carbohydrates (d,e,f,g)

Question 1

what is a monosaccharide?

Answer 1

single sugar e.g. glucose, fructose, ribose

Question 2

what is a disaccharide?

Answer 2

two monosaccharides e.g. lactose, sucrose

Question 3

what is a polysaccharide?

Answer 3

2 or more monosaccharides linked to form a polymer e.g. glycogen, cellulose, starch

Question 4

what is a glucose an example of?

Answer 4

a hexose monosaccharide - composed of 6 carbons

Question 5

difference between alpha and beta glucose

Answer 5

• alpha = H and OH same on both sides

- beta = H and OH alternate on either side

Question 6

properties of glucose

Answer 6

• polar and soluble in water - due to hydrogen bonds that form between the hydroxyl groups + water molecules
• solubility - dissolved in the cytosol of the cell - easily transported
• its chemical bonds contain lots of energy

Question 7

what is ribose an example of?

Answer 7

a pentose monosaccharide - composed of 5 carbon atoms

Question 8

synthesis of disaccharides and polysaccharides

Answer 8

• monosaccharides are joined together by glycosidic bonds
• condensation reaction - a hydrogen atom on one monosaccharide bonds to a hydroxyl group on the other, releasing a molecule of water

Question 9

breakdown of disaccharides and polysaccharides

Answer 9

• the reverse of the condensation reaction is hydrolysis

- a molecule of water reacts with the glycosidic bond, breaking it

Question 10

describe maltose

Answer 10

• 2 alpha glucose molecules joined together by a 1,4 glycosidic bond
• disaccharide

Question 11

describe sucrose

Answer 11

• alpha glucose + fructose joined together

- disaccharide formed from 2 hexose monosaccharides

Question 12

describe lactose

Answer 12

• galactose + either alpha or beta glucose

- disaccharide formed from 2 hexose monosaccharides

Question 13

what is starch and describe its structure

Answer 13

• a chemical energy store - main store in plants

- Starch is a mixture of 2 polysaccharides of alpha-glucose - amylose and amylopectin

Question 14

Describe the structure of amylose

Answer 14

• long unbranched chain of alpha-glucose
• joined by 1,4 glycosidic bonds only
• angles of bond mean the long chain of glucose twists to form a helix which is further stabilised by hydrogen bonding within the molecule

Question 15

describe the structure of amylopectin

Answer 15

• a long branched chain of alpha-glucose

- made of 1,4 glycosidic bonds and 1,6 glycosidic bonds on 2 glucose molecules (once every 25 subunits)

Question 16

how does the structure of amylose relate to the function of starch?

Answer 16

• it is compact - good for storage

- much less soluble than glucose - does not cause water to enter the cells by osmosis which would make them swell

Question 17

how does the structure of amylopectin relate to the function of starch?

Answer 17

• its side branches allow the enzymes that break down the molecule to get at the glycosidic bonds easily - thus glucose can be released quickly

Question 18

what is glycogen?

Answer 18

• a chemical energy store - the main store in animals and fungi
• animals store excess glucose as glycogen - insoluble

Question 19

describe the structure of glycogen

Answer 19

• polysaccharide of alpha-glucose

- similar to amylopectin but more branches so less space needed to store it

Question 20

how does the structure of glycogen relate to its function?

Answer 20

• compact - important for the mobility of animals
• branching means many free ends where glucose molecules can be added or removed, which speeds up the processes of storing or releasing glucose molecules required by the cell - important for energy release in cells

Question 21

what is cellulose?

Answer 21

A major component of cell walls in plants

Question 22

describe the structure of cellulose

Answer 22

• long unbranched chains of beta-glucose

- beta-glucose molecules bond to form straight chains (alternate beta molecules are turned upside down)

Question 23

how are fibres made?

Answer 23

• cellulose molecules make hydrogen bonds with each other to from microfibrils
• these join together to form macrofibrils, which join together to form fibres

Question 24

how does the structure of cellulose and fibres relate to its function?

Answer 24

• fibres are strong and insoluble, providing structural support for cells
• important in a diet - necessary for a healthy digestive system