N5 Biology Unit 1

• Main types of cells

  • Animal
  • Plant
  • Yeast
  • Bacterial
• Organelle


  Structure within a cell that has a specific function
• Organelles and their functions

  • Cell membrane - Controls entry and exit of materials
  • Ribosome - Site of protein synthesis
  • Cytoplasm - Site of chemical reactions
  • Mitochondria - Site of aerobic respiration
  • Nucleus - Controls the cell's activities
  • Cell wall - Support the cell
  • Vacuole - Contains cell sap
  • Chloroplast - Site of photosynthesis
  • Plasmid - Small ring of DNA
• We use a microscope to look at cells and add a stain to the microscope slides so we can see the cell organelles clearly
• Cell membrane


  Made up of proteins and phospholipids
• Passive transport across cell membranes

  • Diffusion - Movement of molecules down a concentration gradient
  • Osmosis - Movement of water molecules from a higher to lower water concentration
• Effects of solutions on different cell types

  • Animal cell in high water/dilute solution - Cell bursts
  • Animal cell in low water/concentrated solution - Cell shrinks
  • Plant cell in high water/dilute solution - Cell becomes turgid
  • Plant cell in low water/concentrated solution - Cell becomes plasmolysed
• Active transport


  Requires energy for membrane proteins to move molecules and ions against the concentration gradient
• DNA


  Carries the genetic information for making proteins and determines characteristics

  
• Gene


  Codes for a particular protein
• DNA structure


  2 strands twisted into a double helix shape, with 4 bases: adenine, thymine, guanine and cytosine
• Base pairs


  Adenine-thymine, Guanine-cytosine
• Proteins


  Made of amino acids in different orders

  
• mRNA


  Carries a complementary copy of the genetic code from DNA to the ribosome

  
• Types of proteins


  • Antibodies - Defend the body
  • Hormones - Chemical messengers
  • Receptors - Allow hormones to bind to cells
  • Structural - Make up the cell membrane
  • Enzymes - Speed up chemical reactions
• Enzymes


  Biological catalysts that speed up chemical reactions without being changed
• Enzyme active site


  Has a shape complementary to only one substrate
• Types of enzyme reactions

  • Degradation - Break down large molecules
  • Synthesis - Build up large molecules from smaller ones
• Enzyme reactions


  • Catalase breaking down hydrogen peroxide
  • Amylase breaking down starch
  • Potato phosphorylase building up starch
• Optimum condition


  The condition at which an enzyme is most active
• Enzyme denaturation


  When the shape of the active site changes, affecting the rate of reaction
• Stages of genetic engineering

  1. Identify required gene

  2. Extract required gene

  3. Extract plasmid

  4. Insert gene into plasmid

  5. Insert plasmid into host cell

  6. Host cell produces protein
• Enzymes are used in genetic engineering to produce human proteins like insulin and growth hormone
• Respiration


  The chemical process that releases energy stored in glucose
• ATP


  The molecule that stores and transfers the energy released from respiration
• Cellular activities powered by ATP


  • Cell division
  • Muscle contraction
  • Protein synthesis
  • Nerve impulse transmission
• Respiration pathways


  • Aerobic respiration - Glucose broken down to CO2 and H2O
  • Fermentation in animal cells - Glucose broken down to lactate
  • Fermentation in plant/yeast cells - Glucose broken down to CO2 and ethanol
• Respiration begins in the cytoplasm, with aerobic respiration completed in the mitochondria and fermentation completed in the cytoplasm
• The higher the energy requirement of a cell, the greater the number of mitochondria present
• Respiration summary word equations

  • Aerobic respiration: Glucose + Oxygen -> Carbon dioxide + Water + Energy
  • Fermentation in animal cells: Glucose -> Lactate + Energy
  • Fermentation in plant/yeast cells: Glucose -> Carbon dioxide + Ethanol + Energy