AQA GCSE Biology - Topic 1: Cell Biology

Vocabulary practice flashcards covering cell structure, cell specialization, microscopy, the cell cycle, stem cells, diffusion, active transport, and osmosis for AQA GCSE Biology.

Nucleus

A subcellular structure found in eukaryotic cells that controls cell activities and contains DNA for protein synthesis.

Cytoplasm

The jelly-like region within a cell where chemical reactions take place.

Cell membrane

A partially permeable barrier surrounding the cell that controls which substances move in and out.

Ribosomes

Tiny subcellular structures responsible for protein synthesis by assembling proteins from amino acids.

Mitochondria

Subcellular structures that release energy through aerobic respiration.

Cell wall (Plant)

An outer layer made of cellulose that provides strength and structural support to plant cells.

Sap vacuole

A structure found in plant cells containing cell sap, which is a sugary solution.

Chloroplast

A plant cell organelle containing the green pigment chlorophyll, which absorbs sunlight for photosynthesis.

Prokaryote

A single-celled organism (such as a bacterium) that lacks a nucleus, mitochondria, and any membrane-bound subcellular structures.

Plasmid

A small ring of DNA in a prokaryotic cell that is separate from the main circular DNA and contains a few genes.

Cell differentiation

The biological process by which undifferentiated cells develop into specialized cells adapted for specific functions.

Dendrites

Branched structures of a nerve cell that connect to and receive impulses from other nerve cells.

Axon

A long projection down the center of a nerve cell that carries electrical impulses around the body.

Insulating sheath

An insulating layer surrounding the axon of a nerve cell that functions to speed up electrical impulses.

Acrosome

A structure located at the tip of a sperm cell containing enzymes to penetrate the egg cell membrane.

Glycogen

A carbohydrate stored in muscle cells that serves as a reservoir of stored energy for muscle contraction.

Xylem cells

Dead, elongated plant cells forming nonliving tubes with no end plates or cytoplasm, adapted to transport water.

Lignin

A woody substance arranged in rings that reinforces xylem cells and prevents the tubes from collapsing.

Phloem cells

Living elongated cells with very little cytoplasm and end plates with pores that form tubes for transporting dissolved substances in solution.

Companion cells

Specialized cells adjacent to phloem cells that provide the energy required for the transport of sugars.

Electron microscope

A microscope that provides much higher magnification and resolving power than a light microscope, allowing biologists to see detailed subcellular structures.

Magnification formula

The relationship used to determine magnification: $\text{Magnification} = \frac{\text{Image size}}{\text{Real size}}$.

Cell cycle (Stage 1)

The stage where the cell grows, increases the number of subcellular structures such as ribosomes and mitochondria, and replicates its DNA into two copies of each chromosome.

Mitosis (Stage 2 of cell cycle)

The process in which chromosomes line up along the center of the cell, are pulled to opposite ends, and the nucleus divides.

Embryonic stem cells

Undifferentiated cells from an early embryo that have the ability to differentiate into most types of specialized body cells.

Adult stem cells

Stem cells found in adult tissues, such as bone marrow, that can differentiate into a limited range of cell types, mainly blood cells.

Meristem tissue

Plant tissue located at shoot and root tips that retains the ability to differentiate into any plant cell type throughout the lifetime of the plant.

Therapeutic cloning

A technique where the nucleus of a patient body cell is transferred into an enucleated donor egg cell to produce genetically matching stem cells that are not rejected.

Diffusion

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

Active transport

The movement of particles against a concentration gradient from an area of lower concentration to an area of higher concentration, requiring energy from respiration.

Surface area to volume ratio ($\text{SA:V}$)

The mathematical relationship between surface area and volume, which becomes smaller as an organism increases in size.

Villi

Finger-like projections on the wall of the small intestine that increase surface area and feature a good blood supply and thin walls for efficient absorption.

Alveoli

Tiny air sacs at the ends of airway tubes in the lungs that provide a large surface area, rich capillary network, and thin walls for gas exchange.

Osmosis

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

Turgid

The firm, swollen state of a plant cell when water enters by osmosis, providing support and keeping the plant upright without bursting due to the cell wall.

Cork borer

A cylindrical cutting instrument used in osmosis practical investigations to cut uniform cylinders of plant tissue.