Carbohydrates 1

Question 1

What are the 4 main properties of carbohydrates?

Answer 1

1. Highly oxidisable and can be easily broken up to yield energy (have high energy H-atom associated electrons). Carbohydrate catabolism is the major metabolic process for most organisms
2. Function to store potential energy (e.g. starch in plants or glycogen in animals)
3. Have structural and protective functions (e.g. cell walls for plants or ECM and connective tissue in animals)
4. Contribute to cell-to-cell communication (ABO blood groups)

Question 2

What are the 3 main monosaccharides?

Answer 2

• glucose
• galactose
• fructose

Question 3

What is a disaccharide?

Answer 3

• When two monosaccharides join and form a glycosidic bond

- covalent bond formed between a hydroxyl group and an anomeric carbon of monosaccharides.

Question 4

What’s an anomeric carbon?

Answer 4

• Different anomers are different mirror images of each other (left/right handed forms)
• It is carbon 1 on glucose residues and stabilizes glucose residues
• It’s the only residue which can be oxidized

Question 5

What are the 3 main disaccharides?

Answer 5

• lactose
• maltose
• sucrose

Question 6

Maltose facts

Answer 6

• Don’t get much maltose from diet
• Break down product of starch
• Found in beer (from starch of barley) and baby foods as sweeteners
• Anomeric C1 can be oxidized so maltose is a REDUCING sugar

Question 7

Lactose facts

Answer 7

• Main sugar in milk
• Formed by a glycosidic bonds between galactose and glucose
• Anomeric C1 on glucose is available for oxidation so it’s a REDUCING sugar

Question 8

Sucrose facts

Answer 8

• table sugar and used as sweetener in processed foods
• approx. 25% of dietary carbohydrate
• only made by plants
• doesn’t have an anomeric C1, so no oxidation site and therefore it’s NON-REDUCING

Question 9

What two glucose monomers is starch made of?

Answer 9

1. Amylose (20-25% of starch): D-glucose residues in (α1→4) linkage and can have thousands of glucose residues
2. Amylopectin (70-75% of starch):Similar structure as amylose but branched and glycosidic (α1→4) bonds join glucose in the chains but branches are (α1→6) and occur every 24 – 30 residues

Question 10

Is starch reducing or non-reducing?

Answer 10

Mainly non-reducing (but it contains very small number of reducing ends)

Question 11

What’s the difference between alpha (1-4) bonds and alpha (1-6) bonds?

Answer 11

-α(14) linkage:
A linear linkage between C-1 of one monomer and C-4 of the adjacent monomer
-α(16) linkage:
A branched linkage between C-1 of one monomer and C-6 of the next monomer

Question 12

What is glycogen used for?

Answer 12

90% is in:

• Liver (acts to replenish blood glucose when fasting
• Skeletal muscle (catabolism produces ATP for contraction)

Question 13

Why is glucose stored as glycogen?

Answer 13

1. Compactness: has non-reducing ends which means it can be synthesised and degraded readily (speeds up formation and degradation)
2. Osmotically inactive since glycogen molecules form hydrated gels and aren’t in solution. Therefore glucose can be stored at high concentration without having any impact on osmotic activity

Question 14

What do carbohydrate molecules attached to proteins (glycoprotein) improve/effect? (4)

Answer 14

• protein solubility
• protein’s conformation and folding
• protects from degradation
• acts as communication between cells

Question 15

What are GAGs made of? (-ve charge)

Answer 15

Unbranched polymers made of repeating unit of hexuronic acid and an amino- sugar

Question 16

Where are GAG’s found?

Answer 16

In mucus and synovial fluid around joints (in slimy substances due to long chains sliding over each other). They act as lubricants and are hydrated

Question 17

Where are glycoproteins found in the body?

Answer 17

• ECM
• outer plasma membrane
• within cell’s secretory system (secretory granules or golgi complex)
• found in cytoplasmic or nucleic proteins

Question 18

What are mucopolysaccharidoses?

Answer 18

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

Question 19

What do mucopolysaccharidoses generally cause in the body?

Answer 19

• build up in connective tissue, blood or body cells
• damages cellular architecture and function
• can cause heart problems, dementia or endothelial cell structure problems (fluid builds up between endothelial cells)
• stunted bones, inflammed joints (both damaged)

Question 20

What are some examples of mucopolysaccharidoses?

Answer 20

Hurler, Scheie, Hunter, Sanfilippo syndromes

Question 21

What are some symptoms of the Hurler syndrome?

Answer 21

• growth development at around 4 years and death at 10 years
• clouding and degradation of cornea
• arterial wall thickening
• dementia: due to build up of CFS or enlarged ventricular spaces