GCSE AQA Biology

Cell

The basic structural and functional unit of all known organisms.

Nucleus

Contains the cell's genetic material (DNA) and controls cell activities.

Mitochondria

Site of aerobic respiration

Cytoplasm

Jelly-like substance filling the cell

Cell membrane

Controls what enters and leaves the cell.

Cell wall

Rigid outer layer in plant and algal cells

Chloroplast

Site of photosynthesis in plant and algal cells.

Vacuole

Large

Ribosome

Site of protein synthesis.

Prokaryotic cell

Cell type lacking a nucleus and other membrane-bound organelles (e.g.

Eukaryotic cell

Cell type containing a nucleus and other membrane-bound organelles (e.g.

Specialised cell

A cell that has adapted a specific structure to carry out a particular function.

Differentiation

The process by which a cell becomes specialised.

Red blood cell

Specialised cell for oxygen transport

Sperm cell

Specialised cell for reproduction

Root hair cell

Specialised plant cell for water and mineral absorption

Palisade cell

Specialised plant cell for photosynthesis

Magnification

How many times larger an image appears compared to the actual size of the object.

Resolution

The ability to distinguish between two separate points.

Light microscope

Uses light and lenses to magnify specimens.

Electron microscope

Uses electrons to magnify specimens

Osmosis

The net movement of water molecules from a region of higher water potential to a region of lower water potential across a partially permeable membrane.

Diffusion

The net movement of particles from a region of higher concentration to a region of lower concentration.

Active transport

The movement of particles against a concentration gradient

Partially permeable membrane

A membrane that allows some substances to pass through but not others.

Concentration gradient

The difference in concentration between two areas.

Enzyme

A biological catalyst

Active site

The specific region on an enzyme where the substrate binds.

Substrate

The molecule upon which an enzyme acts.

Denaturation

The irreversible change in the shape of an enzyme's active site due to extreme pH or temperature

Optimum temperature

The temperature at which an enzyme shows maximum activity.

Optimum pH

The pH at which an enzyme shows maximum activity.

Carbohydrase

Enzyme that breaks down carbohydrates (e.g.

Protease

Enzyme that breaks down proteins (e.g.

Lipase

Enzyme that breaks down lipids (fats and oils).

Photosynthesis

The process by which plants and some other organisms use sunlight to synthesize foods from carbon dioxide and water.

Word equation for photosynthesis

Carbon dioxide + water → glucose + oxygen (light energy).

Balanced symbol equation for photosynthesis

$6CO2 + 6H2O \rightarrow C6H{12}O6 + 6O2$

Limiting factor

A factor that restricts the rate of a process if it is in short supply.

Factors affecting photosynthesis

Light intensity

Respiration

The process by which living organisms release energy from organic molecules (e.g.

Aerobic respiration

Respiration that requires oxygen

Word equation for aerobic respiration

Glucose + oxygen → carbon dioxide + water (energy released).

Balanced symbol equation for aerobic respiration

$C6H{12}O6 + 6O2 \rightarrow 6CO2 + 6H2O$

Anaerobic respiration

Respiration that does not require oxygen

Word equation for anaerobic respiration in animals

Glucose → lactic acid (energy released).

Word equation for anaerobic respiration in yeast

Glucose → ethanol + carbon dioxide (energy released).

Oxygen debt

The amount of extra oxygen the body needs after exercise to react with the accumulated lactic acid.

Ecosystem

All the living organisms (biotic) and non-living components (abiotic) in a particular area

Community

All the different populations of organisms living and interacting in a particular area.

Population

All the individuals of a single species living in a particular area.

Habitat

The natural home or environment of an animal

Producer

An organism that produces its own food

Consumer

An organism that obtains energy by feeding on other organisms.

Prey

An animal that is hunted and killed by another for food.

Predator

An animal that naturally preys on others.

Food chain

A sequence showing how energy is transferred from one organism to another through feeding.

Food web

A network of interconnected food chains in an ecosystem.

Decomposer

An organism that breaks down dead organic matter (e.g.

Biodiversity

The variety of living organisms in a particular area or on Earth.

Abiotic factors

Non-living physical and chemical parts of an ecosystem that affect living organisms (e.g.

Biotic factors

Living parts of an ecosystem that affect other living organisms (e.g.

Carbon cycle

The biogeochemical cycle by which carbon is exchanged among the biosphere

Water cycle

The continuous movement of water on

Decomposition

The process by which organic substances are broken down into simpler forms of matter.

Nitrogen cycle

The process by which nitrogen is converted into various chemical forms as it circulates among the atmosphere

Deforestation

The clearing of forests for other land uses.

Global warming

A gradual increase in the overall temperature of the Earth's atmosphere

Greenhouse effect

The trapping of heat in the Earth's atmosphere by certain gases (e.g.

Genetics

The study of heredity and the variation of inherited characteristics.

Chromosome

A thread-like structure of nucleic acids and protein found in the nucleus of most living cells

DNA (Deoxyribonucleic acid)

The molecule that carries genetic information in all cellular forms of life and some viruses.

Gene

A unit of heredity that is transferred from a parent to offspring and is held to determine some characteristic of the offspring.

Allele

Different forms of a gene.

Dominant allele

An allele that is always expressed if present.

Recessive allele

An allele that is only expressed if two copies are present (no dominant allele).

Homozygous

Having two identical alleles for a particular gene (e.g.

Heterozygous

Having two different alleles for a particular gene (e.g.

Genotype

The genetic makeup of an organism (the alleles present).

Phenotype

The observable characteristics of an organism

Gamete

A mature haploid male or female germ cell that is able to unite with another of the opposite sex in sexual reproduction to form a zygote.

Zygote

A diploid cell resulting from the fusion of two haploid gametes

a fertilized ovum.

Mitosis

Cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus

Meiosis

Cell division that results in four daughter cells each with half the number of chromosomes of the parent cell

Asexual reproduction

Reproduction involving only one parent

Sexual reproduction

Reproduction involving the fusion of gametes from two parents

Genetic engineering

The deliberate modification of the characteristics of an organism by manipulating its genetic material.

Selective breeding

The process by which humans breed animals and plants for particular desirable traits.

Variation

Differences between individuals of the same species.

Evolution

The process by which different kinds of living organisms are thought to have developed and diversified from earlier forms during the history of the Earth.

Natural selection

The process whereby organisms better adapted to their environment tend to survive and produce more offspring.

Mutation

A change in the DNA sequence.

Homeostasis

The maintenance of a stable internal environment in an organism.

Negative feedback

A mechanism that maintains a variable within a narrow range by counteracting any deviation from the set point.

Thermoregulation

The maintenance of a stable internal body temperature.

Insulin

Hormone produced by the pancreas that lowers blood glucose levels.

Glucagon

Hormone produced by the pancreas that raises blood glucose levels.

Diabetes

A metabolic disease in which the body's inability to produce any or enough insulin causes elevated levels of glucose in the blood.

Kidney

Organ responsible for filtering blood and producing urine.