2- biological molecules

Question 1

chemical elements in a carbohydrate

Answer 1

carbon, oxygen, hydrogen

Question 2

chemical elements in a protein

Answer 2

all contain carbon, oxygen, hydrogen and nitrogen

some contain small amounts of other elements

Question 3

chemical elements in an lipid

Answer 3

carbon, oxygen and hydrogen

Question 4

most fats are made up of

Answer 4

triglycerides

Question 5

fats basic unit is

Answer 5

one glycerol molecule chemically bonded to three fatty acid chains

Question 6

fatty acids vary in

Answer 6

size and structure

Question 7

lipids are divided into

Answer 7

fats and oils

Question 8

proteins are formed from

Answer 8

long chains of amino acids

Question 9

proteins shape

Answer 9

different proteins have different amino acid sequences resulting in them being different shapes

Question 10

test for glucose

Answer 10

Benedict’s solution:
-heat in water bath in a test tube for 5 mins
positive test will show colour change from blue-orange/brick red

Question 11

test for starch

Answer 11

iodine;
-add drops of iodine to food sample
positive test shows colour change from orange/brown-blue/black

Question 12

test for protein

Answer 12

biuret solution;
-add drops of buret solution to food sample
positive test shows colour change blue-violet/purple

Question 13

test for lipids

Answer 13

-mix food sample with 4cm3 of ethanol and shake
-allow time for sample to dissolve
-strain the ethanol solution into another test tube
-add ethanol solution to equal volume of cold distilled water
positive test will show cloudy emulsion forming

Question 14

enzymes are proteins that act as

Answer 14

biological catalysts to speed up the rate of a chemical reaction without being changed or used up in the reaction

Question 15

enzymes are necessary to all living organisms because

Answer 15

they maintain reaction speeds of all metabolic reactions at a rate that can sustain life

Question 16

enzymes are specific to one particular substrate as

Answer 16

the active site of an enzyme, where the substrate attaches, is complementary to the substratee

Question 17

when the substrate moves into the enzymes active site they become known as

Answer 17

the enzyme-substrate complex

Question 18

after the reaction has occurred the product leaves the enzymes active site because

Answer 18

they no longer fit and it is free to take up another substrate

Question 19

enzymes work best at their

Answer 19

optimum temperature

Question 20

denatured enzymes

Answer 20

when high temperatures break the bonds that hold the enzyme together and it will lose its shape

Question 21

denaturartion is

Answer 21

irreversible as once the enzymes have denatured they can’t regain their proper shape and the activity will stop

Question 22

increasing temperature affect on enzymes

Answer 22

increrasing temperature towards the optimum increases the activity of enzymes as the more kinetic energy the molecules have the faster they move and the number of collisions with the sub state increases, which increases the rate of reaction

Question 23

low temperature affect on enzymes

Answer 23

doesn’t denature the enzymes but makes them work more slow due to lack off kinetic energy

Question 24

optimum pH for most enzymes is

Answer 24

7

Question 25

pH is too high or low affect on enzymes

Answer 25

the bonds that hold the amino acid chain together to make up the protein can be destroyed, this changes the shape of the active site so the substrate can no longer fit into it reducing the rate of activity

Question 26

amylase is

Answer 26

an enzyme that digests starch into maltose

Question 27

apparatus needed to investigate the affect of temperature on the activity of amylase (temperature affect on enzymes)

Answer 27

spotting tile, measuring cylinder, test tube, syringe, pipette, stopwatch, water, thermometer, water bath, iodine, starch solution, amylase solution

Question 28

method to investigate the affect of temperature on the activity of amylase (temperature affect on enzymes)

Answer 28

1) add 5cm3 of starch to a test tube and heat to a set temperature
2) add a drop of iodine to each of the wells of a spotting tile
3) use a syringe to add 2cm3 of amylase to the starch solution and mix well
4) every minute transfer a droplet of solution to a new well of iodine solution (which should turn blue/black)
5) repeat this until iodine stops turning blue/black (this means amylase has broken down all the starch)
6) record the time taken for the reaction to be completed
7) repeat investigation for a range of temperatures (from 20 degrees to 60)

Question 29

results of experiment to investigate the affect of temperature on the activity of amylase (temperature affect on enzymes)

Answer 29

the investigation shows that at the optimum temperature the iodine stopped turning blue/black the fastest because the enzyme is working at the fastest rate and has digested all the starch. at colder temperatures the iodine took longer to stop turning blue/black because the amylase enzyme is working slower due to low kinetic energy and fewer collisions. at higher temperatures (above optimum) the iodine turned blue/black the whole investigation because the enzyme has become denatured and can no longer bind with the starch or break down

Question 30

apparatus needed to investigate the affect of pH on the activity of amylase (pH affect on enzymes)

Answer 30

spotting tile, measuring cylinder, test tube, syringe, pipette, stopwatch, buffer solutions, iodine, starch solution, amylase solution

Question 31

method to investigate the affect of pH on the activity of amylase (pH affect on enzymes)

Answer 31

1) add a drop of iodine to each of the wells of a spotting tile
2) use a syringe to place 2cm3 of amylase and 1cm3 of buffer solution (at pH 2) to the test tube
3) use another test tube to add 2cm3 of starch solution to the the amylase and buffer solution and start the stopwatch whilst mixing using a pipette
4) every 10 seconds transfer a droplet of the solution to a new well of iodine solution (which should turn blue/black)
5) repeat this transfer process every 10 seconds until the iodine solution stops turning blue-black (this means amylase has broken down all the starch)
6) record the time taken for the reaction to be completed
7) repeat the investigation with buffers at different pH values (ranging from pH 3.0 to pH 7.0)

Question 32

results of experiment to investigate the affect of pH on the activity of amylase (pH affect on enzymes)

Answer 32

at the optimum pH, the iodine stopped turning blue/black and remained orange/brown within the shortest amount of time because the enzymes is working at its fastest rate and has digested all the starch. at higher/ lower pH (above or below the optimum) the iodine took longer to stop turning blue/black because at either side of the optimum pH the enzymes are started to become denatured and as a result are unable to bind with the starch or break it down.