Key Concepts in Biology

• Eye piece lens- to observe the magnified object

  Objective lens-to provide stronger lenses that provide greater image magnification

  Coarse adjustment knob/Focusing wheel- focus the image for a sharper more clearer image

  Fine adjustment- to finely adjust the image focus ona sharper more clearer image

  Stage-a platform to rest the slide and specimen

  Stage clips- to hold the slide and specimen ready
• Method 1- Using light microscope

  1)Step up your microscope using the lowest magnification objective lens(x4)

  2)Use the fine and coarse focusing wheel to achieve a more focused and clear image

  3)Increase the magnification to x10 and the refocus the coarse and fine focus wheel. Repeat until x40.
• Method 2-Preparing slides

  1)Using the forceps(equiment) to remove a very thin layer of the cell and place it on the slide.

  2)Add a drop of stain on the slide.

  3) Place a coverslip onto the slide at an angle.
• Animal cell

  -Cytoplasm-> This is where most of the cells chemical reaction occurs.

  -Nucleus->controls all the activity of the cell, contains DNA

  -Mitochondria->site of respiration/releases energy

  -Ribosomes->site of proteins synthesis(where proteins are made)
• Plant cell

  -Cell walls->supports the cell and is made out of cellulose

  -Vacuole->contains cell sap and keeps the cell turgid

  -Chloroplast-site of photosynthesis
• Bacterial cell

  -Chromosomal DNA-> large loops of DNA containing most of the genetic information

  -Plasmid DNA-> small loops of DNA which carries extra information

  -Flagella->to move around

  -Ribosomes-> site of protein synthesis

  -Cell membrane-> controls what enters and leave the cell

  -Capsule->protects the cell

  -mesosome-> site of respiration in bacteria(no mitochondria)
• Prokaryotes->cells with no nucleus and no membrane bound organelles.

  Eukaryotes->cells with nucleus and membrance bound organelles.
• Red blood cell

  • contains haemoglobin that binds to the oxygen
  • Biconcave shape to increase the rate of oxygen diffusion

  Small intestine

  • microvilli to increase surface area for food consumption
• Sperm cell

  -Acrosome->contains digestive enzyme to digest the membrane of the egg cell

  -Haploid cell-contains the half of the genetic information(23 chromosomes)

  -Mitochondria- releases energy in respiration so the sperm cell can move toward the egg cell.

  -Flagella- to move the cell towards the egg cell
• Egg cell

  -Cell membrane- hardens after fertilisation to prevent other sperm entering the cell

  -Haploid cell- contains half the genetic information(23 chromosome)

  -Large cytoplasm- contains nutrients to supply the fertilised egg with a source of energy for growth of the embryo
• Break down enzymes

  -Carboydrase break down carboydrates into sugars in mouth and small intestine(amlyase break down starch into glucose)

  -Protease break down proteins into amino acid in the stomach(pepsin and trypsin)

  -Lipase break down lipids into fatty acid and glycerol in small intestine

  -Catalyase break down hydrogen peroxide into water and oxygen
• Lock and key hypothesis

  -A substrate with a complementary shape binds to the enzymes active site.

  -To form substrate-enzyme complex

  -The enzyme catalyses reactions to change the substrate into products

  -The products are released
• Temperature affect enzyme action

  1)At low temperature, the enzyme become immobilised so the substrate and the enzyme active site does collide very fequently as rate of reaction is low.

  2)Optimum temperature, the enzyme and substrate has more kinetic energy so the there is more frequent collisions so the rate of reaction is high.

  3)The enzyme denatures losing the shape of the active site as it can no longer bind to the substrate. Rate of reaction is low.