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• Light microscope


  Can see cells and maybe the nucleus, but not subcellular structures
• Electron microscope


  Can see much finer details and subcellular structures, has better resolving power and higher resolution
• Calculating cell size


  1. Measure image size

  2. Divide by magnification
• Cell types


  • Eukaryotic cells
  • Prokaryotic cells
• Eukaryotic cells


  • Have a nucleus where DNA is found
• Prokaryotic cells


  • Don't have a nucleus, DNA is in a ring called a plasmid
• Cell organelles

  • Cell membrane
  • Cell wall
  • Cytoplasm
  • Mitochondria
  • Ribosomes
  • Chloroplasts
  • Vacuole
• Practical: Bacterial culture on agar

  1. Use aseptic technique

  2. Lift lid towards flame

  3. Use sterilized equipment

  4. Incubate at 25°C
• Measuring bacterial culture


  1. Calculate size from initial drop or area where bacteria didn't grow

  2. Use πr^2 or πD^0.5 to calculate area
• Human cells


  • Have 23 pairs of chromosomes (diploid)

  Gametes have 23 chromosomes (haploid)
• Cell division by mitosis

  1. Genetic material duplicated

  2. Nucleus breaks down

  3. Chromosomes pulled to opposite sides

  4. New nuclei form
• Specialized cells

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

  Unspecialized cells that can differentiate into various cell types
• Stem cells can be used to treat conditions like diabetes and paralysis
• Cloning plants can prevent species extinction or produce crops with specific characteristics
• Diffusion

  Movement of molecules/particles from high to low concentration, down concentration gradient, passive process
• Osmosis

  Diffusion of water across a semi-permeable membrane
• Practical: Osmosis experiment

  1. Cut equal potato cylinders

  2. Weigh and place in sugar solutions

  3. Reweigh after a day

  4. Calculate % change in mass

  5. Plot against sugar concentration
• Active transport


  Using energy to move substances against a concentration gradient
• Digestive system processes

  • Acid in stomach breaks down food
  • Bile and enzymes in small intestine break down food further
  • Bile made in liver, stored in gallbladder
• Enzymes


  Biological catalysts that break down specific molecules

  Work on a lock and key principle

  Rate increases with temperature until denaturation, also affected by pH
• Practical: Investigating enzyme activity

  1. Mix amylase and starch at different temperatures or pH

  2. Test for starch breakdown over time using iodine

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

  Iodine for starch, Benedict's solution for sugars, Biuret's reagent for proteins, ethanol for lipids
• Respiratory system structures

  • Trachea
  • Bronchi
  • Bronchioles
  • Alveoli
• Breathing vs respiration

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

  1. Oxygen diffuses into blood vessels

  2. Carbon dioxide diffuses out
• Components of blood


  • Red blood cells
  • Plasma
  • White blood cells
  • Platelets
• Circulatory system

  1. Deoxygenated blood enters right atrium

  2. Pumped to lungs via pulmonary artery

  3. Oxygenated blood returns to left atrium

  4. Pumped to body via aorta
• Heart structure

  • Right ventricle pumps to lungs, left ventricle pumps to body

  Pacemaker cells create electrical pulses to make heart contract
• Blood vessels

  Arteries carry oxygenated blood away from heart, veins carry deoxygenated blood towards heart

  Capillaries allow fast diffusion
• Coronary arteries supply heart muscle with oxygen, blockages can cause heart attacks
• Stents can be used to keep blood vessels open, statins reduce cholesterol buildup
• Non-communicable diseases


  Caused by factors within the body, e.g. cardiovascular disease, allergies, cancer
• Communicable diseases


  Caused by pathogens that can be transmitted, e.g. infectious diseases
• 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
• what is a Stent

  A small tube 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
• Cardiovascular (CV) disease


  An example of a non-communicable disease, caused by factors within the body