BSCI 1510 Exam 1

Cell Theory

* All living organisms are composed of one or more cells
* The cell is the structural unit of life
* Cells can only arise from the division of pre-existing cells

Why is life an autocatalytic process?

Cells produce everything they need to self-replicate and this process can recycle its products to restart transcription.

The Central Dogma

In all living cells, genetic information flows from DNA to RNA (transcription) and from RNA to protein (translation).

However, RNA can go through reverse transcription and become DNA, and proteins can be recycled into RNA

Why are viruses nonliving?

They cannot self replicate without a host and do not undergo metabolic processes.

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They do contain genetic material wrapped in a protein coat.

Cells

Fundamental unit of life

Cell Visualization

Done by techniques such as staining, refractive index, and electron microscopy (in dead cells only)

Prokayrotes

* small
* no nucleus
* no membrane bound organelles
* no cytoskeletal filaments

Eukaryotes

* large
* contains nucleus
* contains membrane-bound organelles
* contains cytoskeletal filaments

Rank bonds from strongest to weakest:

* Ionic, covalent, e stat, h -bonds, hydrophobic interactions, van der Waals
* Covalent, Ionic, e stat, h -bonds, hydrophobic interactions, van der Waals
* h-bonds, covalent, e stat, ionic, hydrophobic interactions, van der Waals

Ionic, covalent, e stat, h -bonds, hydrophobic interactions, van der Waals

Diatomic elements

when elements get too close, the nuclei repel each other; when they get too far, they have no attraction at all. At the right distance, they form a covalent bond.

* H, N, F, O, I, Cl, Br
* (His Nose Fell Off In Cold Brew)

Covalent bonds

sharing of electrons

Ionic bonds

transfer of electrons

Nitrogen makes

triple bonds

Oxygen makes

double bonds

Electronegativity trend

increases up and to the right

Polarity

a polar molecule is a molecule composed of elements with different electonegativities

Methyl (CH3)

nonpolar

Amino (NH2)

positive

Carboxyl (COOH)

negative

Carbonyl (C=O)

polar neutral

Hydroxyl (OH)

polar neutral

Sulfhydryl (SH)

polar neutral

Phosphate (H2PO4)

negative

electrostatic interactions

occur between fully charged groups in IONIC BONDS

hydrogen bonds

* occur between partially charged groups of F, O, N
* if you liken the covalent bond between the oxygen and hydrogen to a stable marriage, the ______ has "just good friends" status

hydrophilic interactions

take place between polar molecules

hydrophobic interactions

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* nonpolar molecules involved
* substances that have many C-H bonds
* stabilized by VDW forces

Van der Waals interactions

at short distances, any two atoms show a weak bonding interaction due to their fluctuating electrical charges (moments where electrons in both atoms concentrate on opposite sides creating temporary magnetism)

How do macromolecules form?

* monomers float around freely until picked up by a carrier
* carrier brings monomer to a polymer chain
* monomer can then bind to polymer through condensation reaction (releases water)
* carrier is then recycled

What are the four major families of small organic molecules?

* Polysaccharides (made by sugars)
* Fats and membrane lipids (made by fatty acids)
* Proteins (made by amino acids)
* Nucleic Acids (made by nucleotides)

How do we define free energy and how can this be used to predict the direction of certain reactions?

* Free energy measures the energy that could be used to do work
* the change in free energy (Delta G) predicts the direction of certain reactions
* a negative Delta G indicates a favorable reaction
* a positive Delta G indicates an unfavorable reaction

How do we interpret energy diagrams?

if an enzyme is added to a reaction, the activation energy will be reduced, leading to a lower “hill” on the diagram

How do enzymes help reactions proceed?

* lower activation energy of a reaction, but do not change the overall Delta G (free energy change)
* speed up reactions

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Reaction Coupling

occurs when an unfavorable reaction can be coupled with a favorable reaction in order to catalyze the unfavorable reaction

Chemical equilibrium

when there is a large enough excess of Y over X such that the rate of X → Y is equal to the rate of Y → X. At this point, the reaction is at equilibrium and the Delta G is 0.