Biology Paper 1

• Transpiration


  Plants require CO2 for photosynthesis which enters through the stomata
• Stomata


  • Guard cells open and close the stoma
  • CO2 goes in
  • O2 goes out
  • Water vapour can escape
• When guard cells lose water

  They become flaccid and the stomata close
• Factors affecting rate of photosynthesis

  • Light intensity
  • Temperature
  • Wind (air movement)
  • Humidity
• Transpiration


  Plants want to reduce transpiration while maximising photosynthesis
• Adaptations to reduce transpiration

  • Thick waxy cuticle
  • Wilting reduces surface area
  • Close stomata
  • Less direct sunlight
• Viral diseases


  Live and reproduce inside host's body cells, destroying them
• Viral diseases


  • Measles
  • HIV
  • Tobacco mosaic virus
• Communicable diseases


  Infectious diseases caused by pathogens
• Bacteria


  • Larger microorganisms that reproduce rapidly and release toxins damaging tissue
• Viruses


  • Smaller microorganisms that reproduce rapidly and damage/destroy host cells
• Plant tissues

  • Upper epidermis - covers and protects
  • Waxy cuticle - waterproof
  • Palisade mesophyll - photosynthesis
  • Spongy mesophyll - gas exchange
• Cancer


  Abnormal cell growth and division
• Benign tumours


  • Don't spread
• Malignant tumours


  • Small parts can break off and spread in blood to other organs
• Radiotherapy


  Uses radiation to kill cancer cells
• Chemotherapy


  Uses chemicals to stop rapidly dividing cells
• Lifestyle and genetic factors can increase cancer risk
• Non-communicable diseases


  Not infectious, can be caused by lifestyle choices
• Non-communicable diseases


  • Cardiovascular disease
  • Type 2 diabetes
• Coronary heart disease


  • Fatty deposits restrict blood flow to the heart
  • Stents can open arteries
  • Statins lower cholesterol
• Blood vessels


  • Arteries - carry blood away from heart, high pressure, small lumen
  • Capillaries - bring blood to cells, substances diffuse in and out
  • Veins - carry blood back to heart, low pressure, thin walls, valves
• Blood


  • Plasma - straw coloured liquid
  • Red blood cells - carry oxygen
  • White blood cells - protect against infection
  • Platelets - help blood clot
• Photosynthesis required practical


  1. Put pond weed in test tube with sodium hydrogen carbonate

  2. Cut stem at angle and place upside down in water

  3. Place lamp 1 metre away

  4. Wait 1 minute for acclimation

  5. Count bubbles produced in 1 minute

  6. Repeat at different distances
• Enzymes required practical


  1. Measure out enzyme and substrate

  2. Place in water bath

  3. Mix and start timer

  4. Every 10 seconds, remove drop and test with iodine

  5. Stop when no colour change
• Osmosis required practical


  1. Cut equal size potato cylinders

  2. Remove excess water

  3. Weigh

  4. Place in different sugar solutions for a day

  5. Reweigh and calculate % mass change
• Microscopy required practical


  1. Peel one-cell layer of onion skin

  2. Place on slide, add iodine, cover with coverslip

  3. Use lowest magnification, then increase
• Food tests required practical

  Test for sugars, starch, lipids, proteins
• Enzymes

  Biological catalysts that break down starch, proteins, lipids
• Digestive system

  • Stomach contains hydrochloric acid and enzymes
  • Liver produces bile
  • Pancreas secretes amylase
  • Small intestine breaks down food
• Mitosis


  1. Genetic DNA duplicates

  2. Two sets of chromosomes move to different sides

  3. Cell organelles duplicate

  4. Cell divides into two genetically identical cells
• Transpiration


  Movement of water through the plant (roots xylem → leaf stomata)
• Translocation movement


  Movement of glucose + amino acids through a plant
• Cells are the basic unit of life and can be classified as prokaryotic or eukaryotic based on their structure.
• Plant cells contain chloroplasts which produce energy from sunlight via photosynthesis.
• Prokaryotes have no nucleus while eukaryotes do.
• Fungi include yeasts and molds, with some species being beneficial while others cause diseases like athlete's foot.
• The cell wall is made up of cellulose fibers and provides support and protection to the cell.
• Vacuoles store water, waste products, pigments, and enzymes involved in digestion.
• Cell

  Controls animal and plant life