MT 6310 LECTURE UNIT 2 PROTEINS

Question 1

Proteins that are the chief constituents of skin, bone, hair, and nails

Answer 1

Collagen and Keratin

Question 2

Agents of catalyzing

Answer 2

Enzymes

Question 3

Proteins involved in muscle movement

Answer 3

Myosin and Actin

Question 4

Protein that transports oxygen from the lungs to cells, other
proteins transport molecules across cell membranes.

Answer 4

Hemoglobin

Question 5

Two types of proteins

Answer 5

Fibrous & Globular

Question 6

A compound that contains both an amino group and a carboxyl group

Answer 6

Amino Acid

Question 7

Term used to describe the un-ionized form of an amino acid

Answer 7

Zwitterion

Question 8

TRUE OR FALSE

The most important aspect of the R groups is their polarity.

Answer 8

TRUE

Question 9

TRUE OR FALSE

With the exception of Cysteine, all protein-derived amino acids have at least one stereocenter and are chiral.

Answer 9

FALSE (Glycine exists naturally with the D-configuration)

Question 10

TRUE OR FALSE

The vast majority of alpha amino acids have the D-Configuration at the alpha carbon.

Answer 10

FALSE (most have the L-configuration)

Question 11

TRUE OR FALSE

Each of the amino acids with one stereocenter exists as 2 enantiomers.

Answer 11

TRUE

Question 12

TRUE OR FALSE

For the 19 of 20 amino acids, the alpha amino group is secondary while for proline it is tertiary.

Answer 12

FALSE (19 of 20 have a primary alpha amino group, proline has a secondary alpha amino group)

Question 13

TRUE OR FALSE

Isoleucine (I) and Threonine (T) contain a second stereocenter.

Answer 13

TRUE

Question 14

TRUE OR FALSE

Amino acids are zwitterions not only in the water solution but also in the solid form.

Answer 14

TRUE

Question 15

The addition of ____ to an amino acid to lower its pH to 0.0 donates a proton to the COO- group of the zwitterion turning it into a positive ion.

Answer 15

strong acid (such as HCl)

Question 16

The addition of a strong base such as NaOH to raise its pH to 14, a proton is transferred from the _____ group to the base turning the zwitterion into a _____ ion.

Answer 16

NH3+; negative

Question 17

The pH at which the majority of molecules of a compound in solution have no net charge.

Answer 17

Isoelectricpoint, pI

Question 18

TRUE OR FALSE

The -SH (sylfhydryl) group of cysteine is easily oxidized to an -S-S- (disulfide)

Answer 18

TRUE

Question 19

The three amino acids that possess an aromatic ring

Answer 19

Phenylalanine (Phe, F)
Tyrosine (Tyr, Y)
Tryptophan (Trp, W)

Question 20

Tryptophan is the precursor to what neurotransmitter?

Answer 20

Serotonin

Question 21

The precursors of norepinephrine and epinephrine are?

Answer 21

Phenylalanine and Tyrosine

Question 22

TRUE OR FALSE

The oxidation of Phenylalanine results in a molecule of Tyrosine.

Answer 22

TRUE

Question 23

The peptide bond refers to the amide bond between what two groups of two amino acids?

Answer 23

alpha carboxyl group and the alpha amino group

Question 24

A biological macromolecule containing at least 30-50 amino acids joined by peptide bonds.

Answer 24

Protein

Question 25

In 1902, who proposed that proteins are long chains of amino acids joined by amide bonds.

Answer 25

Emil Fischer

Question 26

He discovered that there is about 40% double bond character to the C-N bond and that a peptide bond between two amino acids is planar.

Answer 26

Linus Pauling

Question 27

TRUE OR FALSE

Peptides are written from the left to right, beginning with the free -NH3+ group and ending with the free -COO- group.

Answer 27

TRUE

Question 28

At what condition will proteins are least soluble in water at their isoelectric points and can be precipitated from a solution?

Answer 28

pH = pI

Question 29

TRUE OR FALSE

A dipeptide refers to 2 amino acids and 1 peptide bond

Answer 29

TRUE

Question 30

Myoglobin has how many polypeptides?

Answer 30

One

Question 31

Hemoglobin carries oxygen with how many polypeptide chains?

Answer 31

Four

Question 32

TRUE OR FALSE

Resonance is high proton delocalization.

Answer 32

FALSE (it is ELECTRON delocalization)

Question 33

What do you call polypeptides that are more than 3 but less than 10?

Answer 33

Oligopeptides

Question 34

In human insulin, what is the 30th amino acid found in the beta chain?

Answer 34

Threonine, Thr

Question 35

In the alpha chain of human insulin, what are the amino acids found in positions 8, 9, and 10 in order?

Answer 35

Threonine, Serine, Isoleucine

Question 36

A nonapeptide that is an antidiuretic hormone.

Answer 36

Vasopressin

Question 37

Nonapeptide that affects the contractions of the uterus during childbirth and the muscles of the breast that aid in the secretion of milk.

Answer 37

Oxytocin

Question 38

Vasopressin has what amino acids that make it different from oxytocin?

Answer 38

Arginine and Phenylalanine

Question 39

Oxytocin has what amino acids that make it different from Vasopressin?

Answer 39

Leucine and Isoleucine

Question 40

TRUE OR FALSE

The primary structure of a protein determines to a large extent the native secondary and tertiary structures.

Answer 40

TRUE

Question 41

TRUE OR FALSE

Vasopressin also stimulates uterine contractions however to a much lesser extent.

Answer 41

TRUE

Question 42

What are the conditions in which the alpha helix cannot form in the secondary protein structure?

Answer 42

1. ) the presence of proline

2. ) if a chain possesses an ALL POSITIVE/ ALL NEGATIVE/ ALL HYDROPHOBIC amino acid sequence

Question 43

Globular proteins that contain all three kinds of secondary structures in different parts of their molecules (alpha helix, beta pleated sheet, random coil)

Answer 43

Motifs

Question 44

TRUE OR FALSE

The secondary structure can define specific patterns in the domain or functional part of the protein.

Answer 44

TRUE

Question 45

In an alpha helix structure, where does the side chains point toward to?

Answer 45

outward the helix

Question 46

TRUE OR FALSE

The shape of the alpha helix is maintained by numerous intermolecular hydrogen bonds.

Answer 46

FALSE (it is held by INTRAmolecular bonds)

Question 47

TRUE OR FALSE

The shape of the beta pleated sheet is maintained by either intramolecular or intermolecular hydrogen bonds

Answer 47

TRUE

Question 48

In all secondary structures, the hydrogen bonding is between what groups?

Answer 48

-C=O and H-N groups

Question 49

Another repeated pattern classified as a secondary structure that can be seen in collagen

Answer 49

Extended Helix/ Triple Helix

Question 50

In the tertiary structure of proteins, in what ways is it stabilized?

Answer 50

1. ) Covalent bonds
2. ) Hydrogen Bonds
3. ) Salt Bridges
4. ) Hydrophobic interactions
5. ) Metal ion coordination

Question 51

In tertiary structures, what groups interact to form different types of bonds?

Answer 51

R-groups (this makes it different from the secondary group because there it is the C=O and N-H group that bonds.)

Question 52

The arrangement o polypeptide chains into a noncovalently bonded aggregation is called

Answer 52

Quaternary Structure of proteins

Question 53

In the quaternary structure of proteins, the individual chains are held together by?

Answer 53

1. ) hydrogen bonds
2. ) salt bridges
3. ) hydrophobic interactions

Question 54

TRUE OR FALSE

Fetal hemoglobin contains 2 alpha chains and 2 beta chains.

Answer 54

FALSE

Fetal hemoglobin contains 2 alpha chains and 2 gamma chains and they have greater affinity for oxygen than adult hemoglobin.

Question 55

The process of destroying the native conformation of a protein by chemical or physical means.

Answer 55

Denaturation (some are reversible and others can permanently damage the protein)

Question 56

This denaturing agent can disrupt hydrogen bonding. In globular proteins, it can cause unfolding of polypeptide chains with the result that coagulation and precipitation may take place.

Answer 56

Heat

Question 57

This denaturing agent disrupts hydrogen bonding

Answer 57

6 M aqueous urea

Question 58

2- Mercaptoethanol cleaves disulfide bonds by reducing -S-S- groups to -SH groups. It acts as what type of denaturing agent?

Answer 58

Reducing Agent

Question 59

What type of denaturing agent have transition metal ions that form water-insoluble salts with -SH groups

Answer 59

Heavy Metal ions

Question 60

The Denaturing agent that penetrates bacteria and kill them by coagulating their proteins.

Answer 60

Alcohols

Question 61

How many amino acids are there in a turn of an alpha helix structure?

Answer 61

3.6 amino acids