biological molecules

Question 1

what elements do carbohydrates contain (3)

Answer 1

hydrogen and oxygen and carbon

Question 2

a monosaccharide is a

Answer 2

simple sugar (eg. glucose)

Question 3

a disaccharide is made when

Answer 3

2 monosaccharide join together (eg. maltose)

Question 4

a polysaccharide is formed when

Answer 4

lots of monosaccharides join together ( eg. starch, glycogen)

Question 5

are polysaccharides insoluble

Answer 5

yes

Question 6

carbohydrates are made up of

Answer 6

simple sugars

Question 7

proteins are made up of

Answer 7

amino acids

long chains of amino acid

Question 8

proteins contain (atoms)

Answer 8

carbon, hydrogen, oxygen and nitrogen

Question 9

examples of protein (2)

Answer 9

haemoglobin and enzymes

Question 10

how are different proteins formed (amino acid arrangement)

Answer 10

as amino acids can be arranged in any order, it results in hundreds of different proteins

Question 11

lipids are made from

Answer 11

3 fatty acids bonded to 1 glycerol molecule

Question 12

lipids contain (atoms)

Answer 12

carbon, hydrogen and oxygen

Question 13

lipids are divided into (2)

Answer 13

fats (solids at room temp)

oils ( liquids at room temp)

Question 14

how do you prepare a food sample

Answer 14

1- get a piece of food and break it up using pestle and mortar

2- transfer to test tube and add distilled water

3- mix with glass rod to dissolve some of the food

4- filter the mixture using funnel and filter paper to get rid of solid bits of food.

Question 15

test for glucose ( sugar) name

Answer 15

benedicts test

Question 16

benedicts test

Answer 16

• add benedict’s solution to sample solution in a test tube
• heat in a boiling water bath for 5 mins
• take out and observe colour
• if there is glucose colour will have changed from blue to orange/brick red

Question 17

if glucose is present what will the colour change be

Answer 17

blue to orange/ brick red

Question 18

test for starch name

Answer 18

iodine test

Question 19

iodine test

Answer 19

• add drops of iodine to food sample
• if colour changes from orange to blue black then starch is present

Question 20

colour change for starch

Answer 20

orange/brown to blue/black

Question 21

protein test name

Answer 21

biurets test

Question 22

Biurets test

Answer 22

• add drops of biuret solution to food sample
• colour change will be from blue to violet/purple if protein is present

Question 23

colour change for protein

Answer 23

blue to violet / purple

Question 24

name for test for lipids

Answer 24

ethanol test

Question 25

ethanol test

Answer 25

• mix food sample with 4cm³ of ethanol and shake
• allow time for food sample to dissolve in ethanol
• strain ethanol solution into another test tube
• add ethanol solution to 4cm³ of cold distilled water
• positive test will show milky, cloudy emulsion forming

Question 26

colour change for ethanol test

Answer 26

colourless to cloudy, milky

Question 27

what is a catalyst

Answer 27

a catalyst is a substance which increases the rate of reaction without chemically being used up

Question 28

enzymes are

Answer 28

catalysts produced by living things

Question 29

what do enzymes do

Answer 29

act as biological catalysts to speed up rate of chemical reactions without being changed or used up

Question 30

why are enzymes necessary to all living organisms

Answer 30

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

Question 31

enzymes work fastest at

Answer 31

their optimum temperature

Question 32

optimum temperature for enzymes in the human body

Answer 32

37º

Question 33

what happens to an enzyme if temperatures go beyond optimum

Answer 33

the enzyme will denature and so the bonds that keep it together will break and it will lose its shape

Question 34

what happens if an enzyme is denatured

Answer 34

substrate cannot fit into active site and so it doesn’t work anymore

Question 35

can denaturisation be reversed

Answer 35

no, once an enzyme has been denaturedd, they cannot regain their shape

Question 36

effect of temperature on an enzyme

Answer 36

• Increasing the 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 substrate molecules increases, leading to a faster rate of reaction
• This means that low temperatures do not denature enzymes, they just make them work more slowly due to a lack of kinetic energy

Question 37

practical for investigating temp can affect enzyme activity

Answer 37

• add 5cm³ starch solution to a test tube and heat in water bath
• at the same time add 2cm³ of amalyse in a test tube and heat that in a water bath as well
• add a drop of iodine to each of the wells of a spotting tile
• mix the starch and amylase together
• every minute, transfer a droplet of solution to a new well of iodine solution ( which turns blue-black) until colour stops changing
• record time taken for colour change
• repeat with range of temperatures

Question 38

optimum pH for most enzymes

Answer 38

7

Question 39

if the pH is too high or too low,

Answer 39

the bonds holding the amino acid chain can be destroyed so the enzyme is denatured.

the active site changes shape and substrate no longe fits meaning activity stops

Question 40

practical of how pH affects enzyme activity

Answer 40

have a buffer solution, a piece of potato ( which contains catalyse) and some hydrogen peroxide in a test tube,

we are going to measure the amount of oxygen giving off when breaking oxygen peroxide

have a siphon on the test tube which ends into a beaker

then measure/count how many bubbles form in a minute

repeat with buffer solutions of different pH