chapter 4

Question 1

State the 3 main nutrients that are body needs.

Answer 1

carbohydrates, proteins , lipids

Question 2

These nutrients are examples of what? what elements do they contain?

Answer 2

Examples of organic chemicals
Carbs : CHO
Lipid : CHO
Protein : CHON + SULFUR + PHOSPHORUS

Question 3

Break down of carbohydrates ( their basic units , characteristics and form )

Answer 3

C6H12O6
TYPES:
Simple sugars ( sweet, soluble , fast break down and absorption )
Monosaccharides
GLUCOSE
FRUCTOSE
GALACTOSE
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Disaccharides ( 2 molecules )
MALTOSE
SUCROSE
LACTOSE
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Complex sugars ( not sweet, insoluble, slow break down and absorption )
Polysaccharide ( large molecules )
Starch ( in plants )
Glycogen ( in animals )
Cellulose ( plant cell wall )
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Characteristics of glucose:
In humans :
- carried in plasma
- stored in muscle , lives as glycogen
- needed for respiration

In plants:
- transported as sucrose
- stored as starch

Question 4

State the function of carbohydrates

Answer 4

Source of energy

Question 5

Break down of lipids ( their basic units and characterisitcs )

Answer 5

Basic units:
Fatty acid
Glycerol
Fatty acid ( x3 ) + glycerol ( x1 ) = Fats

characteristics:
Fats: solid at rt - animals
Oils : liquid at rt - seed germination
insoluble inwster
can be dissolved in alcohol

Question 6

Function of fats

Answer 6

Source of energy
keep warm, insulation
protect internal organs
make cell membrane

Question 7

break down of protein and its characteristics

Answer 7

Basic unit : amino acid
- 20 different types
- essential is from food
- non essential is made by body

Dipeptide ( 2 animo acids joined together )

Polypeptide ( many amino acids joined , forms 3D shape )

Characteristics:
- soluble ( haemoglobin )
- insoluble ( keratin in hair and finger nails )

Question 8

Functions of protein

Answer 8

growth to make new cells
repair damaged cells
make antibodies
make enzymes
make hormones

Question 9

Enzymes and their substrate and products

Answer 9

Substrate + enzyme = product
starch + amylase = maltose
protein + protease = amino acids
lipids + lipase = fatty acid and glycerol

Question 10

Describe the structure of DNA

Answer 10

• consists of 2 strands of DNA wound to form a double helix
• made up of nucleotides

All nucleotides contain:
- phosphate group
- pentose sugar ( 5-carbon )
- Base ( nitrogenous )

Types of Bases ( A , T , C , G )
Pairing always ( A-T. C-G )

Question 11

What is the test for reducing sugars?

Answer 11

Benedict’s Solution
1. add the food sample in a test tube
2. then add 2cm3 of solution into food sample
3. heat at 60-70 degrees in water bath for 5 minutes
Colour change :
Blue > Green>yellow>orange>red
none alot

Question 12

What is the test for starch?

Answer 12

Iodine solution
1. Add food sample in test tube
2. Add 2cm3 of solution to food sample
Colour change :
Positive ( blue/black )
Negative ( brownish yellow )

Question 13

What is the test for protein ?

Answer 13

Biuret solution
Add 2cm3 food sample
Then add 2cm3 solution

Colour change:
Positive ( deep purple )
Negative ( blue )

Question 14

what is the test for lipids?

Answer 14

Ethanol emulsion
2cm3 of food sample + 2cm3 of solution and shake .
Then add 2cm3 of water

Colour change :
Positive ( white cloudy emulsion )

Question 15

What is benedict’s solution used to test for ?

Answer 15

reducing sugars

Question 16

What is iodine solution used to test for ?

Answer 16

starch

Question 17

What is biuret solution used to test for ?

Answer 17

proteins

Question 18

What is ethanol emulsion solution used to test for ?

Answer 18

lipids

Question 19

what is DCPIP used to test for?

Answer 19

vitamin C

Question 20

What is the test for vitamin C?

Answer 20

DCPIP
Add 1cm3 to food sample

Colour change :
Positive ( colourless )
Negative ( remains blue )