Transcript Chapter 1
INTERMEDIATE 2 BIOLOGY 3 topics: Living Cells, Genetics & Environmental Biology, Animal Physiology Each unit: 1 unit test (NAB) - 45 mins 65% pass mark (only 1 resit) Practical Report: 1 full experimental report Prelim/Exam : 25 MCQ, 65 short answers, 10 essay Structure & Function of Cells All cells contain: Nucleus: - controls cell activities - passes on information to next generation Cytoplasm: site of biochemical reactions Cell Membrane: - controls substances moving in & out of cells Structure & Function of Cells Structures only in plant cells: Chloroplast: - Contains chlorophyll - absorbs light to help photosynthesis Cell Wall: - made of cellulose, - keeps cell shape semi-rigid Vacuole: - regulates water & solute content Yeast - single celled fungus - doesn’t photosynthesise (no chlorophyll) - reproduces by budding - can feed using oxygen - this is aerobic respiration - or without oxygen - this is anaerobic respiration - respiration is the release of energy from food Uses of yeast During anaerobic respiration - Sugar Alcohol + CO2 + energy This is known as alcoholic fermentation In baking - sugar in dough is fermented to alcohol & CO2 - bubbles of CO2 makes dough rise - alcohol is boiled off by the oven Brewing/Wine making Beer making uses maltose Maltose produced by germinating barley grains Wine making uses sugar from crushed grapes Alcohol production stops when yeast get poisoned by the alcohol content Dead yeast must be filtered out Alternative Fuels Gasohol - fuel produced from plant fermentation - mixture of alcohol and petrol Biogas - anaerobic bacteria feed on organic waste - waste converted to methane (‘biogas’) - methane is a useful fuel Antibiotics A natural chemical produced by micro-organisms These chemicals can kill or stop the growth of other micro-organisms If growth is stopped – microorganism is sensitive to the antibiotic If it isn’t stopped – it is resistant Effect of antibiotics on sensitive bacteria Antibiotics damage bacteria in different ways: - damage cell membrane - damage or affect chromosomes - stop synthesis of cell wall - stop chemical reactions in cytoplasm However, many bacteria develop resistance to the antibiotics Some can develop multiple resistance – e.g. MRSA Need for a wide range of antibiotics No one antibiotic is effective against all bacteria Some people are allergic to certain antibiotics New resistant strains appear to a particular antibiotic, so others may be needed instead - in this example 2 antibiotics have no effect Lactic Acid Milk is rich in sugar, protein & fat When milk sours, bacteria feed on the milk They convert lactose into lactic acid Lactic acid makes milk proteins clump together (coagulate) This forms a semi-solid food – yoghurt The acid conditions (low pH) acts as a preservative