bio paper 1

• Light microscope


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


  Can see fine details of organelles
• Magnification


  Image size / Object size
• Cells can be categorised as eukaryotic (have a nucleus) or prokaryotic (no nucleus)
• Eukaryotic cell structures


  • Cell membrane
  • Cell wall (plant cells and bacteria)
  • Cytoplasm
  • Mitochondria
  • Ribosomes
  • Chloroplasts (plant cells)
• Bacteria multiply by binary fission, doubling in number every 10 minutes
• Bacterial culture growth practical

  1. Lift lid towards flame to destroy airborne microbes

  2. Use sterilized equipment

  3. Incubate at 25°C

  4. Calculate culture size or area of inhibition
• Diploid cells


  Cells with 23 pairs of chromosomes
• Haploid cells


  Cells with 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
• Osmosis practical


  1. Cut potato cylinders

  2. Weigh and place in sugar solutions

  3. Reweigh after a day

  4. Calculate percentage change in mass

  5. Plot against sugar concentration
• 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
• Enzyme activity practical


  1. Mix enzyme and substrate

  2. Test for remaining substrate every 10 seconds

  3. Plot time taken for 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 vs respiration


  Breathing provides oxygen for respiration in cells
• Gas exchange in lungs

  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 circulation
• Blood vessel types


  • Arteries (thick walls, narrow lumen)
  • Veins (thin walls, valves)
  • Capillaries (one cell thick)
• Coronary artery


  Supplies heart muscle with oxygen
• Stents


  Tubes inserted into blood vessels to keep them open
• Examples of non-communicable diseases

  • Coronary heart disease
  • Autoimmune conditions
  • Cancer
• Communicable diseases are caused by pathogens 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
• Heart valves


  Can become faulty, resulting in backflow, and may need to be replaced with artificial ones
• Cardiovascular disease (CVD)


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

  • CVD
  • Autoimmune conditions
  • Cancer
• Communicable disease


  Caused by a pathogen that enters the body, resulting in viral, bacterial or fungal infection
• Carcinogens


  Anything that increases the risk of cancer
• Benign cancer


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


  Cancerous cells spread through the body, much worse
• Photosynthesis


  Process in plant cells that uses chlorophyll to produce food (glucose) from light, water and carbon dioxide