Chapter 18: Amino Acids

What are the principle classes of Biomolecules?

proteins, carbs, lipids, and nucleic acids

What are the building blocks of proteins?

amino acids

What functional groups are characteristic of an a-amino acid?

-NH2 amino, -COOH carboxylic acid, -R side chain

Which type of -R side chains are hydrophilic?

basic, acidic, and polar

Which a-amino acid is achiral?

glycine

Which type of -R chains are hydrophobic?

nonpolar

What kind of reaction can take place within an amino acid?

acid-base

Which part of an uncharged amino acid is acidic?

-COOH group

Which part of an uncharged amino acid is basic?

-NH2 group

What is the name for the resulting molecule of an amino acid which undergoes an acid-base reaction?

dipolar ion

What happens to the -COOH group of an amino acid after an acid-base reaction?

loses an H+ ion to become -COO^-

What happens to the -NH2 group of an amino acid after an acid-base reaction?

gains an H+ ion to become -NH3⁺

What is the name of an amino acid with dipolar ions which cancel out to a neutral charge?

zwitterion

What does a zwitterion do in an Acidic solution (low pH)?

-COO^- accepts a proton

What does a zwitterion do in a Basic solution (high pH)?

-NH3⁺ loses a proton

What part of a zwitterion is basic?

-COO^- group

What part of a zwitterion is acidic?

-NH3⁺ group

How do multiple amino acids link togehter?

peptide bonds

How does a peptide bond form?

-NH2 amino group of one amino acid bonds to the -COOH of another amino acid

What other molecule forms from a peptide formation?

H2O

What are the original amino acids in a peptide chain called?

residues

Which residue gets named first for in a peptide?

N-terminal amino residue

Which residue gets named second in a peptide?

C-terminal residue

What forms the backbone of a primary protein structure?

alternating peptide bonds and alpha carbons

What is a linear line of amino acids connected with peptides called?

primary protein structure

What are the flat, rigid blocks containing Cα–C(=O)–N–H–Cα in a protein chain?

planar units

How many atoms does a planar unit contain?

6

What does a proteins function depend on?

order of amino acids

How to find the number of arrangements of a certain number of amino acids?

=n!

What two forms do secondary protein structures take?

a-helix and B-sheet

What is a single protein chain coiled clockwise by many hydrogen bonds?

a-helix

What are multiple straight neighboring protein chains hydrogen bonded together called?

B-sheet

What atoms bond together to make B-sheets?

amide carbonyl O atoms and amide amino H atoms

Which type of protein are secondary protein structures responsible for?

fibrous proteins

The sequence of amino acids connected by peptide bonds in the polypeptide chain; for example, Asp-Arg-Val-Tyr

primary protein structure

The arrangement in space of the polypeptide chain, which includes the regular patterns of the α-helix and the β-sheet formations

secondary protein structure

What forces hold a secondary protein structure together?

hydrogen bonds between backbone acid residues

The folding of a single protein chain into a specific three-dimensional shape held together by noncovalent interactions

tertiary protein structures

Two or more protein chains assembled in a larger three-dimensional structure held together by noncovalent interactions

quaternary structure

Which class of proteins are tough, insoluble, and composed of fibers and sheets?

fibrous proteins

Which class of proteins are water-soluble and have chains folded into compact shapes

globular proteins

Which class of proteins only contain amino acid residues?

simple proteins

Which class of proteins include one or more non–amino acid units?

conjugated proteins

Which class of proteins are the functional shape (secondary, tertiary, and quaternary structure) in which it exists naturally in living organisms?

native proteins

Which class of proteins are soluble and move through the body in extracellular fluid such as blood. An example is serum albumin?

mobile proteins

Which class of proteins are soluble and remain inside a cell. An example is hemoglobin?

cellular proteins

name this noncovalent side chain interaction

hydrogen bonding

What type of side chains can hydrogen bond with each ohter?

polar -R chains

name this noncovalent side chain interaction

ionic attraction (salt bridges)

What type of side chains are involved in ionic attraction (salt bridges)

ionized acidic and basic -R groups

name this noncovalent interaction of a side chain

hydrophilic hydrogen bonding

Which side chains will form hydrophilic bonds with water?

polar and charged -R groups

Which side chain perform hydrophobic interactions?

nonpolar/alkyl -R chains

name this noncovalent side chain interaction

hydrophobic interactions

Name the one covalent side chain interaction of amino acid side chains?

disulfide bonding

What type of interaction is this?

covalent disulfide bond

What happens when a disulfide bond occurs in the same chain?

creates a loop

What do the 5 amino acid side chain interaction determine

tertiary protein structure

The loss of secondary, tertiary or quaternary protein structure due to disruption of noncovalent interactions and/or disulfide bonds that leaves peptide bonds and primary structure intact

denaturation 

How are proteins broken down? 

hydrolysis

hydrolyzes a peptide bond on the carboxyl-terminal side of aromatic amino acids

chymotrypsin

hydrolyzes peptide bonds on the carboxyl side of lysine and arginine

trypsin