Biochemistry Exam 1

What is the ion product constant of water?

[H+] x [OH-] = 1.0 × 10^-14 M²

What is the concentration of OH- in an aqueous solution of 0.2 M HCl (strong acid)?

[OH-] = 1.0×10^-14 M² / 0.2 M = 5 × 10^-14 M

rearrange the [H+] x [OH-] and do 1.0×10^-14/[H+] = [OH-]

What is the concentration of H+ in an aqueous solution of 0.0001 M NaOH (strong base)?

[H+] = 1.0×10^-14/0.0001 M =1×10⁻¹⁰ m

rearrange the [H+] x [OH-] and do 1.0×10^-14/[OH-] = [H+]

What is the absolute difference in [H+] between two aqueous solutions, one of pH 2.0 and one of pH 3.0? and What is the [OH-] of the solution of pH 2.0?

The solution with a pH of 2.0 has a [H+] of 10^-2 M and a [OH-] of 10^-12 M; the solution with a pH of 3.0 has a [H+] of 10^-3 M. The difference in [H+], therefore is: 10^-2 M - 10^-3 = 0.009 M

Calculate the pH of a mixture of 0.1 M acetic acid (weak acid) and 0.2 M sodium acetate. The pKa of acetic acid is 4.76. Use Henderson-Hasselbalch equation due to weak acid.

with pKa = 4.76; [A-] = 0.2 M and [HA] = 0.1 M; pH = pKa + log([A-]/[HA]

pH = 4.76 + log 0.2/0.1

pH = 4.76 + log 2 = 4.76 + 0.3 = 5.06

Calculate the ratio of the concentration of acetate and acetic acid required in a buffer system of pH 5.3. pKa known for this system 4.76 same as before.

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

5.3 = 4.76 + log([A-]/[HA])

0.54 = log([A-]/[HA]); now find the antilog function on calculator

antilog: 0.54 = [A-]/[HA] = 3.47 (antilog button is 2nd log)

What distinguishes living organisms from inanimate objects?

Complexity and organization (molecules —> organelles —> cells —> tissues—> organs —> organisms)

energy use/metabolism (extract, transform and use energy; catabolism (breaking down) and anabolism (building up))

chemical processes (growth, reproduction (pass on genetic information), and repair)

stimuli response (sense and respond)

adaptation/evolution (natural selection - mutations/genetic variation)

What are the structural features of prokaryotes that distinguish them from eukaryotes?

Prokaryotes don’t have a true nucleus they have a nucleotide region that is not membrane bound and absent organelles (no mitochondria, ER, Golgi, etc.) and lipid layers. They also have flagella (movement) or pili for adherence/gene transfer

What might be an advantage of compartmentalization of cells?

Allowing for separation and specialization in biochemical processes (hydrolytic enzymes in lysosomes separated from cytosol to prevent damage), improve efficiencant regulation (organelle own pH and ion concentrations and enzyme activity; metabolic pathways), and complexity.

Nucleus - genetic info storage and transcription

Mitochondria - ATP production

Golgi apparatus - protein modification and sorting

What are the three classes of cytoskeletal proteins? What are the functions of the cytoskeleton?

3 classes - microfilaments, intermediate filaments, and microtubules

Cytoskeleton function - strength/rigidity, shape, ability to move (flagella, cilia, etc), and ability of internal motion of its organelles, membrane proteins anchored and organized cell surface structures.

Review the common families of functional groups or organic compounds that are encountered in biomolecules.

Hydroxyl group (-OH) - sugars

Aldehyde (-CHO) - glucose

Ketone (C=O) - fructose

Carboxyl group (-COOH) - amino acids, fatty acids, organic acids

Amino group (NH2) - amino acids, nucleotides

Phosphate group (-PO4) - nucleotides (ATP, DNA, RNA), phospholipids

Sulfhydryl (-SH) - cysteine (amino acid), some coenzymes

Ester (RCOOR’) - fats, phospholipids

Ether (ROR’) - some sugars and lipids

How are cells able to synthesize polymers if such reactions are thermodynamically unfavorable?

polymerization is unfavorable alone; so cells overcome this by coupling them with favorable reactions, such as hydrolysis of ATP or other energy rich intermediates, effecityl ‘paying’ the energy cost to synthesize ordered macromolecules