Structure And Function Of Carbohydrates

Question 1

What is a carbohydrate

Answer 1

CH2O

It can have structural roles such as DNA and RNA, and other roles such as energetics like glucose and fructose (ATP)

Question 2

Monomers of carbohydrates

Answer 2

Structural carbohydrates such as DNA and RNA: robins and deoxyribose (5 carbon structure, the only difference is at 2nd C there is a H-OH (ribose) bond rather than a H-H bond (deoxyribose)

Question 3

Carbohydrates:

- types of isomers

Answer 3

Structural isomers: such as a change in compound from H to CH2OH in the respect of glucose to fructose
Stereoisomer: such as a switch in the position of the current compounds such as the switching of H-OH to OH-H in the respect of glucose to galactose

Question 4

Glucose anomers

Answer 4

Alpha glucose where at carbon 1 the bond is positioned H-OH

Beta glucose where at carbon 1 the bond is positioned OH-H

Question 5

Forming disaccharides

- sucrose and maltose

Answer 5

Sucrose is from the formation of alpha-glucose and fructose (reversed by invertase)
Maltose consists of 2 glucose molecules
Also lactose from glucose and galactose

Question 6

Alpha glucose polymers

Answer 6

Alpha glucose polymers can have 1-4/1-6 linkages (numbers refer to the carbon number)
1-6 linkages make storage molecules more branched

Question 7

Starch

- structure and function

Answer 7

Solely in plants as an energy store

Consists of amylopectin and amylose

Question 8

Glycogen:

- structure and function

Answer 8

Solely in mammals as an energy store, mainly a 1-4 linkages

Question 9

Cellulose:

- structure and function

Answer 9

Made from beta glucose with 1-4 linkages, cell wall of plant cells

Question 10

Structure of glucose polymers

Answer 10

Cellulose only beta 1-4 linkages
Starch and glycogen only a 1-4 linkages
Form large fibres, aided by hydrogen bond formation between the bonds creating a rigid structure

Question 11

Chitin:

- structure and function

Answer 11

Made from the chitin monomer a substituted glucose:

N-acetyl glucosamine (on carbon 2 the addition of N-acetyl)

Question 12

Glycoproteins:

- structure and function

Answer 12

Addition of a glycan to a protein at specific residues such as Asn, Ser and Thr
Function: for structural purposes such as the mucous proteins (mucin)
Glycan contain sialic acid, these small sugars are polar and -ve charged
Functional role also for blog grouping e.g. for the B type galactose is attached to the blood (at proteins or lipids) or A type N-acetyl galactosamine (at proteins or lipids).

Question 13

Proteoglycans

Answer 13

Contains Hyaluronan: consisting of aggregate core protein, chondritin sulfate, link proteins and keratan sulfate

Question 14

Cartilage and the ECM

- consists of

Answer 14

The ECM is a organised combination of proteoglycans, cross-linked fibres of collagen and fibronectin

Question 15

Proteoglycans:

- types

Answer 15

Chondroitin 6-sulfate
Keratan sulfate
Heparin
Dermatan sulfate
Hyaluronate
Collectively known as glucosaminoglycans (GAGs)

Question 16

Carbohydrate:

- energy quantity

Answer 16

4 kcal kg-1

Question 17

Glucose:

- function

Answer 17

Oxidative respiration

Question 18

Monosaccharide chemical structure

Answer 18

C6H12O6

Question 19

Disaccharide chemical structure

Answer 19

C12H22O11

Question 20

Formation of a disaccharide

Answer 20

By polymerisation called condensation reaction, leaving water

Question 21

Breakdown of a disaccharide

Answer 21

Amylase, biological catalyst

Found in the mouth and gut, contains acid

Question 22

Hydrolysis of starch

Answer 22

By a hydrolysis reaction with the presence of water

Can be broken down by hearing with acid (acid hydrolysis)

Question 23

Glucose uptake

Answer 23

Via GLUT4 transporter

Question 24

Glucose-1-P:

- use

Answer 24

Stored or broken decay depending on demand

Question 25

Characteristics of storage compounds

Answer 25

Need to be energy rich, mobilisation and storable

Question 26

Glycogen:

• location
• characteristics

Answer 26

Stored in the cytoplasm of liver and muscle
Glycogen is a branched polymer of glucose residues, consisting of a-1,6-glycosidic bonds and a-1,4-glycosidic bonds
30,000-50,000 glucose units (non reducing or reducing ends)

Question 27

Glycogen breakdown:

- energy use

Answer 27

Breaking the glycosidic bond by adding orthophosphate to carbon 1 (phosphorylase)
This form alpha-D-glucose-1-phosphate + glycogen residue
Phosphorylase stops 4 residues away from a branching point

Question 28

Debranching glycogen:

- movement

Answer 28

Transferase to shift three glucose residues

Debranching enzyme hydrolyses the alpha-1,6-glycosidic bond (alpha-1,6-glucosidase)

Question 29

G1P to G6P:

- conversion

Answer 29

G1P needs to be converted G6P, via phosphoglucomutase

G6P can now enter glycolysis pathway or the pentose phosphate pathway (ribose)

Question 30

Liver releases glucose

Answer 30

G6P + H2O via G6-phosphotase forms glucose and Pi

Question 31

Glycogen synthesis

Answer 31

1. G6P is converted to G1P
2. Activation of G1P to UDP-glucose (via UTP for activation) also needs UDP-glucose pyrophosphorylase
3. Formation of glycosidic bond (rls) with the help of glycogen synthase, removes uracil and adds to the glycogen chain
4. Branching; glycogen-branching enzyme which adds a-1,6-branch points