b2- organisation

• a tissue- a group of simliar cells that work together to carry out a particular function
• examples of tissues


  muscular tissue- contracts to move whatever its attached to

  glandular tissue- makes and secretes chemicals like enzymes

  epithelial tissue- convers parts of the body, like the inside of your gut
• organs- a group of different tissues that work together to perform a certain function
• organ system- a group of organs working together to perform a particular function
• enzymes are biological catalysts that increase the speed of a reaction without being used up or changed in the reaction
• 'lock and key theory'- every enzyme has an active site with a unique shape that fits onto the substance involved in a reaction. they usually only catalyse one specific reaction each, because the substrate has to fit into its active site and if the substrate doesnt match then the reaction wont be catalysed
• enzymes need the right- temperature + pH for the reaction to work

  • all enzymes have an optimum temperature and pH that they work best at
• carbohydrases convert carbohydrates into simple sugars
• proteases break down proteins into amino acids
• lipases convert lipids into glycerol and fatty acids
• bile neutralises stomach acid and emulsifies fats
• amylase is produced in

  • salivary glands
  • small intestine
  • pancreas
• protease is produced in

  • stomach
  • pancreas
  • small intestine
• lipase is produced in

  • pancreas
  • small intestine
• liver- where bile is produced
• gall bladder- where bile is stored
• use benedicts test to test for sugars

  • colour will change from BLUE to orange/brick red depending on how much sugar is present
• use iodine solution to test for starch, if starch is present it will turn from ORANGE to BLUE/BLACK
• use biuret test to test for proteins

  if protein is present it will turn from BLUE to PURPLE
• use Sudan III test to test for lipids

  • if lipids are present the solution will separate out into two layers and the top layer will be bright red
• lungs-

  • the air that you breathe goes in through the trachea which split into two tubes called bronchi, which split into progressively smaller tubes called bronchioles
  • these finally end at air sacs called alveoli
• alveoli

  • carry out gas exchange in the body
  • alveoli are surrounded by a network of blood capillaries
  • large surface area for a faster rate of diffusion
• the heart-

  • made out of cardiac tissue which doesnt get tired
  • 4 chambers
  • right ventricle pumps de-oxygenated blood to the lungs to take in oxygen
  • left ventricle pumps oxygenated blood all around the body
• arteries-

  • carry blood away from the heart
  • pumps blood under high pressure so the artery walls are strong and elastic
  • thick muscular walls + thin lumen
• veins-

  • carry blood to the heart
  • valves to prevent back flow
  • thin walls as theres low pressure
  • large lumen to encourage blood flow
• capillaries

  • involved in the exchange of materials at the tissues
  • very small
  • carry blood really close to every cell in the body to exchange substances with them
  • permeable walls so substances can diffuse in and out
  • one cell thick- increases rate of diffusion by shortening diffusion distance
• red blood cells-

  • carry oxygen
  • shape= biconcave disc which provides a large surface area for absorbing oxygen
  • no nucleus to allow more room to carry oxygen
  • contain haemoglobin
• white blood cells-

  • defend against infection
  • some change shape to engulf unwanted pathogens- phagocytosis
  • others produce antibodies to fight microorganisms as well as antitoxins to neutralise any toxins produced by microorganismsn
  • they do have a nucleus
• platelets-

  • help blood clot
  • small fragments of cells- no nucleus
• plasma-

  • the liquid that carries everything in blood
  • white blood cells, red blood cells, platelets
  • nutrients
  • carbon dioxide
  • urea
  • hormones
  • proteins
  • antibodies + antitoxins
• stents- metal mesh tubes that are inserted into the arteries to keep them open

  • lowers the risk of a heart attack for people with coronary heart disease
  • effective for a long time and recovery time is relatively quick
• statins- reduce cholesterol in the blood, reduce risk of heart attack
• artificial heart can pump blood around the body
• faulty heart valves can be replaced with biological or mechanical valves
• cancer- caused by the uncontrolled cell growth and division

  • benign- when a tumour grows until there's no more room then it stays in place- normally isn't dangerous and isn't cancerous
  • malignant- where the tumour grows and spreads to neighbouring healthy tissues- dangerous and can be fatal: they are cancers.
• phloem tubes-

  • transport food
  • made of columns of elongated living cells with small pores in the end walls to allow cell sap to flow through
  • they transport food substances to the rest of the plant
  • process goes in both directions- called translocation
• xylem tubes-

  • take water up
  • made of dead cells joined end to end with no end walls between them
  • carry water and mineral ions from the roots to the stem and leaves
  • the movement of water from the roots, through the xylem and out of the leaves in called the transpiration stream
• transpiration=

  • the loss of water from the plant
  • caused by evaporation and diffusion of water from a plants surface- most happens at the leaves
  • this creates a slight shortage of water in the leaf so more water is drawn up from the rest of the plant through the xylem vessels
  • this in turn means more water is drawn up from the roots and so there's a constant transpiration stream of water through a plant
• transpiration rate is affected by

  • light intensity (increases it)
  • temperature (increases it)
  • air flow (increases it)
  • humidity- the drier the air the faster the rate.
• guard cells are found in the stomata and control the opening and closing of the stomata