2.1.2c Carbohydrates

Question 1

Element composition of Carbohydrates

Answer 1

Carbon, Hydrogen, Oxygen

Question 2

Element composition of Lipids

Answer 2

Carbon, Hydrogen, Oxygen

Question 3

Element composition of Proteins

Answer 3

Carbon, Hydrogen, Oxygen, Nitrogen, Sulfur

Question 4

Element composition of Nucleic acids (DNA & RNA)

Answer 4

Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus

Question 5

What are monomers

Answer 5

Small units which are the components of larger molecules.

Eg. Monosaccharides sa glucose, amino acids & nucleotides

Question 6

What are polymers

Answer 6

Molecules made from many monomers joined together

Eg. starch, cellulose

Question 7

Process of monomers into polymers

Answer 7

Polymerization

Question 8

What is a condensation reaction

Answer 8

A reaction in which 2 molecules join together by a chemical bond with the release of a water molecule.

Eg. when 2 glucose molecules bond tg

Question 9

What is a hydrolysis reaction

Answer 9

Hydrolysis is the opposite of a condensation reaction & is when water is added to break a chemical bond between 2 molecules

Eg. Carbohydrates can be broken down into their constituent monosaccharides by hydrolysis

Question 10

See showbie slide 5 to see diagrams of condensation & hydrolysis reactions

Question 11

What is the basic monomer in carbohydrates

Answer 11

Sugar, otherwise known as a saccharide

Question 12

What would a single monomer be called

Answer 12

Monosaccharides

mono = 1
O (hexagon)

Question 13

What would a pair of monomers be called

Answer 13

Disaccharide

When combined in pairs, monosaccharides form disaccharides through a condensation reaction. The 2 monosaccharides are held tg by glycosidic bond

di = 2
O-O

Question 14

What would a large chain of monomers be called

Answer 14

Polysaccharide - macromolecules consisting of more than 2 sugars (monosaccharides) - often a long chain polymer, joined by glycosidic bonds.

Polysaccharides are NOT SUGARS

poly = many
O-O-O-O-O-O

Question 15

How do monosaccharides form disaccharides

Answer 15

2 monosaccharides can join tg by a glycosidic bond in a condensation reaction to form a disaccharide. In this process, a molecule of water is produced

Question 16

How are polymers & disaccharides broken down into monomers

Answer 16

Hydrolysis reaction (breaking chemical bond using a water molecule)

Question 17

What are the bonds in carbohydrates

Answer 17

Glycosidic bonds

Question 18

2 Monosaccharides you need to know

Answer 18

GLUCOSE (hexose monosaccharide) *6 carbon atoms in each molecule

RIBOSE (pentose monosaccharide) *5 carbons

see slide 10 to see their diagrams (ribose on page 22)

Question 19

Different forms of glucose

Answer 19

There are 2 forms (isomers) of the monosaccharide glucose. These are a-glucose (alpha) and B-glucose (beta). They have the same chemical formula, but their structures are slightly different

Question 20

See slide 11-13 for diagrams of alpha and beta glucose & page 22 cgp

Question 21

What are isomers

Answer 21

Molecules with the same molecular formula as eachother, but with the atoms connected in a different way

Eg. alpha and beta glucose

Question 22

3 Disaccharides you need to know

Answer 22

MALTOSE - a disaccharide formed by condensation of 2 glucose molecules

SUCROSE - a disaccharide formed by condensation of glucose & fructose

LACTOSE - a disaccharide formed by condensation of glucose & galactose

Question 23

3 Polysaccharides you need to know

Answer 23

GLYCOGEN - formed by the condensation of alpha glucose molecules

STARCH - formed by the condensation of alpha glucose molecules

CELLULOSE - formed by the condensation of beta glucose molecules

Question 24

Different chains in polysaccharides

Answer 24

Macromolecules that are formed by many monosaccharides joined by glycosidic bonds in a condensation reaction to form chains

These chains may be:
- branched or unbranched
- folded (making the molecule compact which is ideal for storage eg. starch & glycogen)
- straight (making the molecules suitable to construct cellular structures eg. cellulose) or coiled

Question 25

What is the polysaccharide, Glycogen

Answer 25

- The main energy storage molecule in animals - A multi-branched alpha glucose polymer

Question 26

What is Glycogen joined by

Answer 26

- Main chains are joined tg by 1,4 glycosidic bonds - Branches are linked tg by 1,6 glycosidic bonds

Question 27

Structure of Glycogen

Answer 27

- It has a large no. of side branches meaning that energy can be released quickly as enzymes can act simultaneously on these branches

Question 28

Where is Glycogen stored

Answer 28

- In the muscles and in the liver - In times of high energy usage, these organs hydrolyse the glycogen stored & break it down into glucose molecules which can be used in respiration

Question 29

Size of Glycogen

Answer 29

- It is a relatively large but compact molecule thus maximising the amount of energy it can store. - Makes it optimal for an energy storage molecule

Question 30

Is Glycogen insoluble

Answer 30

Yes, being soluble means it will not affect the water potential of cells & cannot diffuse out of cells

Question 31

see showbie slide 19 for diagram of Glycogen

Question 32

What is the polysaccharide, Starch

Answer 32

- Starch is a mixture of 2 polysaccharides called amylose and amylopectin - Both amylose and amylopectin are long-chain a-glucose polymers.

Question 33

Main use of Starch

Answer 33

Starch is the main form of carbohydrate used for energy storage in plants

Question 34

Where is Starch stored

Answer 34

Starch grains are stored in chloroplasts & are insoluble in water so they dont affect water potential up & down the xylem - important for water & nutrient transport in the plant

Question 35

Starch is constructed from 2 different polysaccharides: AMYLOSE

Answer 35

- (10-30% of starch) - long, unbranched, helix-shaped chain with 1,4 glycosidic bonds between a-glucsoe molecules. - The helix shape enables it to be more compact & thus its more resistant to digestion

Question 36

Starch is constructed from 2 different polysaccharides: AMYLOPECTIN

Answer 36

- (70-90% of starch) - shorter, branched chains - its branches allow the enzymes that break down the molecule to get at the glycosidic bonds easily - meaning glucose can be released quickly

Question 37

What is the polysaccharide, Cellulose

Answer 37

- Cellulose is a polysaccharide found in plants - Unbranched, linear chains of B-glucose molecules which are joined by glycosidic bonds in a condensation reaction. - It is a polymer of abt 10,000 B-glucose molecules in a long unbranched chain called a microfibril

Question 38

Structure of Cellulose

Answer 38

- It consists of long chains of B-glucose, so in order to form the 1,4 glycosidic bonds consecutive B-glucose molecules must be rotated 180 to eachother - Cellulose chains linked tg by hydrogen bonds to form strong fibres called microfibrils. The strong fibres mean cellulose provides structural support for cells

Question 39

What are microfibrils

Answer 39

Strong threads which are made of long cellulose chains running parallel to one another that are joined tg by hydrogen bonds forming strong cross linkages

Question 40

Function of Cellulose

Answer 40

Important in stopping the cell wall from bursting under osmotic pressure. This is bc it exerts inward pressure that stops the influx of water. This means that cells stay turgid & rigid, helping to maximise the SA of plants for photosynthesis

Question 41

See slide 39 for diagrams of cellulose, amylose & amylopectin, and glycogen

Question 42

What are carbohydrates made of

Answer 42

Most carbohydrates are **polymers**. A polymer is a molecule made up of small **monomers** bonded tg. The monomers that make up carbohydrates are called **monosaccharides**

Question 43

How is starch adapted to be good for storage

Answer 43

Starch is INSOLUBLE in water, so doesnt cause water to enter cells by osmosis, which would make them swell, making them good for storage

Question 44

Why is glycogen good for storage

Answer 44

Very compact molecules - so good for storage