Carbohydrate Metabolism Overview

Carbohydrate Metabolism

Biochemical process of breaking down carbohydrates.

Carbohydrate Digestion

Di- and polysaccharides hydrolyzed to monosaccharides.

Blood Glucose Level

Amount of glucose in blood, mg/100 mL.

Hypoglycemia

Lower-than-normal blood sugar level.

Hyperglycemia

Higher-than-normal blood sugar level.

Renal Threshold

Blood sugar level where kidneys can't reabsorb glucose.

Glucosuria

Excretion of glucose in urine due to high blood sugar.

Glycolysis

Glucose catabolized to pyruvate in cytoplasm.

Net Glycolysis Reaction

Glucose + 2ADP + 2NAD+ → 2Pyruvate + 2ATP.

Fates of Pyruvate

Oxidized to acetyl CoA, reduced to lactate or ethanol.

Citric Acid Cycle

Acetyl CoA oxidized to CO2, producing NADH and FADH2.

Regulation of Glycolysis

Controlled by hexokinase, phosphofructokinase, pyruvate kinase.

Feedback Inhibition

Glucose-6-phosphate inhibits hexokinase noncompetitively.

ATP Production from NADH

1 NADH generates 2.5 ATP during oxidative phosphorylation.

ATP Production from FADH2

1 FADH2 generates 1.5 ATP during oxidative phosphorylation.

Oxidative Phosphorylation

ADP converted to ATP via electron transport chain.

Chemiosmotic Hypothesis

Proton gradient drives ATP synthesis in mitochondria.

Glycogenesis

Process of converting glucose to glycogen.

Glycogenolysis

Process of breaking down glycogen to glucose.

Gluconeogenesis

Synthesis of glucose from non-carbohydrate sources.

Cori Cycle

Lactate converted back to glucose in liver.

Aerobic Conditions

Metabolism occurs in the presence of oxygen.

Anaerobic Conditions

Metabolism occurs in the absence of oxygen.

Lactate Fermentation

Conversion of glucose to lactate under anaerobic conditions.

Alcoholic Fermentation

Conversion of glucose to ethanol by microorganisms.

NAD+ Regeneration

Essential for glycolysis to continue after pyruvate processing.

Acetyl CoA

Key molecule entering the citric acid cycle.

GTP Production

One GTP produced per cycle in citric acid cycle.

Electron Transport Chain

Electrons reduce oxygen to water, generating ATP.

Cytochromes

Iron-containing enzymes in the electron transport chain.

Oxidation of Pyruvate

Produces acetyl CoA and CO2 in mitochondria.

Energy Yield from Glucose

Complete oxidation yields approximately 32 ATP.

ATP Yield from Glycolysis

Produces 2 ATP and 2 NADH per glucose.

ATP Yield from Citric Acid Cycle

Generates 2 GTP, 6 NADH, and 2 FADH2.

Complete Oxidation of Glucose

Process yielding 686 kcal/mol from glucose.

ATP Synthesis Energy

Energy produced during ATP synthesis is 234 kcal/mol.

Overall Reaction of Glucose

C6H12O6 + 6O2 + 32ADP + 32Pi → 6CO2 + 32ATP + 38H2O.

Energy Capture Efficiency

Living cells capture 34% of released free energy.

Automobile Engine Efficiency

Engines capture 20-30% of energy from gasoline.

Glycogenesis

Synthesis of glycogen from glucose molecules.

Energy Source for Glycogenesis

Hydrolysis of UTP provides energy for glycogenesis.

Glycogen Storage in Liver

Liver can store 110 g of glycogen.

Glycogen Storage in Muscles

Muscles can store 245 g of glycogen.

Glycogen Synthase

Enzyme forming linkages in glycogen synthesis.

Amylo (1,4-1,6)-trans-glycosylase

Enzyme inserting branch points in glycogen.

Glycogenolysis

Breakdown of glycogen to release glucose.

Glycogen Phosphorylase

Enzyme catalyzing cleavage of glycogen linkages.

Glucose-1-Phosphate

Product of glycogen cleavage by phosphorylase.

Debranching Enzyme

Enzyme hydrolyzing branch linkages in glycogen.

Glucose-6-Phosphate Hydrolysis

Conversion of glucose-6-phosphate to glucose.

Muscle Cell Glycogenolysis

Muscles produce glucose-6-phosphate, not free glucose.

Liver Function in Glycogenolysis

Liver releases glucose to maintain blood glucose levels.

Gluconeogenesis

Synthesis of glucose from noncarbohydrate sources.

Cori Cycle

Process converting lactate to glucose between muscle and liver.

Insulin Function

Hormone enhancing glucose absorption and glycogen synthesis.

Glucagon Function

Hormone increasing blood glucose and glycogen breakdown.