organisation

• a tissue is a group of cells with a similar structure or function
• an organ is a group of tissues working together for a specific function

  • stomach = muscle and glandular tissue which release enzymes
• organs are group into organ systems which work together to form organisms
• food contains carbohydrates, proteins and lipids

  these molecules are too large to be absorbed so they have to be digested by enzymes to form smaller molecules which are absorbed into the bloodstream
• Food digestion

  1. Chewed in the mouth

  2. Enzymes begin to digest starch into smaller molecules

  3. Passes into the stomach through the oesophagus

  4. Enzymes begin digestion of proteins, helped by hydrochloric acid

  5. Churning action of stomach muscle turns food into fluid, increasing surface area for enzymes

  6. Fluid passes to small intestine

  7. Chemicals released from liver and pancreas

  8. Pancreas releases enzymes to continue digestion of proteins and starch, start digestion of lipids

  9. Liver releases bile to speed up digestion and neutralise acid from stomach

  10. Small food molecules absorbed into bloodstream through diffusion or active transport

  11. Passes to large intestine

  12. Water absorbed into bloodstream

  13. Faeces released
• enzymes catalyse chemical reactions
• enzymes are large protein molecules with a groove on their surface called active site, where substrates attaches to
• enzymes are specific, lock and key theory
• • proteins are broken down by protease (long chain of amino acids)
  • protease is found in stomach, pancreatic fluid and small intestine
  • when digested protease enzymes covert protein into individual amino acids which are absorbed into the bloodstream
  • when absorbed by body cells, they are joined in a different order to make human proteins
• • starch is broken down by amylase (long chain of glucose molecules)
  • when starch is digested, simple sugars are formed
  • amylase are found in pancreatic fluid and saliva
• • lipids (molecule of glycerol attached to 3 molecules of fatty acids) are broken down by lipase producing glycerol and fatty acids
  • lipase are found in small intestine and pancreatic fluid
• Bile is made in the liver and stored in the gall bladder, NOT AN ENZYME

  • Bile converts large lipid droplets into smaller droplets
  • bile emulsifies the lipid = increasing the surface area
  • bile = alkaline, creating alkaline conditions in small intestine which increases rate of lipid digestion by lipase
• • as we increase the temperature, the reaction gets faster, more collisions between active sites and substrate
  • optimum temperature, maximum frequency of successful collisions
  • past optimum, enzyme stops working, active site is denatured
• • active site denatures if the conditions are too acidic or alkaline
  • lipase works best at alkaline conditions
  • protease works best at acidic
• • small intestine is very large and has villi to increase surface area for absorption of molecules
  • microvilli increases surface area further
  • villi has a good blood supply so the bloodstreams rapidly removes the products of digestion, increases the concentration gradient
  • thin membrane = short diffusion path
• single circulatory (fish)

  1. deoxygenated blood is pumped from heart to gills where it collect oxygen and becomes oxygenated
  2. oxygenated blood passes to the organs where oxygen diffuses out of blood and into body cells
  3. blood return to heart
• single circulation system problem

  • blood loses pressure - travels relatively slowly, cannot carry a lot of oxygen
• double circulatory system (humans)

  • deoxygenated blood is pumped from the heart to the lungs, where oxygen is collected.
  • oxygenated blood returns to heart
  • heart pumps oxygenated blood into organs where blood transfers its oxygen to the body cells
  • blood returns to the heart
• benefits of double circulatory

  • travels rapidly to body cells
• heart

  • 4 chambers
  • right atrium - left atrium
  • right ventricle - left ventricle
• 1. vena cava - carries deoxygenated blood from the body
  2. pulmonary artery - passes the blood into lungs
  3. pulmonary vein - oxygenated blood from lungs to heart
  4. aorta - heart to body
• • blood enters the atriums
  • atria contracts and forces the blood into the ventricle, which contract and force blood out the heart
  • valves stop blood from flowing blood into the atria when the ventricles contract
• • left side has thicker muscular world as it pumps blood to body
• coronary arteries pf the aorta provides oxygen to muscle cells of the heart, used in respiration for contraction
• • resting heart rate is controlled by pacemakers in right atrium
  • artificial pacemakers correct irregularities in the heart rate
• cardiovascular diseases happen in the heart and blood vessels

  • non communicable
• coronary heart disease

  • happens when layers of fatty substances build up inside the coronary arteries, causing it to narrow which reduces flow of blood, resulting in a lack of oxygen for heart muscle (lead to heart attacks)
• statins

  • slows down the rate of fatty substances that build up in arteries
  • proven to reduce risk of coronary heart disease
  • disadvantage = cause liver problems
• stent (total blockage)

  • tube inserted into artery to keep it open
  • blood can flow normally
  • disadvantages = won't prevent other parts of the coronary artery from narrowing
• mechanical valves

  • last a lifetimes
  • but increases risk of blood clots (anticlotting drugs have to be taken)
• valves from animals (pigs)

  • don't last long and may need to be replaced
  • but they don't have to take drugs
• heart failure (donated heart)

  • not enough hearts to be donated
  • take drugs so heart will not be rejected by the immune system
• artificial hearts

  • not long term solution
  • increases risk of blood clotting
• arteries

  • thick muscular walls = withstands the high pressure of blood
  • elastic fibres = stretch when the surge of blood pass through And recoil in between surges to keep blood moving
• capillaries

  substances such as glucose and oxygen diffuse from blood to cells, whilst carbon dioxide diffuses from the cells to the blood

  • thin wall = diffusion pathway is short
• veins

  • thin wall= blood pressure is low
  • valves = stop blood flowing backwards (open and shut when needed)
• • air passes into lungs through trachea (rings of cartilage which prevent trachea from collapsing during inhalation
  • trachea splits into bronchi, which subdivides into many smaller tubes called bronchioles which end in tiny air sacs called alveoli
• alveoli

  where gases diffuse in and out of bloodstream

  • oxygen in air diffuses into the blood stream and carbon dioxide diffuses back into the cell
  • lungs have huge surface area
  • thin walls = short diffusion path way
  • very good blood supply = oxygen is removed rapidly so the concentration gradient is steep
• • breathing increases rate of diffusion, which brings fresh oxygen into the alveoli and takes away the carbon dioxide which makes the concentration gradients higher for these gases, increasing the rate of diffusion
• blood types

  • plasma = transports dissolved substances (glucose), carbon dioxide, urea
  • red blood cells transports oxygen by combining oxygen with haemoglobin to form oxyhaemoglobin in the lungs. at the organs the oxyhaemoglobin is converted back into oxygen + haemoglobin. red blood cells have no nucleus (more space for haemoglobin). shape of a biconcave disc = greater surface area O2 diffuses rapidly
  • white blood cells form part of immune system and contain nucleus (DNA)
  • platelets = tiny fragments of cells that help blood clot