Amino Acids

Question 1

In humans, __(L or D) amino acids are the building blocks of proteins, and there are __ (#) official amino acids coded in the human genome.

Answer 1

L
20 (22 if we include the random ones from the lecture)

Question 2

AA: Nonpolar, Hydrophobic, Small

Answer 2

Glycine, Alanine

Question 3

Why is glycine important?

Answer 3

In collagen triple helixes, every 3rd AA is Gly. Creates tighteness.

Question 4

AA: Nonpolar, Hydrophobic, Larger

Answer 4

Valine, Leucine, Isoleucine, Methionine

Question 5

Name the branched chain amino acids and explain their significance.

Answer 5

Valine, Leucine, Isoleucine.
Maple Syrup Urine Disease is caused by the bodies inability to breakdown these AAs.

Question 6

Why is Methionine significant?

Answer 6

1. Methionine is the start codon AUG in RNA translation to proteins.
2. Met acts as a Methyl Group Donor because of its Sulfur.

Question 7

AA: Nonpolar, Hydrophobic, Weird

Answer 7

Proline; Proline plays a central role in the FORMATION of alpha helices and beta sheets. While proline’s unique structure may also disrupt both alpha helixes and beta sheets, it’s ability to make sharp turns facilitates the FORMATION of both structures, with proline commonly being found at the beginning of alpha helices or at the turns in beta sheets.

Question 8

AA: Nonpolar, Hydrophobic, Aromatic

Answer 8

Phenylalanine, Tryptophan

Question 9

AA: Nonpolar, Hydrophilic, Aromatic

Answer 9

Question 10

AA: Polar, Hydrophilic

Answer 10

Serine, Threonine

Question 11

Polar, Disulfide Bond

Answer 11

Cysteine
- Cysteine’s side chain is capable of forming a disulfide bridge (becoming cystine), which is a covalent bonds between 2 sulfur atoms through side chain oxidation and removal of 2 hydrogen atoms.
- Cysteine is in the free form when in a reducing environment (intracellular space; full of antioxidants, cytoplasm)
- Cysteine is in the disulfide bond when in an oxidizing environment (extracellular space)

*When in the reducing cytoplasm, cysteins are happy and alone. When in an oxidizing environment, the cysteine get scared and hold hands. *

Question 12

AA: Negatively Charged and their Polar derivatives

Answer 12

Aspartate, Glutamate; Asparagine, Glutamine

Question 13

AA: Positively Charged

Answer 13

Histidine (pI of 6 )
Lysine (pI of 11)
Arginine (pKA of 12)

Question 14

Why is lysine significant in the context of DNA and epigenetics?

Answer 14

Histones bind to negatively charged DNA through their positively charged Lysine residues. Methylating or Acetylating the Lysines opens DNA to increase gene expression.

Question 15

Which amino acids can be phosphorylated?

Which ones have -OH groups?

Answer 15

• Tyrosine
• Serine
• Threonine

Question 16

What type of bond links amino acids in a polypeptide chain?

Answer 16

Peptide Bonds

Question 17

Peptide bonds are ________ and don’t rotate because of ____ bond character.

Answer 17

Planar, double bond