Organisation

• Phloem


  • Enables movement of cell sap through pores between adjacent cells
  • Can transport substances in either direction (up or down the plant)
• Xylem tubes


  • Made up of column of dead xylem cells with no ends, forming one long hollow tube strengthened with lignin
  • Transport water and mineral ions from roots to leaves
• Transpiration stream


  Chain of water molecules pulled up the plant as water evaporates from leaves
• At night with no photosynthesis the stomata are closed so very little transpiration
• Temperature increases


  Higher rate of transpiration (water particles have more energy, more likely to evaporate)
• High airflow


  Water molecules quickly blown away, concentration gradient kept high, increasing transpiration rate
• High humidity


  Decreased concentration gradient, less water diffuses out, lower transpiration rate
• Photosynthesis takes place in chloroplasts
• Epidermal cells


  Very thin cells that form the upper and lower epidermis of the leaf
• Upper epidermis


  • Transparent to allow light to pass through
  • Covered with a waxy cuticle to reduce water evaporation
• Lower epidermis


  • Contains tiny pores called stomata that allow carbon dioxide in and oxygen out
  • Has guard cells on either side of the stomata
• Palisade mesophyll


  Packed full of chloroplasts that contain chlorophyll to absorb light energy for photosynthesis
• Spongy mesophyll


  • Full of air spaces that allow carbon dioxide to diffuse to the palisade cells and oxygen to diffuse out
• Xylem


  Transports water and dissolved mineral ions from the roots to the stem and leaves
• Phloem


  Transports dissolved sugars produced by photosynthesis from the leaves to the rest of the plant
• Translocation


  The movement of sugars through phloem tissue
• Meristem tissue


  Contains stem cells that can differentiate into different types of plant tissue
• Meristem tissue is found at growing tips such as shoots and roots
• Cells


  Make up all living things
• Organs


  Formed from a number of different tissues, working together to produce a specific function
• Organ systems


  Organs organised to work together to perform a certain function
• Organs in the digestive system

  • Glands (salivary glands and pancreas)
  • Stomach
  • Small intestine
  • Liver
  • Gall bladder
  • Large intestine
  • Rectum
  • Anus
• Enzymes


  Biological catalysts that increase the rate of reaction without being used up
• Enzymes


  • They can both break up large molecules and join small ones
  • They are protein molecules and the shape of the enzyme is vital to its function
  • Each enzyme has its own uniquely shaped active site where the substrate binds
• Lock and Key Hypothesis

  1. Substrate shape is complementary to active site shape, forming enzyme-substrate complex

  2. Reaction takes place and products are released
• Optimum pH


  The pH at which an enzyme works best
• Optimum temperature


  The temperature range around 37 degrees Celsius at which an enzyme works best
• Denaturation


  When the bonds in the enzyme structure break, changing the shape of the active site so the substrate can no longer fit
• Types of enzymes


  • Carbohydrases (convert carbohydrates into simple sugars)
  • Proteases (convert proteins into amino acids)
  • Lipases (convert lipids into fatty acids and glycerol)
• Soluble glucose, amino acids, fatty acids and glycerol pass into the bloodstream to be carried to all the cells around the body
• Tests for biological molecules


  • Benedict's test for sugars (turns brick red)
  • Iodine test for starch (turns blue-black)
  • Biuret test for protein (turns purple)
  • Emulsion test for lipids (add ethanol which results in a cloudy layer if a lipid is present)
  • Sudan III test for lipids (red layer forms on top)
• Bile


  Produced in the liver and stored in the gallbladder, then released into the small intestine. It is alkaline to neutralise hydrochloric acid and emulsifies large fat droplets
• Investigating effect of pH on enzyme controlled reaction

  Use iodine to detect presence of starch, take samples at regular intervals, record time for complete breakdown, calculate rate
• Rate of enzymatic reactions


  Calculated as change/time
• Heart


  An organ in the circulatory system that pumps blood around the body
• Circulatory system


  Carries oxygen and nutrients to every cell in the body and removes waste products
• Double circulatory system


  Two circuits - deoxygenated blood to lungs, oxygenated blood around body
• Blood flow through the heart

  1. Blood flows into right atrium, then right ventricle, pumped to lungs

  2. Blood flows into left atrium, then left ventricle, pumped around body
• Pacemaker


  Group of cells in right atrium that provide electrical stimulation to make the heart contract
• Artificial pacemaker


  Electrical device that produces a signal causing the heart to beat at a normal speed