biology paper 1

• Light microscope


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


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


  1. Measure image size

  2. Divide by magnification
• Eukaryotic cells


  Have a nucleus where DNA is found (e.g. plant and animal cells)
• Prokaryotic cells


  Don't have a nucleus, DNA is in a ring called a plasmid
• Subcellular structures


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


  1. Number doubles every 10 minutes

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

  3. Calculate size of culture 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 in each new cell
• Cell specialisation


  • Cells specialize to fulfill different functions (e.g. nerve, muscle, root hair)
• Stem cells


  Unspecialized cells that can differentiate into different cell types
• Diffusion


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


  Diffusion of water across a semi-permeable membrane
• Measuring osmosis


  1. Cut equal size vegetable cylinders

  2. Weigh and place in varying 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 tissue
  • Digestive tissue
• Organs


  • Heart
  • Liver
  • Gallbladder
• Organ systems


  • Circulatory system
  • Digestive system
• Enzymes


  • Biological catalysts that break down larger molecules into smaller ones
  • Work on a lock and key principle with specific substrates
• Measuring enzyme activity


  1. Mix enzyme and substrate

  2. Test for remaining substrate every 10 seconds using iodine

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

  4. Find optimum 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


  • 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 away from heart, veins carry deoxygenated blood towards heart
  • Arteries have thicker walls, veins have valves
• Coronary artery


  Supplies heart muscle with oxygen and nutrients
• Cardiovascular disease


  Non-communicable disease caused by factors within the body (e.g. cholesterol buildup)
• Coronary artery


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


  Caused by blockage of coronary arteries, also known as coronary heart disease (CHD)
• 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 heart valves can replace faulty ones to prevent backflow
• Blood


  Carries oxygen, nutrients, white blood cells, and platelets
• Cardiovascular disease (CVD)


  Non-communicable disease caused by factors within the body, e.g. obesity, diabetes, smoking
• Communicable disease


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


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


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


  Cancerous cells spread through the body, much worse
• Plant organs


  Leaves, roots, meristem
• Photosynthesis


  1. Occurs in chloroplasts

  2. Produces glucose for food and energy storage

  3. Requires light energy (endothermic reaction)