cells

• eukaryotic cells have a distinct nucleus and membrane bound organelles
• the rough endoplasmic reticulum is a membrane bound organelle that is involved in the synthesis of proteins and provides pathways for transport
• the smooth endoplasmic reticulum is a membrane bound organelle that is involved in the synthesis of lipids and carbohydrates
• the golgi apparatus is a series of flattened membrane-bound sacs that are involved in the modification and packaging of proteins
• lyosymes hydrolyse material ingested by phagocytes
• inside viruses there is RNA and reverse transcriptase which makes DNA
• a virus is encased in a lipid envelope with attachment proteins on the outside
• bacteria are simple they have cytoplasm encased in a cell wall made from murein
• the attachment proteins on the surface of a virus help it to attach to a host cell
• cell fractionization is the process of breaking cells and splitting organelles
• the first step of cell fractionization is the tissue must be placed in a cold (enzymes), isotonic (osmosis), buffered solution (PH)
• homogenisation is the second step of cell fractionization this is when a blender breaks up the cells releasing the organelles resulting in a fluid which must be filtered
• ultracentrifugation is the last step of cell fractionization it separates the organelles from the cytoplasm as it rotates at different speeds.
• during ultracentrifugation the first speed releases the nuclei, second speed is the chloroplast or mitochondria, fastest speed releases lysosomes
• before mitosis can take place the cell goes through interphase (DNA replication)
• the two copies of DNA are called chromatids and are held together by a protein called the centromere
• 4 stages of mitosis: prophase, metaphase, anaphase, telophase
• prophase is when chromosomes become visible and the nuclear envelope breaks down
• metaphase is when chromosomes line up in the centre of the cell
• anaphase is when the spindle fibres contract causing the chromosomes to be pulled to either side
• telophase is where new nuclei form at opposite ends of the cell and the cytoplasm divides into two daughter cells
• the end result of mitosis is that there are now two identical daughter cells with one set of chromosomes each
• after mitosis, cytokinesis occurs when the cytoplasm splits into two daughter cells
• mitosis happens to grow, repair and reproduce (organic substances)
• the mitotic index is the number of cells that are in mitosis per/total number of cells
• in prokaryotic cells binary fission takes place which is how they divide
• viruses don't replicate by division they insert themselves into the host cell and use the cell's machinery to replicate
• cancer happens when mutation causes uncontrollable mitosis
• the plasma membrane of a cell is made from a phospholipid bilayer
• a phospholipid bilayer means that the hydrophilic heads are on the outside and the hydrophobic tails are on the inside
• a cell surface membrane is made from proteins, cholesterol, glycolipids and glycoproteins
• the proteins in a csm are mostly carrier or channel proteins, which are involved in transport
• the cholesterol in a csm makes it rigid and limits movement of the phospholipids which prevents leakage
• glycolipids act as receptors for recognition of specific molecules
• glycoproteins acts as receptors for hormones and neurotransmitters
• the phospholipid bilayer is arranged in a fluid-mosaic model
• movement across the membranes can happen via: osmosis, diffusion, facilitated diffusion, and active transport
• diffusion is the net movement of particles from an area of high concentration to an area of low concentration
• rate of diffusion is impacted by SA, distance, difference in concentration and temperature
• facilitated diffusion is still a passive process it just involves protein channels at specific points