organisation (b2)

• Principles of organisation

  • Cells
  • Tissues
  • Organs
  • Organ systems
• Organelle

  A structure within a cell that performs a specific function
• Cells

  The basic unit of all living organisms
• Cells to tissues to organs to organ systems

  1. Cells make up tissues

  2. Tissues make up organs

  3. Organs make up organ systems
• Cells make up all living organisms
• Tissue

  A group of cells with similar structure and function
• Organ

  A group of tissues performing a specific function
• Organ system

  A group of organs that work together
• Enzyme

  A biological catalyst that speeds up reactions without being used up
• Enzymes

  • They can break down large molecules
  • They can join small molecules
  • presnent in many reaction so they can be controlled
  • protein molecules
• Protein molecules

  Made of amino acids, shape is essential to function
• Active site

  Where the substrate binds on an enzyme
• lock and key theory - Enzyme-substrate interaction

  1. Substrate binds to active site

  2. Enzyme-substrate complex forms

  3. Reaction takes place

  4. Products are released from surface of the enzyme
• Substrate shape

  Complementary to active site shape
• When the substrate binds, the enzyme's reaction takes place
• After the reaction, the products are released from the enzyme's surface
• Factors affecting enzyme action

  • Temperature
  • pH
• Temperature

  Rate of reaction increases with temperature, above a optimum temperature enzymes start to denature
• pH

  If too low or high, forces that hold amino acid chains together are affected, changing the shape of the active site
• Digestive enzymes

  Break down large molecules into smaller ones that can be absorbed into the bloodstream
• Types of digestive enzymes

  • Carbohydrases
  • Proteases
  • Lipases
• Carbohydrase

  Convert carbohydrates into simple sugars

  amylase breaks down starch into maltose
• Proteases

  Convert proteins to amino acids
• Lipases

  Convert lipids into fatty acids and glycerol
• Bile

  Produced in the liver, stored in the gall bladder, released into the small intestine
• Functions of bile

  • Neutralise stomach acid
  • Emulsify fats to increase surface area for lipase
• Small intestine enzymes have a higher optimum pH than ones in the stomach
• Food testing methods

  • Starch - iodine - turns blue-black
  • Reducing sugars - Benedict's - turns brick red
  • Protein - Biuret - turns purple
  • Lipids - emulsion - cloudy layer if lipid is present
  • lipids - sudan III - red layer forms on top
• Food testing procedure

  1. Grind food sample with water

  2. Filter to remove solids

  3. Add reagent and observe colour change
• effect of pH on amylase activity- required practical

  1. Place drop of iodine in each well of the spotting tile

  2. place two test tubes in a 35 degrees water bath, one with starch solution one with equal volumes of pH buffer solution and amylase

  3. Combine amylase and starch solution and return to water bath

  4. Transfer drops to iodine wells every 30 seconds, iodine will turn blue-black if starch is present

  5. Continue until iodine remains orange-brown, starch is no longer present

  6. repeat twice more and calculate mean

  7. repeat whole experiment with different pH buffers (6,7,8)
• Shorter time for iodine to remain orange-brown indicates a faster rate of reaction
• Heart

  An organ that pumps blood around the body's double circulatory system
• Blood flow through the heart

  1. Deoxygenated blood flows into right atrium, then right ventricle, which pumps it to the lungs

  2. Oxygenated blood flows into left atrium, then left ventricle, which pumps it around the body
• Heart structure

  • Muscular walls
  • Thicker left ventricle wall
  • Separate oxygenated and deoxygenated blood
  • Valves to prevent backflow
  • Coronary arteries to supply heart's own blood supply
• Heart rate

  Controlled by pacemaker cells in the right atrium, can be corrected by artificial pacemakers
• Cardiac output

  Volume of blood pumped per minute
• Arteries

  Carry blood away from the heart, have muscular and elastic walls to withstand high pressure
• Veins

  Carry blood towards the heart, have valves to ensure one-way flow
• Capillaries

  Allow blood to flow very close to cells, have thin walls for efficient gas exchange
• Gas exchange in the lungs

  1. Air enters trachea, then bronchi, then alveoli

  2. Deoxygenated blood in capillaries surrounding alveoli have lots of carbon dioxide as a product of respiration

  3.oxygen diffuse down the concentration gradient into the capillary bloodstream which has a low concentration of oxygen

  4.carbon dioxide diffuses down its concentration gradient from the blood to the alveoli