L10-11: Carbohydrates

Question 1

What is the most abundant main class of biomols?

Answer 1

Carbohydrates

Question 2

What are the major roles carbohydrates play in biological processes?

Answer 2

-Storage and transport of energy
-cell-cell communication/adhesion
-Host-pathogen and host-symbiont interactions
-Structural components of animals, plants & fungi
-components of DNA and RNA

Question 3

What is the main composition of carbs?

Answer 3

Contain C,H and O
2 or more hydroxyl groups
An aldehyde or ketone group

Question 4

What are the 2 simplest carbs?

Answer 4

Glyceraldehyde and Dihydroxyacetone

Question 5

What does it mean when sugars are chirally active?

Answer 5

They have 2 stereoisomers

Question 6

What are the names when carbs contain aldehyde group or ketone group?

Answer 6

Aldehyde- Aldoses
Ketones- Ketoses

Question 7

How do sugars with >4 carbons form rings?

Answer 7

Because the alcohol is part of the same molecule as the aldehyde/ketone

Question 8

What are the names when aldehyde or ketone and alcohol form then when they form rings?

Answer 8

Aldehyde- Hemiacetal, ring- pyran
Ketone- Hemiketal, ring- furan

Question 9

Why do the rings have a chair configuration?

Answer 9

Due to the tetrahedral geometry of carbon atoms

Question 10

What are the 2 orientations on the carb rings?

Answer 10

Axial (up or down, opposite directions)
Equatorial (same plane as ring)

Question 11

How do the alpha and beta forms arise from sugars?

Answer 11

The formation generates and additional asymmetric carbon at position 1 (NOT NEW) (for aldoses)

Question 12

Where does the asymmetric carbon arise in ketoses?

Answer 12

C2

Question 13

How many carbons do most sugars have?

Answer 13

5-6

Question 14

What do L and D stand for?

Answer 14

Laevorotatory and Dextrorotatory

Question 15

What happens when only asymmetric carbon 2,3 or 4 are in a different configuration to glucose?

Answer 15

Molecule is a different structure, they are epimers

Question 16

What can sugars join to become?

Answer 16

Disaccharides
Oligosaccharides
Polysaccharides
(linked by glycosidic bonds)

Question 17

What are the different configurations of the glycosidic bond?

Answer 17

Alpha or beta (from either 2 alpha or a alpha and a beta)

Question 18

What are 3 disaccharides and what are they used as?

Answer 18

Maltose, lactose and sucrose used as an important energy source when hydrolysed

Question 19

What are the main polysaccharide storage molecules?

Answer 19

Starch and glycogen

Question 20

What are starch and glycogen polysaccharides of?

Answer 20

D-glucose

Question 21

What type of glycosidic bonds to starch and glycogen have?

Answer 21

Alpha 1,4-glycosidic bonds

Question 22

What makes a reducing sugar a reducing agent?

Answer 22

It has a free aldehyde or ketone group

Question 23

What are most of the reducing sugars?

Answer 23

They are all monosaccharides and most disaccharides/oligo/poly

Question 24

Why are alpha glycans good storage molecules?

Answer 24

The alpha1,4-linkage causes the polysaccharide to twist into a helical structure which makes it more compact

Question 25

What does branching in starch and glycogen do?

Answer 25

Alpha1,6 branching makes it compact and has many non-reducing terminals so easy to digest

Question 26

What are the structural properties of cellulose?

Answer 26

Plant polysaccharide Long beta1,4-linked glucose chains (form highly crystalline microfibrils) Very strong Most abundant organic molecule on planet

Question 27

How is biofuel formed?

Answer 27

Cellulose hydrolysed to glucose with enzymes then convert glucose to ethanol by microbial fermentation

Question 28

What is the main component of bacterial cell walls?

Answer 28

Peptidoglycan

Question 29

What are properties of the bacterial cell wall?

Answer 29

Without cell wall bacteria are osmotically sensitive and burst Good target for antibiotics as not present in animal cells Lysozyme targets bacterial cell wall

Question 30

What are glycoconjugates?

Answer 30

When carbs are often covalently linked to molecules such as proteins or lipids

Question 31

How is N-glycosylation useful?

Answer 31

As it plays a role in protein folding, stability and cell recognition

Question 32

What are O-linked glycans?

Answer 32

Oxygen linked

Question 33

What are characteristics of O-glycans?

Answer 33

Joined to hydroxyl of serine or threonine Common is GlcNAc (N acetyl glucosamine) Cytoplasmic

Question 34

What are key components of mucus?

Answer 34

Mucins (O-glycoproteins)

Question 35

What are proteins that are attached to mostly O-linked polysaccharides called?

Answer 35

Glycosaminoglycans

Question 36

What are the functions of glycosaminoglycans?

Answer 36

Joint lubricants Structural components of Extracellular Matrix Mediate adhesion of cells the ECM Bind factors that stimulate cell proliferation

Question 37

What are characteristics or proteoglycans?

Answer 37

GAG component determines function Made of disaccharide repeats of amino sugar & uronic acid Heavily sulfated Bind lots of water (hydrated gel withstand high compressive loads)

Question 38

How are complex carbs synthesised?

Answer 38

Glycosyltransferases

Question 39

How are blood groups different?

Answer 39

A- GTA puts GlcNAc on B- GTB puts Gal on O- GTs non-functional AB- GTA and GTB