B3 Digestion

Question 1

Test for starch.

Answer 1

Test for starch:
1 Place a small amount of food on the spotting tile.
2 Add a few drops of iodine solution to the food on the
spotting tile.
3 Yellow–red iodine solution turns blue–black if starch is
present.
4 Record your result in the results table.
5 Repeat steps 1–4 for other types of food.

Question 2

Test for sugar.

Answer 2

Test for sugar:
1 Place a small amount of food in a test tube.
2 Add enough Benedict’s solution to cover the food.
3 Place the test tube in a warm water bath for 10 minutes.
4 Blue Benedict’s solution turns brick red on heating if a
sugar such as glucose is present.
5 Record your result in the results table.
6 Repeat steps 1–5 for other types of food.

Question 3

Test for lipids.

Answer 3

Test for lipids (fat):
1 Place a small amount of food into a test tube.
2 Add a few drops of ethanol to the test tube.
3 Shake the test tube and leave for 1 minute.
4 Pour the solution into a test tube of water.
5 Ethanol added to a solution gives a cloudy white layer if
a lipid is present.
6 Record your result in the results table.
7 Repeat steps 1–6 for other types of food.

Question 4

Test for protein

Answer 4

Test for protein:
1 Place a small amount of food in a test tube.
2 Add 1 cm
3
of Biuret reagent. Alternatively add 1 cm
sodium hydroxide solution and then add a few drops of
copper sulfate solution.
3 Blue Biuret reagent turns purple if a protein is present.
4 Record your result in the results table.
5 Repeat steps 1–4 for other types of food.

Question 5

active site

Answer 5

the site on an enzyme where the reactants bind

Question 6

amino acids

Answer 6

molecules made up of carbon, hydrogen, oxygen, and nitrogen that are the building blocks of proteins

Question 7

amylase

Answer 7

enzyme that speeds up the digestion of starch into sugars

Question 8

bile

Answer 8

neutralises stomach acid to give a high pH for the enzymes from the pancreas and small intestine to work well. It is
not an enzyme

Question 9

carbohydrases

Answer 9

enzymes that speed up the breakdown of carbohydrates into simple sugars

Question 10

carbohydrates

Answer 10

molecules that contain only carbon, hydrogen, and oxygen. They provide the energy for the metabolism and are
found in foods such as rice, potatoes, and bread

Question 11

catalyst

Answer 11

a substance that speeds up the rate of another reaction but is not used up or changed itself

Question 12

denatured

Answer 12

the breakdown of the molecular structure of a protein so it no longer functions

Question 13

differentiate

Answer 13

the process where cells become specialised for a particular function

Question 14

digestive system

Answer 14

organ system where food is digested and absorbed

Question 15

enzymes

Answer 15

biological catalysts, usually proteins

Question 16

fatty acids

Answer 16

part of the structure of a lipid molecule

Question 17

glycerol

Answer 17

part of the structure of a lipid molecule

Question 18

lipase

Answer 18

enzymes that speed up the breakdown of lipids into fatty acids and glycerol

Question 19

lipids

Answer 19

include fats and oils and are found in foods such as butter, olive oil, and crisps. They are made of carbon,
hydrogen and oxygen

Question 20

metabolism

Answer 20

the sum of all the reactions taking place in a cell or the body of an organism

Question 21

organ

Answer 21

an aggregation (collection ) of different tissues working together to carry out specific functions

Question 22

organ system

Answer 22

a group of organs that work together to carry out specific functions and form organisms

Question 23

proteases

Answer 23

enzymes that speed up the breakdown of proteins into amino acids

Question 24

proteins

Answer 24

molecules that contain carbon, hydrogen, oxygen, and nitrogen and are made of long chains of amino acids. They
are used for building the cells and tissues of the body and to form enzymes

Question 25

simple sugars

Answer 25

small carbohydrate units, for example glucose

Question 26

tissue

Answer 26

a group of specialised cells with a similar structure and function