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34 notecards = 9 pages (4 cards per page)

Viewing:

CH 2

front 1

Fig 2.1 Noncovalent bonding interactions between human growth hormone and its cellular receptor

back 1

front 2

DNA strains are maintained by

back 2

covalent bonds

front 3

Protein made up of amino acids linked by

back 3

Covalent peptide bonds

front 4

Types of noncovalent interactions

back 4

- Charge- charge (Ionic Bonds)

- Charge-dipole

- Dipole-Dipole

- Dipole-induced dipole

- Dispersion(van der Waals)

- Hydrogen Bond

front 5

Proteins carry more positive charge at what?

back 5

lower pH levels

front 6

Extreme ph, leading to protein denaturation due to loss of charge and mutual repulsion are called what?

back 6

Salt Bridges

front 7

law describes the force between charged particles, which is reduced in biological environments due to the screening effect of water and other molecules.

back 7

Coulombs law

front 8

Q: How do you calculate the pI of an amino acid like aspartic acid?

back 8

Average the two pKa values around the neutral (zwitterionic) form.

For aspartic acid:

\text{pI} = \frac{2.1 + 3.9}{2} = 3.0

front 9

What happens when pH < pI?

back 9

A: The molecule carries a net positive charge.

front 10

Q: What happens when pH > pI?

back 10

A: The molecule carries a net negative charge.

front 11

Q: What happens when pH = pI?

back 11

A: The molecule is neutral overall (zwitterion).

front 12

Q: What changes the pI of a protein?

back 12

: The types of ionizable groups on its surface:

  • More acidic groups → lower pI
  • More basic groups → higher pI

front 13

What is a polyelectrolyte?

back 13

A: A molecule with many ionizable (charged) groups.

front 14

What’s the difference between strong and weak polyelectrolytes?

back 14

  • Strong: Stay charged over wide pH ranges (e.g., DNA)
  • Weak: Gradually lose/gain protons as pH changes (e.g., polylysine)

front 15

Why is understanding pI important in biochemistry?

back 15

It affects protein solubility, structure, function, and is used in techniques like electrophoresis and isoelectric focusing.

front 16

Where do most biochemical reactions occur?

back 16

A: In aqueous (water-based) environments—except inside hydrophobic membranes.

front 17

Q: What are Brønsted-Lowry acids and bases?

back 17

A: Acids are proton donors; bases are proton acceptors.

front 18

Q: What is the difference between strong and weak acids?

back 18

A: Strong acids fully dissociate; weak acids partially dissociate in water.

front 19

Q: What is the ion product of water (Kw) at 25°C?

back 19

K_w = [H^+][OH^-] = 1 \times 10^{-14}

front 20

Q: What is pH?

back 20

\text{pH} = -\log[H^+]

Lower pH = more acidic; higher pH = more basic.

front 21

What is the physiological pH range for most biochemical reactions?

back 21

A: Between 6.5 and 8.0

front 22

Q: How does pH affect biomolecules?

back 22

A: It changes their protonation state and overall charge, affecting function and interactions.

front 23

Q: What is Ka and pKa?

back 23

  • Ka = acid dissociation constant
  • pKa = –log(Ka) → lower pKa = stronger acid

front 24

What is the Henderson–Hasselbalch Equation?

back 24

A:

\text{pH} = \text{pKa} + \log\left(\frac{[\text{A}^-]}{[\text{HA}]}\right)

front 25

When is pH = pKa in a titration?

back 25

At the midpoint, where [HA] = [A⁻]

front 26

Q: What is a buffer solution?

back 26

A: A mixture of weak acid and its conjugate base that resists pH changes.

front 27

Q: Why is buffering important in biology?

back 27

A: It maintains stable pH for enzymes and cell function, especially in blood and cells.

front 28

Q: What happens if blood pH falls below 7.2?

back 28

A: It can lead to acidemia, a medical emergency linked to diseases like diabetes.

front 29

Q: How do you calculate pI for a molecule with two ionizable groups?

back 29

\text{pI} = \frac{\text{pKa}_1 + \text{pKa}_2}{2}

front 30

What is a zwitterion?

back 30

A: A molecule with both positive and negative charges, but net charge = 0.

front 31

Q: What are ampholytes?

back 31

A: Molecules with both acidic and basic groups that can act as buffers in different pH ranges.

front 32

Q: What happens to a molecule’s charge as pH increases?

back 32

A: It becomes more negatively charged (deprotonated).

front 33

Q: What happens to a molecule’s charge as pH decreases?

back 33

A: It becomes more positively charged (protonated).

front 34

Q: Name two major biological buffer systems

back 34

  1. Phosphate buffer (intracellular, pKa ≈ 6.86)
  2. Bicarbonate buffer (blood, apparent pKa ≈ 6.3)