**MCAT need to knows**

Glycolysis goal

Take 1 Glucose + 2 ATP ---> 2 Pyruvic Acid

What inhibits Glycolysis?

ATP

Does glycolysis require oxygen?

No, it is anaerobic

Where does glycolysis occur?

cytoplasm

list the glycolysis enzymes

"Honey, I'm Pretty Accurately Gonna Punch My Eager PI"

HPi PxAT G3PPK PmEP

Hexokinase
Phosphoglucose Isomerase
Phosphofructose Kinase
Aldolase
Triose phosphate Isomerase
Glyceraldehyde 3 Phosphate Dehydrogenase
Phosphoglycerate Kinase
Phosphoglycerate Mutase
Enolase
Pyruvate Kinase

Hexokinase

Glucose + ATP -> Glucose 6 Phosphate + ADP

(one way reaction)

Phosphoglucose Isomerase

Glucose 6 Phosphate -> Fructose 6 Phosphate

(reversible)

Phosphofructose Kinase

rate limiting step!!

one way reaction

Fructose 6 Phosphate + ATP -> Fructose 1 6 Bisphosphate + ADP

Aldolase

Fructose 1 6 Bisphosphate -> Dihydroxyacetone Phosphate (DHAP) + Glyceraldehyde 3 Phosphate

(reversible)

Triose Phosphate Isomerase

Dihydroxyacetone (DHAP) -> Glucose 3 Phosphate

(reversible)

Glyceraldehyde 3 Phosphate dehydrogenase

Glucose 3 phosphate dehydrogenase + NAD+ + Pi -> 1 3 bisphosphoglycerate (13 BPG)

Phosphoglycerate kinase

13 BPG + ADP + H+ -> 3 phosphoglycerate

substrate level phosphorylation

Phosphoglycerate mutase

3 phosphoglycerate -> 2 phosphoglycerate

Enolase

2 phosphoglycerate -> phosphoenol pyruvate (PEP) + H2O

pyruvate kinase

phosphoenolpyruvate (PEP) + ADP + H+ -> pyruvate + ATP

aerobic decarboxylation

converts pyruvate (3 C) -> acetyl CoA

aerobic decarboxylation location

mitochondrial matrix

pyruvate dehydrogenase

pyruvate + NAD+ + coenzyme A -> Acetyl CoA + NADH + CO2

purpose of fermentation

to regenerate NAD+ to be used in glycolysis

fermentation

Process by which cells release energy in the absence of O2

fermentation process

pyruvate + NADH -> lactase dehydrogenase -> lactate + NAD+

pyruvate is reduced to produce lactate

Gluconeogenesis

formation of glucose from noncarbohydrate sources

What are the "new enzymes" in gluconeogenesis?

- pyruvate carboxylase
- PEP carboxykinase
- fructose 1 6 bisphosphatase
- glucose 6 phosphatase

Gluconeogesis steps

1. pyruvate -> pyruvate carboxylase -> oxaloacetate

2. oxaloacetate -> PEP carboxykinase -> PEP

3. PEP -> enolase -> 2 phosphoglycerate

3. 2 phosphoglycerate -> mutase -> 3 phosphoenolglycerate

4. 3 phosphoenolglycerate -> kinase -> 13BPG

5. 13BPG -> G3P dehydrogenase -> G3P

6. G3P -> Triose Phosphate Isomerase -> DHAP

7. DHAP + G3P -> aldolase -> F16BP

F16BP -> fructose 1 6 bisphosphate -> F6P

F6P -> Phosphoglucose Isomerase -> G6P

G6P -> Glucose 6 Phosphatase -> Glucose

Pentose Phosphate Pathway

A metabolic process that produces NADPH and ribose 5-phosphate for nucleotide synthesis.

When does the pentose phosphate pathway occur?

when the cell is dividing

What step does pentose phosphate intervene in glycolysis?

glucose -> hexokinase -> G6P -> glucose 6 phosphatase dehydrogenase

pentose phosphate pathway location

cytosol

Pentose Phosphate Enzyme

Glucose 6 phosphate dehydrogenase

Purpose of Pentose Phosphate Pathway

forms ribose 5 phosphate (for sugar to make DNA & RNA)
forms NADPH to help build other molecules

Pentose Phosphate Pathway Steps

1. Glucose 6 Phosphate + NAD+ -> Glucose 6 Phosphate dehydrogenase -> 6 phosphogluconate + NADH
2. 6 phosphogluconate + NAD+ -> ribulose 5 phosphate +NADPH
3. ribulose 5 phosphate -> ribose 5 phosphate
4. ribose 5 phosphate -> nucleotides, coenzymes, DNA, RNA

How many ATP does glycolysis produce?

2 ATP per glucose molecule
2 NADH

How many ATP produced in pyruvate oxidation?

2 NADH

How many ATP produced in TCA?

2 ATP
6 NADH
2 FADPH2

What hormones are used to regulate blood glucose levels?

insulin: decreasing glucose levels by promoting glycolysis
glucagon: increasing glucose levels by promoting gluconeogensis

if blood glucose level rises

stimulate insulin (which promotes glycolysis)

if blood glucose decreases

stimulate glucagon (which promotes gluconeogenesis)

glycogenolysis

breakdown of glycogen into glucose

glycogenolysis rate limiting step

glycogen phosphorylase

glycogen phoshorylase

glucose 1 phosphate -> glucose 6 phosphate

found in gluconeolysis (converts glycogen -> glucose)

glycogenesis

synthesis of glycogen granules

glycogenesis rate limiting step

glycogen synthase

glycogen synthase

forms alpha 1 4 glycosidic bond in the granule

stimulated by glucose 6 phosphate and insulin.
inhibited by epinephrine and glucagon

oxidative phosphorylation is driven by

proton gradient

H+ high in the intermembrane space than the matrix

TCA cycle

a series of metabolic reactions that break down molecules of acetyl CoA to carbon dioxide and hydrogen atoms

rate limiting step of TCA

isocitrate dehydrogenase

TCA location

mitochondrial matrix

Citrate

acetyl coa -> isocitrate

isocitrate dehydrogenase

isocitrate -> alpha ketoglutarate

alpha ketoglutarate dehydrogenase

alpha ketoglutrate -> succinyl CoA

succinyl CoA synthetase

succinyl CoA -> succinate

succinate dehydrogenase

succinate -> fumarate

fumarase

fumarate -> malate

malate dehydrogenase

malate -> oxaloacetate