Chapter 3 : Nutrients

Question 1

Function of water in humans (4)

Answer 1

1. Solvent for chemical reactions
2. Essential component of cells, tissue fluids, digestive juices and blood
3. Control body temp
4. Transport dissolved substances around the body

Question 2

Function of Water in plants (3)

Answer 2

1. Essential for photosynthesis
2. Keeps plant cells turgid and up right
3. Needed for transport of mineral salts and food substances

Question 3

Name the elements which make up carbohydrates and the general formula of carbohydrates (2)

Answer 3

Carbon, Hydrogen, Oxygen. CmH2nOn

Question 4

Name all monosaccharides (3) and disaccharides (3)

Answer 4

Monosaccharides
1. Glucose
2. Fructose
3. Galactose

Disaccharides
1. Sucrose ( Glu + Fru )
2. Lactose ( Glu + Gal )
3. Maltose ( Glu + Glu )

Question 5

How are disaccharides formed

Answer 5

Condensation Reaction. 2 simple molecules ( monosaccharides ) join together with the release of water

Question 6

How are disaccharides broken up

Answer 6

Hydrolysis. Disaccharides can be split into 2 monosaccharides with water in the presence of an enzyme ( disaccharidases )

Question 7

Steps for Benedict’s Test

Answer 7

2cm^3 of Benedict’s solution to 2cm^3 of food sample ( for solids
Shake mixture
Heat contents in boiling water bath for 2 - 3 min

In decreasing amounts of sugar
Brick red
Orange
Yellow
Green
Blue

Question 8

Types of complex carbohydrates and where they can be found (3)

Answer 8

Starch ( storage organs in plants )
Glycogen ( storage form in mammals )
Cellulose ( In cell walls )

Question 9

Steps for iodine test

Answer 9

1. 2cm^3 of food sample to a clean test tube
2. Add a few drops of iodine solution to the test tube

Starch present : blue black
Starch absent : Yellow brown

Question 10

Why do humans store carbohydrates as glycogen instead of starch ? (4)

Answer 10

Glycogen is :
1. Insoluble in water - does not change water potential
2. Large molecules - does not diffuse out of the cell easily
3. Easily hydrolysed
4. Compact shape - occupy less space

Question 11

Function of carbohydrates (6)

Answer 11

1. Provide energy
2. Form supporting structures ( cell wall )
3. Conversion into other organic compounds
4. Form nucleic acids
5. Synthesise lubricants
6. Synthesise nectar in flowers

Question 12

What are fats made up of ? What separates saturated fats with unsaturated fats

Answer 12

Glycerol and 3 fatty acid chains. Saturate fats do not have kinks in the fatty acid chain while Unsaturated fats do.

Question 13

Steps for Ethanol Emulsion Test

Answer 13

1. Add 2cm^3 of ethanol to 2cm^3 of food sample
2. Shake contents of the tube vigorously
3. Decant 2 cm^3 of the water into the test tube and shake the mixture

Fats present: Cloudy white emulsion is formed

Question 14

Function of Fats (5)

Answer 14

1. Source and store of energy
2. Insulating material
3. Solvent for fat soluble vitamins
4. Form the main part of the cell membrane
5. Reduce water loss from skin surface

Question 15

What element does protein have which carbohydrates and fats do not have

Answer 15

Nitrogen

Question 16

What are amino acids made of ?

Answer 16

1. Amino group (NH2)
2. Acid group (COOH)
3. Side chain (R)

Question 17

Steps for Biuret test

Answer 17

1. Add 2 cm^3 of NaOH solution to 2 cm^3 of food sample into a test tube
2. Shake mixture thoroughly
3. Add 1% copper sulphate solution drop by drop, shaking the mixture aft each drop

Protein present : Purple or Violet solution is formed

Question 18

Function of proteins (3)

Answer 18

Synthesis of
A) new protoplasm for growth and repair
B) enzymes and some hormones
C) antibodies