Nutrients

Question 1

What is the role/function of water in living things?

Answer 1

Humans:
Solvent in which chemical reactions take place
An essential component of cells, tissues, digestive juices and blood
Helps to control body temperature through sweating
Helps to transport dissolved substances around the body
Plants:
Photosynthesis
Keeping plant cells turgid and plants upright
Transport of mineral salts up the xylem
Transport of dissolved food substances from the leaves to other parts of the plant

Question 2

What is the general ratio of carbohydrates?

Answer 2

Carbohydrates consists of carbon,hydrogen and oxygen in the formula CnH2mOm
The hydrogen and oxygen atoms are present in a fixed ratio of 2:1

Question 3

What are reducing sugars ?

Answer 3

All monosaccharides and disaccharides (except sucrose) are reducing sugars

Question 4

What are monosaccharides / simple sugars? And what’s its chemical formula?

Answer 4

Glucose , fructose and galactose
C6H12O6

Question 5

What makes up maltose,lactose and sucrose?

Answer 5

Fructose + glucose -> sucrose
Galactose + glucose -> lactose
Glucose + glucose -> maltose
(So LaMe)

Question 6

What are disaccharides and what is its chemical formula

Answer 6

Sucrose, lactose, maltose
C12H22O11

Question 7

How does one test for starch?

Answer 7

Using the iodine solution test.
If the solution turns blue-black, starch is present

Question 8

What are fats

Answer 8

Organic compounds made up of carbon,hydrogen and oxygen
In unfixed proportions

Question 9

What are the similarities and differences between fats and carbohydrates

Answer 9

Similarities : they are both made up of carbon, hydrogen and oxygen
: they are both sources of energy
Differences: carbohydrates have a fixed ratio of H to O , 2:1 while fats contains less oxygen in proportion to hydrogen
: proportions of elements are not fixed in fats but they are fixed in carbohydrates

Question 10

What are the products of hydrolysis of fats?

Answer 10

Fat molecule + 3 H2O molecules -> 1 glycerol and 3 fatty acid molecules

Question 11

What is the test for fats and how is it carried out?

Answer 11

Ethanol emulsion test
Ethanol is added to the food sample and then shaken, water is decanted into the test tube and then the mixture is shaken ,

If a cloudy white emulsion forms, fats are present

Question 12

What elements are proteins composed of?

Answer 12

carbon , hydrogen, oxygen and nitrogen , ( sulfur may be produced in some proteins )

Question 13

What are proteins needed for?

Answer 13

The synthesis of new protoplasm for the growth and repair of cells
Synthesis of enzymes and some hormones
Synthesis of antibodies

Question 14

What is the test for proteins and how is it carried out?

Answer 14

Biuret test:
Add biuret solution to the food sample in a test tube and shake thoroughly

If the solution changes colour from blue to purple, proteins are present

Question 15

What happens when proteins (polypeptides) are broken down?

Answer 15

They form amino acids

Question 16

What is a condensation reaction?

Answer 16

A chemical reaction in which 2 simple molecules are joined together to form a larger molecule with the removal of one molecule of water

Question 17

What is the test for reducing sugars and how is it carried out?

Answer 17

Benedicts test:
Solution remains blue: no reducing sugar
Green ppt: traces of reducing sugar
Yellow/orange ppt: moderate amounts of reducing sugar
Brick red ppt: large amounts of reducing sugar

Question 18

Why are glycogen and starch suitable as storage materials in cells?

Answer 18

They are insoluble in water, do not change the water potential of the cells
They are large molecules that cannot diffuse through cell membranes > will not be lost from the cell
Can easily be hydrolysed to glucose when needed; eg in tissue respiration
Their molecules have compact shapes and thus occupy less space than individual glucose molecules that make up a glycogen/starch molecule

Question 19

Functions of Carbohydrates?

Answer 19

A substrate for respiration, provides energy for cell activities
To form supporting structures eg for cell wall in plants
To be converted to other organic compounds like amino acids acids and fats
For the formation of nucleic acids, eg dna
To synthesise lubricants ; eg mucus

Question 20

Which fat, saturated or unsaturated has kinks in its fatty acid chain?

Answer 20

Unsaturated ; they are liquid at room temperature