Definitions topic 2 biology

Cell-Surface Membrane

A phospholipid bilayer with embedded proteins that controls the movement of substances into and out of the cell.

Nucleus

The organelle containing genetic material (DNA) in the form of chromosomes, surrounded by a nuclear envelope.

Mitochondrion

The site of aerobic respiration, providing ATP for cellular functions.

Golgi Apparatus

An organelle responsible for modifying, packaging, and transporting proteins and lipids.

Lysosomes

Membrane-bound vesicles containing hydrolytic enzymes that break down cellular waste.

Ribosomes

Organelles responsible for protein synthesis, found in the cytoplasm or attached to the rough endoplasmic reticulum.

Rough Endoplasmic Reticulum (RER)

A membrane system covered with ribosomes involved in the synthesis and transport of proteins.

Smooth Endoplasmic Reticulum (SER)

A membrane system involved in lipid synthesis and detoxification.

Chloroplast

An organelle found in plant and algae cells, responsible for photosynthesis.

Cell Wall

A rigid structure made of cellulose (plants), chitin (fungi), or other polysaccharides, providing support and protection.

Cell Vacuole

A membrane-bound organelle in plant cells that contains cell sap, aiding in maintaining turgor pressure.

Plasmids

Small, circular DNA molecules in bacteria that can replicate independently of the chromosomal DNA.

Binary Fission

The method of asexual reproduction in prokaryotic cells, involving replication of circular DNA and division of the cytoplasm.

Flagella

Tail-like structures in bacterial cells that aid in movement.

Human Immunodeficiency Virus (HIV)

A virus that infects T cells, leading to AIDS by weakening the immune system.

Viruses Replication

Viruses are acellular and replicate by injecting their genetic material into host cells, using the host’s cellular machinery to produce new virus particles.

Magnification

The ratio of an image’s size to the actual size of the specimen.

Resolution

The ability to distinguish between two separate points in an image.

Fluid-Mosaic Model

The model describing the structure of the plasma membrane as a flexible bilayer with embedded proteins.

Cell Cycle

The sequence of phases (interphase, mitosis, cytokinesis) that prepare a cell for division.

Mitosis

The process by which a eukaryotic cell divides to produce two genetically identical daughter cells.

Cytokinesis

The division of the cytoplasm, following mitosis, to form two separate daughter cells.

Antigen

A marker molecule on the surface of a pathogen that triggers an immune response.

Antibody

A protein produced by plasma cells that binds to specific antigens.

Agglutination

The clumping of pathogens by antibodies, aiding in their destruction.

Phagocytosis

The process by which phagocytes engulf and destroy pathogens.

Helper T Cells

A type of white blood cell that activates other immune cells.

Active Immunity

Immunity developed when the body produces its own antibodies in response to a pathogen.

Passive Immunity

Immunity gained through the introduction of external antibodies (e.g., from breast milk or injections).

Herd Immunity

Protection from disease achieved when a large portion of the population is vaccinated.

Primary Immune Response

The immune system’s first response to a pathogen, typically slower as memory cells are not yet present.

Secondary Immune Response

A faster, stronger immune response due to memory cells recognising a previously encountered pathogen.

Monoclonal Antibodies

Identical antibodies produced from a single cloned plasma cell, often used in medical diagnostics and treatments.

Clonal Selection

The process of selecting the correct B or T lymphocyte with receptors that match the pathogen’s antigens.

Clonal Expansion

The rapid multiplication of the selected lymphocytes to fight the infection.

Simple Diffusion

The passive movement of molecules from an area of high concentration to low concentration.

Facilitated Diffusion

The passive movement of molecules across a membrane via transport proteins.

Osmosis

The diffusion of water molecules from a region of high water potential to low water potential through a selectively permeable membrane.

Active Transport

The movement of molecules against a concentration gradient using ATP and transport proteins.

Co-Transport

A type of membrane transport where two molecules move together, often involving a concentration gradient.