Lecture 2 - Chemical Bonds & Macromolecules

Question 1

What elements make up DNA and proteins?

Answer 1

DNA: C, H, O, P, N
Protein: C, H, O, S, N

Question 2

Why is water the solvent of life?

Answer 2

• polar
• oxygen has a high affinity for electrons (high electronegativity)
• water can associate with other water molecules
• water can associate with any molecule that is charged or has dipole-dipole bonds

Question 3

What are organic macromolecules?

Answer 3

• contain C-H
• C is the backbone of organic molecules because it can bond to 4 other atoms, form C-C chains, and from double and triple bonds
• C is weakly electronegative

Question 4

What are monomers and polymers?

Answer 4

monomer = single building block of a macromolecule
polymer = chain of monomers composed of similar but not identical subunits (DNA)

Question 5

Describe Synthesis (Condensation Rxn)

Answer 5

• add monomers to a growing chain (forms a covalent bond)
• water is a product
  requires energy

Question 6

Describe Breakdown (Hydrolysis Rxn)

Answer 6

• cleavage of covalent bonds between monomers in a polymer
• water is a reactant (added in)
• releases energy
• spontaneous but SLOW

Question 7

What are carbohydrates?

Answer 7

• energy storage, cell structure, cell-cell recognition
• monomers (carbon chains, linear or ring-shaped)
  ex) glucose

Question 8

What are disaccharides?

Answer 8

• formed by a covalent bond between monosaccharides
• bond type: glycosidic
  ex) sucrose

Question 9

What are polysaccharides?

Answer 9

• polymers of monosaccharides

ex) starch, cellulose, glycogen, chitin

Question 10

What are lipids/fats?

Answer 10

• not a true polymer
• classified as a lipid because they are hydrophobic, meaning they aggregate away from water
• made mostly of H-C

Question 11

What is the difference between fatty acids and fats?

Answer 11

fatty acids = can attach to a glycerol backbone, usually about 16-18C long
fats = triacylglyceride (animal fat), energy storage, and insulation

Question 12

What are phospholipids?

Answer 12

• structural comp. of biological membrane
• functions in the cell membrane
• amphipathic = have both hydrophilic and hydrophobic domains

Question 13

What are steroids?

Answer 13

• class of lipids based on cholesterol
• characterized by a backbone of 4 fused HC rings, with a small polar functional group
  functions:
• 1) hormones - estrogen/testosterone
• 2) in animals, cholesterol sits in the plasma membrane to maintain fluidity and increase stiffness

Question 14

What are proteins?

Answer 14

• involved in every biological task
• composition and structure of amino acids
• proteins are polymers of the monomer - amino acid
• 20 biologically relevant a.a

Question 15

What are the different R groups?

Answer 15

1) non-polar - R = CH
2) polar uncharged - R = -OH or -SH
3) polar charged acidic (-) - R = COO -
4) polar charged basic (+) - R = NH3 +

Question 16

What is the structure of proteins?

Answer 16

• function in 3D but are synthesized as linear polypeptides
• a.a are polymerized during translation
• a.a are covalently linked by peptide bonds

Question 17

Describe primary structure

Answer 17

• polymerization of a.a
• determined by the sequence of DNA
• written and translated N –> C
• bond type = peptide
• primary structure dictates folding, folding dictates function

Question 18

Describe secondary structure

Answer 18

• interaction between the backbones of the peptide chain
• local folding of a.a chain into an alpha helix and beta-sheets
• the R group is NOT involved in stabilizing the secondary structure

Question 19

Describe tertiary structure

Answer 19

• 3D pattern of folding
• hydrophobic interactions of non-polar R groups drive away the a.a away from water into the middle of the protein
• forces that maintain the tertiary structure: interactions between R groups, covalent bonds, ionic bonds, hydrophobic interactions, hydrogen bonds

Question 20

Describe quaternary structure

Answer 20

• some proteins form multisubunit complexes that create a functional protein
• ex) hemoglobin, collagen, ribosome

Question 21

What are chaperones?

Answer 21

• proteins that assist in folding other proteins, this folding is essential for protein function
• there are many diseases of protein folding (misfolded proteins aggregate in the cell and cause death)
• ex) bacterial chaperone = “molecular folding chamber”

Question 22

What are nucleic acids?

Answer 22

• DNA and RNA

- store and transmit hereditary info

Question 23

Describe DNA

Answer 23

• transmits info between cell generations
• contains all info essential for life
• polymer of deoxynucleotides
• double-stranded and forms helix with the bases pointing inwards
• form complementary base pairing
• purine always pair with a pyrimidine
• antiparallel

Question 24

Describe RNA

Answer 24

• polymer of ribonucleotides
• many functions: info, translation, regulation, splicing
• singled-stranded
• 2’OH makes the helix more open and more reactive
• free base-pair with itself

Question 25

Be able to describe the basic structure of a nucleotides

Answer 25

refer to notes!!

Question 26

What are pyrimidines and purines?

Answer 26

pyrimidines = single ringed bases (T,C,U)
purines = double ringed bases (A,G)