Carbs

Question 1

What are carbohydrates?

Answer 1

Complex organic molecules formed from carbon dioxide and water which are used as a source of chemical energy by living organisms

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Question 2

What are monosaccharides?

Answer 2

Simple sugars

Question 3

What are oligosaccharides?

Answer 3

Short chains of monosaccharides, less than 20 residues

Question 4

What are polysaccharides?

Answer 4

Consists of hundreds of thousands of monosaccharide units

Question 5

Describe the characteristics of monosaccharides.

Answer 5

Colourless, crystalline solids
Water soluble
Most are sweet tasting
Exist in open chain and ring structures
Two families: aldoses (aldehyde) and ketoses (ketone)

Question 6

What are the roles of sugars?

Answer 6

Energy source
Structural: cell walls, exoskeletons, connective tissue
Information: recognition and nucleic acids

Question 7

Why can sugars have so many roles?

Answer 7

Diverse structural forms
3 different amino acids- 6 tripeptides
3 different hexoses- 1056 different trisaccharides

Question 8

Why is sugar used as an energy source?

Answer 8

Monosaccharides and disaccharides are easily metabolised to provide energy for a cell

Question 9

What do plants store energy as?

Answer 9

Starch, which is a polysaccharide

Question 10

What do animals store energy as?

Answer 10

Glycogen, which is a polysaccharide

Question 11

Why is energy stored in polysaccharide form?

Answer 11

Compact granule
Bonding means less osmotic pull
Little water associated with it

Question 12

What are some structural roles of sugars?

Answer 12

Homopolymers: cellulose and chitin
Heteropolymers: bacterial cell walls
Glycoconjugates: connective tissue

Question 13

What is cellulose?

Answer 13

One of the most abundant organic compounds
Unbranched polymer of glucose residues joined by beta 1-4 linkages
The beta configuration allows formation of very long straight chains
Parallel chains can interact by hydrogen bonding forming Fibrils
These fibres have high tensile strength

Question 14

What is chitin?

Answer 14

Insect exoskeleton
Linear homopolymers composed of N-acetylglucosmine linked by beta 1-4 glycosidic bonds
Differs from cellulose by replacement of C2 hydroxyl group with an acetylated amino group
Parallel chains interact by hydrogen bonding leading to high tensile strength
Second most abundant polysaccharide

Question 15

What are proteoglycans?

Answer 15

Glycans (carbohydrate 95%) with a bit of protein associated with it (5%)
Formed from glycosaminoglycan (GAG)

Question 16

What are glycosaminoglycans?

Answer 16

Anionic polysaccharide chains made of repeating disaccharide units

Question 17

How do gram-positive and gram-negative bacteria differ in terms of proteoglycans?

Answer 17

Gram-positive bacteria contain cross-linked multilayered proteoglycans whereas gram-negative only have a single layer
Gram-positive bacteria retain a dye-iodine complex that gets washed out of gram-negative bacteria

Question 18

What are glycoproteins and glycolipids?

Answer 18

Oligosaccharides associated with proteins and lipids (5% carbs, 95% other)
These play important roles in recognition and communication