3.1.2 Carbohydrates

Question 1

EQ What is the reaction catalysed by the enzyme lactase?

Answer 1

(Lactose +) Water ->(Glucose +) Galactose

Question 2

Monosaccharide definition

Answer 2

Monomers from which larger carbohydrates are made

Question 3

What are carbohydrates made out of?

Answer 3

Carbon
Hydrogen
Oxygen

Question 4

carbohydrates

General formula

Answer 4

(CH2O)n

Question 5

Examples of monosaccharides

Answer 5

Glucose
galactose
fructose

Question 6

What is a hexose sugar?

Answer 6

• A monosaccharide
• Formed from 6 carbon atoms
• 6 carbon ring

Question 7

What is a pentose sugar?

Answer 7

• A monosaccharide
• Contains 5 carbon atoms
• 5 carbon ring

Question 8

hexose sugars

examples

Answer 8

… Glucose
… Fructose
… Galactose

Question 9

pentose sugar

examples

Answer 9

… Ribose

… Deoxyribose

Question 10

glucose

feature related to function

Answer 10

1) Highly soluble

2) Respiration
3) Main form of transporting carbohydrates around the body

Question 11

Give 3 features of fructose

Answer 11

1) Soluble
2) Sweeter than glucose
3) Main sugar in in fruits and nectar

Question 12

Give 2 features of galactose

Answer 12

1) Not as soluble as glucose

2) Plays an important role in the production of glycolipids and glycoproteins

Question 13

Disaccharide Definition

Answer 13

A carbohydrate composed of 2 monosaccharides

Question 14

Disaccharide Formation

Answer 14

Condensation of 2 monosaccharides

Question 15

maltose

Answer 15

a disaccharide formed by condensation of two glucose molecules

Question 16

sucrose

Answer 16

a disaccharide formed by condensation of a glucose molecule and a fructose molecule

Question 17

lactose

Answer 17

a disaccharide formed by condensation of a glucose molecule and a galactose molecule

Question 18

Give 3 main stages of forming glycosidic bonds

Answer 18

1) The hydroxyl groups bind

2) Condensation reaction
- H₂O molecule is lost

3) A 1-4 glycosidic bond is formed

Question 19

Give the position of the H in alpha glucose

Answer 19

H

OH

Question 20

Give the position of the H in beta glucose

Answer 20

OH

H

Question 21

1) Glucose exists in different forms of…

2) Which are…

Answer 21

1) Structural isomers

2) Molecules with the same atoms, but different arrangements of atoms

Question 22

how do you distinguish between Alpha and Beta glucose

Answer 22

distinguish alpha and beta by looking at the position of the hydroxyl molecule on the last carbon plane.

alpha glucose - Hydroxyl molecule is positioned on at the bottom

Both have the molecular formula C(6)H(12)O(6) and both are hexose sugars.

Question 23

Polysaccharide Definition

Answer 23

A polymer composed of many saccharide units

Question 24

Polysaccharide features

Answer 24

Complex sugars.

• High molecular weight
• Insoluble in water
• Tasteless

Question 25

Polysaccharide Formation

Answer 25

Condensation of many glucose units

Question 26

Polysaccharide Bonds

Answer 26

Glycosidic

Question 27

Polysaccharide Examples

Answer 27

glycogen starch cellulose

Question 28

Glycogen formation

Answer 28

formed by the condensation of α-glucose

Question 29

Starch formation

Answer 29

formed by the condensation of α-glucose

Question 30

Cellulose formation

Answer 30

formed by the condensation of β-glucose

Question 31

Glycogen location

Answer 31

Animals Muscle, liver Fungi

Question 32

Glycogen structure

Answer 32

``` Glycosidic bonds Branched chain 1,6 links Contains CHO Joined by 1,4 links Made of alpha glucose Formed in condensation reaction. ```

Question 33

Glycogen structure to function

Answer 33

Insoluble store of glucose in animals Insoluble: → Water potential of cell is not affected; water doesn't diffuse into the cells via osmosis. Large & insoluble: → Doesn't diffuse out of cells. Highly branched: → More ends for enzymes to act on; glycogen can quickly be hydrolysed into α-glucose to be used for respiration. Compact so can store many glucose molecules in a small space

Question 34

two main components of starch

Answer 34

1) Amylose | 2) Amylopectin

Question 35

Starch structure

Answer 35

``` Amylose- A-glucose molecules 1,4 glycosidic bonds Unbranched chain Helical ``` ``` Amypectin- A-glucose molecules 1,4 glycosidic bonds Branched chain 1,6 bonds ```

Question 36

Starch structure to function

Answer 36

Energy storage in plants 1) Large molecule - Doesn't diffuse out of cells 2) Helical - Compact,a lot can be stored in a small amount of space. ... Carbohydrate storage molecule 3) Insoluble - Doesn't affect water potential water doesn't diffuse into the cells via osmosis Branches have many ends: → Can all be acted on simultaneously by enzymes; easily hydrolysed to produce α-glucose, so can be used for respiration. compact and so can fit lots of molecules in a small space

Question 37

starch formation

Answer 37

Formed in condensation reaction.

Question 38

starch location

Answer 38

starch is stored by special organelles, or cell subunits, called amyloplasts

Question 39

Cellulose location

Answer 39

Plants | Cell walls

Question 40

function of cellulose

Answer 40

Used by plants for making cell walls

Question 41

Cellulose structure to function

Answer 41

- Cell walls ... Strengthens ... Prevents cells from bursting when they take in too much water The B-glucose is arranged in a straight chain └ linked by hydrogen bonds to form microfibrils

Question 42

Cellulose structure

Answer 42

``` b-glucose molecules 1,4 glycosidic bonds Molecules rotates 180 relative to its neighbour= Unbranched, straight chain Adjacent chains linked by hydrogen bonds →microfibrils ```

Question 43

What is the main difference between starch and cellulose?

Answer 43

Starch - Weak Cellulose - Strong

Question 44

what are the two classifications of sugars?

Answer 44

- non reducing (e.g sucrose) | - reducing (all monosaccharides e.g glucose and some disaccharides e.g maltose and lactose)

Question 45

What are reducing sugars?

Answer 45

A sugar that can donate an electron to a substance to reduce this substance

Question 46

What is benedicts reagent?

Answer 46

Copper 2 sulfate

Question 47

Benedicts test- reducing sugars

Answer 47

Add Benedicts reagent in excess and heat Negative result= blue Positive result= brick red precipitate

Question 48

how can you compare the amount of reducing sugar in different solutions?

Answer 48

1. observing colour change (the darker, the more concentrated) 2. filter the solution and weigh the precipitate (more accurate)

Question 49

why must you always use benedicts reagent in excess?

Answer 49

ensures that all the sugar has reacted

Question 50

what is the colour change of the precipitate formed (for a positive test for reducing sugar) as the concentration of reducing sugar increase?

Answer 50

(benedicts reagent) blue - green - yellow - orange - brick red

Question 51

Benedicts test- non reducing sugars

Answer 51

``` (hydrolysis) heat with dilute HCL/acid Add hydrolytic enzyme neutralise using sodium hydrogencarbonate Add benedicts reagent and heat Negative result= blue Positive result= red precipitate ```

Question 52

outline the semi quantitative benedict's test

Answer 52

make standards of known concentration dilution series compare unknown to standards

Question 53

EQ: Benedicts test for reducing sugars

Answer 53

- Add Benedict’s and - Heat - for a positive result it will have a red/orange/yellow/green colour

Question 54

EQ: Type of reaction that joins monosaccharides together- definition

Answer 54

-condensation

Question 55

EQ: How you would test a sample of food for the presence of starch

Answer 55

- add iodine/potassium iodide solution to the food sample | - blue/black/purple indicates starch is present

Question 56

EQ: The concentration of glucose in the blood rises after eating a meal containing carbohydrates. The rise is slower if the carbohydrate is starch rather than sucrose, why?

Answer 56

- starch is digested by amylase to maltose - and then maltose is digested by maltase to glucose - whereas sucrose is digested in a single step using sucrose to make glucose