Lesson 2: Reactions and Stability of Proteins

Question 1

Protein Structure: two dimensional (length and height)

Answer 1

Primary

Question 2

Protein Structure: three-dimensional spatial arrangement (around the carbon chain/skeleton)

Answer 2

Secondary

Question 3

Protein Structure: shape in which the entire protein chain folds together in three-dimensional space

Answer 3

Tertiary

Question 4

Protein Structure: two or more folded protein chains come together to form a ‘superstructure’

Answer 4

Quaternary

Question 5

__________ and __________ interactions contribute to the structure of proteins, mainly their __________.

Answer 5

Peptide bonds; side chain; tertiary structure

Question 6

The form is determined mainly by their _________ and is stabilized by _________ and _________ .

Answer 6

amino acid sequence; inter-chain; intra-chain hydrogen bonding

Question 7

Side chains of various amino acids may also interact via the following

Answer 7

1. Hydrogen Bonding
2. Hydrophobic Interactions
3. Salt Bridges
4. Disulphide Bridges
5. Dipole-Dipole and Ion-Dipole Forces

Question 8

The amino acid sequences greatly affect the _____________ of proteins.

Answer 8

physico-chemical properties

Question 9

physico-chemical properties of proteins

Answer 9

1. Solubility
2. Molecular weight
3. Shape
4. Isoelectric pH
5. Precipitation

Question 10

__________ is the term used for any change in the three-dimensional structure of a protein that renders it incapable of performing its
assigned function.

Answer 10

Denaturation

Question 11

Denaturation: Physical means

Answer 11

heat,
violent shaking,
very high pressures,
UV radiation

Question 12

Denaturation: Chemical means

Answer 12

pH,
high salt concentrations,
heavy metal ions,
organic solvents,
surface active agents,
high concentrations of urea.

Question 13

Displays number and types of amino acids and number of peptide chains

Answer 13

Primary

Question 14

Bonds involved in primary

Answer 14

H-bonds

Question 15

Bonds involved in Secondary

Answer 15

Functional <-> R group

Question 16

Bonds involved in Quarternary

Answer 16

(Functional <-> R group) 2 or more

Question 17

Salt bridges other name

Answer 17

Electrostatic interaction

Question 18

cysteine residue thiol group + another cysteine residue thiol group

Answer 18

Disulfide Bridges (Intra)

Question 19

Primary Structure maintained by _______, peptide bonds

Answer 19

covalent

Question 20

Any change in the ________ of amino acids may cause abnormal function of the polypeptide.

Answer 20

sequence

Question 21

__________ is caused by the change in amino acid sequence of __________

Answer 21

Sickle anemia; hemoglobin

Question 22

Hemoglobin in sickle cell anemia lacks ________and has ________ instead

Answer 22

Glutamate; valine

Question 23

arrangement in space adopted by the backbone portion of a protein

Answer 23

Secondary Structure

Question 24

Backbone portion of amino acids

Answer 24

Amino group
cardial Carbon
Carboxylic group
Hydrogen

Question 25

coiled shape held in place by hydrogen bonds between the amide groups (-NH) and the carbonyl (-C=O) groups attached to the α-carbon. R groups are not involved in this level of structure.

Answer 25

alpha helix (α-helix)

Question 26

consists of polypeptide chains arranged side by side held together by hydrogen bonding between the amine and the carbonyl oxygen within the amino acid backbone.

Answer 26

beta-pleated sheet (β-pleated sheet)

Question 27

results from the interactions between amino acid side chains that are widely separated from each other within a peptide chain.

Answer 27

Tertiary Structure

Question 28

three-dimensional spatial “arrangements”

Answer 28

secondary structures of proteins

Question 29

specific three-dimensional “shape”

Answer 29

tertiary structure of a protein

Question 30

Side chain <-> Side chain

Answer 30

Hydrogen bonding

Question 31

relatively weak and are easily disrupted by changes in pH and temperature.

Answer 31

Hydrogen bonding (Intra)

Question 32

Nonpolar side-chains are attracted to other nonpolar side-chains “water-free pockets” in the interior region nonpolar R groups aggregate in the interior portion of the polypeptide chain, leaving the polar portion in the exterior.

Answer 32

Hydrophobic interactions (inter)

Question 33

Hydrophobic interactions (inter) example

Answer 33

London forces

Question 34

between an acidic side chain (R group) and a basic side chain (R group)

Answer 34

Electrostatic interaction/Salt bridges (Intra)

Question 35

highest level of protein organization found only in multimeric proteins two or more peptide chains

Answer 35

Quaternary structure

Question 36

Quaternary structure Example:

Answer 36

hemoglobin

Question 37

(two subunits

Answer 37

dimer

Question 38

four subunits

Answer 38

tetramer

Question 39

Color and Taste

Answer 39

colourless and usually tasteless

Question 40

Shape and Size

Answer 40

simple crystalloid spherical structures to long fibrillar structures.

Question 41

globular

Answer 41

(insulin)

Question 42

oval

Answer 42

(albumin)

Question 43

fibrous or elongated

Answer 43

(fibrinogen)

Question 44

Solubility

Answer 44

▪ influenced by pH ▪ lowest at isoelectric point

Question 45

__________ instead of true solutions in water

Answer 45

colloidal solutions

Question 46

Molecular weight

Answer 46

110

Question 47

Molecular weight majority of proteins/polypeptides:

Answer 47

40 to 4,000 amino acids

Question 48

molecular weight Insulin

Answer 48

5,700

Question 49

molecular weight Myoglobin

Answer 49

17,000

Question 50

molecular weight Hemoglobin

Answer 50

64,450

Question 51

Molecular weight Serum albumin

Answer 51

69,000

Question 52

Precipitate

Answer 52

Flocculum

Question 53

act as acids and alkali

Answer 53

Amphoteric

Question 54

can form salts with both cations and anions based on their net charge

Answer 54

Ion binding capacity

Question 55

Pepsin (pI) -

Answer 55

1.1

Question 56

Casein (pI)

Answer 56

4.6;

Question 57

Human albumin (pI)

Answer 57

4.7;

Question 58

Urease (pI)

Answer 58

5.0;

Question 59

Hemoglobin (pI)

Answer 59

6.7;