Biology

• The nucleus is the control center of the cell.
• Cystoplasm- gel like substance where chemical reactions take place. Contains enzymes
• Mitochondria- where aerobic respiration takes place. This respiration helps the cell to work
• Cell wall- made up of cellulose which gives strength to plant cells
• Chloroplast- site of photosynthesis, contains chlorophyll
• Ribosomes- involved in the translation in the synthesis of proteins.
• Animal cells do not contain a permanent vacuole but instead rely on smaller vesicles called lysosomes to digest materials within the cytoplasm.
• Eukaryotic- complex and multiceular organisms, such as plants and animals
• Prokaryotic- simple, small and unicellular
• The point where two neurones meet, there is a gap called synapse. The impulse reaches the ends of the axon terminal. Chemical neurotransmitters are emitted into the synapse. The neurotransmitters diffuse across the synapse. Receptors on the dendrites of the next neurone detect the neurotransmitters. The receptors generate new nerve impulses.
• Gene- a small section of DNA that codes for a specific protein
• Genome- is the entire set of genetic material in an organism
• Genotype- is the collection of alleles we have
• Phenotype- is the characteristics we get from the genotype
• DNA is the genetic material found in chromosomes in the nuclei of cells
• How our genes can be mutated: One base is substitued for another base, an extra base is added and then take the other base away.
• The Human Genome Project- in 2008 the first human genome was decoded, the results were used to develop new medicines and treatments for diseases. Advantages: person can make lifestyle changes, distinguishing between different forms of diseases, allows doctors to tailor treatments for some diseases to the individual. Disadvantages: people who are at risk of a certain disease may have to pay more to obtain insurance, may not be helpful to tell a person they are at risk of a disease that has no cure.
• Continuous variation: where the characteristics changes gradually over a range of values e.g height. Discontinuous variation: where the characteristic has distinct forms, with no overlap.
• Evolution- The natural selection of genetic changes that give rise to the phenotypes that are best suited for the environment.
• Diffusion is the net movement of particles from areas of high concentration to areas of low concentration. Can happen in both gases and liquids and it is a passive process. 3 factors that affect rate of diffusion are: Concentration gradient, temperature and surface area.
• Osmosis is the net movement of solvent molecules across a partially permeable membrane, from region of higher water concentration to lower water concentration. It is a passive process
• Active transport is the movement of particles against the concentration gradient. Takes place in a cell membrane and requires special proteins since it is a active process. Energy for active transport comes from cellular respiration. Plant cells have to use active transport to absorb mineral ions because their concentration is higher in the cell than the soil.
• Selecetive breeding- when plants or animals with desireable characteristics are bred together to produce an offspring with that desirable characteristic
• Plants with good features are crossed. Plants grown from seed of these crosses are selected for their good features and crossed with each other. Selection and crossing is repeated many times until a high-yielding variety is produced.
• Genetic Engineering- chainging the genome of an organism by introducing genes from another to create genetically modified organisms with desirble characteristics.
• Genetic engineering for human insulin: 1. Isolate the insulin gene from human DNA using restriction enzymes, to produce sticky ends. 2. Use the same restriction enzymes to cut open the bacterial plasmid, forming complementary sticky ends. 3. Insert the insulin gene into the plasmid using the enzyme DNA ligase, to form recombinant plasmid. 4. Insert the recombinant plasmid into the host bacteria. 5. Let the bacteria divide and then produce the insulin protein.
• Virus- Take over a body cell's DNA, causing it to make toxins or causing damage when new viruses are released from the cells. Bacterium- Bacteria may produce toxins which makes us feel ill. Some types of bacteria invade and destroy body cells.
• Chemical defences- Lysozymes: enzymes that kill bacteria by digesting their cell wall, secreted in tears, saliva and mucus. Hydrochloric acid- found in the stomach, kills pathogens because it is so acidic.
• Physical barries- Skin: very thick and covers the whole body, it secrets oils and anti-microbial substances which kill pathogens that rest on it. Mucus: Sticky secretion produced by cells lining the openings, found in the mouth and nose and it traps pathogens and other particles that flow through the air. Cilia: specialised to move substances across their surfaces, found in the nose, tranchea, bronchi and bronchioles, has a wave-like motion moving mucus and trapped pathogens out of the lungs and towards the back of the throat where it is swalled.
• Immune system- Pathogen enters the body. The pathogen has antigens across its surface- these antigens are different to the host's. The pathogen in the blood comes in contact with lymphocytes (type of white blood cell). Different lymphocytes have different antibodies. The lymphocytes with the antibodies that match the pathogens antigens will be activated.The activated lymphocytes divide rapidly, to make lots of clones.
• Some lymphocytes release lots of antibodies in the blood. The antibodies attach to the pathogen's antigens and kill the pathogen. When all pathogens are dead, a few memory lymphocytes remain for years.
• Ethanol(found in alcohol) is poisonous to cells. When absorbed from the gut, it first passes the the liver to be broken down. Therefore, liver cells are more likely than any other cells to be damaged resulting in liver disease.
• Tobacoo smoke contains many harmful substances which damage the lungs, blood vessels, increase blood pressure and increase the risk of blood clotforming in vessels, this leads to cardiovascular diseases such as heart attcks or strokes.
• Malaria: Mosquitoe bites human and injects protist that causes malaria, the liver cells and blood cells arev then infected, the mosquitoe becomes infected with a parasite when taking a blood meal. Mosquitoe bites a second person and spreads malaria.
• Cholera (waterborne)- bacteria, severe diarrhoera. Tuberculousis (airborne)- bacteria, lung damage, blood-speckled mucus after coughing, night sweats, weightloss. Chalara ash-dieback (airborne)-fungi, leaf loss, bark lensions. Malaria (vectors)- protists, weakness, sickness, damage to liver and blood. HIV- destroys white blood cells, weakened immune system, more suspectable to other diseases.