ch13 full review bc

Glucose central molecule in metabolism

Glucose = central metabolite and primary energy source for most cells.

Plants store glucose as

Starch (amylose and amylopectin).

Animals store glucose as

Glycogen, mainly in liver and skeletal muscle.

The main energy-carrying molecules produced in metabolism are

ATP and NADH.

Each metabolic step is catalyzed by

A specific enzyme.

Regulation of metabolism primarily occurs by

Controlling enzyme activity, often through allosteric regulation.

Glycolysis converts

1 Glucose → 2 Pyruvate.

Net yield of ATP per glucose molecule in glycolysis is

2 ATP.

Glycolysis occurs in the

Cytoplasm (cytosol).

The first five reactions of glycolysis are known as the

Energy investment phase.

The second half of glycolysis is the

Energy payoff phase.

The enzyme that catalyzes the first step of glycolysis is

Hexokinase.

The reaction catalyzed by hexokinase uses which energy source

ATP.

The product of the hexokinase reaction is

Glucose-6-phosphate (G6P).

The phosphoglucose isomerase reaction converts b

Glucose-6-phosphate → Fructose-6-phosphate (F6P). b

The key regulatory enzyme of glycolysis is

Phosphofructokinase-1 (PFK-1).

PFK-1 is activated by

ADP and Fructose-2,6-bisphosphate.

PFK-1 is inhibited by

Phosphoenolpyruvate (PEP) and Citrate.

The aldolase reaction splits fructose-1,6-bisphosphate into

Glyceraldehyde-3-phosphate (G3P) and Dihydroxyacetone phosphate (DHAP).

The triose phosphate isomerase reaction interconverts

DHAP ↔ G3P.

The byproduct methylglyoxal, formed from enediol intermediate, is

Toxic byproduct formed nonenzymatically from triose phosphates.

GAPDH uses which cofactor

NAD⁺ (reduced to NADH).

The GAPDH reaction is inhibited by

Arsenate (AsO₄³⁻).

The enolase enzyme is inhibited by

Fluoride (F⁻) and inorganic phosphate (Pi).

The product of the enolase reaction is

Phosphoenolpyruvate (PEP).

The pyruvate kinase reaction produces

Pyruvate and ATP.

3 irreversible steps in glycolysis catalyzed by

Hexokinase, Phosphofructokinase-1 (PFK-1), Pyruvate kinase.

Pyruvate kinase is activated by

Fructose-1,6-bisphosphate (feed-forward activation).

The net yield of glycolysis per glucose is

2 ATP, 2 NADH, and 2 Pyruvate.

Under anaerobic conditions in muscle, pyruvate is converted to

Lactate.

In yeast, pyruvate is converted to

Ethanol.

Glycolysis and gluconeogenesis are coordinated to prevent

Futile cycling and ATP waste.

The fate of pyruvate depends on

Oxygen availability, cell type, and energy needs.

Lactate dehydrogenase is required to

oxidize nadh to nad+

In yeast, pyruvate is converted to ethanol through

(1) Pyruvate → Acetaldehyde (pyruvate decarboxylase); (2) Acetaldehyde → Ethanol (alcohol dehydrogenase).

Coenzyme A is essential for pyruvate decarboxylation because it

Carries and activates the acetyl group.

Pyruvate carboxylase requires which cofactor

Biotin (Vitamin B₇).

Gluconeogenesis is activated when

Glycogen stores are depleted.

The conversion of pyruvate to PEP requires

Pyruvate carboxylase and PEP carboxykinase (PEPCK); consumes ATP and GTP.

Which molecules can serve as gluconeogenic precursors

Pyruvate, lactate, glycerol, and glucogenic amino acids (all except leucine and lysine).

Fatty acids are generally

Not gluconeogenic (cannot form oxaloacetate).

Glycogen synthesis begins with 9

Glucose-6-phosphate, converted to Glucose-1-phosphate. 9

UDP-glucose is formed from

Glucose-1-phosphate + UTP.

The enzyme forming UDP-glucose is

UDP-glucose pyrophosphorylase.

Glycogen synthase forms which type of linkage

α(1→4) glycosidic linkages.

Glycogen phosphorylase catalyzes

Glycogen breakdown (phosphorolysis).

The product of glycogenolysis is

Glucose-1-phosphate.

In the liver, glucose-6-phosphatase converts G6P into

Free glucose.

Glycogen metabolism is regulated by

Hormones (insulin, glucagon, epinephrine).

The PPP uses which substrate

Glucose-6-phosphate (G6P).

The PPP primarily produces

Ribose-5-phosphate and NADPH.

The oxidative phase of the PPP produces

2 NADPH and CO₂.

The key enzyme in the oxidative phase is

Glucose-6-phosphate dehydrogenase (G6PD).

The two major enzymes of the non-oxidative phase are

Transketolase and Transaldolase.

The PPP does not produce o

ATP. o

The PPP is activated when

NADP⁺ levels are high (when NADPH is low).

The PPP is inhibited by

NADPH (feedback inhibition).

Pyruvate links glycolysis with

TCA cycle, gluconeogenesis, fatty acid synthesis, and amino acid synthesis.

Simultaneous glycolysis and gluconeogenesis would

Waste ATP and cause a net energy loss.

The liver supplies glucose to other tissues via

Glucose-6-phosphatase hydrolyzing G6P → free glucose for release into blood.

The PPP supports biosynthesis of

fatty acids and nucleotides

Red blood cells rely on glycolysis because they

Lack mitochondria and depend solely on glycolysis for ATP.

Hexokinase deficiency causes

Reduced glycolysis and less 2,3-BPG, decreasing oxygen delivery to tissues.

Fructose intolerance is due to a deficiency in

Fructose-1-phosphate aldolase, causing phosphate trapping and ATP depletion