AQA Biology A-Level Topic 2 - Cells Definitions

Vocabulary flashcards covering core definitions and concepts for AQA Biology A-Level Topic 2 - Cells.

Active immunity

A form of immunity provided by the immune response of the body upon detection of a pathogen.

Active transport

The active movement of substances from a low concentration to a higher concentration (up their concentration gradient) with the use of energy in the form of ATP.

Agglutination

The clumping together of cells or particles caused by antibodies which assists phagocytosis.

Antibody

A protein found in the blood that is produced by plasma cells which binds to antigens as a part of the immune response.

Antigen

Marker molecules that can be detected by antibodies and trigger an immune response.

Binary fission

The method of cell division used by prokaryotes involving replication of the circular DNA and plasmids followed by cytoplasmic division.

Cell cycle

The series of stages preparing the cell for division consisting of interphase and mitosis.

Cell-surface membrane

A phospholipid bilayer studded with proteins that surrounds cells and separates them from their environment.

Cell vacuole

A membrane bound structure found in plant cells that contains cell sap.

Cell wall

A permeable layer that surrounds plant, algae and fungi cells made of polysaccharides which provides strength to the cell.

Chloroplast

An organelle found in plants and algae that is the site of photosynthesis.

Clonal expansion

The production of many genetically identical daughter cells through cell division of the activated B or T lymphocyte after clonal selection.

Clonal selection

The process of matching the antigens on an antigen presenting cells with the antigen receptors on B and T lymphocytes.

Co-transport

A method of membrane transport where two substances are both transported across a membrane at the same time either in the same direction or opposite directions.

Cytokinesis

Division of the cytoplasm to produce two new cells.

Facilitated diffusion

The passive movement of substances from a high concentration to a lower concentration (down their concentration gradient) through transport proteins without the use of energy.

Flagella

A whip-like structure found on bacterial cells that is used for cell movement.

Fluid-mosaic model

A model that describes membrane structure as a sea of mobile phospholipids studded with various proteins.

Golgi apparatus

An organelle found in eukaryotic cells that is involved in the modification and packaging of proteins.

Helper T cell

A type of T cell in the immune system that stimulates cytotoxic T cells, B cells and phagocytes.

Herd immunity

A type of disease immunity that occurs when a large proportion of a population are vaccinated against a disease which prevents the spread of the disease to unvaccinated individuals.

Human Immunodeficiency Virus (HIV)

A virus that attacks T cells in the immune system and can lead to AIDS (acquired immune deficiency syndrome).

Lysosomes

Membrane-bound vesicles found in the cytoplasm that contain a hydrolytic enzyme called lysozyme.

Magnification

How much bigger an image appears compared to the original object calculated using the following formula: $\text{Image size} = \text{Actual size} \times \text{Magnification}$

Mitochondrion

An organelle found in eukaryotic cells that is the site of aerobic respiration.

Mitosis

The part of the cell cycle in which a eukaryotic cell divides to produce two daughter cells, each with identical copies of DNA.

Monoclonal antibodies

Identical antibodies that have been produced by an immune cell that has been cloned from a parent cell.

Nucleus

An organelle found in eukaryotic cells that stores the genetic information of the cell as chromosomes and is surrounded by a membrane called the nuclear envelope.

Osmosis

The passive diffusion of water molecules from a region of high water potential to a region of lower water potential (down a water potential gradient) through a selectively permeable membrane without the use of energy.

Passive immunity

A form of immunity provided by the introduction of antibodies to a disease into the body.

Phagocytosis

The process where phagocytes engulf and destroy material.

Plasmids

A circular loop of DNA found in the cytoplasm of bacterial cells.

Primary immune response

The response produced by the immune system when it encounters a pathogen for the first time.

Resolution

The ability to distinguish two different points in a specimen.

Ribosomes

Organelles found either free in the cytoplasm or membrane bound that are involved in the synthesis of proteins.

Rough endoplasmic reticulum (RER)

A membrane-bound organelle that is involved in the synthesis and packaging of proteins.

Secondary immune response

The response produced by the immune system when it recognises a pathogen that it has encountered before.

Simple diffusion

The passive spreading out of substances from a high concentration to a lower concentration (down their concentration gradient) without the use of energy.

Smooth endoplasmic reticulum (SER)

A membrane-bound organelle involved in lipid synthesis.

Vaccine

The introduction of dead or inactive pathogens to stimulate an immune response and provide long term immunity.