Biology paper 1

• Prokaryotic cells

  Do not have a nucleus
• Prokaryotic cells

  • Small, single-celled organisms
  • Small, simple cells
• Eukaryotic cells

  Have membrane bound organelles
• Eukaryotic cells

  • Mainly multi-cellular organisms (can be single celled)
  • Usually larger, complex cells
• Animal cell


  • Nucleus
  • Cytoplasm
  • Cell membrane
  • Mitochondria
• Plant cell


  • Nucleus
  • Cytoplasm
  • Cell membrane
  • Cell wall
  • Vacuole
  • Chloroplast
• Nucleus


  • Controls what goes in and out of the cell
  • Controls the activities of the cell, where DNA is found
• Cytoplasm


  • Gel-like substance where chemical reactions occur
  • Where proteins are made
• Cell membrane

  • Made of cellulose, strengthens cell
  • Contains cell sap, supports cell
• Mitochondria


  • Where respiration occurs to release energy
• Chloroplast


  • Where photosynthesis happens to make food, contain green substance called chlorophyll
• Chromosomal DNA

  Controls cell activities and replication. Floats freely in cytoplasm (no nucleus).
• Plasmid DNA (plasmid)

  Contains genes like drug resistance- can be passed between bacteria.
• Flagellum (pl. flagella)

  Long hair-like tail, rotates to make bacterium move.
• Cell wall

  Gives support.
• Cell membrane

  Gives support.
• Total Magnification

  Magnification of eyepiece lens x magnification of objective lens
• Total Magnification

  • x10 Eyepiece lens, x20 Objective lens = x200
• Describe how to use a light microscope

  1. Place the slide on the stage of the microscope and look through the eye piece lens.

  2. Start on the lowest objective lens magnification.

  3. Turn the focusing wheel to get a clear image.

  4. Increase the magnification of the objective lens and refocus.

  5. A stain could be used to make parts of the cells more visible.
• Prepare the slide

  1. Peel off a very thin piece of onion and place on the slide.

  2. Add 1-2 drops of iodine (wear goggles).

  3. Lower the coverslip slowly using the tweezers.
• Draw cells

  1. Using a sharp pencil, draw 3 or 4 cells.

  2. Only draw what you can see with smooth lines.

  3. Use a ruler to draw straight lines to label the structures.

  4. Calculate and write the total magnification.
• Cheek cells

  1. Use a cotton bud to take a swab of your cheek and wipe onto the slide.

  2. Add 1-2 drops of methylene blue (wear goggles).

  3. Lower the coverslip slowly using the tweezers.
• Describe how to use a light microscope (CORE PRACTICAL)

  1. Place the slide on the stage of the microscope and look through the eye piece lens.

  2. Turn the focusing wheel to get a clear image.

  3. Start on the lowest objective lens magnification.

  4. Increase the magnification of the objective lens and refocus.

  5. A stain could be used to make parts of the cells more visible.
• Magnification Calculations

  • S = specimen/actual size (on slide)
  • I = image (what you see)
  • M = magnification
• Egg cell

  Carry the female DNA and feed the developing embryo
• Egg cell

  • Large and contains nutrients in its cytoplasm to feed the embryo
  • After fertilisation, the cell membrane changes structure stopping any more sperm getting in – so only one sperm can fertilise one egg
  • Has a haploid nucleus
• Sperm cell

  Carry the male DNA to the egg
• Sperm cell

  • Has a tail to swim to the egg
  • Lots of mitochondria which release energy for the sperm to swim
  • Has an acrosome – this stores enzymes that digest through the membrane of the egg cell
  • Has a haploid nucleus
• Ciliated epithelial cell

  Moving materials
• Ciliated epithelial cell

  • Epithelial cells line the surface of some organs
  • Some have cilia (tiny hair-like structures) along the top surface
  • These cells move substances by wafting them along the surface of the tissue
  • Eg ciliated epithelial cells in the lining of the airways help to move mucus up to the throat so it can be swallowed
• Enzymes

  Biological catalysts which control (usually speed up) chemical reactions
• Enzymes

  • DNA replication, protein synthesis and digestion
• Lock and key hypothesis

  • A substrate is a specific shape to bind to the active site of an enzyme
  • They bind to form an enzyme-substrate complex
  • The substrate is then broken down into products
• Optimum temperature and pH

  • Enzymes work fastest at an optimum (ideal) temperature and pH
  • The wrong pH or high temperatures will cause the enzyme to denature - the active site changes shape and the substrate cannot bind
  • The reaction will slow down and stop
• As the pH increases

  The rate of enzyme activity increases then decreases
• Enzymes are biological catalysts
• Digestive enzymes

  Break large insoluble food molecules down into small soluble molecules which can be absorbing into the blood in small intestine
• Digestive enzymes

  • Carbohydrase (breaks down carbohydrates into sugars)
  • Amylase (breaks down starch into glucose)
  • Protease (breaks down proteins into amino acids)
  • Lipase (breaks down lipids into fatty acids and glycerol)
• Iodine is used to test for starch
• Iodine solution

  • Stays orange - no starch
  • Turns blue/black - is starch