AQA Biology A Level Key Words CELLS

acellular non living particle that contains DNA or RNA but cannot replicate independently

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

a permeable layer that surrounds plants, algae and fungal cells made of polysaccharides which provides strength to the cell

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

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

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

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

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

a method of membrane transport where two substances are both transported across a membrane at the same time (can be in same or opposite directions)

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

division of the cytoplasm to produce two new cells

the active movement of substances up a concentration gradient with the use of energy in the form of ATP

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

the passive movement of substances down a concentration gradient through transport proteins without the use of energy

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

a series of lines on a microscope which can be used to calculate the size of objects

how much bigger an image appears compared to the original object

a membrane-bound structure found in plant cells that contains cell sap

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

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

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

a membrane-bound organelle involved in lipid synthesis

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

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

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

the ability to distinguish between two different points in a specimen

the passive diffusion of water molecules down a water potential gradient through a selectively permeable membrane without the use of energy

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

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

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

a circular loop of DNA found in the cytoplasm of bacterial cells

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

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

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

the first stage of cell fractionation where cells are broken up by a homogeniser

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

type of electron microscope which passes a beam of electrons through a very thin section of a specimen (which has often been stained with heavy metals to show up fine internal structures)

the passive spreading of substances from a high concentration to a low concentration gradient without the use of energy

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

the process where phagocytes engulf and destroy material

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

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

where the fragments in filtered homogenate are separated in a centrifuge

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

a type of electron microscope which bounces beams off electrons of the surface of an object to develop a 3D image

the process by which cells are broken up to release the organelles they contain