biology paper 1

• 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
  • 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 structures


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


  1. Number of bacteria doubles every 10 minutes

  2. After 1 hour: 2^6 = 64 bacteria

  3. After 6 hours: 2^36 = 6.87 x 10^10 bacteria
• Practical: Bacterial culture


  • Use aseptic technique
  • Incubate at 25°C
  • Measure area of culture or area where bacteria were killed by antibiotics
• Diploid cells


  Cells with 23 pairs of chromosomes
• Haploid cells


  Cells with 23 unpaired chromosomes
• Mitosis


  1. Genetic material duplicated

  2. Nucleus breaks down

  3. Chromosomes pulled to opposite sides

  4. New nuclei form in each new cell
• Specialised cell types


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


  Unspecialised cells that can differentiate into different cell types
• Diffusion


  Movement of molecules/particles from high to low concentration, down concentration gradient, no energy required
• Osmosis


  Diffusion of water across a semi-permeable membrane
• Factors affecting diffusion/osmosis rate

  • Concentration gradient
  • Temperature
  • Surface area
• Practical: Osmosis


  1. Cut equal size vegetable 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


  • Stomach acid breaks down food
  • Bile neutralizes acid and emulsifies fats
  • Enzymes break down food into smaller molecules
• Enzymes


  • Biological catalysts that are specific to certain substrates
  • Work on a lock and key principle
  • Rate increases with temperature until denaturation, also affected by pH
• Practical: Enzyme activity


  1. Mix enzyme and substrate at different temperatures or pH

  2. Measure time taken for all substrate to be broken down

  3. Plot against 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


  • Air moves down trachea, bronchi, bronchioles to alveoli
  • Oxygen diffuses into blood, carbon dioxide diffuses out
• Circulatory system


  • Double circulatory system - blood enters heart twice per cycle
  • Deoxygenated blood enters right side, oxygenated blood leaves left side
• Blood vessels


  • Arteries carry oxygenated blood (except pulmonary artery), veins carry deoxygenated blood (except pulmonary vein)
  • Arteries have thicker walls, veins have valves
• Coronary arteries supply the heart muscle with oxygen
• Stents


  Tubes inserted into blood vessels to keep them open
• Cardiovascular disease


  Non-communicable disease caused by factors within the body, e.g. buildup of fatty deposits
• 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 parasite) 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