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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, use aseptic technique

  3. Calculate culture size from area or initial drop
• 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
• Stem cells

  Unspecialised cells that can differentiate into different cell types
• 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


  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
• Digestive system processes


  • Acid in stomach
  • Bile and enzymes in small intestine
  • Nutrients absorbed by villi
• Enzymes


  Biological catalysts that are specific to certain substrates, work on a lock and key principle
• Practical: Enzyme activity


  1. Mix amylase and starch

  2. Test for starch every 10 seconds with iodine

  3. Plot time to complete reaction against temperature or pH

  4. Find optimum conditions
• Food tests


  • Iodine for starch
  • Benedict's solution for sugars
  • Biuret's reagent for proteins
  • Ethanol for lipids
• Breathing and gas exchange

  1. Air moves down trachea to alveoli

  2. Oxygen diffuses into blood

  3. Carbon dioxide diffuses out
• Double circulatory system


  Blood enters heart twice per cycle, deoxygenated blood to lungs, oxygenated blood to body
• Blood vessel types


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


  Supply heart muscle with oxygen
• Non-communicable diseases


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


  Caused by external pathogens, 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
• Stents


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


  Drugs that reduce cholesterol and fatty deposits
• Heart valve replacement


  Artificial valves can replace faulty ones to prevent backflow
• Blood components


  Plasma, red blood cells, white blood cells, platelets
• White blood cells


  Combat infections
• Platelets


  Clump together to clot wounds and stop bleeding
• Cardiovascular disease (CVD)


  Non-communicable disease caused by factors within the body
• Other non-communicable diseases


  • Autoimmune conditions, allergic reactions, cancer
• Communicable disease


  Caused by a pathogen that enters the body, leading to viral, bacterial or fungal infection
• Type 2 diabetes


  Caused by obesity and too much sugar
• Risk factors for heart disease


  Bad diet, smoking, lack of exercise, alcohol
• Carcinogen


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


  Result of damaged cells dividing uncontrollably, leading to tumours