B2: organisation

• cell > tissue (a group of similar cells) > organ (a group of different tissues) > organ system > organism
• enzymes- catalyse or speed up chemical reactions, each enzyme only catalyses one specific reaction because of the unique shape of the active site
• high temperatures and high or low pH can affect the rate of enzyme action as it changes the shape of the active site so the substrate cannot bond to it
• Digestive enzymes break down big insoluble molecules of food into smaller soluble ones that can be passed through the walls of the digestive system and be absorbed into the blood
• the enzyme amylase (a carbohydrase) produced in the salivary glands, small intestine and pancreas breaks down starch (a carbohydrate) into maltose and other sugars
• the enzyme protease produced in the stomach, small intestine and pancreas breaks down protein into amino acids
• the enzyme lipase produced in the small intestine and pancreas breaks down lipids into fatty acids and glycerol
• bile speeds up digestion by:

  1. making conditions alkaline so enzymes in the small intestine work better
  2. emulsifying fat so there‘s a larger surface area for lipase to work on
• bile is made in the liver and stored in the gall bladder
• the products of digestion can be used to make new carbohydrates, proteins and lipids
• Parts of the lung:

  A) Trachea

  B) Lung

  C) Bronchus

  D) Alveoli

  
• the circulatory system is made up of the heart, blood vessels and blood and humans have a double circulatory system
• circulatory systems:

  1. heart (right ventricle)>lungs>heart
  2. heart (left ventricle)>rest of body>heart
• pacemaker cells in the right atrium wall control resting heart rate
• if natural pacemaker cells do not work an artificial pacemaker (electrical device put under the skin) can control heartbeat
• coronary arteries supply the heart muscle with oxygenated blood
• The heart:

  A) Pulmonary artery (to lungs)

  B) Vena cava (from body)

  C) Aorta (to body)

  D) Pulmonary vein (from lungs)

  E) Valves (stop blood from flowing backward)

  F) Right

  G) Left

  
• 3 types of blood vessel:

  1. arteries
  2. capillaries
  3. veins
• arteries - Carry blood away from the heart
• capillaries- carry blood close to body cells to exchange substances
• veins- carry blood back to the heart
• arteries have thick muscle and elastic layers because blood pressure is high
• capillaries have thin, permeable walls to allow substances to diffuse in and out easily
• veins have valves inside to stop blood flowing backwards and a thin wall to allow blood to flow quickly
• rate of blood flow= volume of blood/time taken
• blood components:

  1. red blood cells
  2. white blood cells
  3. platelets
  4. plasma
• red blood cells carry oxygen around the body
• white blood cells defend against infection
• platelets help blood to clot at a wound
• plasma is a liquid that carries everything in the blood, including hormones, nutrients, and waste products
• red blood cells have no nucleus so more room for oxygen and a biconcave shape which means a bigger surface area for more oxygen absorption, also contains haemoglobin which binds to oxygen
• white blood cells- have a nucleus and produce antibodies, antitoxins and do phagocytosis
• Platelets are fragments of cells
• Cardiovascular diseases- diseases of the heart or blood vessels e.g. coronary heart disease

  A) Fatty deposit

  B) Heart attack

  C) Oxygen

  
• treatments for cardiovascular disease

  1. statins
  2. stents
  3. heart transplant
  4. artificial heart
  5. replacement heart valves
• statins are pills that reduce cholesterol levels in the blood which slows down the forming of fatty deposits, need to be taken long term and can have negative side effects
• stent - tube put in the artery, keeps coronary arteries open for a long time and has a quick recovery time from surgery
• artificial heart - can be used while waiting for a doner or while heart is healing
• heart transplant - can treat heart failure and doner hearts work better than artificial ones
• replacement heart valves - can be biological or mechanical and treat severe valve damage e.g stiff valves that dont open properly or leaky valves