Chapter 4 - Carbohydrates Flashcards
What is the empirical formula of carbohydrates
CH2O
Carbohydrates possess 2 functional groups. What are they?
Carbonyl and hydroxyl
Carbohydrates are ____ in water
soluble
Why do animals use carbohydrates?
for RAPID energy production
What do animals use for long term energy storage?
lipids
Why are sugars more dense than lipids?
More oxygen atoms and they can form H bonds with water
Besides providing energy, what are 2 other functions of carbohydrates?
cell to cell recognition and cell signaling
What are the simplest sugars?
Monosaccharides
Explain the structure of a monosaccharide
1 Carbonyl group attached at the first or second carbon. The remaining carbons have hydroxyl groups attached
What are the 2 classes of monosaccharides
Aldose and Ketose
Ketose have the carbonyl attached at carbon __ while aldose have the carbonyl attached at carbon ____
ketose - carbon 2
aldose - carbon 1
What is the suffix commonly used to define a compound as a sugar
-ose
Sugars have general category names. What is the smallest? What are the 2 exceptions to this naming rule?
triose
2 exceptions are the simplest monosaccharides: glyceraldehyde and dihydroxyacetone
Describe the structure of dihydroxyacetone
symmetrical molecule. 3 carbons. Middle carbon has a carbonyl group attached and the 2 carbons on the ends have -OH groups
Describe the structure of glyceraldehyde
asymmetrical molecule with 1 chiral center. 3 carbons with a carbonyl group on carbon 1 and OH groups attached to the other 2 carbons
What are enantiomers
non superimposable mirror images
What is the greatest significance of enantiomers
Their selective interaction with enzymes
Living systems can metabolize L or D sugars??
D
What are epimers?
Sugars that differ at chiral centers (other than the D/L positions)
Sugars having ____ or more carbons primarily exist in solution as ring form
5
How are carbohydrate rings formed?
Intramolecular nucleophilic substitution in which an OH attacks the carbonyl carbon. These reactions can be hemi acetal or hemiketal
What is the difference between alpha and beta conformations in a cyclic carbohydrate?
If the OH group on the carbon to the right of the oxygen atom is facing up, it is beta. Down, it is alpha
Why are there alpha and beta versions of cyclic sugars in the first place?
The OH can attack from either side
What is the anomeric carbon of the straight chain form of a sugar?
the carbonyl carbon
only ___ and ___ membered rings are stable
5 and 6
The alpha, beta, and open chain conformations are in ________ with each other
equilibrium
2 sugars bonded together are called _________
disaccharides
What are the 3 major monosaccharides??
1, Fructose
2. Glucose
3. Galactose
What is the chemical name for table sugar and how many sugars are in it?
sucrose. It’s a disaccharide
Maltose is a partial digestion of ______ and is common in the production of ______
starch, beer
The linkage between 2 sugars is called a….?
glycosidic bond
maltose is composed of which 2 sugars?
2 molecules of glucose formed from the removal of water
Maltose is considered a _______________. Why?
Maltose is considered a reducing sugar because of the presence of the carbonyl
What classifies a reducing sugar?
Any saccharide that has at least one free anomeric carbon(not involved with glycosidic bond)
name 2 reducing sugars and 2 nonreducing sugars
REDUCING: maltose and lactose
NONREDUCING: sucrose and trehalose
Give the definition of polymers.
Large molecules that are constructed from small, repeating units
What is amylose composed of and how is it linked?
Amylose is biological polysaccharide composed of glucose molecules linked together by alpha 1,4 glycosidic bonds
All UNBRANCHED polysaccharides have a ________end and a _________end. Why?
reducing end, nonreducing end. The anomeric carbon is engaged in a glycosidic bond on one side and not the other. Not engaged = reducing
Which linear form of glucose is linked by BETA 1,4 bonds?
cellulose
Why is cellulose so strong?
All of the hydrogen bonds that exist between glucose molecules
Is cellulose soluble in water? Why or why not?
NO. NOT SOLUBLE. Cellulose has so many hydrogen bonds within itself that it cannot withstand more.
What is the most abundant molecule in the world and where is it primarily found?
cellulose - cell walls, wood
What is an important reason that animals use polysaccharides as energy storage??
Reduces osmotic pressure. Osmolarity only depends on the number of molecules, not the size. This is important because animal cells need to maintain equal levels of water on both sides of their plasma membrane. They can still have a glucose reservoir
What does having a cell wall do for plants?
Their osmotic pressure can be very high without the cell bursting. cell wall is composed of cellulose
How is amylopectin linked?
Alpha 1,4 AND 1,6 linkages
Starch is a mixture of ____ and ____
amylose and amylopectin
In which 2 places in the human body is glycogen mainly found
liver, muscles
What is the function of the liver?
Stores glycogen and releases glucose into the blood stream in times of fasting
What 2 sugars is sucrose composed of
fructose + glucose
What 2 sugars is lactose made of
glucose + galactose
What is a major class of polymers?
Polysaccharides
Alpha or beta — which forms a completely straight chain?
beta. alpha will curve a bit
Many simple modifications of carbohydrates modify….?
hydroxyl groups by a phosphate ester
alcohol—–>aldehyde—-> carbonyl is oxidation or reduction??
oxidation
aldehyde—–> alcohol is oxidation or reduction???
reduction
What is formed when an oxygen is replaced with a nitrogen??
glucosamine
How are deoxy sugars formed??
a hydroxyl group is replaced with an H
How can POLYsaccharides be modified?
Having an internal oxygen bridge between C3 and C6
Agarose + agaropectin =
agar
What are the components of a nucleotide?
- Nitrogenous base
- Sugar
- At least one phosphate ester
Which bases have double rings and what are their names?
purines = adenine and guanine
What are the components of nucleosides?
- Base
- Sugar
Describe the structure of DNA
2 strands covalently linked by hydrogen bonds between bases
There are 2 classes of glycoproteins. What are they?
N-linked and O-linked
What is the sweetest sugar?
fructose
Ribose is a ____ose
pentose
Glucose, fructose, and galactose are all ___ose
hex
Are DL and RS the same in stereochemistry of carbohydrates??
no - DL is more about rotational properties
What is a glycosidic bond and how is it formed
covalent bond between 2 monosaccharides. Formed by dehydration synthesis
Does the formation of a glycosidic bond require energy?
YES. most of the time building molecules requires energy
Give 2 reasons why there is branching in glycogen
- Packing for more glucose in limited space
- Reduces osmotic pressure
