Bio-Tech-lect #3

Question 1

pKa

Answer 1

represents the pH where an weak acid:conjugate base pair is at equilibrium ([HA] = [A-])

Question 2

When is it appropriate to use the Henderson-Hasselbalch (H-H) Equation?

Answer 2

Mixtures of weak acids and their conjugate bases (salt).

Titration of weak acid solutions with strong base, or vice versa.

Buffers!

Biological Environments!!!

Question 3

ampholyte

Answer 3

a molecule with both acidic and basic groups

Question 4

The isoelectric point (pl)

Answer 4

the pH

at which average charge, for all forms of the molecule, is zero.

Question 5

when pH < pI

Answer 5

a molecule

will be positively charged.

Question 6

when pH > pI

Answer 6

the molecule will be negatively charged.

Question 7

use of Thermodynamics

Answer 7

allows us to determine whether chemical processes and reactions occur spontaneously.

Question 8

2nd law of thermo

Answer 8

“The universe tends toward maximum disorder”

doesnt tell us about a rate (thats kinetics) just that it willor wont happen given enough time.

Question 9

how is a spontaneous process characterized?

Answer 9

by the conversion of order to chaos.

Question 10

does enthalpy tell us about spontaneity?

Answer 10

no

Question 11

1st law of thermos

Answer 11

Energy can be neither created or destroyed!

Or, more specifically: “the total energy of an isolated system is conserved

Question 12

system

Answer 12

portion of the universe with which we’re concerned:

• mixture of chemical in a test tube
• single cell, perhaps entire organism

Question 13

surroundings

Answer 13

everything else in the universe thats not the system

Question 14

3 systems

Answer 14

isolated, closed, open

Question 15

isolated system

Answer 15

no exchange of matter or energy

Question 16

closed system

Answer 16

exchange of energy may occur

Question 17

open system

Answer 17

Energy and/or matter exchange may occur.

Question 18

What kind of systems are living things?

Answer 18

Mostly open

exchanging matter: nutrients, waste products
exchanging energy: heat from metabolism

Question 19

internal energy examples and symbol

Answer 19

“U”

rotational, vibrational, translation energies of molecules, energy stored in covalent and noncovalent bonds

Question 20

thermodynamic state

Answer 20

defined by describing the amounts of all substances present and any two of the following three variables:

The temperature (T).
The pressure on the system (P).
the volume of the system (V).

Question 21

The internal energy (U) of a system

Answer 21

Includes all forms of energy that can be exchanged via simple (nonnuclear) physical processes or chemical reactions.

Question 22

when can a system can exchange energy with its surroundings?

Answer 22

as long as its not isolated.

Question 23

what happens in terms of energy when the system is not isolated system?

Answer 23

the internal energy can change (delta U)

Question 24

how does internal energy exchange take place for a closed system?

Answer 24

1. ) Heat (q) may be transferred to or from the system.

2. ) The system may do work (w) on its surroundings or have work done on it.

Question 25

Exothermic

Answer 25

deltaH < 0

Question 26

endothermic

Answer 26

deltaH > 0