Please enable JavaScript.
Coggle requires JavaScript to display documents.
Biology - Coggle Diagram
Biology
Cell structure
Fluid mosaic model (1972) : Cell surface membrane creates enclosed space for intracellular membranes. Also control the exchange of material across them. Membranes are partially permeable and substances can cross by diffusion, osmosis and active transport.
Cellular membranes formed from a phospholipid bilayer. Visible with electron microscope. Phospholipids: Polar head and two nonpolar tails. Phosphate head is hydrophilic and soluble in water. Nonpolar lipid tail is hydrophobic, insoluble.
Micelle- spheres with hydrophilic phosphate heads facing out to protect the hydrophobic tails. Pospholipid bilayer: Two layered structure that is formed in sheets, basic structure of cell membrane.
Structure of membranes: Bilayer also contains proteins. Can be intrinsic or extrinsic. Intrinsic are embedded in the membrane, arrangement determined by the hydrophilic/phobic regions. Extrinsic are found on outer or inner surface of the membrane.
Bilayers can form compartments, establishing a boundary for each cell. Internally, membrane bound compartments provide basic structure of organelles, allowing for specialisation processes. E.g. Lysosome.
Fluid mosaic model: Fluid- Phospholipids and proteins can move via diffusion, phospholipids move sideways in the layers. Many different types of proteins interspread through the layers. Mosaic- scattered pattern by the proteins.
Mitosis and cancer
-
cancer cells divide repeatedly forming a tumor, irregular mass of cells. this starts when changes occur in the genes that control cell division, known as a mutation. gene causing cancer is an oncogene. cancerous tumors are malignant.
mutations are common and don't cause cancer the majority of the time. usually end in early cell death or are destroyed by the immune system. cancer cells do not have early cell death and are not destroyed by the system.
-
nuclear division, two genetically identical daughter cells are produced. same number of chromosomes as their parent cells.
Prophase: chromosomes condense, visible now. consists of two sister chromatids joined at the centrometre. centrosomes move towards opposite poles. spindle fibres appear from centrosomes. nuclear envelope breaks down.
metaphase: centrosomes reach opposite poles. spindle fibres extend. chromsomes line up at the equator. spindnles reach the chromosomes. each sister chromatid is attached to a spindle fibre at the opposite poles.
Anaphase: Sister chromatids separate at the centrometre. Spindle fibres shorten. Separated sister chromatids pulled to opposite poles.
Telophase: Chromosomes at opposite poles and decondense. The nuclear envelope begins to reform around the sets of chromosomes. Spindle fibres then break down. (Cytokinesis: Nuclear envelope breaks down and reforms)
-