AQA Biology GCSE Topic 1: Cell Biology

Vocabulary flashcards covering key terms and definitions from the Cell Biology notes.

Eukaryote

Organisms with complex cells that contain a nucleus and organelles; examples include animal and plant cells.

Prokaryote

Organisms with simple cells that lack a true nucleus; smaller than eukaryotes; includes bacteria; DNA is not enclosed in a nucleus.

Animal cell

A eukaryotic cell that contains membrane-bound organelles such as a nucleus, but does not have a cell wall or chloroplasts.

Plant cell

A eukaryotic cell with a cell wall, chloroplasts, large permanent vacuole, and a nucleus.

Nucleus

The organelle that contains DNA and controls cell activities; enclosed by a nuclear membrane.

DNA

Molecule that carries genetic information; genes code for proteins.

Chromosome

Structure of DNA and proteins; humans have 23 pairs (46 total) in body cells.

Gene

A short section of DNA that codes for a protein and determines a characteristic.

Mitochondrion

Organelle where aerobic respiration occurs; produces energy (ATP) for the cell.

Ribosome

Organelle where protein synthesis occurs; can be free or bound to rough endoplasmic reticulum.

Chloroplast

Organelle in plant cells where photosynthesis takes place; contains chlorophyll.

Chlorophyll

Green pigment that harvests light energy for photosynthesis.

Permanent vacuole

Large vacuole in plant cells that stores cell sap and helps maintain rigidity.

Cell wall

Rigid layer in plant cells made of cellulose; provides structural support and protection.

Peptidoglycan

Substance that makes up bacterial cell walls; different from plant cell walls.

Organelles

Structures within a cell that have specific functions (e.g., nucleus, mitochondria, ribosomes).

Plasmids

Small circular DNA molecules in bacteria that can carry extra genes.

Circular DNA

Single circular strand of DNA found in bacteria; forms the main bacterial chromosome.

Sperm cell

Male gamete; streamlined head and long tail; many mitochondria; acrosome with enzymes to fertilize the egg.

Nerve cell (neurone)

Cell specialised to transmit electrical impulses; long axon and dendrites; neurotransmitters at endings.

Muscle cell

Cell specialised to contract; contains proteins myosin and actin; many mitochondria; stores glycogen.

Root hair cell

Plant cell with a large surface area for water and mineral ion uptake; large permanent vacuole; mitochondria.

Xylem cell

Plant cell that forms hollow, dead tubes to transport water; lignin deposits strengthen walls.

Phloem cell

Plant cell that carries products of photosynthesis (sugars); sieve plates and companion cells support transport.

Differentiation

Process by which a cell becomes specialised by turning on/off certain genes to produce specific proteins.

Stem cell

Undifferentiated cell that can divide to produce similar cells and differentiate into various types.

Embryonic stem cell

Stem cells from an early embryo that can differentiate into any cell type.

Adult stem cell

Stem cells found in mature tissues (e.g., bone marrow) with limited differentiation potential.

Meristem

Plant stem cells found in root/shoot tips; can differentiate into any plant cell; persist throughout life.

Therapeutic cloning

Creating an embryo with the patient’s genes to obtain matching embryonic stem cells for therapy.

Mitosis

Cell division producing two genetically identical daughter cells; part of the cell cycle.

Interphase

Stage of the cell cycle where the cell grows and DNA is replicated before division.

Cytokinesis

Division of the cytoplasm, resulting in two separate daughter cells.

Cell cycle

Series of events that cells go through as they grow and divide (includes interphase, mitosis, cytokinesis).

Diffusion

Passively spreading out of particles from high to low concentration across a membrane or in a gas or solution.

Concentration gradient

Difference in concentration; the greater the gradient, the faster diffusion occurs.

Gas exchange

Process by which oxygen enters and carbon dioxide leaves the body across respiratory surfaces.

Hypertonic

Solution with higher solute concentration outside a cell; water moves out of the cell.

Hypotonic

Solution with lower solute concentration outside a cell; water moves into the cell.

Isotonic

Solution with the same solute concentration inside and outside the cell; no net water movement.

Osmosis

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

Water potential

Potential energy of water; higher in dilute solutions and lower in concentrated solutions.

Turgor

Pressure within plant cells from water uptake; maintains rigidity of leaves and stems.

Plasmolysis

When plant cell membrane pulls away from the cell wall due to water loss; cell may die.

Villi

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

Alveoli

Air sacs in the lungs where gas exchange occurs; large surface area and thin walls.

Guard cells

Cells that regulate the opening and closing of stomata in leaves.

Stomata

Pores on leaf surfaces that allow gas exchange; opened or closed by guard cells.

Lamellae

Thin plates on fish gills where diffusion of oxygen and carbon dioxide occurs.

Gills

Respiratory organs in fish; use countercurrent flow to maximize gas exchange.

Active transport

Movement of substances against a concentration gradient, requiring energy from respiration.

Inoculating loop

Wire tool used to transfer microorganisms to a culture medium; must be sterilised.

Autoclave

Device that sterilises equipment and media using high-pressure steam.

Sterile technique

Procedures to prevent contamination of cultures by unwanted microorganisms.

Binary fission

Asexual reproduction in bacteria where a cell divides into two identical cells.

Colony

A visible group of bacteria growing on an agar plate.

Petri dish

Shallow dish containing agar used to culture microorganisms.

Culture medium

Nutrient source (broth or agar) used to grow microorganisms.

Agar

Gel-like substance derived from seaweed used as a solid culture medium.

Mean division time

Average time a bacterial population takes to divide during growth.

Inhibition zone

Clear area around an antibiotic disc on an agar plate indicating bacterial death; measures antibiotic effectiveness.

Antibiotic

Substance that kills or inhibits bacteria; tested by disc diffusion to observe inhibition zones.

Nutrient broth

Liquid culture medium used to grow microorganisms.

Bacteria

Microscopic single-celled organisms that can multiply rapidly by binary fission.

Gamete

Sex cell with half the number of chromosomes; haploid (23 in humans).

Zygote

Diploid cell formed when a sperm and egg fuse; contains 46 chromosomes.

Sieve plate

Structure in phloem cell where cytoplasm breaks down to allow flow between cells.

Sieve tube element

Phloem cell that transports sugars; relies on companion cells for energy.

Companion cell

Phloem cell that provides energy to sieve tube elements via mitochondria.

Counter-current flow

Exchange system (as in fish gills) where water and blood flow in opposite directions to maximize diffusion.

Xylem lignin

Lignin deposits that harden xylem walls to support water transport; contributes to dead hollow tubes.

Standard form

A way of writing very large or small numbers as a × 10n with 1 ≤ a < 10; simplifies calculations.

Magnification

How many times bigger an image appears compared with the actual object.

Resolving power (RP)

Ability to distinguish two close points as separate; lower RP means higher resolution.

SEM

Scanning electron microscope; produces 3D images and high magnification using electrons.

TEM

Transmission electron microscope; provides high-resolution 2D images of internal structures using electrons.