BioChemistry Exam #2 Key Terms

Biomolecule

Refers to organic compounds that are essential to life

BioChemistry

Study of the compounds and processes that are associated with living organisms

What are important functions of carbohydrates?

• Humans cellular metabolism

• Plants solar energy

• Providing energy through their oxidation

• Supplying carbon for synthesis of cell compounds

• Stored form of chemical energy

• Forming parts of structural elements of cells and tissues

Carbohydrates

C,H, and O with an aldehyde or ketone functional group and a polyhydroxy (OH) group

Monosaccharide

Simple carbohydrate most commonly with 3-6 carbon atoms

Disaccharide

Carbohydrate formed by a combination of two monosaccharide unites

Polysaccharide

Carbohydrate formed by combination of many monosaccharide units

Oligosaccharide

Carbohydrate chain with 3-10 units

Isomer

Same chemical formula with variation in how atoms are connected or spatial arrangement

Structural Isomer

Differ only in atom connectivity

Stereoisomers

Differ in spatial arrangement (cis and trans) but also now includes optical isomers

Optical Isomers

Ability to rotate the plane of plane-polarized light

• Leads to variations in properties

• Has relevance in drug effectiveness

Dextrorotatory

(+) rotates polarized light to the right or clockwise

Levorotatory

(-) Rotates polarized light to the left or counterclockwise

Superimposable

When you lay one object upon another all parts coincide exactly

• Example: right and left hands are mirror images but not super imposable, they are chiral objects

Chiral Carbons

Requires four different groups/atoms attached to main carbon, required for optical activity, does NOT have a plane of symmetry

Enantiomers

Stereoisomers that are non-superimposable mirror images

• L and D designations

  • L larger group on left

  • D larger group on right

Chiral

Compounds/objects that cant be superimposed on their mirror images

What is the formula for maximum of stereoisomers for chiral carbons?

2^n where n= the number of chiral carbons

Fischer Projections

Have the carbonyl at or near the top and the hydroxyl group on chiral carbon farthest from the carbonyl group determines whether L or D designation

Racemic Mixture

Rotates light 0 and is not optically active

• Drugs can be driven in a racemic mixture, but can limit potency and sometimes have problematic complications

How to classify monosaccharides?

As either an aldehyde (aldose) or as a ketone (ketose) and then by number of carbon atoms (triose, tetrose, etc.)

Physical Properties of Mononsaccharides

• Most of them are called sugars because of their sweet taste

• All carbohydrates are solid at room temperature

• Extremely water soluble because of the many -OH groups forming H bonds

Pyranose Ring

Six membered ring containing an oxygen atom. OH group on carbon 5 adds to aldehyde group on carbon 1.

Furanose Ring

Five-membered carbon ring containing an oxygen atom. OH group on carbon 5 atom adds to ketone group on carbon 2.

What happens to the carbonyl carbon when a monosaccharide is cyclized?

Former carbonyl carbon is now chiral and called anomeric.

Anomeric Carbon

Acetal, Ketal, Hemiacetal, or Hemiketal Carbon atom giving rise to two stereoisomers during cyclization (creates alpha and beta option)

Alpha Anomer

-OH group on anomeric carbon points down

Beta Anomer

-OH group on anomeric carbon points up

Anomer

Stereoisomer that differs in 3D arrangement of groups at Carbon of an acetal, ketal, hemiacetal, or hemiketal

Haworth Structures

• Draw ring with oxygen to its back

• Put anomeric carbon on the right side

• Enivsion it planar with up or down

• The CH2OH group is always shown above the ring for D-mono.

Reducing Sugars

Sugar that can be oxidized by weak oxidizing agent. Monosaccharides are reducing sugars.

Phosphate Esters

The -OH groups of monosaccharides can behave as alcohols and react with acids to form phosphate esters

Glycoside

Name for a carbohydrate containing an acetal or ketal group. Formed when cyclic mono. reacts with alcohols in presence of an acid. Are NOT reducing sugars.

Glycosidic Linkage

New carbon-oxygen-carbon linkage that joins components of glycoside to the ring.

Ribose

Important mono. A pentose. Forms long chain of RNA

Deoxyribose

Important mono. Forms long chain of DNA, pentose.

Glucose

Important mono.

• Hexose

• The most nutritionally important mono.

• Called dextrose or blood sugar

• All sugars in body converted to this in the liver

Galactose

Important mono.

• Hexose with a similar structure to glucose

• Component of lactose (milk sugar)

• Present in nerve tissues

Fructose

Important mono.

• Most important ketohexose

• Sweetest mono.

• In corn syrup and fruit sugar

Disaccharide

Two mono. unites linked together by glycosidic linkages

How are glycosidic linkage identified?

By the numbers associated with the Carbon atoms joined by the linkages and the configuration of linkage for any anomeric carbon joined by the linkage.

Maltose

Important Disac.

• Two glucose units joined by an alpha 1-4 linkage

• Formed in digestion of starch

• In germinating grain

• Reducing sugar

• Forms two D-glucoses when hydrolysis occurs

Lactose

Important Disac.

• Galactose and Glucose joined by a beta 1-4 linkage

• Milk Sugar

• Reducing Sugar

Sucrose

Important Disac.

• Fructose and Glucose joined by alpha 1 and beta 2 linkage

• Household sugar, in fruit juices

• Not a reducing sugar

• Hydrolyzed to produce invert sugar

Invert Sugar

Mixture of equal amounts glucose and fructose

Polysaccharides

• Condensation polymer, can be thousands of units.

• Not water soluble, but each individual -OH group can hydrated individually

• Can form thick colloidal dispersions when heated in water (ex. starch)

Starch

Important poly.

• D-glucose units

• Major storage form in plants

• Amylose and amylopectin can be isolated

• Test for presence of starch with Iodine, will turn a dark blue color

What can you use to test for the presence of Starch?

Iodine

Glycogen

Important Poly.

• Glucose unites

• Animal starch, used by animals to store glucose

• Highly branched

Cellulose

Important Poly.

• D-glucose units

• Important structural polymer

• In plant cell walls

• Linear polymer with beta 1-4

Saponifiable Lipids

Contain esters that are hydrolyzed under basic conditions, classified based on number of components in structure (simple or complex)

Simple Lipids

Contain one or more fatty acids and an alcohol

Complex Lipids

Contain more than two types of components (alcohol, fatty acids, etc)

Nonsaponifiable Lipids

Do not contain esters and cannot be hydrolyzed

Functions of Lipids

• Repel water

• Energy rich compounds with low densities

• Structural components in cellular membrane

Fatty Acids

The building blocks of lipids, long-chain carboxylic acids

Micelle

Spherical cluster of molecules with polar chains on surface and nonpolar chains interior. Important biological functions in transport of insoluble lipids in the blood.

Characteristics of Fatty Acids

Usually straight chained-carbon carboxylic acids.

10-20 carbons, usually an even number

Can be both saturated or unsaturated

Characteristics of Unsaturated Fatty Acids

• Cis-configurations creates a kink that prevent chain from closely packing together

  • Weaker intermolecular forces

  • Fatty acids liquid at room temp.

• Melting point decreases as number of carbon double bond increases

Essential Fatty Acids

Not synthesized in body, so must be obtained through the diet

• Linoleic- Omega 3 Fatty Acid

• Linolenic- Omega 6 Fatty Acid

Used to produce hormone like substances that regulate

• Blood pressure and clotting

• Blood lipid levels

• Immune and Inflammation response

What are fats and oils?

Esters that contain an alcohol portion from glycerol, and an acid portion by a fatty acid

Triglycerids

Are the result of an esterification process

Fats

• Animal sources

• Solids at room temp

• Primarily tryglcerides of long chain saturated fatty acids

Oils

• Plant and fish sources

• Liquids at room temp

• Triglycerides that are primarily unsaturated fatty acids