Carbohydrates

Question 1

How many carbons does a hexose have and what is it a form of?

Answer 1

6 carbons

form of glucose

Question 2

What are carbohydrates made out of?

Answer 2

Carbon and water

Question 3

What is the general formula of carbohydrates?

Answer 3

Cn(H2O)n

Question 4

Name the three carbohydrate groups

Answer 4

Monosaccharides
Disaccharides
Polysaccharides

Question 5

What are the properties of monosaccharides?

Answer 5

Colourless, crystalline solids, soluble in water (OH groups), single aldehyde or ketone group

Question 6

What makes up a disaccharide and how are they made?

Answer 6

2 monosaccharides and formed by condensation reaction (removal of H2O)

Question 7

What is a polysaccharide?

Answer 7

Polymers of monosaccharides

Question 8

What are the two forms of polysaccharides?

Answer 8

Homopolysaccharides and heteropolysaccharides

Question 9

Name three carbohydrate functions

Answer 9

Energy storage/supply
structural functions
signalling (between and within cells)

Question 10

What are the 2 structural forms of carbohydrates?

Answer 10

Fischer projections - 2D, linear

Ring (cyclic structure)

Question 11

What are the 3 monosaccharide groups?

Answer 11

Ketone (C-O)
Aldehyde (COH)
Hydroxyl (OH)

Question 12

What is isomerism?

Answer 12

Atomic arrangements within the molecule that can significantly affect the function

Question 13

What is a chiral centre?

Answer 13

Carbon atoms that have 4 different chemical groups attached

Question 14

What is an enantiomer?

Answer 14

When molecules have the same functional group but one is a mirror image of the other

Question 15

What is D configuration in an enantiomer in a Fischer projection?

Answer 15

If the OH group is to the right of the last chiral centre carbon

Question 16

What is L configuration in an enantiomer in a Fischer projection?

Answer 16

If the OH group is to the left of the last chiral centre carbon

Question 17

What is D configuration in a ring enantiomer?

Answer 17

If the oxygen bond to the last chiral centre carbon is at the right

Question 18

What is the L configuration in a ring enantiomer?

Answer 18

If the oxygen bond to the last chiral centre carbon is at the left

Question 19

Where does an epimer occur?

Answer 19

Where functional groups are arranged differently at one or more chiral centres (not mirror images)

Question 20

What happens when a molecule is dextrorotatory?

Answer 20

It rotates light clockwise

Question 21

How are dextrorotatory molecules denoted?

Answer 21

(+)

Question 22

Where do anomers occur?

Answer 22

Only in rings

Question 23

What is an anomeric carbon?

Answer 23

Ones involved in hemiacetal or hemiketal bonding during ring formation

Question 24

Where do anomeres occur?

Answer 24

Only in rings

Question 25

What does alpha mean when denoted on an anomer for hexose?

Answer 25

carbon 6 and new hydroxyl group (OH) are on opposite sides of rings

Question 26

What does beta mean when denoted on an anomer for hexose?

Answer 26

carbon 6 and new hydroxyl group (OH) are on the same side of the ring

Question 27

What does "pyran" mean?

Answer 27

six in the ring

Question 28

What does "furan" mean?

Answer 28

five in the ring

Question 29

What group are aldohexoses predominantly part of?

Answer 29

Pyranose

Question 30

What group are ketohexoses predominantly part of?

Answer 30

furanose

Question 31

Where do conformers occur?

Answer 31

only for rings

Question 32

What causes puckered conformations?

Answer 32

strain

Question 33

What are the 2 conformations that rings flip between?

Answer 33

"boat" and "chair"

Question 34

What test can be use to detect monosaccharides?

Answer 34

Benedict's test for reducing sugars - precipitated as insoluble red

Question 35

What can you do to detect monosaccharides?

Answer 35

Oxidation - only free aldehyde/ketone groups can be oxidised, afterwards the monosaccharide can reduce the metal ions

Question 36

When is an O-glycosidic bond formed in a disaccharide?

Answer 36

When an anomeric carbon of one monosaccharide binds to oxygen from hydroxyl group of another sugar

Question 37

Why does the glycosidic bond name contain alpha or beta?

Answer 37

If the monosaccharide is either alpha or beta

Question 38

Can a glycosidic bond be hydrolysed?

Answer 38

Yes at low pH acids but not by bases

Question 39

When does an N-glycosidic bond occur?

Answer 39

when an anomeric carbon of a sugar joined to a nitrogen atom in glycoproteins and nucleotides

Question 40

Name some important disaccharides

Answer 40

Maltose: glucose + glucose Lactose: galactose + glucose Sucrose: glucose + fructose Trehalose: energy storage compound in some insects, bacteria and fungi

Question 41

What do glycosidic linkages form?

Answer 41

polysaccharides

Question 42

What is a homopolysaccharide?

Answer 42

contain a single type of monosaccharide and used in energy storage/structural components

Question 43

What is a heteropolysaccharide?

Answer 43

contain 2 or more different monosaccharides

Question 44

What are the functions of a heteropolysaccharide?

Answer 44

Structural | cell-cell signalling

Question 45

Name a polysaccharide and what its made out of

Answer 45

Starch - mixture of amylose and amylopectin

Question 46

What are some biological functions of starch?

Answer 46

In plants: stored form of glucose | In animal diets: amylase hydrolyses alpha bond releasing maltose which is converted to glucose by maltase

Question 47

Name 2 polysaccharides for structure?

Answer 47

Cellulose and chitin

Question 48

Where is peptidoglycan found?

Answer 48

In the cell wall of Gram-positive and negative bacteria

Question 49

What are the functions of peptidoglycan?

Answer 49

provides strength and rigidity to the cell wall

Question 50

What is agar made out of?

Answer 50

mixture of heteropolysaccharides (agarose and agaropectin)