Biological Molecules

Question 1

catalyst

Answer 1

a substance which increases the speed of a reaction without being changed or used up in the reaction

Question 2

what are enzymes

Answer 2

-biological catalysts
-proteins made up of chains of amino acids

Question 3

lock and key model

Answer 3

-substrate joins onto enzymes active site
-it has to be the correct shape to fit the active site

Question 4

how does pH affect enzyme function

Answer 4

-if the pH is too high or too low, the pH interferes with the bonds holding the enzymes together
-this changes the shape of the active site and denatures the enzyme

Question 5

how does temperature affect enzyme function

Answer 5

-higher temperatures increases the rate
-because enzyme and substrate have more energy, so they move about more and are more likely to collide and from enzyme-substrate complexes
-if it gets too hot, some of the bonds holding the enzyme together break
-this changes the shape of the enzymes active site, so the substrate will not fit anymore, the enzyme is now denatured

Question 6

experiment to investigate how enzyme activity can be affected by temperature

Answer 6

-use a pipette to add a set amount of hydrogen peroxide to a boiling tube. Put the boiling tube in a water bath at 10C
-add a source of catalase(1cm cubed of potato) to the hydrogen peroxide and quickly attack the bung
-collect the oxygen in a measuring cylinder
-record how much oxygen is produced in the first minute
-repeat 5 times and calculate the mean
-repeat at 20, 30 and 40C
-control variables: pH, the potato used, size of potato pieces)

Question 7

experiment to investigate how enzyme activity can be affected by pH

Answer 7

-use a pipette to add a set amount of hydrogen peroxide to a boiling tube.
-add buffer solution with a set pH level
-add a source of catalase(1cm cubed of potato) to the hydrogen peroxide and quickly attack the bung
-collect the oxygen in a measuring cylinder
-record how much oxygen is produced in the first minute
-repeat 5 times and calculate the mean
-repeat at different pH levels
-control variables: temperature, the potato used, size of potato pieces)

Question 8

elements present in carbohydrates

Answer 8

carbon, hydrogen and oxygen

Question 9

elements present in proteins

Answer 9

carbon, nitrogen, hydrogen and oxygen

Question 10

elements present in lipids

Answer 10

carbon, hydrogen and oxygen

Question 11

what are starch and glucose made of

Answer 11

simple sugars

Question 12

what are proteins made of

Answer 12

amino acids

Question 13

what are lipids made of

Answer 13

fatty acids and glycerol

Question 14

test for glucose

Answer 14

-prepare a food sample and transfer 5cm cubed to a test tube
-prepare a water bath at 75C
-add benedict’s solution(10 drops) using a pipette
-leave test tube in water bath for 5 minutes
-if the food sample contains glucose, test tube will change from its normal blue colour
-high concentration =brick-red
-low concentrations - green or yellow

Question 15

test for starch

Answer 15

-make a food sample, transfer 5cm cubes of sample into a test tube
-add a few drops of iodine solution and gently shake the tube to mix the contents
-if sample contains starch, solution changes from brown orange to blue black

Question 16

test for proteins

Answer 16

-prepare a sample of your food and transfer 2 cm3 of your sample to a test tube
-add 2 cm3 of biuret solution to the sample and mix the contents of the tube by gently shaking it
-if the food sample contains protein, the solution will change from blue to pink or purple
-no protein = stay blue

Question 17

test for lipids

Answer 17

prepare sample of the food
-use a pipette to add 3 drops of sudan III stain solution to the test tube and gently shake the tube
-sudan III stain solution stains lipids.
If the sample contains lipids, the mixture will separate out into two layers. The top layer will be bright red
-if no lipids are present, no separate red layer will form at the top of the liquid