biological molecules!!

Question 1

chemicals elements that make up:
carbohydrates
fats
protein

Answer 1

carb - C H O
fats - C H O
proteins - C H O N
sometimes sulfur

Question 2

large molecules are made from smaller molecules

Describe the structure of a
* lipid/fats and oils
* protein
* starch, glycogen, cellulose

Answer 2

lipid/fats and oils
* 3 fatty acids
* 1 glycerol

protein
* amino acids

starch, glycogen, cellulose
* glucose

Question 3

What is used to test for starch?
What are the positive and negative results?

Answer 3

Iodine solution
orange-brown in color

Positive result
* blue-black

Negative result
* orange-brown

Question 4

What is used to test for reducing sugars?
Steps to conduct test
What are the positive and negative results?

Answer 4

Benedict’s solution
* Blue in color

Step
1. Add benedicts solution to food sample, heat in water bath at 80 C

+ve result
* Gradually changes from blue, green, yellow to orange-red/brick red

-ve result
* Stays blue colored.

Question 5

What is used to test for proteins?
What are the positive & negative results?

Answer 5

Biuret reagent

+ve
Blue to violet

-ve
stays blue

Question 6

What is used to test for fats and oils?
Steps
What are the positive & negative results?

Answer 6

Ethanol emulsion

Steps
1. Shake test substance with ethanol for a minute until it dissolves, then pour slution to water.

+ve
* fats and oils will precipitate; milky emulsion

-ve
* no emulsion/colorless

Question 7

What is used to test for VITAMIN C?
Steps
What are the positive & negative results?

Answer 7

**DCPIP **

Steps
1. Add DCPIP solution using dropper pipettes to food sample.
2. Keep adding until blue color no longer disappears when mixed w sample.
3. Vit C reacts w DCPIP solution, making it colorless. Color stops changing when all VIT C is used up.
4. Higher the volume of DCPIP solution added before blue color stops disappearing, the more vitamin C food sample contains.

+ve
* Colorless

-ve
* blue

Question 8

energy store in animals and plants

Answer 8

Animals
* glycogen in liver

plants
* starch; broken down to glucose when plant needs it.

Question 9

structure of glucose molecules

Answer 9

small hexagon shape

Question 10

Describe structure of DNA molecule

Answer 10

• 2 strands coiled together to form a double
  helix
• Each strand contains chemicals called bases
• Bonds between pairs of bases hold the
  strands together
• The bases always pair up in the same way:
  A with T, and C with G