Principles of Biochemistry Exam 3

Isolated systems

exchange neither matter nor energy with their surroundings.

Closed systems

may exchange energy, but not matter, with their surroundings.

Open systems

may exchange either matter or energy with the surroundings.

Chemotrophs (heterotrophs)

require food molecules that can be oxidized to produce chemically useful energy.

Phototrophs (autotrophs)

obtain their energy by converting the energy of sunlight into a chemically useful form.

Metabolism

the chemical reactions of biomolecules (anabolic + catabolic)

Catabolism

the breakdown of larger molecules into smaller ones; an oxidative process that releases energy

Anabolism

the synthesis of larger molecules from the synthesis of larger molecules from smaller ones; a reductive process that requires energy

The First Law of Thermodynamics

states that the total energy of a system + surroundings always remains constant.

Change in energy of a system depends on ___

the initial state and final state, not on the pathway of the transformation. Cannot be used to predict the spontaneity of a reaction.

The Second Law of Thermodynamics

a process or reaction can occur spontaneously only if the sum of the entropies of the system + surroundings increases

Oxidation

the loss of electrons; the substance that loses the electrons is called a reducing agent.

Reduction

the gain of electrons; the substance that gains the electrons is called an oxidizing agent.

Carbohydrate

a polyhydroxyaldehyde or polyhydroxyketone, or a substance that gives these compounds on hydrolysis

Monosaccharide

a carbohydrate that cannot be hydrolyzed to a simpler carbohydrate. Will have -OH and C=O in the same molecule.

Aldose

a monosaccharide containing an aldehyde group

Ketose

a monosaccharide containing a a monosaccharide containing a ketone group

D-monosaccharide

a monosaccharide that, when written as a Fischer projection, has the -OH on its penultimate carbon on the right

L-monosaccharide

a monosaccharide that when written as a Fischer projection, has the -OH on its penultimate carbon on the left penultimate carbon on the left

Hemiacetal

Interactions between functional groups on C1 and C5 create a cyclical sugar with a carbonyl carbon as the new chiral center

Hemiketal

Interactions between functional groups on C2 and C5 create a cyclical sugar with a carbonyl carbon as the new chiral center

Anomeric carbon

the new stereocenter resulting from cyclic hemiacetal formation

Anomers

carbohydrates that differ in configuration only at their configuration only at their anomeric carbons

-pyran-

Infix for six-membered hemiacetal ring. Ring used for confirmation depiction.

-furan-

Infix for five-membered hemiacetal ring. Haworth projection used for confirmation depiction.

Tollens Reagent

Uses Ag(NH3)3+ as an oxidizing agent. Presence of a reducing sugar (anomeric carbons) will result in silver mirror on the test tube wall.

Alditol

Reduction of the C=O group of a monosaccharide

Deoxy sugar

a sugar in which one of the hydroxyl groups has been reduced to a hydrogen

Glycoside

Carbohydrate in which the -OH of the anomeric carbon is replaced by -OR

Derived from furanoses = furanosides; pyranoses = pyranosides

Glycosidic linkage

responsible for the bonding of monosaccharides to form oligosaccharides and polysaccharides

Phosphoric esters

formed by transfer of a phosphate group from ATP. important in the metabolism of sugars to provide energy

Anthocyanins

Sugars bonded to cyanidin responsible for red and blue pigment in some flowers.

Sucrose

(Table sugar) One unit of D-glucose and one unit of D-fructose joined by an a-1,2-glycosidic bond.

Lactose

Found in milk. Made up of D-galactose and one unit of D-glucose joined by a a-1,4-gylcosidic bond

Maltose

Two units of D-glucose joined by an a-1,4-glycosidic bond. Formed from the hydrolysis of starch. Differs from cellobiose by the conformation of the glycosidic.

Polysaccharide

many monosaccharides linked together

Cellulose

Major structural component of wood and plant fiber. Intra- and intermolecular hydrogen bonding between chains with alternating 180° flips of glucose units.

Starch

used for energy storage in plants cells