B2

• Enzyme


  Biological catalyst
• Catalyse


  Speed up reactions without being used up
• Enzymes


  • They are proteins made by amino acids
  • They have an active site with a specific shape
• Active site shape


  Matches perfectly with the substrate
• Enzymes


  Speed up a reaction by building up larger molecules from smaller molecules or towing a larger molecule and breaking it into smaller ones
• Temperature


  Effects the rate of reaction
• Effect of temperature on reaction rate

  1. Low temperature - slow due to low kinetic energy so fewer effective collisions

  2. High temperature - fast due to high kinetic energy, collide more

  3. Very high temperature - reaction slows due to bonds breaking in amino acids and the enzyme becoming denatured
• Denatured enzyme


  Active site has changed shape, so substrate doesn't fit
• pH


  Can also affect enzyme activity
• Enzymes


  • Amylase found in stomach
  • Enzymes found in small intestine
• Substrate


  The substance an enzyme acts on
• Product


  The substance produced by the enzyme-catalysed reaction
• Investigating enzyme activity


  1. Control optimum temperature at 37°C in a water bath

  2. Add small amounts of amylase, known pH buffer and starch

  3. Add iodine to test for presence of starch

  4. Time how long it takes for iodine to stop turning blue/black

  5. Repeat with a range of pH buffers
• Carbohydrates are broken down into sugars, proteins are broken down into amino acids, and lipids are broken down into glycerol and fatty acids during digestion
• Starch will turn blue with iodine, reducing sugars will turn green, and high levels of protein will turn purple
• Ethanol test turns cloudy when lipids are present
• Digestion


  Breaking down large insoluble molecules into smaller soluble molecules that can be absorbed
• Digestive system


  1. Mouth - mechanical and chemical digestion using salivary amylase

  2. Oesophagus - transports food to stomach

  3. Stomach - chemical digestion of proteins using hydrochloric acid and pepsin

  4. Small intestine - lipids broken down by lipase, bile helps emulsify fats, pancreas provides enzymes for all 3 food types

  5. Large intestine - further absorption of water and nutrients
• Coronary heart disease is caused by the coronary arteries becoming blocked, leading to a heart attack
• Treatments for coronary heart disease

  1. Angioplasty - widen artery using a balloon

  2. Stent - left in artery to keep it open, but can cause blood clots so anticoagulants are needed

  3. Bypass surgery - more dangerous option
• Cholesterol is a lipid made by the body, but excess levels can lead to fatty deposits in arteries
• Poor diet, lack of exercise, and genetics can increase LDL (bad) cholesterol levels
• Statins are medicines that lower cholesterol production, but can cause liver and kidney damage
• Treatments for blood loss

  1. Intravenous fluids to replace lost blood

  2. Pacemaker implanted to regulate electrical impulses and heart contractions
• Red blood cells have no nucleus to provide more space for carrying oxygen, white blood cells defend against pathogens, and platelets help blood clot
• Plasma carries nutrients, hormones, and other dissolved substances in the blood
• Arteries


  • Narrow lumen, high pressure, thick muscle layer
• Veins


  • Wide lumen, low pressure, thin muscle layer
• Capillaries are one cell thick to enable gas exchange
• Communicable diseases can be transmitted between organisms, while non-communicable diseases cannot
• Lifestyle factors like diet, exercise, alcohol, and smoking influence the risk of non-communicable diseases
• Benign tumour


  Non-cancerous, doesn't spread
• Malignant tumour


  Cancerous, spreads around the body
• Cancer treatments


  1. Chemotherapy - drugs that stop cell division or cause cell death

  2. Radiotherapy - targets radiation at the cancer
• Smoking damages blood vessels and increases the risk of cardiovascular disease
• High salt diet increases blood pressure, damaging blood vessels
• Alcohol damages the liver and brain
• Fetal alcohol syndrome causes facial deformities
• Transpiration in plants


  1. Water vapour lost from stomata in leaves by evaporation and diffusion

  2. Water enters root hair cells by osmosis, travels up xylem to leaves

  3. Stomata surrounded by guard cells that open and close
• Potometer equipment is used to investigate transpiration