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• Microscopes


  Normal light microscope can see cells and nucleus, electron microscope can see subcellular structures in more detail
• Calculating cell size


  1. Measure image size

  2. Divide by magnification
• Eukaryotic cells


  Have a nucleus containing DNA
• Prokaryotic cells


  Do not have a nucleus, DNA is in a ring called a plasmid
• Cell structures


  • Cell membrane
  • Cell wall (in plants and bacteria)
  • Cytoplasm
  • Mitochondria
  • Ribosomes
  • Chloroplasts (in plants)
• Bacterial binary fission

  1. Number doubles every 10 minutes

  2. Practical: Grow culture on agar plate using aseptic technique

  3. Calculate culture size from initial drop or area not grown
• Diploid cells


  Have 23 pairs of chromosomes
• Haploid cells


  Have 23 chromosomes (not in pairs)
• Mitosis


  1. Genetic material duplicated

  2. Nucleus breaks down

  3. Chromosomes pulled to opposite sides

  4. New nuclei form
• Specialised cell types


  • Nerve
  • Muscle
  • Root hair
  • Xylem
  • Phloem
  • Sperm
• Stem cells


  Unspecialised cells that can differentiate
• Diffusion


  Passive movement of molecules/particles from high to low concentration
• Osmosis


  Diffusion of water across a semi-permeable membrane
• Measuring osmosis


  1. Cut potato cylinders

  2. Weigh and place in sugar solutions

  3. Reweigh after a day

  4. Calculate % change in mass

  5. Plot against sugar concentration to find no change point
• Active transport


  Using energy to move substances against a concentration gradient
• Enzymes


  Biological catalysts that are specific to certain substrates
• Measuring enzyme activity


  1. Mix enzyme and substrate

  2. Measure time to complete reaction at different temperatures/pH

  3. Plot time vs temperature/pH to find optimum
• Food tests


  • Iodine for starch
  • Benedict's solution for sugars
  • Biuret's reagent for proteins
  • Ethanol for lipids
• Breathing vs respiration


  Breathing provides oxygen for respiration in cells
• Gas exchange in lungs

  1. Air enters trachea, bronchi, bronchioles, alveoli

  2. Oxygen diffuses into blood, carbon dioxide diffuses out
• Circulatory system


  Double circulatory system - blood enters heart twice per cycle
• Blood vessels


  • Arteries (thick walls, narrow lumen)
  • Veins (thin walls, valves)
  • Capillaries (one cell thick)
• Coronary artery


  Supplies heart muscle with oxygen
• Non-communicable diseases


  Caused by internal factors, e.g. cardiovascular disease, cancer
• Communicable diseases


  Caused by external pathogens, e.g. infections
• Coronary artery

  Delivers blood to the heart muscle to supply oxygen
• Coronary heart disease (CHD)


  Occurs when coronary arteries are blocked by fatty deposits, causing a heart attack
• Stents


  Little tubes inserted into blood vessels to keep them open and allow blood flow
• Statins


  Drugs that reduce cholesterol and fatty deposits
• Faulty heart valves


  Result in backflow, can be replaced with artificial ones
• Blood


  Carries oxygen, nutrients, white blood cells, and platelets
• Cardiovascular disease (CVD)


  Non-communicable disease caused by factors within the body, e.g. obesity, diabetes, smoking
• Communicable disease


  Caused by a pathogen (virus, bacteria, fungus, or parasite) that enters the body
• Carcinogen


  Anything that increases the risk of cancer, e.g. ionizing radiation
• Benign cancer

  Doesn't spread through the body and is relatively easy to treat
• Malignant cancer


  Cancerous cells spread through the body, much worse
• Plant organs


  • Leaves - site of photosynthesis
  • Roots - where water and minerals enter
  • Meristem - where new cells are made
• Xylem


  Long continuous tubes that transport water upwards
• Phloem


  Conveyor belts that transport sugars, mineral ions, and sap up and down the plant
• Transpiration

  The evaporation of water from leaves