organisation

• Digestion

  1. Large food molecules broken into small molecules by enzymes

  2. Small molecules absorbed into the blood stream
• Tissue

  A group of cells with a similar function
• Digestive enzymes

  • Enzymes that speed up chemical reactions
  • Have an active site where substrate attaches
  • Follow the lock and key theory
• Starch

  A chain of glucose molecules broken down into simple sugars
• Lipids

  Glycerol attached to fatty acids
• Proteins

  Long chains of chemicals called amino acids
• As temperature increases

  Activity of enzymes increases
• Increased enzyme activity

  More collisions per second
• Optimum temperature

  Fastest possible rate of enzyme catalysis
• Small intestine

  • Covered in villi which increases the surface area
  • Villi have a thin membrane which provides a short diffusion path
• Heart

  Has 4 chambers: right atrium, right ventricle, left atrium, left ventricle
• Blood flow

  1. Vena cava brings deoxygenated blood into the heart

  2. Pulmonary artery carries blood from the heart to the lungs

  3. Pulmonary vein carries oxygenated blood from the lungs to the heart

  4. Aorta pumps blood from the heart to the body
• Arteries

  • Carry high pressure blood from the heart to organs
  • Have thick muscular walls to withstand high blood pressure
  • Contain elastic fibres to allow stretching
• Capillaries

  • Glucose and oxygen diffuse from blood into cells
  • Have thin walls for a short diffusion path allowing rapid diffusion
• Veins

  • Have thin walls as blood pressure is low
  • Contain valves to stop blood from flowing backwards
• Plasma

  Transports soluble digestion products like glucose, CO2 and urea
• Red blood cells

  • Transport oxygen
  • Contain haemoglobin
  • Have no nucleus so more room for haemoglobin
  • Have dimples for greater surface area to allow rapid oxygen diffusion
• White blood cells

  • Have a nucleus containing DNA
• Platelets

  Help blood to clot
• Donated blood uses protein extracted to help in blood clotting
• Problems with donated blood include same blood type and disease
• Cardiovascular disease

  Diseases of the heart and blood vessels
• Coronary heart disease

  Buildup of fatty acids in coronary artery causes it to narrow, reducing oxygen flow
• Statins

  Reduce cholesterol levels in the blood, but can cause liver problems
• Stent insertion

  1. Tube inserted into coronary artery to keep it open

  2. Allows normal blood flow but doesn't prevent other regions from narrowing
• Mechanical heart valves

  Last a lifetime but increased risk of blood clotting so require drugs
• Animal heart valves

  Don't last as long but don't require drugs
• Heart failure

  Disadvantages of donated hearts and artificial hearts
• Lungs

  • Alveoli where gases diffuse in and out of the blood stream
  • Millions of alveoli create a huge surface area
  • Thin walls for a short diffusion path
  • Good blood supply
• Stomata opening

  Guard cells swell and change shape as light intensity increases, causing the stomata to open and allow CO2 to diffuse in
• Xylem

  Transports water from roots to stems/leaves
• Phloem

  Transports dissolved sugars from leaves to the rest of the plant
• Meristem

  Contains stem cells at growing tips
• Translocation

  Movement of sugars and other molecules through phloem tissues
• Leaf epidermis

  • Transparent to let light in
  • Waxy cuticle reduces water evaporation
  • Stomata allow CO2 in and oxygen out
• Palisade mesophyll

  • Absorbs light for photosynthesis
• Spongy mesophyll

  • Full of air, allows CO2 to diffuse to palisade cells
• Benign tumour

  Does not invade other parts of the body, not cancerous
• Malignant tumour

  Invades and moves into the bloodstream, cancerous
• Transpiration

  1. Constant evaporation of water from leaf surfaces

  2. Brings water and dissolved mineral ions to the leaf

  3. Cools the leaf down