AQA GCSE Biology – Topic 1: Cell Biology

80 vocabulary flashcards summarising essential terms from the Cell Biology topic for AQA GCSE Biology.

Eukaryotes

Organisms whose cells contain a nucleus and membrane-bound organelles (e.g., plants and animals).

Prokaryotes

Single-celled organisms lacking a nucleus; DNA is free in the cytoplasm (e.g., bacteria).

Cell membrane

Partially permeable boundary that controls substances entering and leaving the cell.

Cytoplasm

Gel-like substance where most chemical reactions occur; contains enzymes and organelles.

Nucleus

Organelle enclosed by a nuclear membrane that houses DNA and controls cell activities.

Cell wall

Rigid layer outside the cell membrane; in plants made of cellulose, in bacteria of peptidoglycan.

Mitochondria

Site of aerobic respiration, releasing energy for the cell’s activities.

Ribosomes

Tiny organelles where protein synthesis occurs, often attached to rough endoplasmic reticulum.

Plasmid

Small, circular ring of DNA in bacterial cytoplasm that can replicate independently.

Orders of magnitude

Powers of ten used to compare relative sizes (e.g., 10¹, 10³).

Centi (c)

Metric prefix meaning 0.01 × the base unit (10⁻²).

Milli (m)

Metric prefix meaning 0.001 × the base unit (10⁻³).

Micro (µ)

Metric prefix meaning 0.000001 × the base unit (10⁻⁶).

Nano (n)

Metric prefix meaning 0.000000001 × the base unit (10⁻⁹).

Chloroplast

Plant organelle containing chlorophyll; site of photosynthesis.

Permanent vacuole

Fluid-filled space in plant cells containing cell sap; maintains rigidity.

Cellulose

Polysaccharide composing plant cell walls, providing strength.

Peptidoglycan

Complex polymer forming bacterial cell walls.

Differentiation

Process by which a cell gains specialized structures and functions.

Stem cell

Undifferentiated cell capable of dividing and giving rise to specialized cells.

Sperm cell

Male gamete specialized to deliver DNA to the egg; has a tail and many mitochondria.

Acrosome

Enzyme-filled cap on a sperm head that digests egg membranes.

Axon

Long extension of a nerve cell that carries electrical impulses.

Dendrites

Branch-like extensions of neurons forming connections with other nerve cells.

Neurotransmitter

Chemical that transmits signals across a synapse between neurons.

Myosin

Contractile protein in muscle fibers that interacts with actin.

Actin

Protein filaments that slide with myosin to cause muscle contraction.

Glycogen

Storage carbohydrate in animals and muscle cells, broken down for energy.

Root hair cell

Plant epidermal cell with long extensions to absorb water and minerals.

Lignin

Strong, woody substance deposited in xylem walls, making them rigid and waterproof.

Xylem

Hollow plant vessels that transport water and mineral ions upward from roots.

Phloem

Living vascular tissue that transports sugars and other products of photosynthesis.

Sieve plates

Perforated end walls between phloem cells allowing flow of sap.

Companion cell

Phloem cell that supplies energy to adjacent sieve tube elements.

Light microscope

Instrument using light and lenses to magnify specimens up to ~×2000.

Electron microscope

Microscope using electron beams for high magnification and resolution of sub-cellular structures.

Scanning electron microscope (SEM)

Electron microscope producing 3-D images of specimen surfaces; resolving power ~10 nm.

Transmission electron microscope (TEM)

Electron microscope producing 2-D images of thin sections; resolving power ~0.2 nm.

Magnification

How many times larger an image is compared with the actual specimen.

Resolution

Ability to distinguish two close points as separate; higher resolution shows more detail.

Standard form

Way of writing very large or small numbers as a number between 1 and 10 multiplied by 10ⁿ.

Nutrient broth

Liquid culture medium containing carbohydrates, proteins, minerals, and vitamins for growing microbes.

Agar gel

Jelly-like culture medium solidified on Petri dishes for microbial growth.

Inoculating loop

Sterile wire tool used to transfer microorganisms to culture media.

Autoclave

High-pressure steam oven used to sterilize equipment and media.

Binary fission

Asexual reproduction process where a bacterial cell splits into two identical cells.

Mean division time

Average time for one bacterial cell to divide into two.

Inhibition zone

Clear region around an antibiotic disc where bacteria have been killed or growth is prevented.

Chromosome

Thread-like structure of coiled DNA carrying genetic information in genes.

Gene

Short section of DNA that codes for a specific protein and trait.

Mitosis

Type of cell division producing two genetically identical daughter cells.

Interphase

Cell-cycle stage of growth, DNA replication, and preparation for mitosis.

Cytokinesis

Division of cytoplasm and membranes forming two separate daughter cells after mitosis.

Zygote

Fertilized egg cell formed by fusion of sperm and egg; totipotent.

Therapeutic cloning

Creating an embryo genetically identical to a patient to obtain compatible stem cells.

Embryonic stem cell

Pluripotent cell from early embryo capable of forming any body cell type.

Adult stem cell

Multipotent stem cell found in tissues like bone marrow; forms limited cell types.

Meristem

Region of plant tissue (root or shoot tips) containing actively dividing stem cells.

Diffusion

Passive movement of particles from high to low concentration until equilibrium.

Concentration gradient

Difference in concentration between two areas; steeper gradients drive faster diffusion.

Surface area to volume ratio

Measure that influences rate of diffusion; larger ratios allow faster exchange.

Alveoli

Tiny air sacs in lungs where gas exchange occurs with the bloodstream.

Villi

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

Gill lamellae

Thin plates on fish gill filaments where oxygen and carbon dioxide diffuse.

Stomata

Pores on leaf surfaces allowing gas exchange; bordered by guard cells.

Guard cell

Specialized epidermal cell that controls the opening and closing of stomata.

Osmosis

Passive movement of water molecules through a partially permeable membrane from high to low water potential.

Isotonic

Solution with equal water potential to the cell; no net water movement.

Hypertonic

Solution with lower water potential than the cell; water moves out, causing shrinkage.

Hypotonic

Solution with higher water potential than the cell; water moves in, causing swelling.

Turgor

Pressure of cell contents against the plant cell wall, keeping tissues rigid.

Plasmolysis

Process where plant cell membrane detaches from the wall due to water loss in hypertonic solution.

Active transport

Energy-requiring movement of particles against their concentration gradient via membrane proteins.

Water potential

Measure of potential energy of water molecules; determines the direction of osmosis.

Partially permeable membrane

Barrier allowing some molecules (e.g., water) to pass while restricting others.

Gas exchange

Process of obtaining oxygen and removing carbon dioxide across respiratory surfaces.

Aerobic respiration

Energy-releasing process in mitochondria using oxygen to break down glucose.

Passive transport

Movement of substances across membranes without energy input (e.g., diffusion, osmosis).

Culturing microorganisms

Growing large numbers of microbes on nutrient media for study.

Petri dish

Shallow, lidded dish used to culture microorganisms on agar.