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.
Prokaryotic Cells
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.
Viruses
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.
Microscopy & Cell Fractionation
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 & Mitosis
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.
Immune System & Immunity
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.
Membrane Transport
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.
