Bio Chapter 3 - Biological Molecules

Question 1

Why do all lining organisms need food and water?

Answer 1

Contains nutrients essential for us

Question 2

What are the 6 functions of water

Answer 2

Dissolves substances for chemical reactions that take place in living things. Essential for photosynthesis. Keeps cells turgid and firm. Transport mineral salts.regulate body. Transport dissolved substances within the body.

Question 3

Describe sugars

Answer 3

Sweet. Soluble in water → lower water potential of the solution.

Question 4

Give the three classifications of carbohydrates

Answer 4

Single sugars, double sugars and complex carbohydrates

Question 5

What are the two single sugars?

Answer 5

Glucose and fructose

Question 6

What are the two double sugars?

Answer 6

Maltose and sucrose

Question 7

What are the three complex carbs?

Answer 7

Starch, cellulose, glycogen

Question 8

Describe single sugars

Answer 8

Basic unit of carbs, can pass through cell membranes and can be absorbed into cells

Question 9

Describe double sugars

Answer 9

Formed when two single sugars are joined together

Question 10

What’s the structure of maltose?

Answer 10

Glucose + glucose

Question 11

What is the structure of sucrose?

Answer 11

Glucose + fructose

Question 12

What is the structure of starch

Answer 12

Made up of several thousand glucose molecules joined together

Question 13

What is the role of starch?

Answer 13

Stores carbohydrates in plants. in humans, it is digested into glucose to provide energy for cell activity

Question 14

Where is starch found?

Answer 14

Storage organs of plants

Question 15

What is the structure of cellulose?

Answer 15

Made up of many glucose molecules joined together bonded differently from starch

Question 16

What is the role of cellulose?

Answer 16

Protects plants cells from bursting or damage
Cannot be digested so it acts as dietary fibre that aids in digestion/ prevents constipation in humans

Question 17

Where is cellulose found?

Answer 17

Cell walls of plants

Question 18

What is the structure of glycogen?

Answer 18

A branched molecule made up of many glows molecules joined together

Question 19

What is the role of glycogen?

Answer 19

Stores carbohydrates in mammals. Digested into glucose to provide energy for cell activity

Question 20

Where is glycogen found?

Answer 20

Liver and muscles

Question 21

What are the 5 functions of carbohydrates

Answer 21

Source and store of energy,
supporting structures such as cellulose in plants,
formation of nucleic acids such as DNA,
to make lubricants such as mucus,
covering the inner surface of the trachea and traps dust particles preventing dust from entering the lungs
To make nectar in some flowers

Question 22

Give 3 examples of reducing sugars

Answer 22

Glucose, fructose and maltose

Question 23

How to test for reducing sugars?

Answer 23

Benedict’s solution
Add 2cm3 of each food sample into a test tube
Add 2cm3 of Benedicts solution to food sample
Shake mixture and place test tube in boiling water bath for 2 to 3 minutes
Observe colour of solution

Question 24

What are the results of the Benedict’s test?

Answer 24

Blue → none
Blue to green → traces
Blue to yellow / orange precipitate → moderate amount
Blue to brick-red precipitate → large amount

Question 25

How to test for starch?

Answer 25

Iodine solution
Add a few drops of iodine in potassium iodide solution to a food sample
Record observations

Question 26

What are the results of starch test?

Answer 26

Brown → negative
Blue-black → positive

Question 27

What is the structure of fats?

Answer 27

Fat molecule → One glycerol + 3 fatty acid molecules

Question 28

Name 4 sources of fats

Answer 28

Butter, cheese, fatty meat and salmon

Question 29

What are the 5 functions of fats

Answer 29

Source and storage of energy
Insulating material that prevents excessive heat loss
Solvent for fat soluble vitamins and hormones
Essential part of cells
Way to reduce water loss from skin surface

Question 30

Why are fats a better energy source than carbohydrates?

Answer 30

Higher energy value compared to carbohydrates which makes it a suitable long-term storage material

Question 31

How does fats reduce water loss on skin surface?

Answer 31

Glands in skin secrete a thin layer of an oily substance over skin surface called sebum that reduces rate of evaporation of water → reducing rate of heat loss from the skin

Question 32

How to test for fats in the liquid state?

Answer 32

Ethanol emulsion test
Add 2cm3 of ethanol to a drop of liquid sample in a tent tube and shake mixture thoroughly
Add 2cm3 of water into the mixture and shake
Record observations

Question 33

How to test for fats in the solidstate?

Answer 33

Crush solid using mortar and pestle and place pieces in test tube
Add 2cm3 of ethanol into test tube and shake thoroughly
Allow solid particles to settle
Pour ethanol into another test tube containing 2cm3 of water and shake
Record observations

Question 34

What are the results of ethanol emulsion test?

Answer 34

White emulsion → positive
Solution remained colourless → negative

Question 35

What is the structure of polypeptides?

Answer 35

Many amino acid molecules joined together in a linear manner

Question 36

what are some sources of protein?

Answer 36

Milk, eggs, seafood, meat
Soya beans, nuts

Question 37

What are the three functions of proteins

Answer 37

Synthesis of new cytoplasm for growth and repair of worn out body cells
Synthesis of enzymes and some hormones
Formation of antibodies to combat diseases

Question 38

How to test for protein?

Answer 38

Biuret solution
To2cm3 of liquid food sample, add 2cm3 of biuret solution
Shake well and allow mixture to stand for five minutes
Record observation

Question 39

What are the results of the biuret test?

Answer 39

Violet -> has proteins
Blue -> no proteins