conditions
Why does glycolysis occur
Emergency energy producing pathway when oxygen is limiting
Generates precursors for biosynthesis
What is produced overall as a result of glycolysis
2 x pyruvate (C3H4O3)
2 x NADH + H+
2x ATP (two used in previous steps)
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
Glycolysis Summary
Glucose + 2NAD+ + Pi + 2ADP
=
2 pyruvate + 2NADH + 2H+ + 2ATP + 2H2O
-22kcal = not readily reversible
What are the 3 enzyme regulators of glycolysis
Hexokinase
Phosphofructokinase-1
Pyruvate kinase
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
What is the activator and inhibitor for phosphofuctokinase-1
Activator AMP
Inhibitor ATP, citrate, F2,6 BP
What happens to pyruvate in anaerobic conditions
Lactate formation catalysed by lactate dehydrogenase
Regeneration on NAD+
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
What is the equation for lactate in anaerobic conditions
Glucose + 2ADP + 2Pi
=
2 lactate + 2 ATP + 2H2O + 2H+
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)
What is the aerobic conditions to produce acetyl-CoA
inhibited
inactivated
activate
by
Inhibited - high concentrations acetyl-CoA and NADH
Inactivated - phosphorylation
Activated - phosphate removal
What is the Kreb’s cycle also named as
Citric acid cycle
Tricarboxylic acid (TCA) cycle
Where does the kreb’s cycle occur
Mitochondrial matrix - aerobic conditions
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).
