learning concepts

Phospholipid

A molecule that makes up the cell membrane, consisting of a hydrophilic head and hydrophobic tails.

Hydrophilic

Water-loving; refers to the part of the phospholipid that interacts with water.

Hydrophobic

Water-fearing; refers to the part of the phospholipid that repels water.

Osmosis

Movement of water across a semipermeable membrane.

Passive transport

Movement of molecules across a membrane without the use of energy.

Hypertonic

A solution with a higher concentration of solutes outside the cell, causing it to lose water.

Hypotonic

A solution with a lower concentration of solutes outside the cell, causing it to gain water.

Endocytosis

Process by which a cell takes in materials through vesicles.

Exocytosis

Process by which a cell expels materials through vesicles.

Enzyme

A biological catalyst that speeds up reactions without being consumed.

Activation energy

The minimum energy needed for a chemical reaction to occur.

Substrate-level phosphorylation

Direct transfer of a phosphate group to ADP from a phosphorylated intermediate.

Glycolysis

The process of breaking down glucose to extract energy, producing pyruvate, ATP, and NADH.

Krebs Cycle

A series of reactions in the mitochondrial matrix that fully oxidizes acetyl-CoA and produces NADH, FADH₂, ATP, and CO₂.

Electron Transport Chain (ETC)

A series of proteins embedded in the inner mitochondrial membrane that create a proton gradient to produce ATP.

Chemiosmosis

The movement of H⁺ ions across a membrane, driving the production of ATP.

Fermentation

Anaerobic process that occurs without oxygen, producing ATP, lactic acid, or ethanol.

NAD⁺

An electron carrier that accepts electrons to become NADH.

Concentration gradient

The difference in concentration of a substance across a space, driving molecular movement.

Competitive inhibition

A type of enzyme inhibition where an inhibitor binds to the active site, blocking substrate access.

Negative ΔG

Indicates a spontaneous reaction that releases energy.

Positive ΔG

Indicates a nonspontaneous reaction that requires energy input.