Topic 2

• the nuclear envelope is a double plasma membrane with pores allowing movement between nucleus and cytoplasm
• chromatin is the un condensed form of dna
• the nucleolus makes ribosomes
• the outer membrane of the nucleus is continuous with the endoplasmic reticulum
• dna is in un condensed form so that dna code is accessible for protein synthesis
• dna is wrapped around histone proteins
• bilayer made up of phospholipids and proteins
• during binary fission, circular dna is replicated, plasmids are replicated several time, cells elongate producing new cell wall to accommodate increase in size, circular dna moves to opposite poles, cytoplasm divides carrying circular dna and variable number of plasmids
• during virus replication, viral attachment proteins bind to complementary receptor proteins on host cell membrane, viral nucleic acid enters host cell, host cell organelles make multiple copies of viral dna and protein synthesises new viral capsid proteins, new virus particles assembled and released
• during interphase dna is replicated, organelles replicated, cell grows in size
• adhesion proteins hold cells together
• during telophase the nuclear membrane reforms the chromosomes uncondense becoming long thin chromatin fibres that can no long be seen with a microscope
• cancer treatments work by preventing dna replication, damaging dna resulting in apoptosis, inhibiting metaphase by interfering with spindle formation
• dna replicates during s phase
• mitotic index is found by number of cells with visible chromosome/ total number of cells
• during anaphase spindle fibres contract pulling chromatids to opposite poles of the cell
• during metaphase chromosomes align at the equator, spindle fibres from poles of cell attach to centromeres
• apoptosis is cell suicide
• tumours are caused by uncontrolled cell division due to cell mutating
• in prokaryotes, there is no prophase metaphase or anaphase
• mitotic index is the proportion of cells in a sample that are undergoing mitosis at a particular time
• during prophase chromatins condense into tightly coiled visible chromosomes and the nuclear membrane breaks down
• cyctokinesis is the division of the cyctoplasm to form two seperate daughter cells, membrane constricts in the middle to surround each new cell
• glycolipids are recognition sites for chemicals and also help adjacent cells attach when forming tissues
• diffusion is proportional to surface area x difference in concentration/ length of diffusion path
• water potential will be positive when water is under physical pressure eg expelled from a syringe
• co transport is when a substance takes advantage of the diffusion gradient of another substance and the two are transported together
• during active transport molecule binds to receptors on carrier protein atp also binds and is then hydrolysed to give adp releasing energy causing the carrier protein to change shape
• glycoproteins have carbohydrate chains added some of which function as receptor proteins
• channel proteins and carrier proteins are involved in facilitated diffusion
• channel proteins are water filled, selective opening in presence of specific molecules
• carrier proteins change shape when they bind with specific molecules as they change shape this moves molecule to other side of membrane
• glycolipid is a phospholipid with a carbohydrate chain joined
• cholesterol is a type of lipid that fits between normal phospholipids in membrane, binds to hydrophobic tails causing them to pack more closely making membrane less fluid
• circulatory systems are required in some multicellular organisms as they have a small surface area to volume ratio
• diffusion is the net movement of substances from a region of high concentration to a region of lower concentration of the same substance down a concentration gradient
• double circulation means blood passes through heart twice in one full curculation
• osmosis is a special case of diffusion in which water moves from a solution of high water potential to a lower water potential through a partially permeable membrane
• addition of solute will lower water potenital
• dynamic equilibrium is when there is no net movement in one direction but particles are still moving