1. Amino Acids and Proteins

Question 1

Put the following in order of increasing specificity: chromatin, nucleotides, DNA, nucleus.

Answer 1

Nucleus, chromatin, DNA, nucleotides.

Question 2

What are monomeric units joined by when forming what?

Answer 2

Joined by covalent bonds to form macromolecules.

Question 3

What are macromolecules joined by?

Answer 3

Joined by non-covalent interactions.

Question 4

Name four main categories of interactions between biomolecules.

Answer 4

Hydrogen bonds, ionic interactions, hydrophobic interactions and van der Waals interactions.

Question 5

Explain what makes a molecular soluble.

Answer 5

It’s ability to make hydrogen bonds. Polar molecules can make hydrogen bonds and therefore can dissolve. Non polar molecules can’t form hydrogen bonds and are therefore insoluble.

Question 6

What are amphipathic molecules?

Answer 6

Molecules with polar and non-polar regions.

Question 7

What are micelles?

Answer 7

Hydrophobic groups away from water, and the ordered shell of water interacts with the hydrophilic heads.

Question 8

List three key roles that proteins play in biological processes.

Answer 8

Catalysts, transporters, structural support, machines (e.g. with muscle contraction), immune protection, ion channels, receptors, ligand in cell signalling.

Question 9

In what way can proteins be considered polypeptides?

Answer 9

They’re macromolecules made up of amino acids covalently joined.

Question 10

What is the general structure of an amino acid?

Answer 10

NH2
           |
   H - C - COOH
           |
          R

Question 11

What’s the reaction of an amino acid that makes it a base?

Answer 11

NH2 + H+ -> NH3+

Question 12

What’s the reaction of an amino acid that makes it an acid?

Answer 12

COOH -> COO- + H+

Question 13

Which stereoisomers are found in proteins? (Include a diagram.)

Answer 13

L isomers. (CORN is spelt to the left).
          R
           |
   H - C - COOH
           |
          NH2

Question 14

What are the three groups of classification considering chemical properties of amino acids? (Give an examples of one amino acid for each category.)

Answer 14

Non-polar amino acids (hydrophobic):
Glycine, alanine, valine, leucine, isoleucine, methionine, proline, phenylalanine, tryptophan.
Polar, uncharged amino acids (hydrophilic):
Serine, threonine, asparagine, glutamine, tyrosine, cysteine.
Polar, charged amino acids (hydrophilic):
Lysine, arginine, histidine, aspartame, glutamate.

Question 15

What happens if pH solution is less than the pK value?

Answer 15

The group is protonated.

Question 16

What happens if pH solution is more than the pK value?

Answer 16

The group will be deprotonated.

Question 17

How do amino acids join?

Answer 17

In a condensation reaction where a peptide bond is formed.

Question 18

What is the difference between trans and cis peptide bonds?

Answer 18

Trans peptide bonds have the carbon on opposite sides of the peptide bond but carbon is on the same side of the peptide bond in cis peptide bonds.

Question 19

What is the isoelectric point (pI) of a protein?

Answer 19

The pH at which there is no overall net charge.

Question 20

List two key differences between bacterial and eukaryotic cells.

Answer 20

Bacteria have no separate nucleus, but eukaryotes do.

Bacteria have a cell wall as well as plasma membrane, but eukaryotes only have a plasma membrane.