HUMANBIOLOGY_CHAPTERFOUR

energy

the ability to do work.

The first law of thermodynamics

how energy can be converted between different forms. Cannot be created or destroyed.

metabolism

the biochemical reactions of a cell.

metabolism: catabolic

breaking something down to release energy

metabolism: anabolic

building something up and require energy

chemical reactions: endergonic reactions

require energy, products contain more energy than reactants, building complex molecules from simpler ones.

chemical reactions: exergonic reactions

release energy, products contain less energy than reactants, breaking complex molecules into simpler ones.

atp (adenosine triphosphate)

a molecule whose high-energy phosphate bonds power many biological processes.

enzyme

an organic molecule that catalyzes a chemical reaction without being consumed.

activation energy

energy required for a chemical reaction to begin.

negative feedback

regulatory mechanism in which a change in a condition triggers action that reverses the change.

passive transport

movement of a solute across a membrane without the direct expenditure of energy.

diffusion

the passive movement of molecules from an area of higher concentration to an area of lower concentration.

active transport

movement of a substance across a membrane against its concentration gradient, using a carrier protein and energy from ATP.

active transport: movement

move from an area of low concentration to high concentration

concentration gradient

difference in solute concentrations between two adjacent regions

endocytosis

form of transport in which a membrane engulfs substances to bring them into a cell.

endocytosis: pinocytosis

small particles

endocytosis: phagocytosis

large particles

receptor-mediated endocytosis

a specialized form of pinocytosis that uses a receptor protein to recognize compatible molecules and take them into the cell.