Chapter 3-8a Review: Energy Transfer and Carbohydrate Metabolism

Flashcards covering key vocabulary related to energy transfer, carbohydrate digestion, absorption, and metabolism from Chapter 3-8a of the lecture notes.

ATP

The main distributor of energy for metabolic reactions in the body, generated from nutrient molecules.

Major Sources of Dietary Carbohydrate

Starches and disaccharides (sugars) that are hydrolyzed into monosaccharides during digestion.

Glycosidases

Specific enzymes that hydrolyze dietary starches and disaccharides into their component monosaccharides.

Monosaccharides

The primary component sugars (glucose, fructose, and galactose) absorbed into intestine cells.

GLUT Proteins

A family of glucose transporters that mediate the facilitated transport of glucose from the blood across cell membranes into various tissues.

GLUT4

A specific glucose transporter stimulated by insulin, responsible for transporting glucose into muscle and adipose tissue.

Insulin's Role (GLUT4)

Translocates preformed GLUT4 from intracellular vesicles to the cell membrane, increasing glucose uptake.

Substrate-Level Phosphorylation

A process of ATP generation involving the direct transfer of a phosphate group from compounds with very-high-energy phosphate transfer potential to ADP.

Oxidative Phosphorylation

The major route for ATP production, involving the passage of high-energy electrons through the electron transport chain to create an energy gradient for phosphorylating ADP to ATP.

Electron Transport Chain (ETC)

A series of protein complexes in mitochondria where high-energy electrons derived from food molecules flow, ultimately transferring energy to form ATP and producing H₂O from molecular oxygen.

Pentose Phosphate Pathway

A metabolic pathway that generates important intermediates like pentose phosphates (for RNA/DNA synthesis) and NADPH (an electron donor in fatty acid synthesis).

Glucose-6-phosphatase

An enzyme active in the liver that allows it to release free glucose from its glycogen stores into the circulation, a function absent in muscle.

Cori Cycle

Describes the liver's uptake and gluconeogenic conversion of muscle-produced lactate back to glucose.

Gluconeogenesis

Pathways that convert noncarbohydrate substances (like lactate, glycerol, and certain amino acids) into glucose or glycogen, particularly when dietary carbohydrate is low.

Glycerol (from Triacylglycerols)

Enters the glycolytic pathway at dihydroxyacetone phosphate, from which it can be oxidized for energy or used to synthesize glucose or glycogen.

Fatty Acids (from Triacylglycerols)

Enter the TCA cycle as acetyl-CoA, are oxidized to CO₂ and H₂O, but cannot contribute carbon for the net synthesis of glucose.

Hexokinase

An enzyme found in muscle, brain, and adipose tissue that phosphorylates glucose upon entering the cell, using ATP.

Glucokinase

An isoenzyme of hexokinase specific to the liver, responsible for phosphorylating glucose in the liver.

Fructokinase

An enzyme primarily in the liver that phosphorylates fructose.

Galactokinase

An enzyme primarily in the liver that phosphorylates galactose.

Glycolysis

A metabolic pathway that converts glucose from blood or glycogen stores into pyruvate, producing ATP and reduced coenzymes.

Anaerobic Conditions (Pyruvate)

Under these conditions, pyruvate is converted to lactate.

Aerobic Conditions (Pyruvate)

Under these conditions, pyruvate is completely oxidized in the TCA cycle, releasing CO₂ and energy in the form of electrons.