Biology 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
• 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
  • Cytoplasm
  • Mitochondria
  • Ribosomes
  • Chloroplasts
  • Vacuole
• Bacterial binary fission


  1. Number doubles every 10 minutes

  2. After 1 hour: 64 bacteria

  3. After 6 hours: 6.87 * 10^10 bacteria
• Practical on bacterial growth

  • Use aseptic technique
  • Incubate at 25°C
  • Calculate area of culture or area where bacteria were killed by antibiotics
• 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, down concentration gradient
• Osmosis


  Diffusion of water across a semi-permeable membrane
• Practical on 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
  • Enzymes break down food into small molecules
• Enzymes


  Biological catalysts that are specific to certain substrates
• Practical on enzyme activity

  1. Mix amylase and starch at different temperatures or pH

  2. Test for starch every 10 seconds using iodine

  3. Plot time taken for starch to be broken down against temperature or pH
• Food tests


  • Iodine for starch
  • Benedict's solution for sugars
  • Biuret 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 cycle - deoxygenated blood to lungs, oxygenated blood to body
• Heart structure and function

  • Right side pumps deoxygenated blood to lungs, left side pumps oxygenated blood to body
  • Pacemaker cells create electrical pulses to make heart contract
• Blood vessels


  • Arteries carry oxygenated blood away from heart, veins carry deoxygenated blood towards heart
  • Arteries have thicker walls, veins have valves
• Coronary arteries supply heart muscle with oxygen
• Cardiovascular disease


  Non-communicable disease caused by internal factors, e.g. coronary heart disease, heart valve problems
• Communicable diseases are caused by external 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
• Carcinogen


  Anything that increases the risk of cancer
• Benign cancer


  Doesn't spread through the body, relatively easy to treat