biology paper1

• 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 (plant cells and bacteria)
  • Cytoplasm
  • Mitochondria
  • Ribosomes
  • Chloroplasts (plant cells)
• 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
• Stem cells


  Unspecialised cells that can differentiate
• Diffusion


  Movement of molecules/particles from high to low concentration, no energy required
• 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 concentration to find no change point
• Active transport


  Using energy to move substances against a concentration gradient
• Tissues


  • Heart
  • Digestive
• Enzymes


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


  1. Mix enzyme and substrate

  2. Test for remaining substrate every 10 seconds

  3. Plot time taken to break down all substrate against temperature or pH

  4. 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)
• Heart


  Needs its own blood supply via coronary arteries
• Cardiovascular disease


  Example of a non-communicable disease
• Communicable diseases have causes from outside the body
• 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 within 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
• Leaves


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


  The diffusing of water out of leaves, allowing water and minerals to be drawn up from the roots