Enzymes + Food tests

Question 1

Why do we have enzymes?

Answer 1

to speed up the useful chemical reactions in our body

Question 2

what are enzymes?

Answer 2

biological catalysts

Question 3

what are catalysts?

Answer 3

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

Question 4

what are enzymes made of?

Answer 4

proteins which are made up of long chains of amino acids that are folded into unique shapes to do their job

Question 5

What is the active site in an enzyme?

Answer 5

a unique shape that fits onto the substance involved in a reaction

Question 6

Why won’t the reaction be catalysed if the substrate doesn’t fit the active site?

Answer 6

because for the enzyme to work, the substrate must fit into the enzymes active site.

Question 7

what is the name of the diagram that shows catalyse reaction steps?

Answer 7

Lock and key diagram

Question 8

what is a substrate?

Answer 8

the substance that an enzyme works on

Question 9

what is it called when the substrate fits into the enzyme?

Answer 9

enzyme substrate complex

Question 10

Why do enzymes have an optimum pH?

Answer 10

if pH is too high or too low, the pH interferes with the bonds holding the enzyme together which changes the shape of the active site causing the enzyme to denature.

Question 11

what two things can denature an enzyme and why?

Answer 11

temperature - if temp too hot, bonds break changing shape of enzymes active site so substrate no longer fits and enzyme is denatured
pH - if too pH too high or too low, bonds holding enzyme together are broken and changes shape of active site which denatures enzyme

Question 12

what pH do enzymes often work best at?

Answer 12

neutral pH 7

Question 13

How can you test for sugar?

what colour does it go?

Answer 13

Benedict’s test

blue to brick red

Question 14

how can you test for starch?

what colour will it turn?

Answer 14

iodine solution test

brown to black

Question 15

how can you test for proteins?

what colour does it go?

Answer 15

biuret solution

blue to purple

Question 16

how can you test for lipids?

what colour will it go?

Answer 16

emulsion test, milky white

sudan III test, red

Question 17

how can you work out rate of reaction?

Answer 17

1000/time

Question 18

how can you calculate how much something changes over time with rate of reaction?

Answer 18

amount it has changed over time/time taken

Question 19

bile emulsifies fats, explain what this means and how it aids digestion

Answer 19

it breaks the fats down into tiny droplets to giving larger surface area for lipase enzyme to work upon. making digestion faster

Question 20

what would you observe shaking Sudan III stain solution with a food sample containing lipids?

Answer 20

the mixture will separate into two layers, the top layer being red

Question 21

what are the 3 jobs of enzymes?

Answer 21

chemical digestion (break down)
assimilation - building up new molecules
transforming molecules - used in metabolic pathways
catalyst - speeds up rate of reaction

Question 22

state the steps of the Benedict’s test

Answer 22

1) prepare a food sample and transfer 5 cm3 to a test tube
2) prepare a water bath so that its set to 75 degrees Celsius
3) add some Benedict’s solution to the test tube (about 10 drops) using a pipette
4) place the tube in the water bath using a tube holder and leave it in there for 5 mins, make sure the tube is pointing away from you
5) if the food sample contains a sugar, the solution in the test tube will turn from blue to green, yellow or brick red depending on how much sugar is in the food.

Question 23

name steps in the iodine test

Answer 23

1) make a food sample and transfer 5cm3 of your sample to a test tube
2) add a few drops of iodine solution and gently shake the tube to mic the contents. if sample contains starch, colour of solution will turn from brown to black

Question 24

name steps of biuret test

Answer 24

prepare a sample of food and transfer 2cm3 of sample to a test tube
add 2cm3 of buret solution to the sample and mix the contents of the tube by gently shaking
if food contains solution will change from blue to purple

Question 25

state steps of Sudan III test

Answer 25

prepare a sample of the food you’re testing, transfer 5cm3 into a test tube
use a pipette to add 3 drops of Sudan III stain solution to test tube and gently shake
Sudan III stains lipids, if sample contains lipids, mixture will separate into two layers, the top layer will be bright red

Question 26

state the adaptations of the small intestine

Answer 26

large blood supply to maintain high concentration gradient
large surface area for maximum absorption
thin wall of villi for shorter diffusion
blood capillaries close to wall for shorter diffusion

Question 27

what is the independent variable?

Answer 27

the one thing you change

Question 28

what is the dependent variable!

Answer 28

the change that happens because of the independent variable

Question 29

what is the controlled variable?

Answer 29

what stays the same (eg type of acid used)