Chapter 7 Flashcards
What are the physiological roles of carbohydrates?
Sources of energy Energy storage Structural roles Cellular interaction Cellular identification Information transfer (DNA RNA) Signaling
What is the empirical formula of carbohydrates?
(CH2O)n
Where n > or equal to 3
What are the two major classes of carbohydrates?
Aldoses- have aldehyde groups CHO (double bonded O)
Ketoses- have ketose groups
A C attached to two CH2OH’s and a double bonded oxygen
Memorize the 6 common monosaccharide sugars
Aight
What are epimers?
Sugars that differ at a single chiral center (H and OH are switched around)
Ex: C3 epimer of _______
H and OH at third carbon are switched
What happens to carbohydrates of 5 carbons or longer in solution?
They tend to be cyclized
Wrap in a circle
What is the formation of the cyclical structure of carbohydrates a result of?
A reaction of alcohol with either:
- An aldehyde (aldoses) to form hemiacetal
- A ketone (ketoses) to form hemiketal
Look at diagrams on slide 8
What are the two forms of cyclized carbohydrates?
Six-membered sugar ring is a pyranose
glucopyranose
Five-membered sugar ring is a furanose
ribofuranose
What bonds form to create cyclized structures of carbohydrates?
The free hydroxyl of C-5 and the aldehyde group of C-1
What two stereoisomers are produced by C-1 in cyclizing?
α and β
Alpha and beta stereoisomers are produced
α is where the H is above the OH on C-1 on the very right of the molecule
β is where the OH is above the H on C-1 on the very right of the molecule
Alpha and beta are anomers of eachother
On slide 10
What is mutarotation?
Where the α and β configurations interconvert through a linear intermediate
Change in configuration
Diagram on slide 12
Is a carbohydrate is swapped from D to L how does that affect the α and β of the cyclized form?
It will change the α to β or vice versa
Ex: β-L-Fucose has H over OH on C-1
Do practice naming on slide 15
How do plants use glucosinate and myrosinase as defence?
The myrosinase acts on glucosinolate to produce glucose and isothiocyanate which has a sharp and bitter taste
This bitter taste functions to discourage herbivores from eating plant
Slide 16
How do reducing agents work with monosaccharides?
Monosaccharides can be oxidized by mild oxidizing agents like Iron and copper
When this happens the carbonyl group (CHO) is oxidized to a carboxyl group (COOH)
Allows for quantifications of sugars present in blood or urine
What is a gylcosidic bond?
What are the two types?
Primary structural linkage in all polymers of monosaccharides
O-glycosidic bonds occur through oxygen
N-glycosidic bonds occur through nitrogen
How do you name disaccharides?
You put both monosaccharides involved in the linkage together with their beta or alpha configurations and their ring types of either puran or Duran and in between you out the linkage (C1-C4, etc)
What is the reducing end of a polymer?
The end of the chain with a free anomeric carbon (carbon at end with O and H bonded
What generates higher order carbohydrate structures?
The action of glycosyltransferases
These use monosaccharides that are activated through linkage with UDP
When naming disaccharides, what do you put at the end of each individual monosaccharides name?
For the non reducing residue, you put “osyl” at the end
This is the monosaccharide you put first in the name
For the reducing sugar, you put “ose”
At the ends
This is the monosaccharide you put second in the name
What is the difference between galactose and glucose?
Galactose has the hydroxyl group above H on carbon 4 (far left)
Glucose has the hydroxyl group below H on Carbon 4 (far left)
Diagram on slide 22
What are some of the biological function of polysaccharides?
Energy storage, structural roles, cushioning and lubrication, etc
What are homopolysaccharides and heteropolysaccharides?
Homo- polymers containing a single type of monosaccharide
Hetero- polymers containing more than one type of monosaccharide
Both can be branched or unbranched
(Branched being a stacked section of sugars branching from main group)
Slide 24
How is glucose stored in plants compared to animals?
Plants- it’s formed in polymeric forms as starch
Animals- it’s formed in polymeric forms as glycogen
Start and glycogen are both heavily hydrated structures
What is starch?
A mixture of two molecules, amylose (unbranched) and amylopectin (branched)
Found in plants and fungi
Where is glycogen stored?
Structurally identical to amylopectin with higher frequency of branch points (10 residues)
It is stored in the liver and skeletal muscles of animals
Liver to power rest of body and skeletal muscle to power muscles
It’s present in all cells but most prevalent in muscle and liver
What is the structure of amylose and amylopectin?
Amylose- linear polymer of glucose residues through α(1-4) bonds
Amylopectin- consists of α(1-4) linked glucose residues with α(1-6) branch points every 24-30 residues
Diagram on slide 26
What does the greater frequency of branching allow for glycogen?
It allows for rapid mobilization in times of need for energy
What is cellulose?
Primary component of plant cells (fiber)
It is a linear, homopolysaccharide of glucose residues
Linear arrangement of β(1-4) glycosidic residues
Cannot be cut by amylase
What is chitin?
Primary component of hard exoskeletons (insects, lobsters)
Linear, homopolysaccharide of N-acetylglucosamine residues
What is the difference between cellulose and chitin?
The replacement of hydroxyl group at C2 with acetlyated amino group
What are the difference in α and β linkages in terms of chain formation?
α forms hollow helical structure (compact accessible storage)
β forms long straight chains
(Rigid supportive high tensile strength)
How are sugars related to blood group antigens?
Sugars are covalently linked to lipid molecules to form glycolipids
Glycolipids form blood group antigens
Diagram on slide 32
What are glycoproteins compared to proteoglycans?
Glycoproteins- proteins with covalently attached sugars
Protein is largest component by weight
Proteoglycans- protein component is linked to a particular carbohydrate called glycosaminoglycan
Carbohydrate is biggest component by weight
What do sugars attach to on proteins?
- the slide nitrogen of the side chain of an asparagine (N-linked)
- the hydroxyl oxygen of the aids chain of serine or threonine (O-linked)
What is Erythropoietin (EPO)?
EPO is a glycoprotein that stimulates production of red blood cells
Glycosylation is essential for the biological action of EPO
Increases oxygen carrying capacity
Has three N-linked and O-linked glycosylations
