B1 revision

• Microscopes


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


  Image size / Object size
• Cell types


  • Eukaryotic cells (have nucleus)
  • Prokaryotic cells (no nucleus)
• Eukaryotic cells


  • DNA is found in the nucleus
  • Examples: plant and animal cells
• Prokaryotic cells


  • DNA is found in a ring called a plasmid
  • No nucleus
• Cell structures


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


  1. Number of bacteria doubles every 10 minutes

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

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


  Cells with 23 pairs of chromosomes (e.g. human body cells)
• Haploid cells


  Cells with 23 single chromosomes (e.g. gametes)
• Mitosis


  1. Genetic material duplicated

  2. Nucleus breaks down

  3. Chromosomes pulled to opposite sides

  4. New nuclei form in each new cell
• Cell specialisation


  • Cells specialize to perform specific functions (e.g. nerve, muscle, root hair cells)
  • Stem cells are unspecialized
• Diffusion


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


  Diffusion of water across a semi-permeable membrane
• Osmosis practical


  Cut potato cylinders, weigh, place in sugar solutions, reweigh, calculate % change in mass, plot against concentration
• Active transport


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


  • Acid in stomach
  • Bile and enzymes in small intestine
  • Emulsification of fats
• Enzymes


  • Biological catalysts that break down specific substrates
  • Active site has specific shape to bind substrate
  • Rate increases with temperature until denaturation, also affected by pH
• Enzyme activity practical


  Mix amylase and starch, test for starch every 10 seconds, plot time to complete reaction against temperature or pH
• 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, bronchi, bronchioles to alveoli

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


  • Heart
  • Blood vessels (arteries, veins, capillaries)
  • Blood (red blood cells, white blood cells, platelets)
• Blood flow through heart

  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
• Blood vessels


  • Arteries have thicker walls, veins have valves
• Coronary arteries supply the heart muscle with oxygen</b>
• Cardiovascular disease


  Non-communicable disease caused by factors within the body (e.g. cholesterol buildup)
• Communicable diseases are caused by pathogens that can be transmitted between organisms
• Coronary artery


  Delivers blood to the heart muscle to supply oxygen
• Heart attack


  Occurs when coronary arteries are blocked by buildup of fatty deposits, causing coronary heart disease (CHD)
• Stents


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


  Drugs that reduce cholesterol, which reduces fatty deposits
• Faulty heart valves


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


  Carries plasma, red blood cells, white blood cells (combat infections), and platelets (clot wounds)
• Cardiovascular disease (CVD)


  An example of a non-communicable disease, caused by factors inside the body
• Examples of non-communicable diseases

  • Cardiovascular disease
  • Autoimmune conditions
  • Cancer
• Communicable disease


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


  Anything that increases the risk of cancer
• Benign cancer


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

  Cancerous cells spread through the body, much worse
• Leaves


  Where photosynthesis takes place, producing food for the plant
• Transpiration

  The diffusing of water out of leaves, allowing water and mineral ions to enter through the roots