PAPER 1

• 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 using aseptic technique

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


  Have 23 pairs of chromosomes
• Haploid cells


  Have 23 single chromosomes
• 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 various cell types
• Diffusion


  Passive movement of molecules/particles from high to low concentration
• 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 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
• Measuring enzyme activity


  1. Mix enzyme and substrate

  2. Test for remaining substrate every 10 seconds

  3. Plot time taken 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, bronchi, bronchioles to alveoli

  2. Oxygen diffuses into blood, carbon dioxide diffuses out
• Double circulatory system


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


  • Arteries (thick walls, narrow lumen)
  • Capillaries (one cell thick walls)
  • Veins (thin walls, valves)
• Coronary arteries supply heart muscle with oxygen
• Cardiovascular disease


  Non-communicable disease caused by internal factors
• Communicable diseases are caused by external factors like pathogens
• 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
• Carcinogens


  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
• Photosynthesis


  Process in plant leaves that produces food for the plant
• Transpiration


  Process of water leaving the plant through the leaves
• Xylem


  Long continuous tubes that transport water up the plant