Topic 1 - Key concepts in bio

• Eukaryotic cells


  Cells with a nucleus and membrane bound organelles
• Prokaryotic cells


  Cells with no nucleus and no membrane bound organelles
• Animal cells


  • Nucleus, cell membrane, mitochondria and ribosomes
• Plant cells


  • Nucleus, cell membrane, cell wall, chloroplasts, mitochondria, vacuole and ribosomes
• Bacterial cells


  • Chromosomal DNA, plasmid DNA, cell membrane, ribosomes and flagella

  
• Sperm cells


  • Acrosome, haploid nucleus, mitochondria and tail

  
• Egg cells


  • Nutrients in the cytoplasm, haploid nucleus and changes in the cell membrane after fertilisation
• Electron microscopy has enabled us to see cell structures and organelles with more clarity and detail than in the past and increased our understanding of the role of sub-cellular structures
• Calculations with numbers written in standard form
• Core Practical: Investigate biological specimens using microscopes

  1. Set up microscope using lowest-magnification objective lens

  2. Increase magnification and refocus

  3. Draw labelled diagrams of the specimens

  4. Calculate magnification

  
• Enzyme action


  Active site and enzyme specificity

  
• Enzymes can be denatured due to changes in the shape of the active site

  
• Factors affecting enzyme activity

  • Temperature
  • Substrate concentration
  • pH
• Understand rate calculations for enzyme activity
• Enzymes


  Biological catalysts that speed up the synthesis of carbohydrates, proteins and lipids and their breakdown into sugars, amino acids and fatty acids and glycerol
• Diffusion


  Movement of substances from an area of high concentration to an area of low concentration down the concentration gradient
• Osmosis


  Movement of water from an area of high concentration to an area of low concentration through a partially permeable membrane
• Active transport


  Movement of substances from an area of low concentration to an area of high concentration against a concentration gradient which require energy

  
• Calculate percentage gain and loss of mass in osmosis
• pH


  Most enzymes work best at about pH7 (neutral)
• Effect of pH on enzyme activity

  1. At low pHs the enzyme denatures, losing the shape of its active site so it no longer binds with the substrate so the rate of reaction is low

  2. At optimum pHs the enzyme and substrate are intact so there are more successful collisions so the rate of reaction is high

  3. At high pHs the enzyme denatures, losing the shape of its active site so it no longer binds with the substrate so the rate of reaction is low

  
• Effect of substrate concentration on enzyme activity

  1. As the substrate concentration increases, there are more molecules that can bind to the active sites of enzymes→rate of reaction increases

  2. However, at very high substrate concentrations, all the active sites of the enzymes are occupied all the time, the enzymes can't work any faster, adding more substrate will make no difference to the rate of reaction, The enzyme has become the limiting factor

  
• Biology Core Practical 2 - pH and Enzyme Activity


  1. Drop one drop of iodine solution into each depression of the spotting tile

  2. Measure 0.5cm3 of amylase solution into a test tube using a syringe

  3. Add 1 cm3 of your pH solution to the test tube using a second syringe

  4. Add 2cm3 starch solution to the mixture and start the stop clock

  5. After 20 seconds, take a small amount of the mixture in the pipette and place one drop of it on the first iodine drop on the tile, repeat this step every 10 seconds until the iodine solution remains yellow/brown

  6. Record the time it takes for the iodine solution to remain yellow
• Rate of reaction

  Calculated by dividing the amount of product produced by the time taken
• Isotonic solutions


  The number of solutes are equal on both sides of the membrane, there will be no net movement of water
• Hypotonic solutions


  The number of solutes is lower outside of the cell, water will move by osmosis into the cell, the cell's mass will increase
• Hypertonic solutions


  The number of solutes is higher outside of the cell, water will move by osmosis out of the cell, the cell's mass will decrease
• Biology Core Practical 3 - Osmosis in Potato Strips

  1. Cut a 1cm3 section of potato

  2. Weigh the potato

  3. Put the potato in a test tube with 2cm3 of 0% solution

  4. After 15 minutes, remove the potato, blot it dry and reweigh it

  5. Repeat with different concentrations of glucose solution
• Active transport


  Molecules move from an area of lower concentration to an area of higher concentration, this process requires energy