B2: Organisation

• Tissue


  When similar cells are connected
• Organ


  Tissues form organs, e.g. heart
• Organ system


  Organs work together, e.g. circulatory system
• Digestive system


  1. Breaks down food into useful nutrients

  2. Acid in stomach breaks down food

  3. Bile and enzymes in small intestine break down food further

  4. Bile neutralizes acid and emulsifies fats

  5. Enzymes break down larger molecules into smaller ones

  6. Villi in small intestine absorb nutrients into bloodstream
• Enzymes


  Biological catalysts that break down larger molecules into smaller ones
• Enzymes


  • Amylase breaks down starch into glucose
  • Carbohydrases break down carbohydrates
  • Proteases break down proteins
  • Lipases break down lipids
• Enzymes


  • They are specific and only break down certain molecules
  • They work on a lock and key principle where the substrate binds to the enzyme's active site
• As temperature increases


  The rate of enzyme activity increases
• Enzyme active site changes shape


  Substrate no longer binds, enzyme has denatured
• Optimum temperature/pH


  The temperature or pH at which the enzyme has the maximum rate of activity
• Practical on enzyme activity

  1. Mix amylase with starch at different temperatures or pH

  2. Remove samples every 10 seconds and test with iodine

  3. Plot time taken for starch to be broken down against temperature or pH

  4. Optimum is the lowest point on the curve
• Food tests


  • Tests to identify nutrients in food
  • Iodine turns black in presence of starch
  • Benedict's solution turns orange in presence of sugars
  • Biuret's reagent turns purple in presence of proteins
  • Cold ethanol goes cloudy in presence of lipids
• Respiration


  The process that uses oxygen to release energy from food, breathing provides the oxygen for this
• Respiratory system


  1. Air moves down trachea into bronchi and bronchioles

  2. Reaches alveoli where gas exchange occurs

  3. Oxygen binds to hemoglobin in red blood cells

  4. Transported to cells for respiration

  5. Carbon dioxide and water are expelled
• Circulatory system


  The transport system of the body, a double circulatory system
• Blood flow through the heart

  1. Deoxygenated blood enters right atrium

  2. Passes through right ventricle to lungs

  3. Oxygenated blood returns to left atrium

  4. Passes through left ventricle to body
• Heart


  • Left ventricle has thicker walls to pump blood to whole body
  • Electrical pulses from cells near right atrium cause heart to beat
• Blood vessels


  • Arteries carry oxygenated blood away from heart, veins carry deoxygenated blood towards heart
  • Arteries have thicker walls, veins have valves to prevent backflow
• Coronary arteries supply the heart muscle with oxygen and blood
• Blockage of coronary arteries can cause a heart attack
• Stents


  Tubes inserted into blood vessels to keep them open
• Statins


  Drugs that reduce cholesterol and fatty deposits
• Faulty heart valves


  Can be replaced with artificial ones
• Non-communicable diseases


  Diseases caused by factors within the body, e.g. cardiovascular disease, autoimmune conditions, cancer
• Communicable diseases


  Diseases caused by pathogens that enter the body, e.g. viral, bacterial, fungal infections
• Obesity and high sugar


  Can cause type 2 diabetes
• Bad diet, smoking, lack of exercise

  Can increase risk of heart disease
• Alcohol


  Can cause liver diseases
• Smoking


  Can cause lung disease or cancer
• Carcinogen


  Anything that increases the risk of cancer, e.g. ionizing radiation
• Benign cancer


  Doesn't spread through the body, relatively easy to treat
• Malignant cancer


  Cancerous cells spread through the body, much worse
• Plant organs


  • Leaves - site of photosynthesis and transpiration
  • Roots - where water and minerals enter the plant
  • Meristem - where new cells are made
• Xylem


  Long continuous tubes that transport water upwards in the plant
• Phloem


  Conveyor belts of cells that transport sugars, food and sap up and down the plant
• Increasing temperature, decreasing humidity, increasing air movement


  Increases the rate of transpiration in plants
• Lack of nitrate ions


  Prevents effective protein synthesis, stunts plant growth
• Chlorosis


  Yellowing of leaves, can be due to magnesium deficiency
• Leaf structure


  • Cuticle - waterproof layer
  • Upper epidermis - transparent cells
  • Palisade mesophyll - site of photosynthesis
  • Spongy mesophyll - gas exchange
  • Vascular bundle - xylem and phloem
  • Lower epidermis - stomata
• Stomata


  Holes in lower epidermis of leaf, size controlled by guard cells to regulate gas exchange