Amino Acids

Question 1

What components make up amino acids?

Answer 1

A carboxyl group (COOH-), an amine group (NH3+) and an R-group

Question 2

How do amino acids differ one one another?

Answer 2

They have different R-groups

Question 3

What are the functions of proteins?

Answer 3

Transport, as catalysts, structure, and motion

Question 4

What type of bonds join amino acids and how do they form?

Answer 4

Peptide bonds
Formed by hydrolysis, the -OH from the carboxyl group and the -H from the amine group split ad join to form a water molecule and a peptide bond between amino acids

Question 5

All amino acids are chiral except ______

Answer 5

glycine

Question 6

What are the five groups for classification of amino acids?

Answer 6

Polar, non-polar, positive, negative, aromatic

Question 7

Which amino acids are polar and what are their characteristics?

Answer 7

• serine, threonine, cysteine, asparagine, glutamine

- hydrophilic

Question 8

Which amino acids are non-polar and what are their characteristics?

Answer 8

• glycine, alanine, valine, proline, methionine, leucine, isoleucine
• hydrophobic

Question 9

Which amino acids are aromatic and what are their characteristics?

Answer 9

• phenylalanine, tyrosine, tryptophan

- relative non-polar, absorb UV light, can form H-bonds

Question 10

Which amino acids are positive and what are their characteristics?

Answer 10

• histamine, lysine, arginine

- the most hydrophilic, acids

Question 11

Which amino acids are negative and what are their characteristics?

Answer 11

• aspartate, glutamate

- basic

Question 12

What are essential amino acids?

Answer 12

Amino acids humans cannot synthesis at all or synthesize enough of to satisfy the bodys needs, must be included in diet

Question 13

Which amino acids are essential?

Answer 13

histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine

Question 14

What are conditionally essential amino acids?

Answer 14

Amino acids that aren’t synthesized enough at certain periods of life

Question 15

Which amino acids are conditionally essential?

Answer 15

arginine, cysteine, glutamine, glycine, proline, tyrosine

Question 16

How can amino acids be ionized?

Answer 16

Both the carboxyl group and amine group are ionizable as they have charges, they can both be protonated

Question 17

The carboxyl group has a(n) _____ pKa and is protonated at ____ pH, the amine group has a(n) _____ pKa and is protonated at _____ pH

Answer 17

acidic/low/basic/high

Question 18

At low pH the amino acid is a(n) ____ and at high pH it is a(n) _____ because …

Answer 18

cation/anion
because at low pH the negatively charged COOH is protonated and only the positive charge from the NH3 remains, the reverse is true for high pH

Question 19

What is a zwitterion?

Answer 19

When the amino acids are between pKas and both charges are present, making it neutral

Question 20

How does the side chain affect ionization?

Answer 20

If the side chain has a positive or negative charge it will affect whether the amino acid is a cation or anion at a given pH

Question 21

Isoelectric point (pI) = ?

Answer 21

pI=[pK1][pK2]/2 (net=0) unless the side chain is ionizable)

Question 22

Primary protein structure:

Answer 22

All peptide bonds linking amino acids into a polypeptide chain, not functional

Question 23

Secondary structure:

Answer 23

Spatial arrangement of the polypeptide chain, stabilized by H-bonds, not functional

Question 24

What are the types of secondary structure?

Answer 24

α helix: H-bonds between nearby amino acids, order affects stability
β pleated sheet: H-bonds between adjacent amino acids, not necessarily nearby, sheets are held together by H-bonds between them which are either parallel (diagonal) or antiparallel (horizontal)
random coil: irregular arrangement of polypeptide chain

Question 25

Tertiary structure:

Answer 25

Overall spatial arrangement of the protein, stabilized by side chain interactions (hydrophobic, polar, or disulphide), functional

Question 26

What are the types of tertiary structure?

Answer 26

Fibrous: insoluble PRO, usually structural or protective, mostly have the same secondary structure
Globular: soluble PRO with a globular shape

Question 27

Quaternary structure:

Answer 27

Assembly of individual polypeptide chains into a cluster, functional, optional

Question 28

What are the advantages of a quaternary structure?

Answer 28

Increased stability, reduced exposed surface, cavities form for activity, improves catalysis

Question 29

What are the disadvantages of quaternary structure?

Answer 29

Not optimal for rapid diffusion, not optimal for radio degradation