Biological Molecules Flashcards
What is the general molecular formula for carbohydrates?
Cn(H2O)m
What are the three main functions of carbohydrates?
*Energy storage (e.g., glucose)
*Recognition and interaction (e.g., blood types)
*Structural components (e.g., cell walls)
What is the difference between an aldose and a ketose?
Aldose: A sugar with an aldehyde group (e.g., glucose).
Ketose: A sugar with a ketone group (e.g., fructose)
What are monosaccharides?
Simple sugars that cannot be hydrolyzed into smaller units. Examples include glucose and fructose.
What are the three criteria for classifying monosaccharides?
*Functional group: Aldose or ketose
*Stereochemistry: D or L configuration
*Number of carbons: Trioses (3C), Tetroses (4C), Pentoses (5C), Hexoses (6C), etc.
What is an epimer?
Sugars that differ only by the stereochemistry at a single carbon (e.g., glucose and mannose at C2).
What is a hemiacetal and how does it form?
*A hemiacetal is a functional group that contains both an –OH and –OR group.
*It forms when an aldehyde or ketone reacts with an alcohol.
What is an anomeric carbon?
The carbon that was part of the carbonyl group in the open-chain form and is now linked to two oxygens in the cyclic form
What are the two types of anomers?
α-anomer: The OH group on the anomeric carbon points down.
β-anomer: The OH group on the anomeric carbon points up
What is mutarotation?
The interconversion between α- and β-anomers in solution
What are the three common disaccharides and their glycosidic linkages?
*Maltose: α-1,4’ glycosidic bond
*Lactose: β-1,4’ glycosidic bond
*Sucrose: α-1, β-2’ glycosidic bond
What is the difference between oligosaccharides and polysaccharides?
Oligosaccharides: 3–10 monosaccharide units (e.g., raffinose).
Polysaccharides: Hundreds or thousands of monosaccharide units (e.g., starch, cellulose).
What are the two main types of polysaccharides and examples?
*Storage polysaccharides: Starch (plants), Glycogen (animals).
*Structural polysaccharides: Cellulose (plants), Chitin (exoskeletons)
Why can’t humans digest cellulose?
Humans lack the β-glucosidase enzyme needed to break β-1,4’ glycosidic bonds in cellulose.
What is the significance of glucosamine?
A derivative of glucose with an amino group at C2, commonly used in joint health supplements
How do oxidation and reduction affect sugars?
Oxidation converts aldehydes to carboxylic acids (e.g., glucose → glucuronic acid).
Reduction converts aldehydes or ketones to sugar alcohols (e.g., glucose → sorbitol)
What is a glycosidic bond?
A covalent bond between the anomeric carbon of a sugar and an alcohol or another sugar.
What are the different ways of representing sugars?
*Fischer projection: Linear structure, used to show D/L configuration.
*Haworth projection: Cyclic form, shows α/β-anomers.
*Chair conformation: More accurate 3D representation of the cyclic form.
What are the three main types of carbohydrates?
*Monosaccharides (single sugar units)
*Oligosaccharides (3–10 sugar units)
*Polysaccharides (many sugar units)
How are monosaccharides classified?
*By functional group: Aldoses (contain aldehyde) vs. Ketoses (contain ketone).
*By number of carbons: Trioses (3C), Tetroses (4C), Pentoses (5C), Hexoses (6C), etc.
*By stereochemistry: D-sugars (OH on right in Fischer projection) vs. L-sugars (OH on left).
What are isomers, and what are the types found in monosaccharides?
Molecules with the same molecular formula but different structures.
Structural isomers: Different connectivity (e.g., glucose vs. fructose).
Stereoisomers: Same connectivity, different spatial arrangement (e.g., D- vs. L-glucose).
Epimers: Differ at one carbon only (e.g., glucose vs. mannose at C2).
Anomers: Differ at the anomeric carbon (α vs. β).
What is a Fischer projection?
A 2D representation of sugars showing stereochemistry. The most oxidized carbon is placed at the top.
What is a Haworth projection?
A cyclic representation of sugars, showing α- and β-anomers.
How do you convert from Fischer to Haworth projection?
Groups on the right of the Fischer projection point down in the Haworth projection; groups on the left point up.
What happens when monosaccharides form rings?
The carbonyl group reacts with an OH group to form a hemiacetal (aldoses) or hemiketal (ketoses), creating a ring structure
Name three important disaccharides and their glycosidic bonds
Maltose: α-1,4’ glycosidic bond (glucose + glucose).
Lactose: β-1,4’ glycosidic bond (galactose + glucose).
Sucrose: α-1, β-2’ glycosidic bond (glucose + fructose).
What are the key differences between starch, glycogen, and cellulose?
*Starch: α-1,4’ and α-1,6’ glycosidic bonds, used for energy storage in plants.
*Glycogen: Highly branched α-1,4’ and α-1,6’ glycosidic bonds, energy storage in animals.
*Cellulose: β-1,4’ glycosidic bonds, structural component in plants (not digestible by humans).
What are the major chemical reactions of carbohydrates?
Oxidation: Aldehydes → carboxylic acids (e.g., glucose → glucuronic acid).
Reduction: Aldehydes/ketones → sugar alcohols (e.g., glucose → sorbitol).
Acylation: Hydroxyl groups → esters (e.g., glucose → acetate esters).
Alkylation: Hydroxyl groups → ethers (e.g., methylation using CH₃I).
Glycoside formation: Conversion of hemiacetal to acetal by reacting with alcohols
What is glucose monitoring, and how does it work?
A method to measure blood glucose using electrodes that detect oxidation of glucose by glucose oxidase.
What is glucosamine, and why is it important?
A glucose derivative with an amino group at C2, used in joint health supplements.
What is N-acetylglucosamine (NAG), and what is its role?
A glucose derivative involved in bacterial cell wall structure, forming N-acetylmuramic acid (NAM).
How do carbohydrates determine blood type?
Type A: Contains N-acetyl-D-galactosamine.
Type B: Contains D-galactose.
Type AB: Contains both A and B sequences.
Type O: Lacks both modifications
What does reduction of sugars lead to?
Reduction of sugars results in the corresponding polyalcohol called sugar alcohol or alditol.
Those are widely used in industry, primarily as food additives and sugar substitutes (e.g. Sorbitol,
mannitol – 60% as sweet as sucrose - table sugar).
What does sorbitol do?
Sorbitol is also used in the manufacture of softgel capsules to store single doses of liquid
medicines. As an over-the-counter drug, sorbitol is used as a laxative to treat constipation.
What are some extra reactions of carbohydrates?
Acylation of OH -> ester formation
Acetic anhydride and pyridine convert all the hydroxy groups of a sugar to acetate
esters.
Alkylation of OH -> formation of ethers
Treatment with methyl iodide (CH3I) and silver oxide (Ag2O) converts the hydroxy groups
to methyl ethers.
