BIBC 100 Midterm 3

What are the three main types of carbohydrates?

Monosaccharides, oligosaccharides, polysaccharides.

What is a monosaccharide?

A single polyhydroxy aldehyde or ketone unit

Give examples of monosaccharides.

Ribose, D-glucose, fructose, galactose.

What are oligosaccharides?

Carbohydrates with 2-20 monomers

Give examples of disaccharides.

Sucrose, lactose, maltose

What are polysaccharides?

Carbohydrates with 20+ monomers

Give examples of polysaccharides and their functions

Starch (plant energy storage), glycogen (animal energy storage), cellulose (plant structure)

What are the characteristics of monosaccharides?

Colorless, water-soluble, crystalline, containing a carbonyl group and two or more hydroxyl groups.

What is an aldose?

A monosaccharide with an aldehyde group (carbonyl at the end)

What is a ketose?

Monosaccharide with a ketone group (carbonyl at any position other than the end)

What is this?

Ketone

What is this?

Aldehyde

How are 4-carbon and 5-carbon ketoses named

By inserting “ul” into the name of the corresponding aldose

How would you name a ketone ribose?

ribulose

What is a chiral carbon?

A carbon atom attached to four different groups.

How do you determine the number of possible stereoisomers for a monosaccharide?

2^n, n = # chiral carbons

L vs D isomers?

L-isomers have OH on the left, D-isomers have OH on the right

What is a Fischer projection?

A 2D, vertical representation of a 3D carbohydrate

What is an anomeric carbon?

The carbon derived from the carbonyl group during cyclization of a sugar

How do you distinguish between alpha and beta anomers?

In alpha anomers, the OH group is opposite to the CH2OH group; in beta anomers, they are on the same side.

Is this an alpha or beta anomer

alpha

Is this an alpha or beta anomer?

Beta

What is a glycosidic linkage?

A bond formed between an anomeric carbon and a hydroxyl carbon of another monosaccharide

What are homopolysaccharides?

Polysaccharides made of repeating monosaccharide units

Give an example of homopolysaccharides and their functions

Starch/glycogen (energy storage), cellulose (Structural support)

What are heteropolysaccharides?

Polysaccharides made of different monosaccharide units

Give examples of heteropolysaccharides

agarose, peptidoglycan, hyaluronan, heparin

Describe starch

Plant storach polysaccharide containing unbranched amylose and branched amylopectin

is amylose branched or unbranched

unbranched

is amylopectin branched or unbranched

branched

describe glycogen

animal storange polysaccharide, stored in liver and muscle

describe cellulose

linear, unbranched homopolysaccharide with D-glucose residues

what kind of glycosidic linkages does cellulose have?

beta 1-4

what are the primary functions of carbohydtrates?

energy source, stuctural support, protection

why store carbs as polymers and not monomers?

to avoid high osmotic pressure that would cause cells to be lysed

what is a puranose

six membered ring

does a puranose always have 6 carbons?

no

furanose

five membered ring

does a furanose always have 5 carbons?

no

How do you identify the anomeric carbon?

it’s usually carbon #1 and drawn on the far right corner in hexagon/pentagon shapes

what is sucrose made of

glucose and fructose

what is lactose made of

glucose and galactose

what is maltose made of

glucose and glucose

ketose or aldose

ketose

ketose or aldose

aldose

what’s the name for a 6 carbon aldose?

aldohexose

what’s the name for a 4 carbon ketose?

ketotetrose

what’s the name for a 5 carbon monosaccharide? (unspecified aldose/ketose)

pentose

what monosaccharide is not a chiral compound?

dihydroxyacetone

why does stereochemistry matter?

interactions between biomolecules are stereospecific

are most biologically relevant monosaccharides L or D?

D

what kind of glycosidic linkage is common in sucrose?

alpha 1-2

what kind of glycosidic linkage is common in trehalose?

alpha 1-1 linkage

how often do branches occur in amylopectin?

24-30 residues

how often do branches occur in glycogen?

8-12 residues

why is having more branching more efficient?

more branches —> more ends —> faster hydrolysis —> sugars released faster

what kind of linkage is found in amylose

alpha 1-4

what kind of linkage is found in amylopectin

alpha 1-6

what kind of linkage is found in glycogen

alpha 1-4 and alpha 1-6

where are storage carbohydrates usually located?

amyloplasts, liver, skeletal muscle

why can’t vertebrate animals digest cellulose?

we can’t break the beta 1-4 linkages

what is this

cellulose-diagram

what is this

amylose-diagram

what is this

amylopectin-diagram

what is this

cellulose-shape

what is this

glycogen-diagram

what is this

amylopectin-shape

what is this

amylose-shape

what is this

glycogen-shape

which carbohydrates are plants?

cellulose, amylose, amylopectin

which carbohydrates are animal?

glycogen

why is h bonding important for polysaccharide folding?

they have lots of hydroxyl groups

what do polysaccharide folding conformations favor?

h-bonding

what kinds of bonds dictate polymer subunits?

covalent

what kind of bonds stabilize 3d polymer structures?

weak interactions: h bonds, hydrophobic, van der waals, electrostatic

what do amylose chains form

helices

why can we stain starch blue?

amylose helix can hold iodine

what does cellulose form?

rigid chain

how does cellulose form it’s conformation?

hydrogen bonds between cellulose strands

what are exoskeletons made of?

chitin, second most abundant polysaccharide in nature

what is agarose composed of?

repeating dimers of D-galactose

what kind of linkages are in agarose?

beta 1-4 linkage to 3-6 anhydrogalactose

what do agarose polymers form?

double helix crosslinked together

what is peptidoglycan made of?

repeating disaccharides (NAG and NAM)

what kind of shape does peptidoglycan form?

strong sheet structure with chains cross linked together

describe the general structure of a lipid

hydrophilic polar head, hydrophobic nonpolar tail

Fatty Acid Nomenclature Names

chain length:# double bonds (double bond location)

saturated fatty acid

no double bonds, straight and packed closely together

what stabilizes saturated fatty acid structure?

hydrophobic and van der waals forces

do saturated fatty acids have high or low melting points

high

what does desaturation do for a fatty acid?

a kink in hydrocarbon chain that prevents close packing

more double bonds = __ bends = __ interactions = __ melting point

more, weaker, lower

longer chain = __ interactions = __ melting point

more, higher

what are the five classes of structural fatty acids?

glycerophospholipids, galactolipids/sulfolipids, archaea tetraether lipids, sphingolipids, cholesterols

describe the general structure of a glycerophospholipid

glycerol backbone with two fatty acids ester linkaged together

what is this

glycerophospholipid

describe the general structure of a galactolipid

galactose residues forming a sugar headgroup glycosidicly linked to C3 of the glycerol backbone with no phosphate

what differentiates a sulfolipid from a normal galactolipid?

sulfolipids have a sulfated sugar as their head group, allowing them to carry a negative charge

what is this

galactolipid

what is this

sulfolipid