Chapter 11: Carbohydrates and Glycoproteins

Monosaccharides are the

Simplest carbohydrates

What is carbohydrates?

Carbon-based molecules high in hydroxl groups

Carbohydrates can have

Additional groups of modifications

Carbohydrates are also called 

Polyhydroxyl aldehydes and ketones (and their derivatives)

How many carbons in length are there in carbohydrates?

3-7

Monosaccharides exist in what froms?

Many isomeric forms

Carbohydrates are also called

simple sugars

What is a 3 carbon monosacchaide?

trioses

What is a four carbon monosaccharide?

Tetroses

What is a 5 carbon monosaccharide?

Pentoses

What is 6 carbon mononsaccharide?

Hexoses

What is a seven carbon monosaccharide?

Heptoses

Nomenclature is also based on?

The identity of the most oxidized group

What is a keto group in monosacchaide?

Ketose

What is a aldehyde group in monosaccharide?

Aldose

What are constitutional isomers?

Molecules with identical molecular formulas that differ in how the atoms are ordered

What is a stereoisomer?

Molecules that differ in spatial arrangement but not bond order

Stereoisomers have either what configuration?

L or D

Stereoisomers can be

Enantiomer (mirror images of each other) or diastereoisomers (not mirror images of each other)

What is number possible in stereoisomers?

2n where n is the number of asymmetric carbon atoms

What is a common monosaccharides?

Epimers

What is an epimer?

Sugars that are diastereoisomers differing in configuration only at a single asymmetric center

Most monosaccharides exist as

Interchanging cyclic forms

An aldehyde can reat with

An alcohol to form a hemiacetal

A ketone ca react with

An alcohol to form a hemiketal

Pyranose formation is called pyranose because

Of similarity to pyran

Furanose formation is called furanose because

Of similarity to furan

What is an anomer?

A diastereoisomeric form of sugars that forms when a cyclic hemiacetal is formed and an additional asymmemtric center is created

In glucose, C-1 (the anomeric carbon atom) becomes..

An asymmetric center, forming 2 ring structures

α-D-glucopyranose (hydroxyl group attached to C-1 is on
the opposite side of the ring as C-6)
– β-D-glucopyranose hydroxyl group attached to C-1 is on
the same side of the ring as C-6)

4 dis

D-fructose rapidly interchanges between?

4 distinct ring structures

What is the anomeric carbon atom in D-fructose ?

C-2

The pyranose form predominates in solution due to

Reduced steric hindarances

The furanose form predominates in

fructose derivativesT

The most common monosaccharides exist primarily in

Their ring forms

Pyranose and frunanose rings can assume

Different conformations

Pyranose rings are not planar because

Of the the tetrahedral geometry of its saturated carbon atoms

Pyranose and furanose canadopt two types of conformation:

Boat and chair

In chai form, substituents on the carbon ring atoms can be

Axial (nearly perpendicular) or equatorial (nearly parallel)

Axial substituents sterically hinder each other if 

On the same side of the ring

The chair form predominates because

All axial positions are occupied by hydrogens

The boat form is disfavored because

It is sterically hindered

What is an important fuel for most organisms?

D-glucose

What is blood sugar?

D-glucose circulating in the blood

Blood sugar only fuel used by

The brain in non-starvation conditions

Blood sugar only fuel used by

Red blood cells

What are potential reasons why D-glucose is important fuel:

• glucose is formed from formaldehyde under prebiotic conditions and may have been available as a fuel source for primitive biochemical systems 

• Glucose is relatively inert

• The most stable ring structure is B-D-glucopyranose

What is glycation?

Nonenzymatic addition of carbohydrate ot another molecule

What is an example of glycation?

Reducing sugars nonspecifically react with free amino groups on proteins (often Lys or Arg) to form a stable covalent bond

G-glucose has a low tendency to glycate proteins unless

Concentrations of sugar and protein are very high for long periods of time

Advanced glycation end products (AGEs)

Products resulting from corss-linking following the primary modification

AGEs are implicated in

aging, arteriosclerosis, diabetes, and other pathological conditions

Assessing treatments for diabetes mellitus by

Monitoring A1C levels

D-glycose reacts with what to form what??

Hemoglobin to form glycates hemoglobin (hemoglobin A1c, A1C)

In nondiabetic individuals, <6% of the hemoglobin is

Glycated

In patients with uncontrolled diabetes,

Almost 10% of the hemoglobin is glycated

Monosaccharides are joined to ? Through what?

Alcohols and amines through glycosidic linkages

Monosaccharide biochemical properties can be modified by reactions with"?

• alcohols

• Amines

• Phosphates

Modifications increase biochemical versatility can serve as

Signal molecules

Modifications increase biochemical versatility can facilitate

Metabolism

O-glycosidic linkage

Covalent linkage formed between the anomeric carbon atom of a carbohydrate and the oxygen atom of an alcohol

N-glycosidic linkage

Covalent linkage fromed betweent eha nomeric carbon atom of a carbohydrate and the nitrogen atom of an amine

Monosaccharides can be modified by the

Addiction of substituents other than hydroxyl groups

Phosphorylated. sugars are

Key intermediates in metabolism

Phosphorylation is a common modification of sugars in

Metabolic reactions

What is the purpose of phosphorylated sugars?

• makes sugars anionic to prevent crossing the lipid bilayer membranes and interacting with transporters of the unmodified sugar

• BLocks the formation of alternative ring conformation

• Creates reaction intermediates that more readily undergo metabolism

Several intermediates in the breakdown of glucose are

Phosphorylated sugars

Monosaccharides are linked to

Form complex carbohydrates

What is oligosaccharides?

Sugars that contain two or more monosaccharides linked by O-glycosidic bonds

Oligosaccharides have directionality defined by

Their directionality defined by their reducing and nonreducing ends

What is reducing end?

Has a free anomeric carbon atom that can form the open-chain form

What is nonreducing end?

Has an anomeric carbon in a glycosidic linkage that cannot convert to the open chain form

Maltose is

A disaccharide of D-glucose

a-1,4-glycosidic linkage?

glycosidic linkage between the a-anomeric form of C-1 on one suguar and the hydroxyl oxygen atom on C-4 of the adjacent sugar

What are common disaccharides?

Sucrose, lactose, and maltose

What is a disaccharide?

Two sugars joined by an O-glycosidic linkage

Cleavage of products of disaccharides can be processed to provide energy in the form of?

ATP

What is sucrose?

Disaccharide of sugar can or sugar beets that consists of glucose linked to fructose

The anomeric carbon ofo glucose is linked to the

Anomeric carbon of fructorse

In sucrose, the configuratioin is

a for glucose and b for fructorse

Sucrose is or is not a reducing sugar

Is not

Sucrose can be cleaved by?

Sucrase (invertase)

What is lactose?

disaccharide of milk that consists of a galactose linked to a glucose

Lactose is linked by

A b-1, 4-glycosidic. l inkageL

actose can be hydrolyzed by

Lactase in human beings and by B-galactosidase in bacteria

Lack of lactase leads to

Lactose intolerance

What is maltose?

A disaccharide resulting from the hydrolysis of large oligoaccharides that consists of two linked. glucose molecules

Maltose is joined by?

a-1, 4-glycosidic linkage

Maltose can be hydrolyzed to?

Glucose by maltose (a-glucosidase)

Human miilk oligosaccharides protect newborns from

Infection

How many oligosaccharides have been nidentified in human milk?

>150

Is oligosaccharides digested by breastfed infant?

No

Oligosaccharides play a significant role in

Protecting them against bacterial infection 

These oligosaccharides may serve as?

A fuel source for beenfical bacteria

These oligosaccharides may prevent?

the attachment of microbial pathogens to the intestinal wall of the newborn

Glycogen and starch are

Storage forms of glucose

Free glucose cannot be stored because

High concentrations will disturb the cell’s osmotic balance

What are polysaccharides (glycans)?

Large polymeric oligosaccharides formed by the linkage of multiple monosaccharied

Polysaccharides play roles in?

Energy storage and structural integrity

What is homopolymer?

Polymer in which all the monosaccharide units are the same