BIOLOGY Triple Science Revision: Key Terms (Higher)

Vocabulary flashcards covering key terms from cell biology to ecology, based on the revision notes.

cell membrane

A phospholipid bilayer surrounding the cell that controls which substances enter and leave.

nucleus

Membrane-bound organelle containing the cell’s DNA and the control centre of the cell.

cytoplasm

Jelly-like internal component where many metabolic reactions occur.

mitochondria

Organelles where most of the cell’s respiration happens; produces ATP.

chloroplast

Plant cell organelle containing chlorophyll where photosynthesis occurs.

ribosome

Small organelle where protein synthesis takes place.

prokaryotic cell

A cell without a nucleus, e.g., bacteria; DNA floats in cytoplasm.

eukaryotic cell

A cell with a nucleus and membrane-bound organelles (plant/animal cells).

diffusion

Movement of particles from a region of high concentration to low concentration.

osmosis

Diffusion of water across a partially permeable membrane from high to low water potential.

active transport

Movement of substances against a concentration gradient using energy.

specialised cell

A cell that has developed to perform a specific function (e.g., nerve, muscle, root hair).

stem cell

An undifferentiated cell that can become other cell types; embryonic vs adult.

meristem

Plant tissue containing stem cells that can produce clones of the plant.

xylem

Dead, hollow plant vessels that transport water and minerals upward.

phloem

Living plant tissue that transports sugars (glucose) around the plant.

guard cell

Cells that control the opening of stomata for gas exchange and water loss.

stomata

Pores in the leaf surface that allow gas exchange and water loss.

transpiration

Loss of water from a plant through evaporation from surfaces, mainly leaves.

translocation

Movement of sugars through phloem in all directions.

alveoli

Air sacs in the lungs where gas exchange occurs (oxygen uptake, CO2 release).

villi

Finger-like projections in the small intestine that increase surface area for absorption.

gas exchange

Process of obtaining oxygen and removing carbon dioxide between air and blood.

antigen

Molecule that triggers an immune response; recognised by antibodies.

antibody

Protein produced by B cells that binds to an antigen.

phagocytosis

White blood cells engulf and digest pathogens.

monoclonal antibodies

Identical antibodies produced from one B cell clone for specific targeting.

vaccine

A preparation that stimulates the immune system to produce antibodies against a pathogen.

placebo

Inactive substance used in clinical trials for comparison.

blind trial

Trial in which participants do not know whether they receive the drug or placebo.

double‑blind trial

Neither participants nor researchers know who receives the drug or placebo.

rejection

Immune response against a transplanted organ because it is foreign.

tissue typing

Matching donor and recipient tissue antigens to reduce transplant rejection.

immunosuppressant

Drugs that reduce the immune response after organ transplantation.

photosynthesis

Process by which green plants convert CO2 and water into glucose and oxygen using light.

chlorophyll

Green pigment in plants that absorbs light for photosynthesis.

endothermic

A reaction that absorbs heat from the surroundings.

limiting factor (photosynthesis)

Factor that limits the rate of photosynthesis (light, CO2, temperature).

light intensity

Amount of light available; affects the rate of photosynthesis.

carbon dioxide (CO2)

Gas used in photosynthesis; level can limit photosynthesis rate.

temperature (photosynthesis)

Ambient temperature; too high/low can limit enzyme activity.

respiration

Chemical process that releases energy from glucose; can be aerobic or anaerobic.

aerobic respiration

Respiration with oxygen producing CO2 and water and ATP.

anaerobic respiration

Respiration without oxygen; yields less energy (lactic acid or ethanol and CO2).

lactic acid

Product of anaerobic respiration in muscles; causes fatigue.

cardiac output

Volume of blood pumped by the heart per minute (heart rate × stroke volume).

stroke volume

Volume of blood pumped by the heart per heartbeat.

pulse/heart rate

Beats per minute of the heart.

haemoglobin

Protein in red blood cells that carries oxygen.

oxyhaemoglobin

Haemoglobin bound to oxygen.

erythrocyte

Red blood cell.

platelet

Small blood cell fragment essential for clotting.

plasma

Liquid component of blood carrying cells and dissolved substances.

artery

Blood vessel carrying blood away from the heart; usually oxygenated.

vein

Blood vessel carrying blood toward the heart; usually deoxygenated.

capillary

Smallest blood vessels where exchange with cells occurs; walls are thin.

SAN (sino‑atrial node)

Pacemaker region of the heart that initiates the heartbeat.

AVN (atrioventricular node)

Part of the heart that coordinates ventricular contractions.

enzymes

Biological catalysts that speed up reactions; highly specific.

substrate

Substrate that binds to the enzyme’s active site.

active site

Part of the enzyme where the substrate binds.

denature

Loss of enzyme shape and function due to extreme conditions.

glucose

Simple sugar; main energy source for cells.

glycogen

Stored form of glucose in liver and muscle.

diabetes (Type 1)

Pancreas does not produce enough insulin; treated with injections.

diabetes (Type 2)

Cells become less responsive to insulin; managed by lifestyle changes.

insulin

Hormone that lowers blood glucose by promoting uptake into cells.

glucagon

Hormone that raises blood glucose by stimulating glycogen breakdown.

osmoregulation

Control of water and salt balance in the body.

ADH (antidiuretic hormone)

Hormone that regulates water balance by reducing urine production.

kidney

Organ that filters blood and forms urine; maintains water and ion balance.

nephron

Functional unit of the kidney that filters blood and forms urine.

dialysis

Treatment that filters wastes from the blood when kidneys fail.

kidney transplant

Replacement of a diseased kidney with a donor kidney.

urine

Waste liquid excreted by the kidneys.

root hair cell

Plant cell with large surface area to absorb water and minerals.

xylem vessels

Dead, lignified tubes that transport water upward in plants.

phloem vessels

Living tubes that transport sugars in plants.

guard cells

Specialised cells that control stomatal opening and closing.

stomata

Pores in leaves for gas exchange and water loss control.

translocation (plants)

Transport of sugars through phloem to where needed.

plant hormones (auxins)

Hormones that regulate growth such as phototropism and gravitropism.

auxins

Plant hormones controlling growth and responses to light and gravity.

gibberellin

Plant hormone that promotes germination and flowering.

ethylene (gas)

Plant hormone involved in ageing and fruit ripening.

phototropism

Growth response of a plant toward light due to auxin distribution.

gravitropism/geotropism

Growth response to gravity in shoots and roots.

pollen

Male gamete in plants; involved in fertilisation.

genome

The entire genetic material of an organism.

gene

A small section of DNA that codes for a specific protein.

allele

Alternative form of a gene.

dominant

Allele that is expressed when present (even if only one copy).

recessive

Allele expressed only when two copies are present.

genotype

Genetic makeup of an organism (the alleles it has).

phenotype

Physical appearance or characteristics resulting from the genotype.

mutations

Changes in DNA that can introduce new variations.

natural selection

Process where advantageous traits become more common over generations.

speciation

Formation of new species when populations can no longer interbreed.

fertilisation

Fusion of male and female gametes to form a zygote.

selective breeding

Humans choose parents with desirable traits to breed.