Topic 1 The nature and variety of organisms

Movement

Organisms moving towards or away from stimuli.

Respiration

The release of energy from food sources.

Sensitivity

The ability of organisms to react to changes in their environment.

Growth

Increase in size, which includes growth of cells and tissues and aging.

Reproduction

The process of producing offspring.

Excretion

The removal of waste products, such as carbon dioxide and urine.

Nutrition

The intake of substances needed to provide energy and materials for growth.

Organelle

A specialized subunit within a cell that has a specific function.

Nucleus

The organelle that contains genetic material.

Cell membrane

The barrier that controls what enters and exits the cell.

Cytoplasm

The fluid inside cells where chemical reactions occur.

Mitochondria

Organelles responsible for aerobic respiration and energy production.

Ribosomes

Cell structures where proteins are synthesized.

Chloroplast

Organelles in plant cells that contain chlorophyll and carry out photosynthesis.

Cell wall

The rigid structure that supports plant cells.

Vacuole

Organelles that contain cell sap and provide support to plant cells.

Specialized cells

Cells that perform specific functions in the body.

Embryonic stem cells

Undifferentiated cells that can develop into any type of cell.

Cell differentiation

The process by which a cell becomes specialized for a specific function.

Stem cells

Cells that can differentiate into specialized cells and divide to produce more undifferentiated cells.

Eukaryotic cell

A type of cell with a nucleus and organelles, including plant and animal cells.

Prokaryotic cell

A type of cell without a nucleus, such as bacteria.

Catalyst

A substance that increases the speed of a reaction without being used up.

Enzyme

A protein that acts as a biological catalyst.

Active site

The region of an enzyme where substrate molecules bind.

Diffusion

The net movement of particles from an area of high concentration to an area of low concentration.

Osmosis

The movement of water molecules across a selectively permeable membrane.

Active transport

Movement of particles against a concentration gradient using energy.

Factors affecting diffusion

Surface area, distance, temperature, and concentration gradient.