Biology option

• How do you calculate magnification and actual size of an image?


  Magnification = image size/actual size

  Actual size = image size/magnification

  1. Actual length of the scale bar/scale bar value (convert to same unit) = magnification

  2. Actual length of object/magnification = actual size of object
• How do you estimate the osmolarity of the cytoplasm in potatoes?

  1. Osmosis: water moves from high concentration to low concentration along a concentration gradient

  2. Using a cork borer, produce 30 potato cores

  3. All of the strips need to be the same length to begin with - cut them down to 4 cm and remove skin

  4. Mark each core with a beaker number and letter

  5. Dry and weigh each core

  6. Prepare solutions: 100, 80, 60, 40, 20 and 0 % NaCl (table salt) with distilled water

  7. Place the potato cores in their respective beakers and begin timing

  8. After 20 minutes, remove the cores, dry them and weigh them again

  Results:

  - The lower salt concentrations will have a larger mass as water has entered the potato cores as there is a higher water potential inside the solution than the potato (hypotonic solution)

  - The higher salt concentrations will have a smaller mass as water has left the potato because the water potential is lower inside the solution (hypertonic solution)

  - The solution is isotonic at about 1.4g of salt per 100 ml of water
• How is lactase enzyme immobilized with sodium alginate beads?


  1. Sodium alginate containing lactase enzyme is added to calcium chloride

  2. This forms small beads in which the lactase enzyme is immobilised

  3. The beads are then separated from the calcium chloride solution

  4. The immbolized lactase beads are then placed inside the syringe which is attached to a tube

  5. Milk is then added over the immbolized lactase beads and cycled while the glucose concentration of the milk is tested

  6. After each cycling, the glucose concentration should increase as the lactase breaks down the lactose into glucose and galactose

  7. This process can be used on an industrial scale to treat lactose intolerance
• How do you do separate photosynthetic pigments using paper chromatography? (Chlorophyll chromatography)


  1. Obtain a plant that contains the pigments you wish to separate

  2. Break up a leaf into small pieces. Use a pestle + mortar, add acetone and sand to help grind up the leaves

  3. Grind leaves until pigments are released

  4. Draw a line in pencil 2cm from the bottom of the chromatography paper (starting line)

  5. Place a spot of concentrated pigment on the line with capillary tube + allow to dry

  6. Put running solvent into a vile ensuring it doesn't go above 2cm

  7. Place the chromatography paper into the solvent and allow the pigment to move up the paper

  8. Mark how far the solvent moved up the chromatography paper and measure the distance from the point of origin

  9. Mark the point of each pigment and measure their distance from the point of origin

  10. To calculate the Rf value: (distance moved by pigment/distance moved by solvent front)

  
  

  -Smaller compounds move further

  
• How to create a mesocosm:


  -A mesocosm is an experimental tool that brings a small part of the natural environment under controlled conditions.

  -Can be used to measure temperature, CO2 concentration + pH levels

  -Energy enters + leaves. Matter does not. It's a closed ecosystem

  
  

  1. Rocks at the base

  2. Potting mix on top of rocks

  3. Plant

  4. Water

  5. Seal in glass jar

  
• Advantages of mesocosms


  -Food webs can be established

  -Treatments are easily replicated

  -Direct + indirect effects can be examined

  -Multiple environmental factors can be manipulated

  
• Disadvantages of mesocosms


  -Does not perfectly imitate the environment

  -May cause stress to an organism

  -Use of growth chambers for a lab experiment can be an disadvantage due to the limited amount of space

  
• How do you measure the impact that exercise has on ventilation? (Measuring ventilation using a spirometer)


  1. All participants do a singers breathing exercise 3 times

  2. Count the number of breaths of a participant sitting still in a chair over the course of 2 minutes

  3. Count the number of breaths of a participant doing 80 steps per minute over the course of 2 minutes

  4. Leaving a minute in between, count the number of breaths of a participant jogging at 160 steps per minute over the course of 2 minutes

  Results: There should be more breaths after exercise and your body has to use oxygen for cellular respiration and therefore releases more co2

  
• Investigating factors affecting enzyme activity


  -Catalase + Hydrogen peroxide --> H20 + O2

  -Independent variable: Temperature

  -Control variables: pH + substrate concentration

  -Dependent variable: volume of O2 produced in a measured set of time (measured using a gas syringe)

  -Rate of reaction can be calculated from this

  -Equipment: Water bath, conical flask + gas syringe, measuring cylinder, mass balance (potato)

  
  

  -Potato cubes are placed in conical flask (source of catalase)

  
• Minerals


  specific elements such as calcium and iron
• vitamins


  chemically diverse carbon compounds needed in small amounts that cannot be synthesized by the body
• example of 2 vitamins


  ascorbic acid and calciferol
• example of fatty acids that, along with some amino acids allow the production of proteins at ribosomes to continue

  omega-3 fatty acids
• malnutrition


  deficiency, imbalance or excess of specific nutrients in the diet
• what can carbohydrates, lipids and amino acids all be used for as a source of energy

  aerobic cell respiration
• what happens when the energy in the diet is insufficient


  reserves of glycogen and fats are mobilised and used.
• starvation


  prolonged shortage of food
• what happens when glycogen and fat reserves are used up


  body tissues have to be broken down and used in respiration (starvation & anorexia)
• Anorexia


  an individual does not eat enough food to sustain the body even though it is available
• what can happen in advanced cases of anorexia


  heart muscle is broken down
• obesity


  excessive storage of fat in adipose tissue, due to prolonged in take of more energy in the diet than is used in cell respiration
• obesity can lead to which health issues


  hypertension (high blood pressure) and Type 2 diabetes
• what is responsible for feelings of appetite or satiety

  hypothalamus
• joules of energy need to heat 1ml of water by one degree

  4.2 joules
• energy content of a food=


  (temp rise X water volume (ml) X 4.2L)/mass of food (g)
• what type of cholesterol is implicated in CHD

  low-density lipoprotein
• what effect does reducing dietary cholesterol have on blood cholesterol levels

  very small
• what organ can synthesise cholesterol meaning dietary cholesterol is not the only source

  liver
• what are considered more important than dietary intake when talking about heart disease


  genetic factors, some families have high cholesterol even with low dietary intake
• what does the positive correlation between dietary intake of saturated fats and intake of cholesterol mean when discussing links to heart disease


  possible that saturated fats, not cholesterol, caused increase of CHD in people
• what happens when there is insufficient vitamin D in the body

  calcium is not absorbed from food in the gut to large enough quantities
• osteomalacia


  inadequate bone mineralization due to calcium salts not being deposited or being reabsorbed so bones become softened
• osteomalacia in children


  rickets
• where is vitamin D found


  oily fish, eggs, milk, butter, cheese and liver
• what is unusual about vitamin D


  can be synthesised in the skin but only by UV light
• what is ascorbic acid needed for


  synthesis of collagen fibres in many body tissues including skin and blood vessel walls
• lack of vitamin c causes


  scurvy
• why were attempts to induce scurvy in rats unsuccessful


  most mammals (apart from humans) have enzymes needed for synthesis in ascorbic acid
• two other animals that require ascorbic acid in diet

  chimpanzees and guinea pigs
• what is phenylalanine


  essential amino acid