Carbohydrates

Question 1

Describe the structure of an alpha glucose

Answer 1

Hexagon. On the top is ch2oh. On carbon 1 and 4 the h is up and the oh is down

Question 2

Describe the structure of beta glucose

Answer 2

On carbon 4 h is up and oh is down. On carbon 1 oh is up and h is down

Question 3

Describe condensation reactions

Answer 3

When two molecules join together covalently and as the reaction occurs a water molecule is formed

Question 4

What is the bond between monosaccharides called

Answer 4

A glycosidic bond

Question 5

What is a hydrolysis reaction

Answer 5

A molecule of water is added and the covalent bond is broken

Question 6

Properties of lactose

Answer 6

Made from glucose and galactose
1,4 glycosidic bond
Present in milk and important in infants diets

Question 7

Properties of sucrose

Answer 7

Made from glucose and fructose
1,2 glycosidic bonds
Present in sugar cane
Way in which sugar is transported in plants

Question 8

How are disaccharides hydrolysed

Answer 8

By using enzymes or by heating in acid eg HCl

Question 9

What is maltose made from

Answer 9

Two glucose molecules

Question 10

What are starch and glycogen polymers of and how are the monomers joined

Answer 10

Alpha glucose monomers
Condensation reaction

Question 11

What is the function of both starch and glycogen

Answer 11

To store glucose molecules within cells
Starch=plant
Glycogen=animal

Question 12

Properties of both starch and glycogen

Answer 12

Compact-don’t take up too much space in cell
Insoluble- can’t be lost from cells by dissolving
No osmotic effect- don’t pull water into cell
Easily hydrolysed- release glucose when needed for respiration

Question 13

What are the two forms of starch

Answer 13

Amylose and amylopectin

Question 14

Structure of amylose

Answer 14

• chains of alpha glucose joined by 1,4 bonds therefore it is unbranched
• coils into helix held by hydrogen bonds

Question 15

Structure of amylopectin

Answer 15

• branched chain of alpha glucose (new branches only at the beginning)
• has 1,4 and 1,6 glycosidic bonds
• helix

Question 16

Structure of glycogen

Answer 16

-highly branched
- helix
- 1,4 and 1,6 bonds, branch points every 8-12 glucose (more branches =more ends=hydrolysed quicker= more glucose related for respiration)

Question 17

Properties of cellulose

Answer 17

High tensile strength- resits large pulling force
Insoluble and flexible- good for building cell walls
Strong- resists turgar pressure
Resisitant to human digestion- needs a specific enzyme

Question 18

Structure of cellulose

Answer 18

Polymer of beta glucose, unbranched
In the chain glucose number 2,4,6 etc is flipped to allow the oh groups to match up
Microfibrils- individual chains held adjacently by hydrogen bonds
Fibres- microfibrils bound together
Cell wall- fibres laid down on top of eachother in many directions

Question 19

Test for starch

Answer 19

Iodine in potassium iodide solution
Orange/brown to blue /black if starch is present

Question 20

Test for protein

Answer 20

Biruets
Blue to purple

Question 21

How does the biruets test work

Answer 21

Add biruets reagent ( sodium hydroxide and copper sulphate)
A complex forms between the N atoms on the peptide chain and the Cu2+ ions

Question 22

Test for reducing sugars

Answer 22

Benedicts
Heat in boiling water bath
Low level of sugar = blue/green
Medium = orange
High=brick red