Amino Acids etc

Question 2

What is the range of amino acids in polypeptides?

Answer 2

10-50 amino acids

Example: Insulin hormone.

Question 3

What is insulin and where is it produced?

Answer 3

A peptide hormone produced by beta cells in the pancreas.

Question 4

What does insulin regulate?

Answer 4

Metabolism of carbohydrates and fats.

Question 5

What are proteins?

Answer 5

The most common biological macromolecules occurring in all cells.

Question 6

What defines the primary structure of a protein?

Answer 6

Its unique sequence of amino acids.

Question 7

What is a functional protein?

Answer 7

One or more polypeptides precisely twisted, folded, and coiled into a unique shape.

Question 8

What are the four levels of protein structure?

Answer 8

• Primary
• Secondary
• Tertiary
• Quaternary

Question 9

What is the secondary structure of a protein?

Answer 9

Results from hydrogen bond formation between peptide bonds.

Question 10

What is an α-helix?

Answer 10

A spiral structure resulting from hydrogen bonding between peptide bonds.

Question 11

What is a β-sheet?

Answer 11

A secondary structure where two or more polypeptides are linked by hydrogen bonds.

Question 12

What is the role of hydrogen bonds in α-helices?

Answer 12

They stabilize the helical structure.

Question 13

What is a tripeptide?

Answer 13

A molecule consisting of three amino acids linked by two peptide bonds.

Question 14

What is glutathione composed of?

Answer 14

Glu-Cys-Gly (glutamic acid, cysteine, and glycine).

Question 15

What is a dipeptide?

Answer 15

Two amino acids joined by one peptide bond.

Question 16

What is the significance of peptide bond formation?

Answer 16

Links amino acids together to form peptides and proteins.

Question 17

What are metalloproteins?

Answer 17

Proteins conjugated with metal ions such as iron, copper, or zinc.

Question 18

What is the function of glycoproteins?

Answer 18

Proteins conjugated with sugar (carbohydrates).

Question 19

What are nucleoproteins?

Answer 19

Basic proteins conjugated with nucleic acids (DNA or RNA).

Question 20

What is collagen?

Answer 20

The most important protein in mammals, forming about 30% of total body proteins.

Question 21

What is the structure of collagen?

Answer 21

Three helical polypeptide chains twisted around each other.

Question 22

What is the isoelectric pH of a protein?

Answer 22

The pH at which a protein has no net charge.

Question 23

What occurs during denaturation of proteins?

Answer 23

Loss of secondary and tertiary structures without breaking primary structure.

Question 24

What is renaturation?

Answer 24

The process where denatured proteins regain their structure under certain conditions.

Question 25

What does the Biuret test indicate?

Answer 25

The presence of proteins.

Question 26

What are the elements composing proteins?

Answer 26

* Carbon (C) * Hydrogen (H) * Oxygen (O) * Nitrogen (N) * Sulfur (S) * Phosphorus (P)

Question 27

What is the role of lipoproteins?

Answer 27

Help transport lipids in blood and assist in cell membrane structure.

Question 28

What are simple proteins?

Answer 28

Proteins that yield only amino acids upon hydrolysis.

Question 29

What are conjugated proteins?

Answer 29

Proteins that yield both a protein part and a non-protein part upon hydrolysis.

Question 30

What are scleroproteins?

Answer 30

Structural proteins that are not digested.

Question 31

What is the role of elastin?

Answer 31

Provides elasticity in large blood vessels and tissues.

Question 32

What are b-turns in proteins?

Answer 32

Allow the protein backbone to make abrupt turns.

Question 33

What stabilizes the tertiary structure of proteins?

Answer 33

Interactions among R groups and between R groups and the polypeptide backbone.

Question 34

What are disulfide bridges?

Answer 34

Strong covalent bonds that stabilize protein structures.

Question 35

What is the quaternary structure of a protein?

Answer 35

Aggregation of two or more polypeptide subunits held together by non-covalent interactions.

Question 36

What is the primary function of hemoglobin?

Answer 36

Transport oxygen in the blood.

Question 37

What is the significance of peptide bond planarity?

Answer 37

The six atoms associated with the peptide group are coplanar.

Question 38

What is the role of hydrophobic interactions in protein structure?

Answer 38

Help stabilize the tertiary structure.

Question 39

What is the effect of heating on proteins?

Answer 39

Causes denaturation.

Question 40

What is the general definition of proteins?

Answer 40

Polymers of amino acids linked by peptide bonds.

Question 41

What is the difference between peptides and proteins based on amino acid count?

Answer 41

Peptides have less than 50 amino acids; proteins have more than 50.

Question 42

What forms peptides and proteins?

Answer 42

Peptide bond ## Footnote Peptides are chains with less than 50 amino acids; proteins have more than 50.

Question 43

How many amino acids are found in proteins?

Answer 43

20 amino acids ## Footnote Though about 300 amino acids occur in nature, only 20 are found in proteins.

Question 44

What are the two classifications of amino acids based on COOH and NH2 groups?

Answer 44

Monobasic, monocarboxylic amino acids ## Footnote These are neutral or uncharged amino acids.

Question 45

Name three branched-chain amino acids.

Answer 45

* Valine * Leucine * Isoleucine

Question 46

What is the difference in branching between leucine and isoleucine?

Answer 46

Leucine branches on γ carbon; isoleucine branches on β carbon

Question 47

Which amino acids are considered neutral sulfur-containing amino acids?

Answer 47

* Cysteine * Methionine

Question 48

What are neutral aromatic amino acids?

Answer 48

* Phenylalanine * Tyrosine * Tryptophan

Question 49

What is the classification of proline?

Answer 49

Neutral heterocyclic amino acid

Question 50

What is the common structure of amino acids?

Answer 50

Each has 4 groups attached to α-carbon: NH2, COOH, H, and R

Question 51

What forms a zwitter ion at physiological pH?

Answer 51

Dissociation of -COOH group and protonation of NH2 group

Question 52

What is the stereochemical reference for amino acids?

Answer 52

Fischer projection of L-serine

Question 53

Which amino acids are classified as basic?

Answer 53

* Lysine * Arginine * Histidine

Question 54

What are the two types of amino acids classified based on their charge at physiological pH?

Answer 54

* Acidic amino acids (negative charge) * Basic amino acids (positive charge)

Question 55

What are essential amino acids?

Answer 55

Amino acids that cannot be formed in the body and must be obtained from diet ## Footnote Examples include Valine, Leucine, Isoleucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan.

Question 56

What are semiessential amino acids?

Answer 56

Amino acids formed in the body but not in sufficient amounts ## Footnote Examples include Arginine and Histidine.

Question 57

What are non-essential amino acids?

Answer 57

Amino acids that are formed in sufficient amounts in the body

Question 58

What are ketogenic amino acids?

Answer 58

Amino acids that produce ketone bodies ## Footnote Lysine and Leucine are the only pure ketogenic amino acids.

Question 59

What are mixed ketogenic and glucogenic amino acids?

Answer 59

* Isoleucine * Phenylalanine * Tyrosine * Tryptophan

Question 60

What is the isoelectric point (pI)?

Answer 60

The pH at which the zwitter ion is formed

Question 61

What occurs during electrophoresis of amino acids?

Answer 61

Positively charged amino acids move toward the negative electrode; negatively charged amino acids move toward the positive electrode

Question 62

What happens to an amino acid at its pI?

Answer 62

It does not migrate

Question 63

What is the formula for calculating pI?

Answer 63

pI = (pKCOOH + pKNH2)/2

Question 64

What reactions do amino acids undergo due to their COOH group?

Answer 64

* Salt formation with alkalis * Ester formation with alcohols * Amide formation with amines * Decarboxylation

Question 65

What is the ninhydrin reaction?

Answer 65

A test that yields a blue color indicating the presence of amino acids

Question 66

What color does the ninhydrin reaction give for imino acids?

Answer 66

Yellow color

Question 67

What is the Millon reaction used for?

Answer 67

Detecting phenolic compounds, giving a red color for tyrosine

Question 68

What does the Rosenheim reaction detect?

Answer 68

Presence of tryptophan in proteins, giving a violet ring

Question 69

What test is used for histidine?

Answer 69

Pauly reaction, gives yellow to reddish product

Question 70

What do lead sulfide tests detect?

Answer 70

Sulfur-containing amino acids like cysteine, giving a brown color

Question 71

What is the Cannizzaro reaction associated with?

Answer 71

Proteins containing aromatic benzene rings, giving yellow color

Question 72

What is the significance of titration curves for amino acids?

Answer 72

They show the gradual addition or removal of protons

Question 73

What is the effect of pH on amino acids?

Answer 73

At different pH levels, amino acids can exist in different ionic forms