biology test 28/02/2024

• what chemical elements are present in carbohydrates?

  carbon, hydrogen and oxygen typically in a ratio of 1:2:1
• what smaller basic unit is starch made up of? what are some examples?

  simple sugars such as glucose, fructose or lactose can join together to form larger molecules
• what chemical elements are present in proteins?

  carbon, hydrogen, oxygen and nitrogen
• what is the structure of proteins?

  chains of amino acids which are twisted and folded to give its overall shape
• what chemical elements are present in lipids?

  carbon, hydrogen and oxygen
• what is the structure of lipids?

  a glycogen molecule and three attached fatty acids
• define an enzyme

  a biological catalysts that speed up the rate of reaction
• what three things are enzymes involved in?

  building large molecules from lots of smaller ones, breaking down large molecules into smaller ones and changing one molecule into another
• if i was using Benedict's solution to test a sample, what would i be testing the presence of?

  presence of glucose
• if a reducing sugar is present what colour will Benedict's solution change to?

  orange
• what is a brief method for Benedict's test?

  add double the volume of Benedict's compared to the volume of the sample. then heat to more than 80 degrees for five minutes
• what are the colour changes of Benedict's depending on glucose concentration?

  blue to green to orange to brick red
• what are some examples of protein?

  enzymes such as amylase and keratin
• what test is used to find the concentration of sugar?

  Benedict's test
• what test is used to test the presence of starch?

  iodine test
• if i was using the iodine test, what substance would i be looking for the presence of?

  starch
• what is a brief method for the iodine test?

  add multiple drops of iodine solution to the food sample
• what are the colour changes of the iodine test depending on the starch concentration?

  from yellow to blue-black if starch is present
• if i were to test a sample for protein, what test would i use?

  biuret test
• if i was carrrying out the biuret test, what sample would i be searching the presence of?

  protein
• what is a brief method for the Biuret test?

  add several drops of Biuret's reagent to the sample
• what are the colour changes of the biuret test depending on protein concentration?

  pale blue to pink if protein is present
• if i were using the emulsion test, what sample would i be searching for the presence of?

  lipids
• if i was searching for the presence of lipids, what test would i use?

  emulsion test
• what is a brief method for the emulsion test?

  grind up some food particles then add 3 cm cubed of ethanol and shake. leave to sit until the particles have settled to allow the lipids to dissolve into the ethanol. strain the ethanol solution into another test tube and add 3 cm cubed of water to the solution
• what changes would be seen if a lipid was present in the emulsion test?

  from clear to cloudy white
• what is the role of enzymes in metabolic reactions?

  enzymes are necessary to all living organisms as they maintain reaction speeds of all metabolic reactions at a rate that can sustain life
• what is a metabolic reaction?

  a metabolic reaction is a biochemical reaction that transforms food into energy in our body and its cells
• how can low temperature affect enzyme function?

  the molecules have less kinetic energy and it takes longer for the substrate to travel to the active site of the enzyme therefore reaction rates are slower at lower temperatures
• how can high temperature affect enzyme function?

  the enzyme’s active site becomes denatured meaning that the enzyme no longer catalyzes the reaction. This causes the enzyme to stop working permanently
• what is the optimum temperature?

  this is the temperature that enzymes work best at due to a high number of collisions between the enzyme and substrate making more enzyme-substrate complexes leading to an increase in enzyme activity
• plan a practical to investigate how enzyme activity can be affected by changes in temperature

  take a dimple tile and add a drop of iodine to each dimple. place amylase in a test tube and 5 cm cubed of starch in a second test tube and place in a water bath for 5 mins. transfer some drops of amylase solution to the starch solution (now the reaction mixture). at 1 minute intervals, transfer a drop of the reaction mixture to a drop of iodine . note the time taken for the starch to disappear from the reaction mixture. repeat steps 2 to 6 but use a different temperature in the water bath
• how can an acidic solution affect enzyme function?

  below the optimum pH, the active site becomes denatured and stops working permanently
• how can an alkali solution affect enzyme function?

  above the optimum pH, the active site is denatured and stops working permanently
• what is the optimum pH?

  at the optimum pH, 7, the active site has a shape that fits the substrate therefore the enzyme can function at its best
• Testing for Amylase Activity

  1. Place single drops of iodine solution in rows on the tile

  2. Label a test tube with the pH to be tested

  3. Place 2cm3 of amylase into the test tube

  4. Add 1cm3 of buffer solution to the test tube

  5. Add 2cm3 of starch to amylase/buffer solution

  6. Start the stop clock and leave it on throughout the test

  7. Use a plastic pipette to mix

  8. After 10 seconds. Use the plastic pipette to place one drop of the mixture on the first drop of iodine

  9. Wait another 10 seconds. Then remove a second drop of the mixture to add to the next drop of iodine

  10. Repeat step 7 until the iodine solution and the amylase/buffer/starch mixture remains orange

  11. Count how many iodine drops you have used

  12. Repeat the whole procedure with another of the pH buffers
• what is cormms?

  Change - what is being changed in the investigation (independent variable)

  Organism - a control related to the organism being used (if relevant)

  Repeat - repeats must be carried out for reliable results

  Measurement 1 - how will you measure your dependent variable

  Measurement 2 - what time scale will you use

  Same - what will you control in the investigation
• define the independent variable?

  the variable that is changed in the investigation
• define the dependent variable?

  the variable that is measured in the investigation
• define the control variable?

  the variable that is kept the same throughout the investigation