Additional biology revision guide
- 1. Cells Plant & animal cells have: Nucleus – controls cell. Cytoplasm – reactions (enzymes) Cell membrane – Controls in and out. Mitochondria – Respiration (energy) Ribosomes - Makes proteins Plants have: Chloroplasts – Photosynthesis. Cell wall – strength. Vacuole – contains sap. Cells can be specialised: e.g. muscles and sperm need energy so have lots of mitochondria. Diffusion and Osmosis: How things get in and out of cells. Osmosis – water. Diffusion – gases or solutes e.g. oxygen. From high to low concentrations.
- 2. Photosynthesis Uses light (trapped by chloroplasts.) CO 2 + Water Glucose + Oxygen Might be used in respiration. Excess stored as starch. Slow if: Too cold. Not enough CO 2 . Not sunny. Fast if: Warmer, lots of CO 2 , sunny. Plants need minerals: Nitrates – making proteins – not enough = stunted growth. Magnesium – making chlorophyll – not enough = yellow leaves.
- 3. Energy Flows Biomass = mass of living material. Less energy because: Lost in waste Movement Maintaining body temp. Factory Farming – keep animals still and warm – more energy for growth Decay: Micro-organisms. Faster if warm, moist, and there’s oxygen. Carbon Cycle: Carbon in air as CO 2. Enters plants for photosynthesis. Returns to air when plants, animals or microbes respire. Passes from plants to animals when eaten.
- 4. Enzymes Speed up reactions. Are proteins. Have a special shape, important for function. High temp or wrong pH shape changes stops working. Respiration Controlled by enzymes. Glucose + Oxygen CO 2 + Water Releases ENERGY. For movement. To maintain body temp. To build up small molecules into larger ones. Digestion: Protease: Proteins Amino acids Lipase: Fats Fatty acids & glycerol. Amylase: Starch Sugar Stomach acid – helps protease work better. Bile – neutralises acid. Industry: Detergents. Protease in baby food. Isomerase converts glucose to fructose (sweeter so use less)
- 5. Homeostasis Waste: CO 2 – made during respiration – excreted by lungs. Urea – made in liver, removed by kidneys. Urine stored in bladder. Body temp: Monitored by thermoregulatory centre (blood & skin receptors.) Sweat to cool body. Shiver to warm up. Blood sugar Monitored by pancreas. Insulin moves glucose from blood into cells. Diabetes Not enough insulin. Blood sugar can get too high. Treated by controlling diet and injecting insulin.
- 6. Inheritance Body cells – Chromosomes found in pairs (one from Mum, other from Dad). Gametes (sex cells) – Only one set of info. During fertilisation, two sets join. Stem cells – Can differentiate into many types of cell. Might be used in medical treatments. E.g. repair spine, cure paralysis. Females – XX Males - XY Allele = version of a gene. Can be dominant or recessive. Cystic fibrosis – Recessive allele – disorder of cell membranes – must be inherited from both parents. Huntingtons – Dominant allele – disorder of nervous system – can be inherited from one parent. Embryo screening can test for disease alleles.