biology b2

• Enzyme


  Biological catalyst that speeds up chemical reactions without being changed or used up
• How enzymes speed up reactions

  Lowers the activation energy required for the reaction to occur
• Active site


  Where the substrate (reactants) fits into
• Enzymes


  • Very specific and will only catalyse one specific reaction
  • Work optimally at specific conditions of pH and temperature
  • In extremes of pH or temperature, the enzyme will denature and the active shape will deform
• The Heart is a Double Pump
• If the reactants are not the complimentary shape

  The enzyme will not work for that reaction
• Bile


  • Produced in the liver and stored in the gall bladder
  • Alkaline substance which neutralises the hydrochloric acid in the stomach
  • Works to emulsify fats into small droplets to increase the rate of digestion by lipase
• Heart


  Large muscular organ which pumps blood carrying oxygen or waste products around the body
• Lungs


  Site of gas exchange where oxygen from the air is exchanged for waste carbon dioxide in the blood
• Respiration reaction


  1. Oxygen is used to release energy for the cells

  2. Carbon dioxide is made as a waste product
• glucose + oxygen - carbon dioxide + water
• Capillaries


  • Narrow vessels which form networks to closely supply cells and organs between the veins and arteries
  • Walls are only one cell thick, which provides a short diffusion pathway to increase the rate at which substances are transferred
• Artery


  • Direction of blood flow: away from the heart
  • Oxygenated blood (except pulmonary artery)
  • High pressure
  • Thick elastic muscular wall structure
  • Narrow lumen
• Vein


  • Direction of blood flow: towards the heart
  • Deoxygenated blood (except pulmonary vein)
  • Low pressure
  • Thin less muscular wall structure
  • Wide lumen
• The heart works as a double pump for two circulatory systems; the pulmonary circulation and the systemic circulation.

  the putmonary circulation serves the lungs and bring deoxygenated blood to exchange waste carbon dioxide gas for oxygen at the alveoll.

  The systemic circulation serves the rest of the body and transports oxygen and nutrients from digestion to the cells of the body, whilst carrying carbon doxide and other waste away from the cells.

  The systemic circulation flows through the whole

  body. This means the blood is flowing at a much higher pressure than in the pulmonary circuit.
• Coronary heart disease

  A condition resulting from blockages in the coronary arteries, the main arteries which supply blood to the heart itself
• In the UK and around the world, coronary heart disease is a major cause of many deaths
• Main symptoms of coronary heart disease

  • Chest pain
  • Heart attack
  • Heart failure
• Not all people suffer the same symptoms, if any at all
• Lifestyle factors that can increase the risk of coronary heart disease

  • Diet (high-fat diet containing lots of saturated fat)
  • Smoking (chemicals in cigarette smoke)
  • Stress (prolonged exposure to stressful situations)
  • Drugs (illegal drugs like ecstasy and cannabis)
  • Alcohol (regularly exceeding unit guidelines)
• Diet - high-fat diet


  Can lead to higher cholesterol levels and this cholesterol forms the fatty deposits which damage and block the arteries
• Smoking

  Chemicals in cigarette smoke, including nicotine and carbon monoxide, increase the risk of heart disease. Carbon monoxide reduces the amount of oxygen which can be transported by the red blood cells and nicotine causes an increased heart rate. The lack of oxygen to the heart and increased pressure can lead to heart attacks.
• Stress

  Prolonged exposure to stress or stressful situations (such as high pressure jobs) can lead to high blood pressure and an increased risk of heart disease
• Drugs

  Illegal drugs (e.g. ecstasy and cannabis) can lead to increased heart rate and blood pressure, increasing the risk of heart disease
• Alcohol

  Regularly exceeding unit guidelines for alcohol can lead to increased blood pressure and risk of heart disease
• Blood flow through the heart

  1. Right atrium receives deoxygenated blood via the vena cava

  2. Pumped down through the valves into the right ventricle

  3. Forced up through the pulmonary artery towards the lungs where it exchanges carbon dioxide for oxygen

  4. Oxygenated blood enters the left atrium via the pulmonary vein and down into the left ventricle

  5. Muscular wall of the left ventricle pumps the blood more forcefully out of the heart and around the entire body, via the aorta
• The blood only flows in one direction due to valves in the heart which close under pressure and prevent the backward flow of blood
• Cancer

  Uncontrolled cell growth and division
• Tumour

  Uncontrolled growth of cells
• Benign Tumour


  • Grows slowly
  • Grows within a membrane and can be removed
  • Does not normally grow back
  • Does not spread around the body
• Malignant Tumour

  • Cancerous
  • Grows rapidly
  • Can spread around the body via the bloodstream
  • Can break away and cause secondary tumours
• Leaves

  • Typically flat and thin with a large surface area
  • Reduces the distance for diffusion of water and gases
• Xylem

  Vessels that transport water and dissolved minerals toward the leaves
• Phloem

  Vessels that transport glucose and other products from photosynthesis around the plant
• Spongy mesophyll layer

  Large air spaces between the cells that allow for the diffusion of gases
• Carbon dioxide enters the leaves


  Oxygen exits the leaves
• Guard cells

  • Specially adapted cells located on the underside of the leaf
  • Positioned in pairs, surrounding the stomata
  • Change shape to open and close the stomata
  • Control the rate of gas exchange in the leaf
• Plants absorb water

  1. By osmosis through the root hair cells of the roots

  2. Dissolved in the water are important minerals for the plants growth and development

  3. Absorbed by active transport
• Root hair cells

  • Finger-like projection in the membrane increases the surface area available for water and minerals to be absorbed across
  • The narrow shape of the projection can squeeze into small spaces between soil particles, bringing it closer and reducing the distance of the diffusion pathway
  • The cell has many mitochondria, which release energy required for the active transport of some substances
• Xylem vessels


  Transport water through the plant, from roots to leaves