1.1 Carbohydrates

Question 1

Carbohydrates

Answer 1

These are organic compounds containing carbon, oxygen and hydrogen.

It’s basic unit is a monosaccharide.

2 monosaccharides=disaccharide

Many monosaccharides=polysaccharide

Question 2

Monosaccharides

Answer 2

An individual sugar molecule.

It’s general formula (CH20)n

Name determined by carbon number.

Triose=3 Pentose=5 Hexose=6

Question 3

Isomer definition

Answer 3

Molecules with the same chemical formula but a different arrangement of atoms.

Question 4

Isomers of glucose

Answer 4

Alpha and beta glucose

Draw them out

Question 5

Functions of monosaccharides

Answer 5

•They are a source of energy in respiration.

—>Their bonds are broken to release energy which is used to make ATP.

•they are building blocks for larger molecules.

—>glucose is used to make polysaccharides such as starch, glycogen and cellulose.

•intermediates in reactions, e.g. triose in respiration and photosynthesis.

Question 6

Draw structures of monosaccharide sugars triose and hexose.

Answer 6

Check with textbook to see if you were correct.

Question 7

Test for presence of sugar

Answer 7

The Benedictus test detects reducing sugars in solution.

•needs to be at least 70 degrees.

If a reducing sugar is present, the solution will turn from blue through green, yellow and orange to brick red.

BGOR

Question 8

Disaccharides

Answer 8

Composed of 2 monosaccharide units bonded by a glycosidic bond and the elimination of a water molecule.

This is an example of a condensation reaction where water is a product.

Draw reaction of 2 alpha glucose to form maltose and water

Question 9

Polysaccharides

Answer 9

• These are large and complex polymers.

* formed from large numbers of monosaccharide units joined by glycosidic bonds.

Question 10

Definition of polymer

Answer 10

A large molecule comprising repeated units, monomers, that are bonded together.

Question 11

Glucose explained

Answer 11

• It is the main source of energy in cells.
• It must be stored in appropriate forms, starch in plants, glycogen in animals.
• Glucose is soluble in water so it would increase the conc of the cell contents and draw water in by osmosis.

—> this is avoided by converting glucose to a storage product

Question 12

Features of starch

Answer 12

It is insoluble so it has no osmotic effect.

It cannot diffuse out of the cell.

It is a compact molecule.

Carries lots of energy in its C-C and C-H bonds.

Question 13

What is starch?

Answer 13

Starch is the main Stephen of glucose in plants.

It is found in high concentrations in seeds and potato tubers.

It is made up of alpha glucose molecules bonded together in two ways.

—> forming 2 polymers. Amylose and amylopectin

Question 14

Featured of amylose

Answer 14

Amylose is a linear, unbranched molecule with alpha 1,4-glycosidic bonds forming between the first carbon(C1)of one glucose molecule and the fourth carbon(C4) of an adjacent carbon.

—> this is repeated forming a helix.

Question 15

Draw out amylose

Answer 15

Check if correct

Question 16

Amylopectin

Answer 16

•Has chains of glucose monomers joined with alpha 1,4-glycosidic bonds.

—> crosslinked with alpha 1,6- glycosidic binds and fit inside the amylose.

•When a glycosudic bond forms between the C1 of a glucose and the C6 atom of another, a side branch is seen.

Question 17

Test for presence of starch

Answer 17

Iodine solution reacts with starch, resulting in a colour change form brown to blue/black.

This is a qualitative test so an accurate concentration cannot be determined.

Question 18

Glycogen

Answer 18

• Main storage product in animals.
• has alpha 1,4 and 1,6 glycosidic bonds.

—> difference is that glycogen has shorter chains but is more branched.

Question 19

Cellulose

Answer 19

• a structural polysaccharide.
• most abundant organic molecule.
• it consists of many long, parallel chains of beta glucose units.

—> joined by beta 1,4-glycosidic bonds and the link roasters 180 degrees adjacent.

—> this allows hydrogen bonds to form on (OH) groups, contributing to structure.