Carbohydrates 1

Question 1

What are the properties of carbohydrates?

Answer 1

• Highly oxidizable
• Function to store potential energy
• Have structural and protective functions
• Contribute to cell-cell communication

Question 2

In what form are carbohydrates stored?

Answer 2

• Starch in plants

- Glycogen in animals

Question 3

Where do carbohydrates exhibit structural and protective functions?

Answer 3

• In plant cell walls

- Extra cellular matrices of animal cells

Question 4

How are carbohydrates highly oxidizable?

Answer 4

-Sugar and starch molecules have high energy H atom- associated electrons

Question 5

What is another name for a monosaccharide?

Answer 5

Hexose

Question 6

What are the 3 important hexoses?

Answer 6

• Glucose (Glc)
• Galactose (Gal)
• Fructose (Fru)

Question 7

How are disaccharides formed/

Answer 7

• From monomers that are linked by glycosidic bonds

- Covalent bonds formed when hydroxyl group one monosaccharide reacts with anomeric carbon of another

Question 8

What is an anomeric carbon/

Answer 8

• Different anomers are mirror images of each other
• It is carbon #1 on the glucose residue
• It stabilises the structure of glucose
• It is the only residue that can be oxidised

Question 9

What are the 3 important disaccharides?

Answer 9

• Maltose
• Lactose
• Sucrose

Question 10

What is maltose?

Answer 10

• Break down product of starch

- Found in beer and baby foods

Question 11

Why is maltose a reducing sugar?

Answer 11

Anomeric C-1 is available for oxidation

Question 12

What is lactose?

Answer 12

-Main sugar in milk

Question 13

How is lactose formed?

Answer 13

From a glycosidic bond between galactose and glucose

Question 14

Why is lactose a reducing sugar?

Answer 14

Anomeric carbon the glucose is available fro oxidation

Question 15

What is sucrose?

Answer 15

• Common sugar
• Only made y plants
• Sweetener in most processed foods

Question 16

Why is sucrose not a reducing sugar?

Answer 16

It does not have a free anomeric C-1 so ther is no oxidation site

Question 17

What are polysaccharides?

Answer 17

Polymers of medium to high molecular weight

Question 18

How are polysaccharides distinguished from each other?

Answer 18

• Identity of their recurring monosaccharide units
• Length of their chain
• Types of bond linking monosaccharide units
• Amount of branching they exhibit

Question 19

Homopolysaccharide

Answer 19

Single monomeric specie

Question 20

Heteropolysaccharide

Answer 20

Have 2 or more monomer species

Question 21

What 2 kind of glucose does starch contain?

Answer 21

• Amylose

- Amylopectin

Question 22

Describe amylose.

Answer 22

• Can have thousands of glucose residues

- D-glucose residues in (a1-4) linkage

Question 23

Describe amylopectin.

Answer 23

• Similar structure as amylose but branched.

- Glycosidic (a1-4) bonds join glucose in the chains but branches are (a1-6) and occur every 24-30 residues

Question 24

Describe the structure of starch.

Answer 24

Has many non-reducing ends and very few reducing ends

Question 25

How are amylose and amylopectin arranged in starch?

Answer 25

They are believed to form alpha helices

Question 26

Describe the structure of glycogen.

Answer 26

- Polymer of glucose (a1-4) linked to sub units with (a1-6) branches every 8-12 residues - This makes glycogen more extensively branched than starch

Question 27

Where is glycogen found in the body?

Answer 27

90% is in: - Liver (acts to replenish blood glucose when fasting) - Skeletal muscle (catabolism produces ATP for contraction)

Question 28

Why is glucose stored in polymers?

Answer 28

- Compactness - Amylopectin and glycogen have many non-reducing ends - The polymers form hydrated gels and are not really in solution

Question 29

What does the many non-reducing ends of amylopectin and glycogen allow?

Answer 29

-Allows them to be synthesised and degraded to and from monomers respectively thus speeds up formation or degradation

Question 30

What is meant by 'The polymers form hydrated gels and are not really in solution'?

Answer 30

-They are osmotically inactive -If free glucose were in the cells then [Glc]inside >> [Glc]outside Either Glc would move out of the cell down the concentration gradient or the cell would use huge amounts of energy keeping it in the cell

Question 31

What are glycoproteins?

Answer 31

Proteins that have carbohydrate covalently attached

Question 32

Glycoproteins: What may the carbohydrates attached to the protein do?

Answer 32

- Increases the protein solubility - Influence protein folding and conformation - Protect it from degradation - Act as a communication between cells

Question 33

What is the carbohydrate content of glycoproteins

Answer 33

1-80% by mass

Question 34

What is another name for glycosaminoglycans?

Answer 34

Mucopolysaccharides

Question 35

Where do GAGs function?

Answer 35

In mucus and also synovial fluid

Question 36

What are GAGs/

Answer 36

Un-branched polymers made from repeating units of hexuronic acid and an amino-sugar which alternate through the chains

Question 37

What are proteoglycans?

Answer 37

- Macromolecules found on the surface of cells or in between cells in the ECM - Carbohydrate >> Proteins

Question 38

How are proteoglycans formed?

Answer 38

From GAGs covalently attaching to proteins

Question 39

What do proteoglycans for part of?

Answer 39

Many connective tissues

Question 40

What are glycoproteins?

Answer 40

-Very similar to glycoproteins but protein>> carbohydrate

Question 41

Where are glycoproteins usually found?

Answer 41

-On the outer plasma membrane and ECM but also in the blood and within cells in the secretory system

Question 42

What are exampled of glycoproteins?

Answer 42

Some cytoplasmic and nuclear proteins

Question 43

What are mucopolysaccharidoses?

Answer 43

Group of genetic disorders caused by the absence or malfunction of enzymes that are required for the breakdown of GAGs

Question 44

How does mucopolysaccharidoses occur?

Answer 44

- Over time GAGS build up in connective tissue, blood and other somatic cells - The build up damages cellular architecture and function

Question 45

What can mucopolysaccharidoses cause?

Answer 45

?-Severe dementia - Heart problems - Build up of GAGs between endothelial cells causing damage - Stunted bones - Inflammed joints

Question 46

What are examples of mucopolysaccharidoses

Answer 46

- Hurler Syndrome - Scheie Syndrome - Hunter Syndrome - Sanfilippo Syndrome

Question 47

What are the characteristics of Hurler Syndrome?

Answer 47

- Severe developmental delays - Clouding and degradation of the cornea - Areterial wall thickening - Dementia

Question 48

What is the dementia in Hurler syndrome caused by?

Answer 48

- Build up of CSF | - Enlarged vermicular spaces

Question 49

What are the sever developmental delays seen in Hurler syndrome?

Answer 49

- Stop developing at around 4yo | - Death at around 10yo

Question 50

What experimental therapies currently exist for Hurler syndrome?

Answer 50

- Gene therapy | - Enzyme replacement therapies