1.1 Carbohydrates

Question 1

name 2 uses of carbohydrates

Answer 1

as energy sources

for structure

Question 2

what elements are found in carbohydrates?

Answer 2

carbon, hydrogen, and oxygen

Question 3

what is the general formula for carbohydrates?

Answer 3

Cx(H20)y

Question 4

what is a structural isomer?

Answer 4

same molecular formula, different structure

Question 5

give one similarity and one difference between an alpha and beta glucose

Answer 5

similarity- both are hexose sugars

difference- alpha has hydroxyl group at bottom whereas beta has hydroxyl group at top

Question 6

name the type of reaction when two monosaccharides join

Answer 6

condensation

Question 7

what two monosaccharides is maltose made from?

Answer 7

2 alpha glucoses

Question 8

what two monosaccharides is lactose made from?

Answer 8

glucose + galactose

Question 9

what two monosaccharides is sucrose made from?

Answer 9

glucose + fructose

Question 10

how do you break a disaccharide?

Answer 10

use water in a hydrolysis reaction

Question 11

what is a long chain of monosaccharides joined by?

Answer 11

glycosidic bonds

Question 12

name three types of polysaccharides, what they are used for and where they are found?

Answer 12

starch- storage in plants
cellulose- structure in plants
glycogen - storage in animals

Question 13

describe the structure of cellulose

Answer 13

• polymer of beta glucose
• has beta-1,4-glycosidic bonds
• forms straight chains called cellulose molecules
• hydrogen bonds link cellulose molecules to form a microfibril
• 3D lattic shape
• gives it a high tensile strength

Question 14

describe the structure of starch

Answer 14

• polymer of alpha glucose
• large molecule found in anything that photosynthesises
• insoluble (no osmotic effect)
• compact (large amount stored in a small space)
• usually stored as intracellular starch grains in plastids (amyloplasts and chloroplasts)
• made up of amylose and amylopectin

Question 15

describe the structure of amylose

Answer 15

straight chain molecule
alpha 1,4 glycosidic bonds
forms a coil

Question 16

describe the structure of amylopectin and how this relates to its function

Answer 16

branches
alpha 1,4 and 1,6 glycosidic bonds
side branches that make it readily hydrolyseable- it allows enzymes that break down molecules to easily access glycosidic bonds so glucose can be released quickly

Question 17

describe the structure of glycogen and where it can be found

Answer 17

polymer of alpha glucose
alpha 1,4 and 1,6 glycosidic bonds
branched - readily hydrolyseable
insoluble - no osmotic effect
compact- large amount in small space
found mostly in liver and muscle cells

Question 18

give the equation for photosynthesis

Answer 18

6CO2 + 6H2O –> C6H12O6 + 6O2

Question 19

describe the test for starch

Answer 19

add iodine
if starch is present, colour changes to blue/black
if there is no starch, colour remains brown

Question 20

describe the test for reducing sugars

Answer 20

add Benedict’s reagent
if reducing sugars are present, it turns red, yellow or green
if no reducing sugars are present, remains blue

Question 21

give three examples of reducing sugars

Answer 21

monosaccharides
maltose
lactose