Comprehensive IGCSE Biology Revision

A set of vocabulary flashcards covering the key terms, definitions, organelle functions, and physiological processes from the lecture notes.

Movement

The ability of an organism to change position or place.

Respiration

The chemical process that releases energy from glucose.

Sensitivity

Detecting and responding to environmental changes.

Growth

A permanent increase in size and dry mass.

Reproduction

The process of producing offspring.

Excretion

Removal of waste products from metabolism.

Nutrition

Taking in and using nutrients.

Homeostasis

Maintaining a stable, constant internal environment.

Organelle

A specialised structure within a cell that performs a specific function.

Cell Membrane

A structure that controls the movement of substances into and out of the cell.

Mitochondria

The site of aerobic respiration, which releases ATP energy.

Ribosomes

The organelles responsible for protein synthesis.

Cell Wall

A rigid structure made of cellulose that supports and strengthens plant cells.

Chloroplasts

Organelles containing chlorophyll that carry out photosynthesis.

Vacuole

A permanent plant cell organelle that contains cell sap and maintains turgor pressure.

Cell Differentiation

The process by which a cell becomes specialised to perform particular functions efficiently.

Stem Cell

An unspecialised cell that can divide and differentiate into other cell types.

Enzyme

A protein that acts as a biological catalyst to speed up metabolic reactions without being used up.

Active Site

The region of an enzyme with a specific shape where the substrate binds.

Denature

A permanent change in the shape of an enzyme active site that prevents the substrate from fitting.

Diffusion

The net movement of particles from a region of high concentration to a region of low concentration down a concentration gradient.

Osmosis

The movement of water molecules through a partially permeable membrane from a dilute solution to a concentrated solution.

Active Transport

The movement of substances from low concentration to high concentration against a concentration gradient using energy in the form of ATP.

Turgid

The state of a plant cell being swollen and firm due to water uptake.

Plasmolysis

The process where the cell membrane pulls away from the cell wall due to severe water loss.

Peristalsis

Wave-like contractions of muscles that move food through the gut.

Bile

A non-enzymatic alkaline liquid produced by the liver and stored in the gall bladder that neutralises stomach acid and emulsifies fats.

Emulsification

Breaking large fat droplets into smaller droplets to increase their surface area for lipase action.

Villus

A finger-like projection lining the small intestine that provides a large surface area for absorbing digested food molecules.

Haemoglobin

A protein inside red blood cells that combines with oxygen to form oxyhaemoglobin.

Phagocytes

White blood cells that engulf and digest pathogens through phagocytosis.

Lymphocytes

White blood cells that produce specific antibodies matching antigens on pathogens.

Pathogen

A disease-causing microorganism.

Platelets

Cell fragments involved in blood clotting to prevent blood loss and stop microorganisms from entering.

Plasma

The liquid part of blood that transports carbon dioxide, nutrients, hormones, urea, and heat.

Vaccine

A preparation containing weakened or dead pathogens given to stimulate immunity and produce memory cells.

Coronary Heart Disease

The narrowing or blockage of the coronary arteries that supply oxygenated blood to the heart muscle.

Double Circulation

A circulatory system in which blood passes through the heart twice for each complete circuit of the body.

Aerobic Respiration

Respiration that uses oxygen to produce a large amount of ATP energy, represented by $\text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 + 6\text{H}_2\text{O}$.

Oxygen Debt

The extra oxygen needed to break down accumulated lactic acid after vigorous exercise.

Alveoli

Tiny air sacs in the lungs with thin walls and a rich blood supply where gas exchange takes place.

Ventilation

The movement of air into and out of the lungs involving inhalation and exhalation.

Saprotrophic Nutrition

A mode of nutrition seen in fungi where enzymes are secreted outside the body to digest food before the soluble products are absorbed.

Prokaryote

A single-celled organism whose cells lack a nucleus and membrane-bound organelles, such as bacteria.

Virus

A non-living, non-cellular particle made of genetic material surrounded by a protein coat that can only reproduce inside living cells.

Photosynthesis

The process by which plants make glucose and oxygen using light energy, carbon dioxide, and water, represented by $6\text{CO}_2 + 6\text{H}_2\text{O} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2$.

Stomata

Tiny pores in the epidermis of plant leaves that allow gas exchange and transpiration, controlled by guard cells.

Xylem

Dead, hollow plant vessels strengthened with lignin that transport water and dissolved mineral ions upwards from roots to leaves.

Phloem

Living plant tissue that transports sucrose and amino acids bidirectionally throughout the plant.

Transpiration

The evaporation and diffusion of water vapour from plant leaves, primarily through the stomata.

Potometer

A device used to measure water uptake in a leafy shoot, which estimates the rate of transpiration.

Stimulus

A detectable change in the internal or external environment of an organism.

Receptor

A specialised cell or sense organ that detects a specific stimulus.

Effector

A muscle or gland that carries out a response to a nervous or hormonal signal.

Vasodilation

The widening of blood vessels near the surface of the skin to increase heat loss when body temperature rises.

Vasoconstriction

The narrowing of blood vessels near the surface of the skin to reduce heat loss when body temperature falls.

Nephron

The functional microscopic unit of the kidney responsible for filtering blood and producing urine.

Ultrafiltration

The non-selective filtration of small molecules from the blood under high pressure inside the Bowman capsule of the kidney.

Selective Reabsorption

The process by which useful molecules, such as all glucose, are absorbed back into the blood from the proximal convoluted tubule.

Osmoregulation

The control and regulation of the water content and solute concentration of the blood.

Antidiuretic Hormone

A hormone released by the pituitary gland that increases the water permeability of kidney collecting ducts, causing more water to be reabsorbed.

Synapse

A small gap between two neurones across which chemical neurotransmitters diffuse to transmit impulses.

Reflex Arc

The direct pathway taken by electrical impulses during an automatic, rapid reflex action: stimulus, receptor, sensory neurone, relay neurone, motor neurone, effector, response.

Accommodation

The process by which the eye changes the shape of its lens using ciliary muscles and suspensory ligaments to focus light from near or distant objects.

Hormone

A chemical messenger produced by endocrine glands and transported in the blood to target organs.

Insulin

A hormone secreted by the pancreas that lowers blood glucose levels by causing cells to absorb glucose and converting it to glycogen.

Tropism

A plant growth response in direction towards or away from a directional stimulus such as light or gravity.

Auxin

A plant hormone produced in shoot and root tips that controls tropisms by stimulating cell elongation in shoots and inhibiting it in roots.

Mitosis

A type of nuclear cell division that produces two genetically identical diploid cells for growth, tissue repair, and asexual reproduction.

Meiosis

A type of reduction cell division that produces four genetically different haploid gametes.

Gamete

A specialised haploid sex cell involved in sexual reproduction, such as a sperm cell or an egg cell.

Zygote

A diploid cell formed by the fusion of male and female haploid gametes during fertilisation.

Pollination

The transfer of pollen grains from the anther to the stigma of a flower.

Acrosome

An organelle capping the head of a sperm cell that stores digestive enzymes to penetrate the outer layers of the ovum.

Placenta

An organ connecting the mother's blood supply to the developing fetus that allows exchange of oxygen, nutrients, and metabolic wastes without mixing blood.

Gene

A distinct section of DNA on a chromosome that codes for a specific sequence of amino acids to make a protein.

Transcription

The first stage of protein synthesis in the nucleus where a complementary mRNA copy of a gene is synthesised.

Translation

The stage of protein synthesis occurring at the ribosome where the mRNA base sequence is translated into a polypeptide chain of amino acids.

Codon

A triplet sequence of three nitrogenous bases on an mRNA molecule that codes for a specific amino acid.

Anticodon

A sequence of three complementary bases on a tRNA molecule that binds to a matching codon on an mRNA strand during translation.

Allele

An alternative version or form of a specific gene found at the same locus on homologous chromosomes.

Genotype

The specific combination of alleles an organism carries for a particular gene.

Phenotype

The observable physical or biochemical characteristics of an organism resulting from its genotype interacting with the environment.

Dominant Allele

An allele that is expressed in the phenotype whenever at least one copy is present in the genotype.

Recessive Allele

An allele that is only expressed in the phenotype when an organism carries two copies.

Mutation

A spontaneous, permanent change in the DNA base sequence of a gene or chromosome.

Natural Selection

The mechanism of evolution wherein organisms better adapted to their environment tend to survive, reproduce, and pass advantageous alleles to their offspring.

Selective Breeding

The artificial selection process by which humans deliberately choose individuals with desired traits to breed together over generations.

Fossil

The preserved remains, impressions, or traces of organisms from past geological ages found buried in sedimentary rock.