lecture 2

Question 2

2.1 - What is the major difference between organic chemistry and biochemistry?

Answer 2

Organic chemistry is the study of all carbon-containing compounds, while biochemistry is the study of chemical processes in living organisms.

Question 3

2.1 - How many valence electrons does carbon have, and why is this important?

Answer 3

Carbon has 4 valence electrons, allowing it to form 4 covalent bonds → basis of complex biological molecules.

Question 4

2.1 - What is the biological importance of ethene?

Answer 4

Ethene (ethylene) is a plant hormone that promotes fruit ripening, breakdown of cell walls, and conversion of starch to sugars.

Question 5

2.2 - Define bond energy.

Answer 5

The bond energy is the amount of energy required to break 1 mole of a bond (kcal/mol).

Question 6

2.2 - Why are weak non-covalent bonds important in biology?

Answer 6

Although weak individually, their cumulative effect stabilizes biological molecules, critical for protein folding and DNA structure.

Question 7

2.2 - Why can’t visible light break covalent bonds?

Answer 7

Visible light has lower energy than covalent bond energies. Only higher energy UV can break them.

Question 8

2.2 - What damage can UV light cause to cells?

Answer 8

It can damage DNA, proteins, and carbohydrates, leading to mutations and cell death.

Question 9

2.3 - Define an asymmetric (chiral) carbon.

Answer 9

A carbon with 4 different substituents attached → leads to stereoisomers.

Question 10

2.3 - How many stereoisomers can isoleucine have?

Answer 10

Isoleucine has 2 asymmetric carbons, so it has 2^2 = 4 stereoisomers.

Question 11

2.3 - Why is dopamine ineffective as a treatment for Parkinson’s disease?

Answer 11

Dopamine cannot cross the blood-brain barrier. Instead, L-DOPA is used as it can be converted to dopamine in the brain.

Question 12

2.3 - Why is thalidomide dangerous?

Answer 12

Although R-thalidomide is a sedative, in the body it interconverts to S-thalidomide, which is a teratogen → causes birth defects.

Question 13

2.4 - Why is water considered the universal solvent?

Answer 13

Because of its polarity and ability to form hydrogen bonds, dissolving many polar/charged molecules.

Question 14

2.4 - What property of water allows insects to walk on it?

Answer 14

Water’s cohesiveness → hydrogen bonding between molecules → high surface tension.

Question 15

2.4 - Define specific heat and why it’s important for cells.

Answer 15

Specific heat = energy required to raise 1 g of substance by 1°C. Water’s high value prevents cells from overheating.

Question 16

2.5 - What does amphipathic mean in relation to phospholipids?

Answer 16

Molecule has both hydrophilic (polar) head and hydrophobic (nonpolar) tails.

Question 17

2.5 - Rank molecule permeability across membranes.

Answer 17

1) Small nonpolar, 2) Small uncharged polar, 3) Large uncharged polar, 4) Ions, 5) Large charged molecules.

Question 18

2.6 - List the 3 major classes of macromolecules.

Answer 18

Proteins, nucleic acids, polysaccharides.

Question 19

2.6 - What is a condensation reaction?

Answer 19

Reaction where monomers join to form polymers with loss of water.

Question 20

2.6 - What carrier molecule is used for glycogen synthesis?

Answer 20

UDP (uridine diphosphate) is the carrier for glucose monomers.

Question 21

2.7 - Define denaturation and renaturation.

Answer 21

Denaturation: unfolding of proteins → loss of function. Renaturation: refolding under proper conditions → may restore function.

Question 22

2.7 - What is the role of molecular chaperones?

Answer 22

Assist proteins in folding correctly by preventing incorrect interactions. Example: Hsp70.

Question 23

2.8 - List 4 major non-covalent interactions important in protein folding.

Answer 23

Hydrogen bonds, ionic bonds, van der Waals interactions, hydrophobic interactions.

Question 24

2.8 - How do hydrophobic interactions increase entropy?

Answer 24

Nonpolar groups cluster → water’s ordered hydration shells collapse → entropy increases.