Carbohydrates

Question 1

What is the chemical formula of carbohydrates

Answer 1

Cn(H2O)n

Question 2

3 functions of carbohydrates

Answer 2

1. Energy source and energy storage
2. Structural use in cell walls and exoskeletons
3. Used in cell-cell signaling

Question 3

What are aldoses and ketoses

Answer 3

Aldoses have an aldehyde functional group (C=O at the end)
Ketoses have a ketone functional group

Question 4

What is a chiral carbon

Answer 4

A carbon with 4 different functional groups surrounding it

Question 5

Define stereoisomers

Answer 5

Molecules with the same molecular formulae,
but different spatial arrangement of atoms

Question 6

Define optical isomers

Answer 6

A form of stereoisomerism where the
molecules are mirror images of each other.

Question 7

Define enantiomers

Answer 7

D (right) and L (left) stereoisomers are enantiomers of each other

Question 8

Do enzymes work the same for both enantiomers

Answer 8

No, enzymes are specific for one or the
other

Question 9

What’s the difference between linear and cyclic structures of carbohydrates

Answer 9

• sugars can exist in “open” or “closed” forms: as linear molecules, or rings
• In solution there is an equilibrium between linear and cyclic forms

Question 10

How to number carbons in ring form carbohydrates

Answer 10

Find the oxygen then number clockwise

Question 11

How to make maltose and where is it found

Answer 11

2 x D Glucose
Starchy foods and brewed beverages

Question 12

How to make sucrose and where is it found

Answer 12

D Glucose + D Fructose
Dates, peaches and mangoes

Question 13

How to make lactose and where is it found

Answer 13

D Glucose + D Galactose
Milk

Question 14

What is the difference between homopolysaccharides and heteropolysaccharides

Answer 14

Homo - all the same type of sugar molecule e.g. all glucose
Hetero - different sugars bonded together

Question 15

Can polysaccharides be branched

Answer 15

Yes

Question 16

What are the two types of starch

Answer 16

1. Amylose (unbranched)
2. Amylopectin (branched)

Question 17

How is starch stored in humans

Answer 17

As glycogen (branched)

Question 18

What are 3 types of carbohydrates

Answer 18

1. Starch (amylose unbranched, amylopectin branched) ALPHA GLUCOSE
2. Glycogen ‐ branched ALPHA GLUCOSE
3. Cellulose BETA GLUCOSE

Question 19

What is an enantiomer?

Answer 19

Mirror image molecules that are non-superimposable.

Question 20

How are D and L sugars defined?

Answer 20

By the configuration around the chiral carbon furthest from the carbonyl group.

Question 21

What form do most hexoses in organisms take?

Answer 21

D-enantiomers.

Question 22

What forms can sugars exist in?

Answer 22

Linear (open) or cyclic (closed ring) forms.

Question 23

What is an anomeric carbon?

Answer 23

The carbon derived from the carbonyl group (C1).

Question 24

What distinguishes α and β anomers in glucose?

Answer 24

α: OH group down; β: OH group up relative to the ring plane.

Question 25

What is a glycosidic bond?

Answer 25

A covalent bond formed between an anomeric carbon and a hydroxyl group.

Question 26

What sugars make up maltose?

Answer 26

Two D-glucose molecules via a 1→4 bond.

Question 27

What sugars make up sucrose?

Answer 27

D-glucose and D-fructose.

Question 28

What sugars make up lactose?

Answer 28

D-glucose and D-galactose.

Question 29

What is a homopolysaccharide?

Answer 29

A polysaccharide with only one type of monosaccharide.

Question 30

What is a heteropolysaccharide?

Answer 30

A polysaccharide with more than one type of monosaccharide.

Question 31

What carbohydrate is found in plant cell walls?

Answer 31

Cellulose.

Question 32

What carbohydrate is the main storage form in plants?

Answer 32

Starch.

Question 33

What carbohydrate is the main storage form in animals?

Answer 33

Glycogen.

Question 34

What is a homopolysaccharide?

Answer 34

Polysaccharide made of only one kind of monosaccharide.

Question 35

What is a heteropolysaccharide?

Answer 35

Polysaccharide made of different kinds of monosaccharides.

Question 36

What type of polysaccharide is glycogen?

Answer 36

Branched homopolysaccharide of glucose.

Question 37

What are the glycosidic linkages in glycogen?

Answer 37

α1→4 links in chains and α1→6 at branch points.

Question 38

What is the primary function of glycogen?

Answer 38

Main storage polysaccharide in animals.

Question 39

What type of polysaccharide is starch composed of?

Answer 39

Homopolysaccharides of glucose (amylose and amylopectin).

Question 40

What are amylose and amylopectin?

Answer 40

Amylose is unbranched; amylopectin is branched.

Question 41

How does starch differ from glycogen?

Answer 41

Branch points in starch are less frequent than in glycogen.

Question 42

What type of bonds are found in cellulose?

Answer 42

β1→4 linkages between glucose units.

Question 43

Why is cellulose tough and insoluble?

Answer 43

Extensive hydrogen bonding between and within chains.

Question 44

Why can't most animals digest cellulose?

Answer 44

They lack the enzyme cellulase.

Question 45

What organisms can digest cellulose and how?

Answer 45

Ruminants and termites via symbiotic microorganisms.

Question 46

What is chitin made of?

Answer 46

Chains of N-acetylglucosamine linked by β1→4 bonds.

Question 47

Where is chitin found?

Answer 47

Fungi cell walls, insect exoskeletons, mollusc shells.

Question 48

What is chitosan and how is it derived?

Answer 48

Deacetylated chitin forming a heteropolysaccharide.

Question 49

What are some industrial uses of chitosan?

Answer 49

Drug delivery, surgical dressings, food thickeners.

Question 50

What enzymes break down chitin?

Answer 50

Chitinases (endochitinases and exochitinases).

Question 51

Why is increased chitinase expression linked to asthma?

Answer 51

Chitinase overproduction may trigger allergic responses.

Question 52

What is the extracellular matrix (ECM)?

Answer 52

A network of polysaccharides, proteoglycans, and proteins outside cells.

Question 53

What are the components of the ECM?

Answer 53

Polysaccharides, proteoglycans, collagen, elastins, fibronectins, laminins.

Question 54

What are the roles of the ECM?

Answer 54

Hold cells together, provide strength, allow diffusion, act as barriers.

Question 55

What are glycosaminoglycans (GAGs)?

Answer 55

Long unbranched heteropolysaccharides forming ECM meshworks.

Question 56

What is the basic structure of GAGs?

Answer 56

Repeating disaccharide units, often containing N-acetylglucosamine or galactosamine.

Question 57

What is hyaluronan?

Answer 57

Non-sulfated GAG found in all human tissues and fluids.

Question 58

What are the roles of hyaluronan?

Answer 58

Provides strength, elasticity, lubrication in joints, and eye structure.

Question 59

What is chondroitin sulfate?

Answer 59

A sulfated GAG giving tensile strength to cartilage and heart valves.

Question 60

Where is chondroitin sulfate found?

Answer 60

Cartilage, tendons, ligaments, heart valves, and aorta walls.

Question 61

What is keratan sulfate?

Answer 61

Found in cornea, cartilage, bones, and horn-like structures.

Question 62

What are glycolipids?

Answer 62

Lipids with covalently bound carbohydrate chains.

Question 63

What roles do glycolipids play?

Answer 63

Structure of membranes and determination of blood groups.

Question 64

What is heparin?

Answer 64

Highly sulfated GAG with strong negative charge density.

Question 65

What is the function of heparin?

Answer 65

Activates antithrombin to prevent blood clotting.

Question 66

What are glycoconjugates?

Answer 66

Proteins or lipids with carbohydrate chains attached.

Question 67

What are proteoglycans?

Answer 67

Proteins with one or more GAG chains attached.

Question 68

What distinguishes glycoproteins from proteoglycans?

Answer 68

Glycoproteins have shorter, more branched carbohydrates; proteoglycans have long GAG chains.

Question 69

What are syndecans and integrins?

Answer 69

Membrane proteins that link cells to the ECM.

Question 70

How does the ECM contribute to cancer invasion?

Answer 70

Tumor cells may degrade ECM by secreting enzymes like heparinase.

Question 71

How does the ECM allow nutrient diffusion?

Answer 71

By allowing oxygen and nutrients to pass through while blocking pathogens.