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