biological molecules

Question 1

Identify the chemical elements present in carbohydrates, proteins and lipids

Answer 1

carbohydrates: carbon hydrogen oxygen (CHO)
protein: carbon hydrogen oxygen nitrogen (CHON)
Lipid: carbon hydrogen oxygen (CHO)

Question 2

Describe the structure of carbohydrates as large molecules made up from smaller basic units

Answer 2

basic unit of starch and glycogen = simple sugars( a monosaccharide)
2 glucose molecules join together maltose is formed (a disaccharide)
lots of glucose molecules join together starch or glycogen is formed (polysaccharides)

Question 3

Describe the structure of lipid as large molecules made up from smaller basic units

Answer 3

Made up by triglycerides.
basic unit: 1 glycerol molecule and 3 fatty acid chains
fatty acids vary in size and structure

Question 4

Describe the structure of protein as large molecules made up from smaller basic units

Answer 4

basic unit: the amino acid
amino acids are joined together a protein is formed
amino acids can be arranged in any order, resulting in many different proteins

Question 5

what solutions are required to find the presence of Glucose starch and protein.

Answer 5

Glucose= Benedict’s solution
Starch=  iodine solution
protein= Biuret solution

Question 6

investigate test for glucose

Answer 6

1. Benedict’s solution into sample solution in test tube
2. Heat at 60 – 70 °c in water bath for 5 minutes
3. Take test tube out of water bath and observe the colour
4. .A positive test will show a colour change from blue to orange or brick red

Question 7

investigate test for strach

Answer 7

1. Add drops of iodine solution to the food sample

2. A positive test will show a colour change from brown to blue-black

Question 8

investigate test for protein

Answer 8

1. Add drops of Biuret solution to the food sample

2. A positive test will show a colour change from blue to violet / purple

Question 9

investigate test for lipid

Answer 9

1. Food sample is mixed with 2cm3 of ethanol and shaken
2. The ethanol is added to an equal volume of cold water
3. A positive test will show a cloudy emulsion forming