Carbohydrates

Question 1

Define monomer.

Give examples

Answer 1

Smaller units that join together to form larger molecules

Monosaccharides (glucose, fructose, galactose, ribose)
Amino acids
Nucleotides

Question 2

Define polymer.

Give examples

Answer 2

Long chain molecules formed when many monomers join together

Polysaccharides
Proteins
DNA/ RNA

Question 3

condensation + hydrolysis reactions

Answer 3

Condensation = Chemical bond forms between 2 molecules + molecule of water is produced

Hydrolysis = a water molecule is used to break a chemical bond between 2 molecules
EG peptide bonds in proteins
ester bonds between fatty acids and glycerol in lipids

Question 4

elements found in carbohydrates, lipids, proteins and nucleic acids

Answer 4

Carbohydrates + lipids = C, H, O

Proteins = C, H , O, N, S

Nucleic acids = C, H, O, N, P

Question 5

Carbohydrates

Answer 5

Also known as saccharides or sugars

Question 6

Glucose

Answer 6

C6H12O6 - white crystalline solid
Monosaccharide composed of 6 carbons = hexose monosaccharide

2 isomers: alpha and beta

In both, carbon 1 is bonded to a hydrogen atom and an OH group

Polar + soluble (hydrophilic) due to hydrogen bonds between OH group and water - this is important as glucose dissolves in the cytosine of cells do it can be easily transported

Question 7

Alpha glucose

Answer 7

OH below plane/ring

Question 8

Beta glucose

Answer 8

OH above plane/ring

Question 9

Pentode monosaccharide

Answer 9

Monosaccharide composed of 5 carbons

EG Ribose
Present in RNA nucleotides
Deoxyribose present in DNA nucleotides

Question 10

Other important sugars

Answer 10

Fructose :
Hexose monosaccharide
Occurs naturally in fruit

Galactose:
Hexose monosaccharide

Fructose is sweeter than glucose
Glucose is sweeter than galactose

Question 11

Monosaccharide + monosaccharide =

Answer 11

Disaccharide + water

Question 12

Glucose + fructose =

Answer 12

Sucrose + water (cane sugar)

Question 13

Glucose + galactose =

Answer 13

Lactose + water (found in milk)

Question 14

Alpha glucose + alpha glucose =

Answer 14

Maltose + water

Question 15

Condensation reaction

Answer 15

A chemical reaction in which two or more molecules combine to produce water and another larger molecule

EG alpha glucose + alpha glucose = maltose + glucose
- 2 hydrogens + 1 oxygen atom are removed + join to a form a water molecule

• a glycosidic bond forms between carbon 1 and carbon 4 on the glucose molecule

Question 16

Hydrolysis reaction

Answer 16

A chemical reaction that breaks up a larger molecule into two smaller molecule by adding a molecule of H2O

Glucose is stored as starch by plants, or glycogen by animals and fungi until needed for respiration

• to release glucose for respiration, starch and glycogen undergo hydrolysis reaction
• the reaction is catalysed by enzymes

Question 17

Enzymes that break down carbohydrates

Answer 17

Carbohydrases

Amylase
Maltase

Question 18

Starch

Answer 18

Storage polysaccharide of plants

Many alpha glucoses join together to form 2 polysaccharides - known collectively as starch

Chemical energy store

Amylase + amylopectin

Question 19

Amylose (starch)

Answer 19

Formed by alpha molecules joined 1-4 glycosidic bonds

structure:

• Angle of bond means long chain of glucose twists to form a helix which is further stabilised by hydrogen binding in the molecule
• unbranched structure

Property:
Makes polysaccharides more compact, it is also not soluble

Function
Compactness makes it well suited for energy storage as it takes up little space so more can be stored but it does take longer to release.
Insoluble nature doesn’t affect water potential

Question 20

Amylopectin (starch)

Answer 20

Alpha glucose molecules joined together by 1-4 glycosidic bonds AND glycosidic bonds for,Ed by condensation reactions between Carbon 1 and 6 on two glucose molecules

Structure:
Branched structure, 1-6 branching points occurs 1 in every 25 glucose subunits

Properties
Branches increase surface area = compact + insoluble

Function
Increases surface area so molecule can be hydrolysed for respiration quickly
Compactness makes it well suited for energy store age as it takes up little space
Insoluble nature doesn’t affect water potential

Question 21

Glycogen

Answer 21

Storage form in animals (glucose)
Polysaccharide of alpha glucose monomers
1-6 glycosidic bonds = branched structure
More branches than amylopectin
More coiling = more compact = less space
- ideal as animals are mobile

Branching = free ends where glucose molecules can be added or embedded = speeds up process of storing + releasing glucose molecules = increased enzyme activity

Insolubility doesn’t affect water potential

Question 22

Key properties of amylopectin + glycogen

Answer 22

Insolubility
Branched structure
Compactness = suitable for storage roles

Question 23

Cellulose

Answer 23

Polysaccharide with linear chain of beta glucose molecules
Cellulose molecules make H-bonds with each other = forms microfibrils = forms macrofibrils = fibres

Fibres are strong = structural support for plants
Insoluble = won’t affect water potential

Held together by C1-4 linkages
Human body doesn’t have the enzymes needed to break the bonds so they pass through our bodies as roughage