BIOLOGY Paper 1

• Microscope

  Normal light microscope can see cells and nucleus, electron microscope can see subcellular structures in more detail
• Magnification

  Image size / Object size
• Cell types

  • Eukaryotic cells (have nucleus)
  • Prokaryotic cells (no nucleus)
• Eukaryotic cells

  • DNA is found in the nucleus
  • Examples: plant and animal cells
• Prokaryotic cells

  • DNA is found in a ring called a plasmid
  • No nucleus
• Cell structures

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

  1. Prepare agar dish using aseptic technique

  2. Incubate at 25°C

  3. Measure culture size or area of inhibition around antibiotics
• Diploid cells

  Cells with 23 pairs of chromosomes (e.g. human body cells)
• Haploid cells

  Cells with 23 single chromosomes (e.g. gametes)
• Mitosis

  1. Genetic material is duplicated

  2. Nucleus breaks down

  3. Chromosomes pulled to opposite sides

  4. New nuclei form in each new cell
• Cell specialisation

  • Cells specialize to perform specific functions (e.g. nerve, muscle, root hair cells)
  • Stem cells are unspecialized
• 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 % change in mass

  5. Plot against sugar 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
  • Stomach
  • Small intestine
• Organ systems

  • Circulatory system
  • Digestive system
• Enzymes

  • Biological catalysts that are specific to certain substrates
  • Rate increases with temperature until denaturation
  • Rate also affected by pH
• Enzyme activity practical

  1. Mix amylase and starch

  2. Test for starch presence over time

  3. Plot time to complete reaction against temperature or pH

  4. Find optimum conditions
• Food tests

  • Iodine for starch
  • Benedict's solution for sugars
  • Biuret reagent for proteins
  • Ethanol for lipids
• Respiratory system

  • Air moves through trachea, bronchi, bronchioles to alveoli
  • 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
  • Heart has thicker left ventricle wall to pump to whole body
• 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 the heart muscle with oxygen and nutrients
• Cardiovascular disease (CVD)

  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


  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 in turn 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