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 – micro-organism 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