Biology paper 1 weak areas

• Name the positive test for test for starch + iodine


  orange-brown to blue black
• Name the positive test for benedict's test for sugar


  Blue to orange/brick red
• Name the positive test for biuret solution for proteins


  blue to purple/lilac
• Sudan III test for lipids - describe the method

  1. Place 5cm3 of your food sample in a test tube.
  2. Add 3 drops of Sudan III stain solution.  
  3. Gently shake.
  4. If a red layer separates out on top, then lipid was present.
• Does the Benedict's test require heating the sample in a water bath? 


  yes for 5 mins at 75c
• What do we call the movement of cell sap (a mixture of sugar and water) up and down the plant?


  Translocation
• Phloem cells have _________ in their end walls to allow cell sap to pass along the phloem tube. 


  Pores
• What does the xylem transport in a plant?


  Water and dissolved mineral ions
• How do root hair cells absorb water from the soil?


  Osmosis
• How do root hair cells absorb mineral ions from the soil?

  Active transport
• Which substance are xylem cells reinforced with to make them stronger? 


  Lignin
• What is transpiration?

  The evaporation of water from the leaves
• Why does the rate of transpiration increase if the light intensity is increased?


  The stomata open wider to let more carbon dioxide into the leaf for photosynthesis.
• What happens to the rate of transpiration if wind speed increases?

  It increases-The wind blows away water vapour as soon as it diffuses out of the leaf. This maintains a strong concentration gradient between the inside and outside of the leaf, which increases the rate at which water diffuses out.
• Which of the following are treatments for coronary heart disease? 

  Stent  and Statins
• How does a stent help treat coronary heart disease?

  It expands within the artery to widen the lumen
• What are the benefits of stents when treating coronary artery disease?

  The stents have an almost immediate effect

  Surgery is quick
• How do statins help treat coronary heart disease?

  They decrease the amount of LDL cholesterol in the blood and They increase the amount of HDL cholesterol in the blood 
• What are the disadvantages of statins when treating coronary artery disease?


  -It can take months to see the positive effects 

  The pills have to be taken every day an They have side effects such as kidney failure and headaches
• What are two problems that may be caused by faulty heart valves?

  Blood can pass backwards through the valve

  Not enough blood can pass though the valve
• what are treatments for heart failure?

  Replacement with artificial heart

  Replacement with biological heart 
• If there is plenty of water in the leaf, guard cells become .................... which opens the stomata. This allows carbon dioxide to ....................the leaf, but also allows .............. to escape. 

  turgid, enter, water
• What is meristem tissue and where is it found? 


  Meristem tissue is made up of plant stems cells. It's found in the growing parts of the plant such as the tips of shoots and roots. 
• How viruses spread and multiply

  1. Viruses can pass between humans via the air, contaminated food or water, or by direct contact.
  2. As they can't reproduce themselves, viruses have to enter one of our cells, and then use it to create multiple copies of the virus itself.
  3. Once there are lots of copies, the viruses cause the cell to burst, and then go on to infect neighbouring cells. 
• The difference between antigens and antibodies. 

  An antigen is any substance that your body sees as foreign, which then causes your immune system to produce antibodies against it. For example, the toxins and cell walls of pathogens would be considered antigens. 

  An antibody on the other hand is a protein produced by our white blood cells that binds to specific antigens. This acts as a signal to our immune system to destroy the antigen (or the pathogen it is part of).
• How does skin help to defend against disease?

  It covers the body, physically preventing pathogens from entering

  It secretes oils and antimicrobial substances that kill pathogens
• Stages of phagocytosis

  1. Phagocytosis is carried out by a special type of white blood cell called a phagocyte. 
  2. The first step is for the phagocyte to track down a pathogen, and then bind to it. 
  3. The phagocyte's membrane will then surround the pathogen and engulf it.
  4. Finally, enzymes inside the phagocyte break down the pathogen in order to destroy it.
• stages of binary fission 


  1)the circular dna and plasmids replicate

  2)the cells gets bigger andd circular DNA moves to opposite sides of the cell

  3)cytoplasm divides and new cell walls form

  4)cytoplasm divides and 2 daughter cells are produced.