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MCB 2 > Biochemistry: Introductory Principles (lecture 1) > Flashcards

Biochemistry: Introductory Principles (lecture 1) Flashcards

1
Q

Describe C-C and C-H bonds

A
  • Electrons shared equally
  • Non-polar
  • Unreactive
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2
Q

Describe C-O and C-N bonds

A
  • Electrons shared unequally
  • Polar
  • Reactive
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3
Q

Describe Oxidation

A
  • Is a loss of electrons
  • Generally energy releasing (exergonic)
  • Examples: direct loss of electrons, loss of hydrogen, gain of oxygen
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4
Q

Describe Reduction

A
  • Gain of electrons
  • Generally energy absorbing (endergonic)
  • Examples: direct gain of electrons, gain of hydrogen, loss of oxygen
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5
Q

C=C vs C-C

A

C=C is more oxidized (and less reduced) than C-C

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6
Q

In RedOx reactions, electrons are transferred from molecules with…

A

…Lower affinity for electrons to molecules with higher affinity for electrons

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7
Q

Reducing agent (reductant)

A
  • The electron donor

- Lower electron affinity

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8
Q

Oxidizing agent (oxidant)

A
  • The electron acceptor

- Higher electron affinity

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9
Q

Standard Reduction Potential (SRP)

A
  • Is a quantitative measure of the tendency of redox pairs to lose electrons
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10
Q

The lower the SRP, _____

A

The greater the tendency to LOSE electrons

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11
Q

The higher the SRP, _____

A

The greater the tendency to ACCEPT electrons

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12
Q

Naming for undisassociated acid?

A

“…ic acid,” like “acetic acid”

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13
Q

Naming for disassociated acid?

A

“ate,” like “acetate”

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14
Q

Nitrogen-containing groups are usually ____ and can acquire a proton, becoming ____

A

Basic, positively charged cations

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15
Q

Unequal sharing of electrons between atoms generates…

A

Polarity

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16
Q

Nucleophile

A
  • Nucleus / positive-charge loving

- Provides an electron pair to form a covalent bond

17
Q

Electrophile

A
  • Electron / negative-charge loving

- Accepts an electron pair to form a covalent bond

18
Q

T/F: Conjugate acids are usually protonated.

A

True!

19
Q

Equilibrium Constant (Keq)

A

[B] / [A]; the rate of the forward and reverse reactions are equal

20
Q

What is the pKa?

A

It is the pH at which [acid] = [base]; 50% dissociated. The lower the pKa, the stronger the acid!

21
Q

Dissociation of a weak acid

A

HA ⇌ H+ + A-

22
Q

Henderson-Hasselbach equation

A

pH = pKa + log([A-]/[HA])

23
Q

If pH > pKa…

A

A- > HA, and is strongly dissociated

24
Q

If pH < pKa…

A

HA > A-, and is not dissociated (or weakly)

25
Q

Know logs!

A

Log 1 = 0
Log 10 = 1
Log 100 = 2
Log 1000 = 3

Antilog 1 = 10
Antilog 2 =100
Antilog 3 = 1000

Antilog -1 = 1/10
Antilog -2 = 1/100
Antilog -3 = 1/1000

26
Q

If Lactic acid has a pKa of ~3.7, at which pH would it be present as an acid?

A

Present at pH 2, compared to a pH of 5, 7 and 9.

27
Q

What is a buffer?

A

Buffers are solutions of weak acids and their conjugate bases

28
Q

Function of buffers?

A

To resist pH changes when an acid or base is added to the solution

29
Q

Maximum buffering capacity is when…

A

pH = pKa

30
Q

What is the main acid produced by the body?

A

Carbon dioxide! CO2 is also its own buffer.

31
Q

Bicarb and RBCs

A

Large amounts of carbonic anhydrase are found in RBC. As carbonic acid dissociates, the H+ is taken up by Hb because an unbound His residue has a pKa of 6.7. RBC exchanges HCO3- with Cl- in plasma so high [HCO3-] is in plasma. In the lung, CO2 released from RBC into blood, Hb-H loses proton to facilitate O2 binding.

32
Q

Concentration of chloride in the peripheral tissues vs lungs

A

[Cl] is lower in the blood plasma of peripheral tissues because Cl is being taken up by the RBCs

Near the lungs, this is reversed; Cl leaves the cell and enters teh blood, so the level of Cl in the blood plasma is higher

33
Q

Diabetic Ketoacidosis

A

Fatty acids circulating in the blood leads to ketoacidosis, a lowering of blood pH

34
Q

DKA, continued

A

As pH increases, breathing increases and becomes rapid; this results in a loss of CO2, so pH increases, as well.

35
Q

Anxious breathing

A

As breathing increases, CO2 decreases (is exhaled out)

Can treat with paper bag, so not as much CO2 is breathed out.

36
Q

How to calculate pI

A
  • Choose the species that is at zero overall charge

- Take the average of the 2 pKa values that flank it

37
Q

Other important buffer systems

A
  • H2PO4 -> HPO4
  • NH3 + H -> NH4
  • Serum and intracellular proteins containing Histidine
38
Q

pH and drug absorption

A
  • Aspirin is more likely to cross membranes if uncharged (protonated); it will only be protonated if its pH is below the pKa of 3.5.
  • Absorption is more efficient in the stomach than in the intestine

MCB 2 (22 decks)

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