1.2: Carbohydrates

Question 1

list the elements that carbohydrates are made from

Answer 1

carbon, hydrogen and oxygen

Question 2

how many monosaccharides make up a monosaccharide and give an example

Answer 2

1 - glucose

Question 3

how many monosaccharides make up a disaccharide and give an example

Answer 3

2 - sucrose, maltose, lactose

Question 4

how many monosaccharides make up a polysaccharide and give an example

Answer 4

many - starch, cellulose, glycogen

Question 5

what is the general formula for monosaccharides

Answer 5

CnH2nOn

Question 6

What is the name for a monosaccharide with 3 carbons

Answer 6

triose

Question 7

What is the name for a monosaccharide with 5 carbons and give 2 examples

Answer 7

pentose - deoxyribose, ribose

Question 8

What is the name for a monosaccharide with 6 carbons and give 3 examples

Answer 8

hexose - glucose (alpha /beta),fructose, galactose

Question 9

give 3 examples of disaccharides

Answer 9

maltose, lactose, sucrose

Question 10

what two monosaccharides make up maltose

Answer 10

glucose and glucose

Question 11

what two monosaccharides make up lactose

Answer 11

glucose and galactose

Question 12

what two monosaccharides make up sucrose

Answer 12

glucose and fructose

Question 13

Monosaccharides are all sugars, list 3 properties of these sugars

Answer 13

sweet, soluble, crystalline

Question 14

what is a monomer

Answer 14

a single unit that joins together with other monomers to form a polymer e.g. amino acid

Question 15

what is a polymer

Answer 15

a chain of repeating units (monomers) e.g. protein is made from amino acids

Question 16

Describe what a condensation reaction is

Answer 16

when one monomer joins to another and a water molecule is removed

Question 17

Describe what a hydrolysis reaction

Answer 17

when water molecules are added in the process of breaking bonds between molecules

Question 18

Name two polymers that are formed from alpha glucose monomers and what type of polysaccharide are they?

Answer 18

starch and glycogen
- glucose store

Question 19

name one polymer that is formed from beta glucose monomers and what type of polysaccharide is it?

Answer 19

cellulose
- structural polymer

Question 20

what is the difference in structure of alpha and beta glucose

Answer 20

hydroxyl group is below carbon 1 for alpha glucose whereas for beta glucose, it is above carbon 1

Question 21

Describe the structure of fructose compared to alpha glucose

Answer 21

6 carbons but carbon 2 (with its hydrogen and hydroxyl group) is branched off of carbon 1 making a pentagon shape

Question 22

describe the structure of galactose compared to alpha glucose

Answer 22

hydroxyl group is above carbon 4 instead of below

Question 23

What are structural isomers

Answer 23

compounds with the same chemical formula but different structure

Question 24

list the 3 structural isomers of alpha glucose and explain why

Answer 24

beta glucose, fructose, galactose
because they all have the same number of carbons, oxygens and hydrogens, but have different structures

Question 25

what is made when reacting two alpha glucose molecules

Answer 25

maltose and water

Question 26

what is made when reacting beta glucose and galactose together

Answer 26

lactose and water

Question 27

what is made when reacting alpha glucose and fructose together

Answer 27

sucrose and water

Question 28

name the covalent bond that is formed between adjacent monomers in a disaccharide/polysaccharide

Answer 28

glycosidic bond

Question 29

what type of reaction occurs during the formation of a glycosidic bond

Answer 29

condensation reaction

Question 30

How can you break a glycosidic bond to release monomers

Answer 30

hydrolysis reaction - add water

Question 31

describe the process by which sucrose can be absorbed into the gut

Answer 31

1 - sucrose is hydrolysed by sucrase into glucose and fructose
2 - glucose and fructose are soluble and can be absorbed through the wall of the ileum

Question 32

describe the structure and bonding in starch

Answer 32

Polymer of alpha glucose. 30% Amylose: 1-4 bonds, all bonds face downward, helical shape due to strain
70% Amylopectin: 1-4 AND 1-6 bonds, branched

Question 33

Describe how the structure of starch relates to its function (4 points)

Answer 33

1 - compact shape - takes up little space inside cell
2 - insoluble - osmotically inert
3 - increased surface area (branched) for hydrolysis to release glucose and so faster release of glucose
4 - easily hydrolysed by amylase to provide glucose for respiration

Question 34

Describe the structure and bonding of cellulose

Answer 34

polymer of beta glucose. Every alternate beta glucose molecule is rotated 180 degrees on horizontal axis. 1-4 glycosidic bonds alternate up/down. Resulting in a straight chain. Multiple cellulose chains form a microfibril. H-bonds form cross links between chains

Question 35

Describe how the structure of cellulose relates to its function (2 points)

Answer 35

1 - high tensile strength and rigidity due to H bonds between beta glucose polymers
2 - This forms microfibrils suitable for component of plant cell walls for storage

Question 36

Describe the structure and bonding of glycogen

Answer 36

Similar structure to amylopectin - 1-4 and 1-6 bonds, branched - but more 1-6 bonds and so more branched.

Question 37

Describe how the structure of glycogen relates to its function (3 points)

Answer 37

1 - very compact shape, so a lot of glucose can be condensed for storage inside cell
2 - insoluble and so osmotically inert
3 - Easily hydrolysed by glycogen phosphorylase to provide glucose for respiration

Question 38

explain how glycogen in animals means animals have a higher metabolic rate than plants

Answer 38

glycogen in animals is more branched than starch in plants and so a higher surface area for hydrolysis and so more glucose released for respiration