Chapter 1 Amino Acids

7/27/2019 Chapter 1 Amino Acids

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1.A buffer is a solution

that RESISTS change

in pH following the

addition of an acid or

base. A buffer can be

created by mixing a

weak acid (HA) withits conjugate base (A-

). If an acid such as

HCl is added to such a

solution, A- can

neutralize it, in the

process being

converted to HA.

If a base is added, HA

can neutralize it, in

the process being

converted to A-.

Maximum buffering

capacity occurs at a

pH equal to the pKa

but a conjugate

acid/base pair can

still serve as an

effective buffer when

the pH of a solution is

what?

within approximately 1 pH unit of

the pKa - (example) - solution

containing acetic acid (HA = CH3-

COOH) and acetate (A- = CH3-

COO-) with a pKa of 4.8 resists a

change in pH from pH 3.8 to 5.8,

with maximum buffering at pH =4.8. [Note: At pH values less than

the pKa the protonated acid form

(CH3-COOH) is the predominant

species. At pH values greater than

the pKa the deprotonated base form

(CH3-COO-) is the predominant

species in solution.]

2.A zwitterion is the

isoelectric form of a

molecule having an

overall charge of zero,

what else is this

called? (form)

Dipolar form

3.All amino acids found

in proteins are of the

L-configuration. So

where would the D-

amino acids be found?

Some antibiotics and in bacterial

cell walls.

4.All of the amino acids

with uncharged

POLAR side chains

are hydrophilic except

which one?

Tyrosine

5.All of the NONpolar

amino acids are

hydrophobic except?

Methionine - hydrophillic -

contains SULFUR

6.Amino acids are

classified by their side

chains (R-groups). If

the amino acid has an

even distribution of

electrons, is it polar or

nonpolar?

Nonpolar

7. Amino acids are classified by their side

chains (R-groups). If the amino acid has

an uneven distribution of electrons, is it

polar or nonpolar?

Polar - ie

Acids or Bases

8. Amino acids in aqueous solution

contain weakly acidic -carboxyl groups

and weakly basic -amino groups and

each of the acidic and basic amino acids

contains an ionizable group in its side

chain. Thus, both free amino acids and

some amino acids combined in peptide

linkages can act as what?

Buffers

9. Amino acids that have an asymmetric

center at the -carbon can exist in two

forms, designated D and L, that are

mirror images of each other. What are

the 2 forms called?

Stereoisomers,

optical

isomers, or

enantiomers

10.Are ketogenic amino acids basic oracidic? What are the ketogenic amino

acids?

Acidic1. Leucine

2. Lysine

11. Concept question: Which amino acid

will increase your respirations or

increase your potassium levels?

Leucine,

Lysine

12. Concept question: Which hormones

have a lot of cysteine?

If they have

cysteine - they

have

dissulfide

bonds

(Insulin,

inhibin,growth

hormone,

prolactin)

13. Cysteine's side chain has a -SH group

which is an important component of the

active site of many enzymes, which other

amino acid has a side chain that is an

important component of the active site

of many enzymes?

Serine

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14. Define dissociated vs

soluble vs. bioavailable

in reference to

acid/base?

Dissociated is loss of H+ (removal

of hydrogens)

Bioavailable is neutral, can cross a

fat soluble membrane

Soluble (POLAR) has a charge and

will a ttract H2O (can not cross

BBB)

15. Describe the amino

group and carboxyl

group of an amino

acid at physiologic

pH.

CHARGED at physiologic pH -

Amino group is protonated (NH2

to NH3+) Carboxyl Group is

dissociated (COOH to COO-)

16. Explain the equation:

Ka = [H+] [A-]

-----------------

[HA]

Dissociation constant: The larger

the Ka, the stronger the acid,

because most of the HA has been

converted into H+ and A+.

Conversely, the smaller the Ka, the

less acid has dissociated and,

therefore, the weaker the acid.

17. For a base w/ pH = 7and pKa = 8, how

much is dissociated

and how much is

bioavailable?

pH = pKa - 1 = 10% dissociated(10% bioavailable)

18. For and acid w/pH = 5

and pKa = 4, how

much is dissociated

and how much is

bioavailable?

pH = pKa - 1 = 10% dissociated

(90% bioavailable)

19. If your body is acidic,

what effect does this

have on your

potassium?

Acidic = Hyperkalemic

20. In proteins found in

aqueous solutions,

where are the

nonpolar acids found?

Nonpolar (oily) - are found

clustered together in the interior of

the protein = hydrophobicity of the

R-groups - help give it, its 3-D

shape.

21. In proteins, the -SH

groups of two

cysteines can become

oxidized forming a

covalent cross-linkcalled a dissulfide

bond, this is called

what?

Cystine (a dimer)

22. Ketones are broken

down and made from

Acetyl-CoA, so what is

the building block for

ketones?

Acetyl-CoA

23. Most enzymes have

serine, threonine or

tyrosine in their active

sites, what is important

about this?

These amino acids have an

OH group that is used to make

bonds

24. N-linked glycosylation of

proteins - post

translational

modification of proteins

associated with what cell

organelle?

Endoplasmic Reticulum

25. O-linked glycosylation of

proteins - post

translational

modification associated

with which cell organelle?

Golgi Apparatus

26. Proteins located in a

hydrophobic

environment, such as a

membrane, where are thenonpolar amino acids

found?

Nonpolar R-groups are found

on the outside surface of the

protein, interacting w/the lipid

environment - they function tostabilize the protein structure

27. Substances that can act as

either an acid or a base

are defined as what and

are referred to as what?

1. Amphoteric

2. Ampholytes (amphoteric

electrolytes)

28. The alpha carbon of each

amino acid is attached to

four different chemical

groups and is therefore

considered to be a chiral

carbon or optically active

carbon. What protein is

the exception?

Glycine - its alpha carbon has

2 hydrogens attached

29. The alpha carbon of each

amino acid is attached to

four different chemical

groups and is therefore

considered to be what

type of carbon atom?

Chiral Carbon or Optically

active carbon atom

30. The amino acids (with

acidic side chains)

aspartic and glutamicacid: are they proton

donors or proton

acceptors?

Proton Donors - side chains

are fully ionized at neutral pH

containing a negativelycharged carboxylate group (-

COO) so called Aspartate and

Glutamate to emphasize that

these amino acids are

negatively charged at

physiologic pH

31. The amino acids (with

basic side chains) Lysine

and arginine: are they

proton donors or proton

acceptors?

Proton Acceptors - side chains

are fully ionized at physiologic

pH being positively charged


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53.Which amino acid has an Inole group? Tryptophan the "Largest"

amino acid

54.Which amino acids are glucogenic and Ketogenic? 1. Phe

2. Iso

3. Thr

4. Trp

Mr. PITT

55.Which amino acids have uncharged POLAR side chains? 1. Ser2. Thr

3. Tyr

4. Asn

5. Cys

6. Glu

56.Which free amino acid is weakly basic and largely uncharged at physiologic pH? Histidine

57.Which NONpolar amino acid can form Serotonin & niacin? Tryptophan

58.Which protein is the best buffer in the body? Histidine

59.Which three amino acids have a polar hydroxyl group that can participate in hydrogen bond

formation?

1. Serine

2. Threonine

3. Tyrosine

60.Which three amino acids have side chains that can serve as a site of attachment for

oligosaccharide chains in glycoproteins?

1. Asparagine - amide grou

2. Serine or Threonine -

hydroxyl group

Chapter 1 Amino Acids

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