Lecture 2: Cell Chemistry II

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Atomic mass of one hydrogen atom

Covalent Bond

-Sharing of electrons to fill orbital
-Strongest, most stable bond between two atoms
-Low energy state (strong, requires energy to break bond)
-Act at a short distance

Resonance

-Electrons are delocalized (shared between carbon atoms)
-Very stable

Non-Covalent Bonds

-Ionic
-Electrostatic Interactions
-Hydrogen Bonds
-van der Waals attractions
-Act at a longer distance
-Reversible (can be broken by heat)

Ionic Bond

-electrons are transferred from one atom to another to fill/empty the outer orbital

cation

Positive Ion

anion

Negative Ion

Electrostatic Interaction

-Similar to Ionic bond
-Between two partial charges rather than two fully charged atoms on separate molecules

Polar

-Can have an overall neutral charge but has non-cancelling dipoles between less and more electronegative atoms. (i.e., Water)

Hydrogen Bond

-Electrostatic interaction between the permanent (+) dipole of Hydrogen and the (-) dipole of an atom on an adjacent molecule.
-Very weak but can occur in massive numbers to increase strength.
-Hold together DNA strands.

van der Waals Attraction

-Continuous flipping of temporary polarization in a covalent bond
-This is because shared electrons are not actually shared identically between the two atoms, even if their electronegativity is similar or identical
-Much weaker than hydrogen bonds

Condensation

A-OH + B-OH ⇌ A-O-B + H₂O

-Release of water.

Hydrolysis

A-O-B + H₂O ⇌ A-OH + B-OH

-Breaks water and a polymer, then binds an -OH group to each monomer in question.

Metabolism

Set of chemical reactions occurring in a living organism in order to maintain life.

Anabolism

-Set of chemical reactions that build cellular order.
-Usually requires energy input.

Catabolism

-Set of chemical reaction that break down cellular macromolecules.
-Usually releases energy as heat.

Hydrophilic Molecules in H₂O

-Charged and polar compounds are easily dissolved in water.
-Water will orient and neutralize charge or polarization.

Hydrophobic Molecules in H₂O

-The lack of polarized bonds makes it difficult for water to orient and surround the molecule.

Unsaturated Fatty Acid

-Contain C-C double bonds.

Saturated Fatty Acid

-Contains no C-C double bonds.
-Full C-H saturation.

Triacylglycerols (Triglycerides)

-Link of up to three fatty acids to one molecule of glycerol.
-Efficient, high density energy storage.
-Condensation reaction of monomers forming oligomers.
-Not a "true" polymer because it is limited to three.

Phospholipids

-two fatty acids
-a glycerol
-a charged head group

Saccharides

-Simple carbohydrates
-Formula is (CH₂O)n where n is generally 3-7
-Have reactive aldehyde/ketone (C=O) and hydroxyl (OH) groups
-Exist in open and closed form

Glycogen

-Highly branched structure
-Created from condensation of multiples glucose sugars
-Can be hydrolyzed back to individual sugars and converted to useful energy

Cellulose

-Straight chain structure
-Requires a dedicated set of enzymes