Organisation

• what are cells?


  the building blocks that make up all living organisms
• when does differentiation occur?

  during the development of a multicellular organism - specialised cells form tissues which form organs which form organ systems
• what is a tissue?


  a group of similar cells working together to carry out a specific function, it can include more than one type of cell
• what are some examples of tissues in mammals?


  muscular tissue - contracts to move whatever it is attached to

  glandular tissue - makes and secretes chemicals like enzymes and hormones

  epithelial tissue - covers some parts of the body e.g. inside the gut
• what is an organ?


  a group of tissues that work together to perform a specific function in the body
• what tissues is the stomach made up of?


  muscular tissue - makes the stomach move and churn the food

  glandular tissue - makes digestive juices to digest food

  epithelial tissue - covers the outside and inside of the stomach
• what is an organ system?


  a group of organs that work together to perform a specific function in the body - the digestive system and the cardiovascular system
• what is a catalyst?


  a substance which increases the speed of a reaction without being changed or used up in the reaction
• describe the 'lock and key' method.

  • every enzyme has an active site but the substrate has a specific shape so can only fit into a specific enzyme to be broken up
  • the enzyme acts as the lock and the substrate acts as the key and it binds to the active site, which catalyses the reaction resulting in the substrate being broken into its products
• what is meant by the enzyme denatures?


  if the temperature gets too hot then some of the bonds holding the enzyme together start to break which changes the shape of the active site so the substrate will no longer fit - denatured enzyme.
• how does pH affect enzymes?

  if the pH is too high or too low then it interferes with the bonds holding the enzyme together which changes the shape of the active site and denatures the enzyme.
• why are enzymes needed in digestion?


  starch, proteins and fats are too big to pass through the walls of the digestive system so enzymes break them down into smaller molecules like sugar - these smaller and soluble molecules can pass through easily allowing them to be absorbed into the blood stream
• Amylase

  • converts carbohydrates into simple sugars
  • an example of carbohydrase
  • starch + amylase enzyme --> maltose
  • made in the salivary glands, pancreas and the small intestine
• Protease

  • convert proteins into amino acids
  • proteins + protease enzymes --> amino acids
  • made in - the stomach, pancreas, small intestine
  • called pepsin in the stomach
• Lipase

  • converts lipids into glycerol and fatty acids
  • lipid + lipase enzymes ---> glycerol and fatty acids
  • made in the - pancreas and small intestine
• why is bile important?

  • produced in the liver and is stored in the gall bladder before being released to the small intestine
  • HCl makes the stomach acid's pH too acidic so bile neutralises the acid and makes it more alkaline
  • emulsifies fats - creates a bigger SA of fat for enzymes to break down - speeds up digestion
• Digestive System

  salivary glands - produce amylase in the saliva

  liver - where bile is produced

  gall bladder - where bile is stored before it's released into the small intestine

  pancreas - produces protease, lipase and amylase

  large intestine - absorbs excess water from the food

  small intestine - produces enzymes to complete digestion - where digested food is absorbed out of system and into the blood
• why is the stomach important in digestion?

  • pummels the stomach with its muscular walls & produces the protease enzyme, pepsin
  • produces HCl - to kill bacteria and to give the right pH for protease to work
• what is benedict's test for?


  sugars
• how do you test for sugars?

  • prepare a food sample and put 5cm3 into a test tube - prepare a water bath and set the temp to 75 degrees
  • add some benedict's solution to the tube - about 10 drops - using a pipette
  • place tube in water bath for about 5 mins - tube pointing away from you
  • if food contains reducing sugar it will turn from blue to green, yellow or brick red - depends on how much sugar is present
• what is iodine solution for?

  testing for starch
• how do you test for starch?

  • make a food sample and transfer 5cm3 to a test tube
  • add a few drops of iodine solution using a pipette and shake gently to mix the contents
  • if starch is present the colour of the solution will change from a browny-orange to black or blue-black
• what is biuret test used for?

  to test for proteins
• how do you test for proteins?

  • prepare a sample of food and transfer 2cm3 to a test tube
  • add 2cm3 of biuret solution to the sample and mix the contents by gently shaking
  • if protein is present the solution will change from blue to purple
• what is the Sudan III test used for?

  to test for lipids
• how do you test for lipids?

  • prepare a sample of food and transfer 5cm3 to a test tube
  • use a pipette and add 3 drops of Sudan III stain solution to the tube and gently shake
  • if lipids are present the mixture will separate out into two layers - the top layer will be bright red
• the lungs

  • the air that we breathe in goes through the trachea which then splits into two tubes called bronchi, one going to each lung
  • these bronchi split into progressively smaller tubes called bronchioles which finally end at small bags called alveoli - where gas exchange takes place
• how does alveoli carry out gas exchange?

  • blood passing right next to the alveoli have returned from around the body so are full of CO2 and very little oxygen
  • oxygen diffuses out of the alveolus - high concentration - to the blood - low concentration - and the CO2 does the opposite
  • when oxygen reaches the body cells oxygen diffuses into the cells and CO2 diffuses out and then goes back to the lungs
• what is the name of the pigment in the blood?

  haemoglobin
• what is the double circulatory made up of?

  the heart, lungs, blood vessels and blood
• right ventricle

  • pumps deoxygenated blood to the lungs to take in oxygen then returns to the heart
• left ventricle

  • pumps oxygenated blood all around the body - gives up its oxygen so becomes deoxygenated and returns to the right ventricle to be pumped to the lungs again
• what is the heart?

  • a pumping organ that keeps the blood flowing around - walls made of muscular tissue
  • has valves which stopped the blood flowing in the wrong direction
  • had 4 chambers - right atrium, right ventricle, left atrium and left ventricle
• how does the heart pump blood around the body?

  1. blood flows into the right atrium via the vena cava to the right ventricle which is then pumped through the pulmonary artery to the lung
  2. after collecting oxygen it is pumped back into the heart via the pulmonary vein, through the left ventricle and the aorta pumps the blood around the body
• what is an artery?


  a blood vessel that carries blood away from the heart
• how are arteries adapted for there function?

  • walls are thick, strong an elastic as the heart pumps blood at high pressure
  • elastic fibres allow them to stretch and spring back
  • the lining is coated in lumen
• what is a capillary? 


  involved in the exchange of substances at the tissues
• how is a capillary adapted for its function?

  • permeable walls so substances can diffuse in and out
  • supply food and oxygen - take away waste like CO2
  • walls are only one cell thick - increases rate of diffusion by decreasing the distance over which it occurs
• what is a vein?


  carry blood away from the heart
• how is a vein adapted for its function?

  • blood is at low pressure so walls do not have to be as thick as artery walls
  • bigger lumen to help blood flow despite the low pressure
  • valves to help keep blood flowing in the right direction