Carbohydrates Flashcards
A carbohydrate is made up of _
C, O and H, with H and O in a 2:1 ratio
What are the two simplest monosaccharides?
Glyceraldehyde and dihydroxyacetone
A monosaccharide is a carbohydrate with _
At least 3C, one in a double bond with oxygen, the others with hydroxyl groups
In aldose sugars, the oxygen group is attached to _
A terminal end of the carbon chain
In ketose sugars, the oxygen group is attached to _
A central carbon
What is the name of the C=O bond group that characterises aldose sugars?
formyl/aldehyde
What is the name of the C=O bond group that characterises ketose sugars?
ketone
Chemical properties of enantiomers are _
Similar/the same
Optical properties of enantiomers are_
Different
Dihydroxyacetone is a _ sugar
Glyceraldehyde is a _ Sugar
Ketotriose/Ketose
Aldotriose/Aldose
What is exceptional about dihydroxyacetone?
It has no chiral carbon atoms
All saccharides with 4 or more carbon atoms _
Have at least one chiral carbon
Aldotetrose sugars are diastereomers. What does this mean?
They have multiple chiral carbon atoms, and multiple pairs of enantiomers
Number of pairs of enantiomers differs between ketose and aldose sugars in what way?
Ketose sugars have one less chiral carbon than aldose at the same total number of carbons.
In a Fischer projection, vertical bonds represent
Bonds existing below the plane
In a Fischer projection, horizontal bonds represent
Bonds existing above the plane
What is the name given to cyclic forms of monosaccharides?
Furanose
What name is given to the cyclic form of aldohexose sugars
Pyranose
The alpha and beta forms of glucopyranose have different _
positioning of hydroxyl group on first carbon
Alpha and beta forms of furanoses are _
Anomers
A typical solution of d-glucose will contain which forms?
Both alpha and beta forms of glucopyranose in mixture. Some of the linear form in small amount
What name is given to the conversion between anomeric alpha and beta forms?
Mutarotation
What are steromers?
Isomers with same sequence of atoms, but with differing arrangement around one or more asymmetric centers
What are epimers?
Diastereomers that differ in structure only at one chiral centre
What two monomeric units compose sucrose (table sugar)?
Glucose and fructose
What two monomeric units compose lactose?
Glucose and galactose
What monomeric units compose maltose?
Glucose and glucose
What is the name given to the linkage between hydroxyl groups on units in disaccharides?
O-glycosidic
Can a unit of a disaccharide convert between its alpha and beta form?
Sometimes, depending on particular arrangement
Why are oligosaccharides significant?
They function as a side chain group for some proteins
What is the name for the process of attaching glycans to protein side chain?
Glycosylation
Where are glycans attached to proteins?
Golgi apparatus
In what way might the units of glycans have been modified?
Some hydroxyl groups may have been replaced by other groups
How do you get glucosamine?
Replace a hydroxyl group on glucose with an amino group
Glycans linked on hydroxyl groups are said to be _
O-linked
Glycans linked on amino groups are said to be _
N-linked
Adding an acetyl group to glucosamine gives _
N-acetylglucosamine
Which molecule is derived from the nine carbon ketose neuraminic acid
N-acetylneuraminic acid
What is a homopolysaccharide?
A polysaccharide with only one kind of monomeric unit
What is a heteropolysaccharide?
A polysaccharide with multiple kinds of monomeric units
Which type of bonding links monosaccharide units in polysaccharides?
Glycosidic
What units make up starch?
Exclusively d-glucose
What are the two type of starch molecules?
Amylose, amylopectin
Roughly what is the range of number of units composing starch molecules?
300-5000+
Which specific bonds link glucose units in both amylose and amylopectin
alpha 1->4 glycosidic
Which bonds are branch points of amylopectin?
1->6
How frequently do branches occur in amylopectin?
Around every 24-30 units in each linear chain
What is the structure that starches take?
Tightly packed in to spherical granules
How does starch function as energy storage?
Glucose units can be cleaved off of ends and used in energy generating processes
What is the non-reducing end of starch molecules?
The glucose units with a free hydroxyl group on carbon number 4
What can a reducing agent do?
Donate electrons to other molecules
for linear configurations, ketose sugars __ aldose sugars
exist in equilibrium with the equivalent
Why are ketose sugars slightly reducing?
In solution there will be a small amount of equivalent aldose sugars
Why is there not a greater amount of interconversion between aldose and ketose sugars in the body?
The process prefers a higher pH
How does the structure of glycogen compare to the structure of amylopectin?
It is very similar, but it has more branching points
Cellulose is a _ chain with _ linkages between _ units
linear
beta 1->4
glucose
Why is cellulose able to give rigidity to structure?
The chains of molecules line up and participate in hydrogen bonding, forming closely associated networks
What polysaccharide is a main component of bacterial cell walls?
Peptidoglycan
Give an example of a heteropolysaccharide with its function
Hyaluronic acid - major component of extracellular matrix - vitreous humor - jelly stuff in the eyeball
How are polysaccharides joined together in peptidoglycan?
By peptide bonds
The group of molecules glycosaminoglycans are disaccharides of
N-acetyl and carboxylated units
Lysozome, an enzyme in tears, saliva and mucus provides protection against bacteria by _
Breaking the beta 1->4 links between units of cell walls
How does penicillin prevent bacterial growth?
It inhibits synthesis of peptidoglycan cell walls
