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Biology. topic 8: health virus reproduction: lytic pathway: 1) They replicate their DNA and protein coats. 2) These are then assembled into new virus particles. 3)This causes the host cell or cells to burst. This is called lysis. 4)Other nearby cells can then be infected with the virus. This process can be as quick as twelve hours in the case of the norovirus or several days for the process of Ebola. Lysogenic pathway: 1) The virus injects its DNA into the host cell and the DNA becomes incorporated into the host DNA 2) As the host cell replicates, the viral DNA replicates also, but no new virus particles are made during this time. 3) Changes in the environment cause the viral DNA to move to the lytic pathway to make new virus particles. Monoclonal antibodies: 1) An antigen is injected into a mouse. The mouse naturally produces lymphocytes, which produce antibodies specific to the antigen 2) Spleen cells which produce the lymphocytes are removed during a small operation 3) The spleen cells are fused with human cancerous white blood cells called myeloma cells to form hybridoma cells which divide indefinitely 4) These hybridoma cells divide and produce millions of monoclonal antibodies specific to the original antigen Core practical: growing microbes. 1) Glass Petri dishes and agar gel must be sterilised before use in an autoclave, or pre-sterilised plastic Petri dishes can be bought. Pour the sterile agar plates and allow to set fully. 2) Sterilise the inoculating loop, by heating it in the Bunsen burner flame. Dip the inoculation loop into the microorganism solution and make streaks on the surface of the agar plate. 3) Replace the lid as soon as possible, secure with tape. Label and invert the plate, and store upside down. Incubate at a maximum temperature of 25°C in schools and colleges. Body mass index = mass/height2. BMI = m/h2 Waist:hip ratio = waist circumference/hip circumference. Cardiovascular disease: Generally associated with blocked arteries. When fat builds up in the arteries, it can restrict blood flow and cause high blood pressure. Statins are drugs that reduce the bad cholesterol in blood that need to be taken regularly. Antihypertensives reduce blood pressure by flushing out excess water, relax blood vessels or cause heart beat to slow down. Anticoagulants prevent blood clots in the arteries, but they can also prevent blood clots from an injury, meaning that the bleeding wouldn’t stop. Stents are meshes that are placed into the arteries to force them open and squashing fat build up. Coronary bypass surgery is used when stents aren’t enough and an artery from elsewhere and bypasses the blockage. Topic 9: plants. Core practical: photosynthesis. 1)Set up a boiling tube containing 45 cm3 of sodium hydrogen carbonate solution (1%). Allow the tube to stand for a few minutes and shake to disperse any air bubbles that might form 2) Cut a piece of the pond weed. Use forceps to place the pond weed in the boiling tube carefully. The pond weed should be put in boiling tube, with the cut end uppermost. Make sure that you don’t damage the pond weed or cause the liquid to overflow. 3) Position the boiling tube so that the pond weed is 10 cm away from the light source. Allow the boiling tube to stand for five minutes for the pond weed to acclimatise. Count the number of bubbles emerging from the cut end of the stems in one minute. Repeat the count five times and record your results. 4) Calculate the average number of bubbles produced per minute. Repeat the experiment at different distances away from the light source. Light intensity = 1/distance. Plant hormones: Auxin is a hormone that affects the plants growth. They are found in the tip of the plant and its roots. Phototropism is where the plant grows up wards and bends towards the light and more auxin is on the shaded side, making it bend upwards. Gravitropism is where the plant grow sideways but bend due to gravity and auxins are in the roots. Auxins gather in the lower side of root which makes it grow up. Auxin is used in weedkillers which causes weeds to grow too much and die. Gibberellins are used to produce seedless fruit by growing unpollinated plants which won’t grow any seeds. Topic 10: hormones. Hormones are chemical messengers that travel in the blood to activate cells in large organs. Endocrine system: Pituitary gland is in the brain and controls body conditions. Thyroid gland is in the throat and releases thyroxine to control metabolism, heart rate and temperature. Pancreas produces insulin to regulate glucose in blood. Adrenal glands are above the kidney and release adrenaline for fight or flight response. Ovaries release oestrogen which is part of the menstrual cycle. Testes release testosterone which controls sperm and puberty. Negative feedback loops are when a condition in the body changes, the steps required to revert it back to normal. Menstrual cycle: Stage 1 is when the cycle starts where the uterus lining breaks down and releases for four days. Stage 2 is where uterus lining is repaired from day 4-14 ready for a fertilised egg to develop. Stage 3 is where the egg is released on day 14. Stage 4 is lining is maintained for 14 days till day 28. If no egg is in the uterus, then the cycle restarts. Oestrogen stimulates the growth of uterus lining and progesterone stimulates the uterus breaking down. FSH matures the egg in the ovaries and LH bursts a follicle to release the egg and turn the remains into corpus luteum. Homeostasis: After meal containing carbs is digested, the glucose levels rise. Pancreas responds by producing insulin which causes cells to use more glucose. Liver cells turn the glucose into glycogen. If a person’s glucose level drops, the pancreas releases glucagon to turn glycogen into glucose. Diabetes: Diabetes is caused when there is not enough insulin produced to control glucose levels. type 1 diabetes is where the person has insulin therapy and insulin is manually injected into the blood throughout the day. type 2 diabetes is where there isn’t enough insulin, or the body is resistant to insulin which can become dangerous. Thermoregulation: Thermoregulation is where the body monitors body temperature using the hypothalamus. Receptors in the hypothalamus are sensitive to temperature change and will alert if there is a change. When the body is too warm, erector muscles in the upper layer of the arm make hairs lay flat to remove an insulating layer of air to allow heat to leave. Sweat is produced and released on the skin to evaporate and convert energy to surroundings. When the body is too cold, the hairs stand up to trap air as an insulating layer to reduce the amount of energy lost to surroundings. Osmoregulation: Osmoregulation keeps the concentration of water in blood under control to keep cells working normally. If it’s too high, then water will move into the body cells with osmosis which can burst them with too much. If it’s too low, then water leave the cells via osmosis causing them to shrink. The kidneys make urine by removing waste from blood. Substances are filtered out of the blood by ultrafiltration and selective reabsorption takes back in the good things. Nephrons are structures in the kidney where selective reabsorption and ultrafiltration occur. Ultrafiltration starts at the renal artery where the blood enters and travels through the glomerulus which is surrounded by bowman’s capsule. The plasma containing the good stuff is forced out of glomerulus into bowman’s capsule at high pressure. ADH is released by the pituitary gland to make collecting ducts of nephrons more permeable, so more water is reabsorbed into blood. Kidney failure: If the kidney fails, you can get dialysis treatment which is where a machine acts as a kidney by filtering out the bad stuff and sending it back into the body. Dialysis fluid and blood flow in the opposite direction to it catches the bad stuff without the concentration changing. Dialysis takes up to 6 hours multiple times a week which can disrupt the patient’s personal life so they can get a kidney transplant instead.