Frequently Used Biology Keywords

Movement of Substances

• Diffusion – The net movement of particles from a high to low concentration.

• Osmosis – The diffusion of water molecules from a high water potential to a low water potential, across a partially permeable membrane.

• Active Transport – The movement of particles from low to high concentration, using energy (ATP) from respiration

Enzymes & Reactions

• Enzyme – A biological catalyst that speeds up reactions without being used up.

• Denature – When high temperature or incorrect pH changes the active site of an enzyme, so the substrate no longer fits.

• Substrate – The molecule that fits into an enzyme’s active site.

Respiration & Photosynthesis

• Aerobic Respiration – Uses oxygen, releases more energy than anaerobic respiration.

  • Equation: glucose + oxygen → carbon dioxide + water + energy (ATP)

• Anaerobic Respiration – No oxygen used, produces less energy and lactic acid (in animals).

  • In plants/yeast: glucose → ethanol + carbon dioxide + energy

• Photosynthesis – Plants use light energy to convert CO₂ + water into glucose + oxygen.

  • Equation: carbon dioxide + water → glucose + oxygen (with chlorophyll & light energy)

Circulatory System & Blood

• Arteries – Carry oxygenated blood away from the heart at high pressure. Thick walls.

• Veins – Carry deoxygenated blood toward the heart at low pressure. Valves present.

• Capillaries – Tiny blood vessels with one-cell-thick walls for rapid diffusion of oxygen & nutrients.

• Red Blood Cells – Contain haemoglobin (binds to oxygen), no nucleus, biconcave shape.

• White Blood Cells – Fight infections (phagocytes engulf bacteria, lymphocytes produce antibodies).

Genetics & Inheritance

• Gene – A section of DNA that codes for a specific protein.

• Allele – A different version of a gene.

• Dominant Allele – Always expressed in the phenotype (only need one copy).

• Recessive Allele – Only expressed if two copies are present.

• Homozygous – Two identical alleles (AA or aa).

• Heterozygous – Two different alleles (Aa).

• Mutation – A change in DNA sequence, can be harmful, beneficial, or neutral.

• Natural Selection – Survival of the fittest, beneficial mutations help organisms survive & reproduce.

Ecology & the Environment

• Producer – An organism that makes its own food (e.g., plants using photosynthesis).

• Consumer – An organism that eats other organisms.

• Decomposer – Breaks down dead material & recycles nutrients (e.g., bacteria, fungi).

• Biodiversity – The variety of species in an ecosystem.

• Carbon Cycle – Includes respiration, photosynthesis, combustion, and decomposition.

• Eutrophication – Excess nutrients in water → algae bloom → oxygen depletion → fish die.

Homeostasis & Hormones

• Homeostasis – The maintenance of a constant internal environment.

• Insulin – Lowers blood glucose by converting it into glycogen (stored in the liver).

• Glucagon – Raises blood glucose by breaking down glycogen into glucose.

• Adrenaline – Prepares the body for "fight or flight", increases heart rate & blood flow to muscles.

• Reflex Arc – Automatic response that bypasses the brain, includes receptor → sensory neuron → relay neuron → motor neuron → effector.

Microorganisms & Disease

• Pathogen – A microorganism that causes disease (bacteria, virus, fungi, protists).

• Antibody – A protein produced by lymphocytes that binds to specific antigens to destroy pathogens.

• Antigen – A foreign substance that triggers an immune response.

• Vaccination – Introduces a weakened/inactive form of a pathogen, so the body produces memory cells.

Food Tests (Common in Practical Questions!)

• Benedict’s Test (Sugar) – Blue → Brick red (glucose present).

• Iodine Test (Starch) – Brown → Blue-black.

• Biuret Test (Protein) – Blue → Purple.

• Emulsion Test (Fats/Lipids) – Clear → Cloudy white layer.