W3 - Monosaccharides (lecture)

Question 1

What is the empirical formula of a carbohydrate?

Answer 1

[CH2O]n

Question 2

What are polyhydroxy aldehydes/ketones referred to?

Answer 2

Aldose sugars and ketose sugars

Question 3

Glucose is the most abundant carbohydrate absorbed in the bloodstream even though starch is the most ingested, why is this?

Answer 3

Due to digestion, breakdown of starch

Question 4

Glucose is a major fuel for all tissues but where is it the only fuel molecule?

Answer 4

Brain and RBCs

Question 5

What is it that can cause diabetes, galactosaemia, fructose/lactose intolerances?

Answer 5

Abnormal carbohydrate metabolism

Question 6

Give 4 examples of monosaccharides

Answer 6

Glucose, fructose, galactose, ribose

Question 7

What molecules make up maltose, sucrose and lactose (disaccharides)?

Answer 7

Maltose - glucose x2, Sucrose - glucose + fructose, Lactose - glucose + galactose

Question 8

How many monosaccharide units are in an oligosaccharide and polysaccharide?

Answer 8

O - 3-10, P - 11 and up

Question 9

Are cellulose or glycogen/starch linear/branched?

Answer 9

Cellulose - linear, glycogen/starch - branched

Question 10

Simple polysaccharides such as aldose/ketose sugars can act as what in reactions?

Answer 10

Alcohols and aldehyde/ketone

Question 11

What is the minimum number of Cs a monosaccharide can have (no max)?

Answer 11

3

Question 12

What are all aldose sugars derived from?

Answer 12

Glyceraldehyde

Question 13

When drawing a fisher projection of glyceraldehyde does the CHO or the CH2OH group go at the top or the bottom?

Answer 13

CHO - top, CH2OH - bottom

Question 14

Which series of glyceraldehyde is encountered in human metabolism?

Answer 14

D- series ONLY

Question 15

What is the general rule for calculating the number of isomers for a monosaccharide when you know the number of Cs? Use glucose as an example

Answer 15

2 to the power of number of asymmetric Cs, Glucose = 2^4 = 16

Question 16

Glucose contains OH groups and is therefore water soluble, it can also have amine groups on C2, what is it called when this happens?

Answer 16

Glucosamine

Question 17

When a hydroxyl on glucose is replaced with a H what type of sugars does this produce?

Answer 17

Deoxysugars

Question 18

When glucose acts as an alcohol reacting with an acid/phosphoric or sulfuric acid what does it produce?

Answer 18

Acid - ester, phosphoric/sulfuric acid - phosphates + sulfates

Question 19

Can the aldehyde group on glucose be oxidised/reduced or both?

Answer 19

Both

Question 20

What type of rings form when pentoses and hexoses cyclise?

Answer 20

Pent - furanoses, Hex - pyranoses

Question 21

D- glucose is the open chain form, what are the two cyclic forms called?

Answer 21

Alpha/beta-D-Glucopyranose

Question 22

D-Fructose is the open chain form, what are the two cyclic forms called?

Answer 22

Alpha/beta-D-fructofuranose

Question 23

Pyranose and furanose rings can be drawn in chair, envelope and boat form, what does this tell us about it’s structure?

Answer 23

The rings aren’t planar

Question 24

What forms when glucose reacts with alcohols or amines?

Answer 24

Alcohols - glucosides with O-glycosidic bonds, Amines - Glucosamines with N-glycosidic bonds

Question 25

Can glucose or glucosamine be readily oxidised?

Answer 25

Glucose

Question 26

Phosphorylated sugars are key intermediates in energy generation and biosynthesis but why? (2 reasons)

Answer 26

-ve charge means they cannot cross membrane and they become more reactive in important pathways