Lesson 4 : Proteins

Question 1

Proteins is also called ______________ since it is a chain of ___________ linked by ______________.

Answer 1

polypeptide
amino acids
peptide bonds

Question 2

Characteristics (definition) of proteins

Answer 2

● It is a naturally occurring, unbranched polymer in which the monomer units are amino acids.
● It is a peptide in which at least 40 amino acid residues are present.
● It contains Carbon, Hydrogen, Oxygen, and Nitrogen.
● It sometimes contains Sulfur and Phosphorus.

Question 3

Function of Protein

Answer 3

● Structural component (skin, hair, muscles)
● Chemical messenger (hormones)
● Disease defense (antibodies)
● Enzymes (catalase, lactase)

Question 4

Characteristics (definition) of amino acids

Answer 4

● Building blocks of proteins.
● There are 700 different naturally occurring amino acids, but only 20 are normally present in proteins.

Question 5

There are __ amino acids present in proteins are called the ______________ ____________ ___________.

Answer 5

20
Standard Amino Acids

Question 6

CHEMICAL STRUCTURE OF AMINO ACIDS

Answer 6

● Amino acid is an organic compound that contains both an amino group and a carboxyl group.
● Amino group acts like a base and tends to be positive.
● Carboxyl group acts like an acid and tends to be negative.
● “R” group is a variable and can range from 1-2 atoms.
● Two amino acids can join to form a dipeptide.

Question 7

What is a Peptide bond

Answer 7

linkage of carbon and nitrogen.

Question 8

CLASSIFICATION BASED ON SIDE CHAIN POLARITY

Non-Polar Amino Acids
Polar Neutral Amino Acids
Polar Acidic Amino Acids
Polar Basic Amino Acids

Answer 8

Non-Polar Amino Acids
1 amino group
1 carboxyl group
1 non polar side chain

Polar Neutral Amino Acids
1 amino group
1 carboxyl group
1 polar neutral side chain

Polar Acidic Amino Acids
1 amino group
2 carboxyl group
(1 is part of side chain)

Polar Basic Amino Acids
2 amino group
1 carboxyl group
(1 is part of side chain)

Question 9

What are the essential amino acids

Answer 9

○ Histidine
○ Isoleucine
○ Leucine
○ Lysine
○ Methionine
○ Phenylalanine
○ Threonine
○ Tryptophan
○ Valine

Question 10

What are the conditionally non-essential amino acids

Answer 10

○ Arginine
■ Required for growth in children but is not an essential acid for adults.
○ Cystine
○ Glutamine
○ Glycine
○ Proline
○ Tyrosine

Question 11

What are the non-essential amino acids

Answer 11

○ Alanine
○ Asparagine
○ Aspartate
○ Glutamate
○ Serine

Question 12

Amino acids have___________ : Right and Left based on the _____________ of the amino group.

Answer 12

mirror images
location

Question 13

Nature prefers the ______________ of amino acids.

Answer 13

L-isomers

Question 14

All 20 standard amino acids have chiral centers except __________.

Answer 14

Glycine

Question 15

What is Chirality

Answer 15

refer to having a mirror image.

Question 16

it is a molecule that has both positive and negative charges. It is made up of two (or more) functional groups. One of its components has a positive charge and another one with a negative charge.

Answer 16

Zwitterion

Question 17

the net charge of a zwitterion is

Answer 17

zero

Question 18

The pH at which an amino acid has no net charge because equal number of positive and negative charges are present.

Answer 18

ISOELECTRIC POINT

Question 19

Through _____________ ____________ of proteins or amino acids, it produces dipeptide that is linked to carbon-nitrogen bond.

Answer 19

dehydration synthesis

Question 20

What does IUPAC and what is it’s purpose

Answer 20

International Union of Pure and Applied Chemistry
Helps in naming small peptides.

Question 21

IUPAC RULES IN NAMING PEPTIDES

Answer 21

RULE 1
● The C-terminal amino acid residue keeps its full amino acid name.

RULE 2
● All the other amino acid residue names ending in -ine or -ic acid will be replaced with -yl, except:
○ Tryptophan - Tryptophyl
○ Cysteine - Cysteinyl
○ Glutamine - Glutaminyl
○ Asparagine - Asparaginyl

RULE 3
● The amino acid naming sequence begins at the N-terminal amino acid residue.

Question 22

CLASSIFICATION OF PROTEIN: BASED ON NUMBER OF PEPTIDE CHAIN

● Monomeric Protein
● Multimeric Protein

Answer 22

● Monomeric Protein - only one peptide chain is present. ● Multimeric Protein - more than one peptide chain is present.

Question 23

CLASSIFICATION OF PROTEIN: BASED ON CHEMICAL COMPOSITION

● Simple Protein
● Conjugated Protein

Answer 23

● Simple Protein - only amino acid residues are present.
● Conjugated Protein - one or more non-amino acid entities present in its structure in addition to one or more peptide chains.

Question 24

The pleated sheet structure of the Beta Sheet is held together by the _______ between the ______ of ______________.

Answer 24

Hydrogen Bonds
amide groups
linear polypeptide chains

Question 25

The average number of amino acid residues in a typical Beta Sheets is ___ with an average of ___ strands bonding together.

Answer 25

six

Question 26

CLASSIFICATION OF PROTEIN: BASED ON SHAPE

● Fibrous
● Globular

Answer 26

● Fibrous - have an elongated shape with one dimension much longer than the others.
● Globular - have peptide chains folded into spherical and globular shapes.

Question 27

What is PROTEIN HYDROLYSIS

Answer 27

● Splits peptide bonds to smaller peptides and amino acids.
● Occurs in the digestion of proteins.
● Occurs in cells when amino acids are needed to synthesize new proteins and repair tissues.
● In the lab, hydrolysis of a peptide requires acid or base, water, and heat.
● In the body, enzymes catalyze the hydrolysis of proteins.

Question 28

What is PROTEIN DENATURATION

Answer 28

Involves the disruption of bonds in the secondary, tertiary, and quaternary structures.

Question 29

● Heat and organic compounds
● Acids and Bases
● Heavy metal ions
● Agitation (Whipping or Shaking)

Answer 29

● Heat and organic compounds - break apart H+ bonds and disrupt hydrophobic interactions.
● Acids and Bases - break H+ bonds between polar R groups and disrupt ionic bonds.
● Heavy metal ions - react with S-S (Sulfur-Sulfur) bonds to form solids.
● Agitation (Whipping or Shaking) - stretches peptide chains until bonds break.