Biology

• cells-tissues-organs-organ systems- organisms
• tissues - group of cells that work together to carry out a particular function.
• organs - group of tissues that work together to perform a specific function
• organ system - a group of organs that work together to perform a specific function
• organisms - organ systems working tohether
• pancreas - makes enzymes
• liver makes bile
• gall bladder stored bile
• small intestine - digested food is absorbed into blood
• large intestine - where water and minerals are absorbed into blood
• bile is alkaline and neutralises stomach acid
• Breathing in


  1. Air moves into the body through the mouth and nose

  2. Down the trachea

  3. Into the bronchi

  4. Through the bronchioles

  5. Into the alveoli (air sacs)
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  • Red blood cells - bind to oxygen and transport it around the body
  • Plasma - transports substances and blood cells around the body
  • Platelets - form blood clots to create barriers to infections
  • White blood cells - part of the immune system to defend the body
• Artery


  Carries blood away from the heart
• Artery


  • Thick, muscular, and elastic walls
  • The walls can stretch and withstand high pressure
  • Thick layer of muscle and elastic fibres
• Vein


  Carries blood to the heart
• Vein


  • Relatively thin wall
  • Large lumen
  • Often have valves to stop blood flowing the wrong way
  • Low pressure
• Capillary


  • Carries blood to tissues and cells
  • Connects arteries and veins
  • One cell thick - short diffusion distance for substances to move between the blood and tissues
• Capillary


  • Very narrow lumen
  • Vessel is one-cell thick
• Heart


  • The organ that pumps blood around your body
  • Made from cardiac muscle tissue
  • Supplied with oxygen by the coronary artery
• Double circulatory system


  1. Right ventricle pumps blood to the lungs where gas exchange takes place

  2. Left ventricle pumps blood around the rest of the body
• Heart rate


  • Controlled by a group of cells in the right atrium that generate electrical impulses, acting as a pacemaker
  • Artificial pacemakers can be used to control irregular heartbeats
• enzymes are large proteins that catalyse (speed up) reactions
• the enzymes active site is a specific shape
• the enzyme is the lock
• the substrate is the key
• the enzyme will only catalyse a specific reaction as the substrate fits into its active site
• at extremes of pH or high temperatures the enzymes active site can change - the enzyme becomes denatured
• digestive enzymes convert food into small, soluble molecules that can be absorbed into the bloodstream
• amylase - breaks down starch into glucose
• proteases - breaks down proteins into amino acids, found in the stomach and pancreas
• lipases - break down lipids into fatty acids and glycerol
• stomata are tiny openings in the undersides of leaves - placement reduces water loss through evaporation
• stomata control has exchange and water loss from leaves by:

  • allowing diffusion for carbon dioxide into the plant for photosynthesis
  • allowing diffusion for oxygen to get out the plant
• guard cells are used to open snd close the stomata
• transpiration - water is lost through the stomata by evaporation - pulls water up from roots through the xylem
• transpiration provides water to cells for photosynthesis and transports mineral ions to leaves
• Transpiration


  Water is lost through the stomata by evaporation. This pulls water up from the roots through the xylem.
• Transpiration stream


  The constant movement of water up the plant
• Importance of transpiration


  • Provides water to cells to keep them turgid
  • Provides water to cells for photosynthesis
  • Transports mineral ions to leaves