Carbohydrates

Question 1

Carbohydrates?

Answer 1

polyhydroxy aldehydes and ketones

• Cx(H2O)y
• more complex carbs (contain N,P, or S)

Question 2

Monosaccharides

Answer 2

e.g. glucose, ***fructose, galactose

Question 3

Oligosaccharides

Answer 3

carbohydrates that comprise 2 – 10 monosaccharide units

-including the disaccharides, e.g: sucrose, lactose, maltose

Question 4

Polysaccharides

Answer 4

large polymers of monosaccharides: examples - glycogen, starch, cellulose

Question 5

Aldose vs. ketose

Answer 5

• contains a Ketone group - (Carbonyl, 2 R groups)

- contains an aldehyde group (Carbonyl, one H, one R group)

Question 6

note: many monosaccharides have the same structural formula but different spatial arrangement of atoms or groups

Answer 6

• we would call these stereoisomers

- D-glucose, D-mannose, D-galactose

Question 7

if the difference in spatial arrangement is only around ONE C atom, then what do we call these 2 sugars?

Answer 7

Epimers

-D-glucose and D-galactose

Question 8

asymetric carbon / mirror images of each other

Answer 8

four different atoms connected / ENANTIOMERS (rotate light in different directions - D or L sugars)

Question 9

All of the sugars in our body are L or D sugars?

Answer 9

• Our body can only recognize or metabolize D sugars

- The OH group furthest from the Carbonyl group must be on the right!

Question 10

Glucose being a blank, would form a blank (ring structure)

Fructose being a (blank) would form a (blank)

note; monosaccharide with 5 or more carbons = present mostly in ring form

Answer 10

aldose, aldohexose (pyranose - 6 member-ed ring)

ketose, ketohexose (furanose - 5 member-ed ring)

Question 11

G6P = glucose-6-phosphate

Answer 11

interestingly enough glucose is often phosphorylated in order to keep it in the cell (maintain the gradient / keep it moving into cell via insulin dependent transport following a meal - so we can use it for cellular energy (glycolysis = ATP + reduced electron carriers for oxidative phosphorylation) or store it as glycogen,

Question 12

What happens when the aldehyde group of glucose or galactose gets reduced?

Answer 12

• forms polyol

- sorbital and ducitol (galactitol) respectively)

Question 13

What causes cataracts in diabetics?

Answer 13

At high blood glucose concentrations, excessive glucose accumulates in the lens! This glucose is reduced to sorbitol
-the sorbitol causes uptake of water, which causes the aggregation of crystallin proteins of the lens

note: accumulation of ducitol in galactosemia (few month old baby can’t break down galactose) causes same issues as sorbitol

Question 14

The glycosidic linkage forms when an anomeric carbon reacts with an OH or NH group from another compound.

explain sugar, milk, potato/flour (starch - storage form of carbohydrates in plants)

glycogen = storage form of carbohydrates in humans

Answer 14

sugar = sucrose = glucose + fructose (alpha; 1,2)
milk = lactose = glucose + galactose (Beta; 1,4)

Potato or Flour = starch = glucose + glucose (alpha 1,4 amylose / alpha 1,6 amylopectin)

maltose = glucose + glucose (alpha; 1,4) 
cellulose = glucose + glucose (BETA; 1,4)

Question 15

A 6-week-old male is admitted to the ICU with jaundice, lethargy and feeding difficulties. History is significant for intermittent vomiting since birth. Physical examination reveals hepatomegaly and the initial stages of cataract formation. A diagnosis of galactosemia is made. Which of the following is the most likely mechanism of cataract formation in this patient?

Answer 15

*Osmotic uptake of water into the lens, causing aggregation of crystallin proteins