4.1 Molecules

Question 1

What do carbohydrates contain in terms of chemical elements?

Answer 1

Carbon, hydrogen and oxygen.

Question 2

What are monosacharrides what does it consist of

Answer 2

-one unit of sugar
- glucose and fructose

Question 3

What are disaccharides and what does it consist of?

Answer 3

• two monosaccharides bonded
• maltose and sucrose

Question 4

What are carbohydrates made of?

Answer 4

monosaccharides, disaccharides and polysacchides

Question 5

What is a polysaccharide? What is an example of it?

Answer 5

It is :
- Many monosaccharides bonded
- e.g : Starch and glycogen

Question 6

What are proteins made up of?

Answer 6

• smaller units called amino acids

Question 6

What do proteins contain?

Answer 6

• carbon
• hydrogen
• oxygen
• nitrogen

Question 7

What do lipids contain?

Answer 7

-carbon
-hydrogen
- oxygen

Question 8

What are the states of lipds in room temp

Answer 8

-oil if liquid
- fats if solid

Question 9

Food test: Startch
1) what do i use to determine whether startch is present? Example of food sample to experiment on?
2) What is the procedure?
3) What colour does it change to if its :
(i) +ve
(ii) -ve

Answer 9

1) Iodine e.g with bread
2) Add a few drops
3) (i) blue-black colour
(ii) brown

Question 9

What are lipids comprised?

Answer 9

Two smaller units:
-glycerol
- fatty acids

Question 10

Food test: Reducing sugars
1) what do i use to determine whether it is present? Example of food sample to experiment on?
2) What is the prodedure?
3) What colour does it change to if its :
(i) +ve
(ii) -ve

Answer 10

1) BENEDICT’S reagent
2) The mixture is heated in water bath for 2 to 3 minutes.
3) (i) +ve: brick-red precipitate
(ii) -ve: remains blue

Question 11

Food test: Protein
1) what do i use to determine whether it is present? Example of food sample to experiment on?
2) What is the prodedure?
3) What colour does it change to if its :
(i) +ve
(ii) -ve

Answer 11

1) BIURET reagent
2) Add a few drops
3) (i) +ve: mauve/purple colour
(ii)-ve: remains light blue

Question 12

Food test: Fats
1) what do i use to determine whether it is present? Example of food sample to experiment on?
2) What is the prodedure?
3) What colour does it change to if its :
(i) +ve
(ii) -ve

Answer 12

1) Use an emulsion test : with ethanol, e.g experiment with butter.
2) Ethanol is added to mixture and this is poured into a test tube with a equal amound of distilled water,
3) (i) +ve: milky-white emulsion
(ii) -ve: no emulsion will form

Question 13

Food test: Vitamin C
1) what do i use to determine whether it is present? Example of food sample to experiment on?
2) What is the prodedure?
3) What colour does it change to if its :
(i) +ve
(ii) -ve

Answer 13

1) DCIPIP, e.g experiment with orange
2) The more drops you need to add the less concentrated the vitamin c is and vice versa.
3) (i) colourless
(ii) remains dark blue

Question 14

What does emulsion mean?

Answer 14

A mixture of liquids that do not dissolve in each other.

Question 15

Food test: Vitamin C
which of these samples have the most concentration of vitamin c?
sample 1: 1 drop of DCPIP needed to become colourless

sample 2 : 8 drops of DCPIP needed to become colourless

sample 3 : remains dark blue

Answer 15

Sample 1: the lesser the drops the more concentrated.
Sample 3 means there are no vitamin c at all!!

Question 16

Describe the structure of a DNA molecule:

clue! :)
(a) ts => dh
(b) es cc (b)
(c) b <-> pob hst
(d) b ptsw : … & …

Answer 16

(a) two strands coiled together to form a double helix
(b) each strand contains chemicals called bases
(c) bonds between pairs of bases hold the strands together
(d) The bases are always paired the same way:
- A with T
- C with G

Question 17

Objective :
When a food substance is tested with iodine solution, which colour shows the presence of starch?
(a) blue-black
(b) brown
(c) orange
(d) purple

Answer 17

(a) blue-black

Question 18

The bases on one of the strands of a DNA molecule have the sequnce shown.

A-A-T-C-T-G

What is the corresponding sequnce of bases on the other strand?

Answer 18

T-T-A-G-A-C

(A with T)
(C with G)

Question 19

What is the basic unit of glycogen?

Answer 19

fats and oils

Question 20

what is the basic unit of oils?

Answer 20

glycerol

Question 21

The description shows the result of food tests carried out on a fruit.

test: Benedict’s
result : Positive

test: Biuret
result : Positive

test: Ethanol
result: Negative

test : iodine
result: negative

What did the fruit contain?

Answer 21

• Protein and reducing sugar

(Benedict’s is for reducing sugar, biuret is for protein. ethanol is for fats and oils and iodine is for starch)

Question 22

State that: large molecules are made from smaller molecules such as….???

Answer 22

starch, glycogen and cellulose => glucose

proteins => amino acids

fats and oils => fatty acids and glycerol