FREE BIOCHEMISTRY AND STUDY GAMES ABOUT BIOC-

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FREE BIOCHEMISTRY AND STUDY GAMES ABOUT BIOC-

CARBS EXAM QUESTIONS

Actual Qs and Ans Expert-Verified Explanation

This Exam contains:

-Guarantee passing score -62 Questions and Answers -format set of multiple-choice -Expert-Verified Explanation

Question 1: What type of sugar is fructose?

Answer:

reducing ketose (ketoses can also be reducing but react more slowly than aldoses)-under basic conditions ketoses slowly isomerize into aldoses)

Question 2: What are the two trioses?

Answer:

Aldose (glyceraldehyde) and ketose (dihydroxyacetone)

Question 3: glycolysis is what type of metabolic pathway?

Answer:

catabolism - converts glucose to pyruvate Question 4: For a carbon chain of a given number what is the relationship between the number of ketoses and aldoses?

Answer:

There are always twice as many aldoses compared to ketoses for a given number of carbons

Question 5: How can branching happen in polysaccharides?

Answer:

sugars have several OH each of which can act as the nucleophile in forming a glycosidic bond.Question 6: A pair of sugar isomers that are identical except for chirality at one carbon atom

Answer:

epimers (a special case of diasteromers)

Question 7: Chemical properties that all monosaccharides share

Answer:

very water soluble, poorly soluble in organic solvents, colorless, and most are sweet

Question 8: Chiral

Answer:

Four substituents on carbon are all different allowing it to exist in either a right handed or left handed form.

Question 9: Aldehyde + alcohol =

Answer:

hemiacetal (see p.268)

Question 10: What affect does CU2+ ion have on sugars?

Answer:

Some oxidants such as the cupric ion can oxidize the aldehyde groups of aldose sugars to the corresponding acids. The cupric ion (CU2+) gets reduced to the cuprous ion (CU+) which forms a red precipitate. =reducing sugar

Question 11: If the anomeric OH group is still free it can ___

Answer:

open up into the open chain aldehyde form therefore making it a reducing sugar (also reducing sugars can undergo mutarotation and exist in either alpha or beta form Question 12: If polysaccharides are built from two or more kinds of subunits they are referred to as..

Answer:

heteropolysaccharide

Question 13: What is the name for a five membered ring and a six membered ring?

Answer:

5=furanose 6=pyranose

Question 14: What is the most important rxn for sugars?

Answer:

glycoside formation Question 15: What is a common property of all sugars?a) taste sweet b)contain OH group c)contain aldehyde group d)have at least 4 C atomse) are reducing agents

Answer:

They all contain an OH group Question 16: Every time another C atom is added to a sugar carbon chain what happens to the number of isomers?

Answer:

doubles Question 17: polysaccharides can have thousands of sugar subunits. If they are all the same subunits it is referred to as ...

Answer:

homopolysaccharide (polysaccharides are often highly branched)

Question 18: All the aldo-hexoses form predominantly ______rings

Answer:

pyranose (ie. glucose has a strong tendency to form pyranose)

Question 19: How is a disaccharide built?

Answer:

from 2 simple sugars by condensation (glycosidic bond) the anomeric C of one sugar is the electrophile and any one of the OH groups of the second sugar is the nucleophile

Question 20: Why do we get different sizes of rings? (pyranose vs. furanose)

Answer:

it depends on the relative stabilities of the possible cyclic products and this depends on the geometry of the molecule.

Question 21: glycogenesis is what type of metabolic pathway?

Answer:

Anabolic - generates glycogen from glucose molecules

Question 22: What is the simplest aldose sugar?

Answer:

glyceraldehyde Question 23: If the OH group points to the left in the fischer formula it goes where in the ring?

Answer:

It goes above the ring in the Haworth formula (OH to the right goes below) *note rule is opposite for L sugars Question 24: Who detected the presence of sugar and measured blood glucose when isolating insulin in the 1920s?

Answer:

Dr. Banting

Question 25: If the anomeric OH group is above the ring what form is it in?

Answer:

beta (left above beta)

Question 26: Why is the anomeric carbon atom of a sugar so reactive?

Answer:

It is the only carbon atom bonded to two O's. H+ is added to the anomeric carbon, H2O is released resulting in a resonance stabilized structure with a free proton therefore making anomeric carbon reactive (can react with alcohol)p.277

Question 27: gluconeogenesis is what type of metabolic pathway?

Answer:

ANABOLIC - generates glucose from non carb carbon substrates Question 28: Looking at the D form of a sugar you should be able to write the L form

Answer:

only the second carbon from the end farthest from the carbonyl group is changed. In D form the OH is on the right.