B2 Organisation

• Describe the test for starch

  1. prepare a food sample and add 5cm^3 to a test tube
  2. add a few drops of iodine to the test tube and gently shake to stir the mixture
  3. if starch is present, the solution should go from orangey-brown to blue-black
• Describe the test for sugars

  1. prepare a food sample and add 5cm^3 to a test tube
  2. prepare a water bath to 75•C
  3. add 10 drops of benedict’s solution to the test tube
  4. place the test tube in the water bath using a test tube rack and leave for 5 minutes
  5. if sugars are present: solution should turn from blue to green, yellow or brick red depending on how much sugar
• Describe the test for lipids

  1. prepare a food sample (without filtering) and transfer 5cm^3 to a test tube
  2. using a pipette, measure 3 drops of sudan III stain solution and add to the test tube
  3. sudan III stain solution turns lipids bright red
  4. if lipids are present: mixture separates into two layers- the top one being bright red
  5. if not present: no seperate layer forms on top of the mixture
• Explain the ‘lock and key theory’

  • substrate binds to the active site
  • as the active site is complimentary to the substrates shape
  • a chemical reaction occurs to produce smaller molecules
• Describe the test for protein

  1. prepare a food sample and transfer 2cm^3 to a testube
  2. add 2cm^3 of biuret solution and mix by shaking gently
  3. if protein is present: blue to purple/lilac
• Describe how to prepare a food sample.

  1. get a food piece and break it up using a pestle and mortar
  2. transfer the ground up food to a beaker and add distilled water
  3. stir the mixture to dissolve some of the food
  4. filter the solution using a funnel lined with filter paper to remove any solid food pieces
• Explain why the circulatory system is described as a double circulatory system

  • it consists of two circuits joined together
  • the first pumps deoxygenated blood to the lungs to take in oxygen and returns oxygenated blood to the heart
  • the second one pumps oxygenated blood around the body and returns deoxygenated blood to the heart
• Describe how pH affects enzyme action

  • if the pH is too high or too low, it lowers the rate of reaction
  • some of the bonds holding the enzyme together start to break
  • so the active site starts to change(the substrate still fits but less well so the rate is slow)
  • active site then changes shape so much it can’t fit and is no longer complimentary
  • so no reaction can take place as the enzyme has been denatured
• Describe how temperature affects enzyme

  • high temperatures start to break apart the bonds holding the enzyme together
  • so the active site starts to change shape
  • so the enzyme won’t be able to bind to the substrate
  • the enzyme has been denatured so reaction can’t take place
  • which can’t be reversed
• Where is bile produced + stored

  • bile is produced in the liver
  • bile is stored in the gall bladder
• What is the role of bile

  • the HCl in the stomach makes the pH too acidic for the enzymes in the small intestine to work properly so because bile is alkaline it neutralises the acid and makes conditions alkaline.
  • as the enzymes in the small intestin work the best in alkaline conditions
  • Emulsifies fats - breaks down fats into small droplets which has a bigger SA of fat for lipase to work on, making digestion faster
• Why does the stomach produce hydrochloric acid

  • to kill bacteria
  • to provide the protease enzymes with the optimum conditions to work (pH 2)
• What is coronary heart disease

  • when coronary arteries (which supply blood to the heart) get blocked due to the build of of layers of fatty material
  • so lumen becomes narrower so less oxygen reaches the heart
  • which puts strain on the heart, potentially causing a heart attack
• What are stents 


  an expandable tube placed inside the artery to hold them open to ensure the blood keeps flowing
• What are the benefits and issues of stents?

  Benefits

  • surgery is quick
  • last a long time

  Issues

  • surgery has risks - induce heart attack, infection, blood clot near stent (thrombosis)
• What are statins?

  • a medication that alters the balance of cholesterol in the blood stream.
  • statins decrease the amount of LDL cholesterol and increase the HDL cholesterol which lowers the overall risk of CHD and other diseases
• What does LDL and HDL cholesterol do?

  LDL (bad cholesterol) - too much causes fatty deposits in the coronary artery to form

  HDL (good)- helps us get rid of fatty deposits, we normally have too little.
• What are the benefits and issues of statins?

  Benefits

  • no risks of surgery
  • easy to take

  Issues

  • taken regularly
  • side effects (headache, kidney failures)
• what happens when valves get damaged or weakened?


  stops blood flowing, valve can’t close properly (blood can leak backwards)
• Name 2 types of treatment for faulty valves 


  Replace valves

  • biological valves (human, pig, cow)
  • mechanical (man made) - can increase the risk of blood clots
• What causes heart failure?


  when there is a loss of blood supply to the heart.
• What is heart failure?


  a condition when the heart is unable to pump blood around the body efficently
• What are tumours?

  an abnormal mass of cells that forms when a group of cells undergo uncontrolled growth and division
• What is a bengin tumour?

  • non cancerous
  • contained within one area
  • dont spread
• What is a malignant tumour?

  • cancerous
  • able to invade other tissues
  • can spread to different parts of the body
  • can create secondary tumours
  • cause a lot of damage
• What are the risk factor for cancers?

  • smoking- mouth, lung, stomach and cervical
  • obesity- bowel, liver and kidney
  • ultraviolet light- skin
  • genes- BRCA- breast and ovarian
• Examples of plant tissues

  • Epidermal tissue
  • Palisade mesophyll tissue
  • Spongy mesophyll tissue
  • Xylem
  • Phloem
  • Meristem tissue
• Xylem

  Transports water and mineral ions around the plant
• Phloem

  Transports dissolved sugars around the plant
• Meristem tissue


  • Found at the tips of roots and shoots
  • Able to differentiate into different types of plant cells
  • Allows the plant to grow
• Epidermal tissue

  • covers the whole plant
  • structure: covered in a waxy cuticle which helps to reduce water loss by evaporation
• Palisade mesophyll tissue

  • part of the leaf where the most photosynthesis happens
  • structure: lots of chloroplasts as they’re at the top of the leaf
• Spongy mesophyll tissue

  • contains big air spaces to allow gasses to diffuse in and out of cells
  • structure: have air spaces in the tissue to increase the rate of diffusion of gases
• Xylem and phloem

  • form a network of vascular bundles which delivers water and other nutrients to the entire leaf and take away the glucose produced by photosynthesis
  • also help support the structure
• Upper epidermis


  structure: transparents so that light can pass through into the palisade layer
• Lower epidermis


  structure: full of little holes called stomata which let co2 directly into the leaf and are controlled by guard cells in response to environmental conditions
• Describe the path of blood through the heart

  1. Blood flows into the two atria from the vena cava and the pulmonary vein.
  2. The atria contract, pushing the blood into the ventricles.
  3. The ventricles contract, forcing the blood into the pulmonary artery and the aorta, and out of the heart.
  4. The blood then flows to the organs through arteries, and returns through veins
  5. The atria fill again and the whole cycle starts over.
• what is an artificial pace maker + what does it do?

  • it’s a small device that’s implanted under the skin and has a wire going to the heart
  • produces an electric current to keep the heart beating regularly
  • used to treat an irregular heartbeat
• How do the group of cells in the right atrium wall act as a pacemaker?

  • they produce a small electrical impulse that causes the muscle cells to contract
• What is plasma and what does it do?

  • plasma is the pale straw coloured liquid that carries everything in the blood