AQA GCSE Biology: Cell Structure, Microscopy, and Transport

Comprehensive vocabulary flashcards covering sub-cellular organelles, plant vs. animal cell structures, light and electron microscopy, eukaryotic vs. prokaryotic cells, specialised cells, differentiation, stem cells, diffusion, osmosis, active transport, and surface area to volume ratios based on AQA GCSE Biology B1.

Nucleus

The sub-cellular structure in eukaryotic cells that contains the chromosomes and genetic information needed for growth, repair, and reproduction, and controls the activities of the cell.

Cytoplasm

A jelly-like substance where most chemical reactions take place, containing enzymes that control these reactions.

Cell Membrane

A flexible outer boundary present in both animal and plant cells that controls the entry and exit of substances into and out of the cell.

Mitochondria

Sub-cellular structures that serve as the site of aerobic respiration, an enzyme-controlled reaction that releases energy.

Ribosomes

Small organelles found in animal and plant cells that serve as the sites of protein synthesis (such as enzymes and pigments).

Cell Wall

A rigid layer surrounding plant, algal, and bacterial cells that provides structure and support, preventing the cell from bursting if too much water enters.

Cellulose

A carbohydrate that forms the rigid cell wall in plant and algal cells to strengthen them.

Chloroplast

An organelle found in plant cells that contains the green pigment chlorophyll and acts as the site of photosynthesis.

Chlorophyll

A green pigment located in chloroplasts that absorbs light energy transferred from the Sun for photosynthesis.

Permanent Vacuole

A large fluid-filled space in plant cells that stores cell sap and products of photosynthesis, helping support the cell's shape.

Magnification Formula

The mathematical relationship used to calculate magnification: $\text{Magnification} = \frac{\text{size of image}}{\text{size of real object}}$.

Resolution

The ability of a microscope to distinguish between two separate points; a higher resolution means a smaller distance can be clearly distinguished.

Light Microscope

A microscope developed in the mid-17th century that uses a beam of light to form 2D images, reaching up to $2000\times$ magnification and a resolving power of approximately $200\,nm$.

Transmission Electron Microscope (TEM)

A type of electron microscope invented in the 1930s that transmits electrons through specimens to produce 2D images of internal cell structures, capable of magnifying over $500{,}000\times$ with a resolution of $0.2\,nm$.

Scanning Electron Microscope (SEM)

An electron microscope that bounces electrons off cell surfaces to produce 3D images, capable of magnifying around $100{,}000\times$ with a resolution of $10\,nm$.

Eukaryotic Cell

A cell type (such as animal and plant cells) characterized by having a cell membrane, cytoplasm, and genetic material enclosed within a nucleus.

Prokaryotic Cell

A smaller, simpler cell type (such as a bacterium) that lacks a membrane-bound nucleus and mitochondria, whose genetic material consists of a single DNA loop and plasmids.

Plasmid

A small circular ring of DNA found in prokaryotic (bacterial) cells that carries extra genes.

Flagellum

A long, whip-like tail-like structure present in some bacterial cells that is used for movement.

Peptidoglycan (Murein)

The molecular substance that comprises the cell wall of prokaryotic (bacterial) cells, distinct from plant cellulose.

Cell Specialisation

The adaptation of a cell's structure to perform a specific function within a tissue, organ, organ system, or organism.

Red Blood Cell

A specialised animal cell adapted to carry oxygen, featuring a biconcave disc shape for a large surface area, packed with haemoglobin, and lacking a nucleus to provide more internal space.

Haemoglobin

The iron-containing protein packed inside red blood cells that reversibly binds to oxygen molecules for transport throughout the body.

Sperm Cell

A specialised male reproductive cell containing half the chromosomes of a normal body cell, a tail to swim, numerous mitochondria to release energy, and digestive enzymes in its head to penetrate an egg cell.

Root Hair Cell

A specialised plant root epidermal cell with a long projection that provides a large surface area to absorb water and mineral ions, featuring a thin cell wall and no chloroplasts.

Xylem

Tubes of dead, empty cells joined end-to-end with walls reinforced by lignin, specialized for conducting water and dissolved minerals upwards from the roots in one direction.

Phloem

Tubes of living transport cells joined end-to-end with perforated end walls (sieve plates) that transport dissolved sugars and organic molecules both up and down a plant.

Lignin

A tough chemical compound that strengthens and waterproofs the cell walls of dead xylem vessels to withstand pressure and provide structural support.

Cell Differentiation

The developmental process by which an unspecialised cell changes shape and acquires specific sub-cellular structures to become specialised for a particular job.

Stem Cell

An undifferentiated, unspecialised cell capable of dividing repeatedly to replicate itself or differentiating into specialized cell types.

Zygote

A single fertilised egg cell formed by the fusion of a sperm cell and an egg cell, which subsequently divides by mitosis to form an embryo.

Diffusion

The spreading out of particles of any substance in solution, or particles of a gas, resulting in a net movement from an area of higher concentration to an area of lower concentration.

Concentration Gradient

The difference in the concentration of a chemical substance between two regions; a larger difference creates a steeper gradient, resulting in a faster rate of diffusion.

Osmosis

The diffusion of water molecules from a dilute solution to a concentrated solution across a partially permeable membrane.

Partially Permeable Membrane

A barrier (such as a cell surface membrane) that permits the passage of small molecules like water while blocking larger solute molecules.

Dilute Solution

A solution containing a high proportion of solvent (water) relative to a low concentration of dissolved solute.

Concentrated Solution

A solution containing a high amount of dissolved solute particles and a relatively low amount of solvent (water).

Active Transport

The movement of substances across a membrane from a more dilute solution to a more concentrated solution (against a concentration gradient), which requires energy released from cellular respiration.

Surface Area to Volume Ratio (SA:V)

The relationship between the external surface area of an organism and its total internal volume; as an organism increases in size, this ratio decreases.

Alveoli

Tiny air sacs in the lungs that provide an enormous surface area and maintain a rich capillary blood supply to maximize the rate of gas exchange.

Villi

Small, finger-like projections lining the wall of the human small intestine that dramatically increase the surface area available for absorbing nutrients into the bloodstream.