Biochemistry intro 3 - Water, pH and amino acids

Question 1

How is water a polar molecule?

Answer 1

Water is polar because the electrons are shared unequally due to differences in the electronegativities of hydrogen and oxygen

Question 2

What type of substances can dissolve in water?

Answer 2

Ionic and polar substances can dissolve in water since they have hydrophilic (water loving) parts

Question 3

When can hydrogen bonding occur and how strong it is?

Answer 3

Hydrogen bonding only occurs in molecules where the hydrogen is covalently bonded to either nitrogen, oxygen or fluorine and doesn’t occur in non-polar substances. Individually, hydrogen bonds are much weaker than covalent bonds but can be very strong collectively

Question 4

What is meant by the “hydrophobic effect”?

Answer 4

This is when two layers are created when oil and water are tried to be mixed as water and oil don’t mix

Question 5

True or False: Compounds containing only carbon and hydrogen are very polar

Answer 5

False - compounds containing only carbon and hydrogen are very NON-POLAR

Question 6

What is meant by hydrophilic and hydrophobic?

Answer 6

Hydrophilic means water-loving and is a polar substance. Hydrophobic means water-hating and is a non-polar substance

Question 7

What is the term given to molecules that have BOTH hydrophilic and hydrophobic parts and give an example of this type of molecule?

Answer 7

These types of molecules are called amphiphilic molecules. An example of one of these is a fatty acid as it has a hydrophilic head and a hydrophobic tail

Question 8

What are amino acids made up of?

Answer 8

Amino acids are the building blocks of proteins and they contain an amine group (NH2), carboxyl group (COOH), a hydrogen and a side chain

Question 9

What are stereoisomers and in nature chemistry what form are they in?

Answer 9

Stereoisomers are non-superimposable mirror images of each other. All the amino acids involved in nature biochemistry is in the L form

Question 10

What classifications of amino acids are there?

Answer 10

Amino acids can be:

1. Non-polar, Hydrophobic
2. Polar
3. Basic
4. Acidic

Question 11

What type of bonds join amino acids together?

Answer 11

Peptide bonds are strong, planar bonds that join amino acids together to produce a chain of amino acids called a polypeptide (Only Christ kNows How) The side with the NH3+ is called the N-terminus and the side with the COO- is called the C terminus

Question 12

What is the definition of an acid and a base?

Answer 12

An acid is a molecule that donates protons. Where as a base is a molecule that accepts protons

Question 13

What is Ka a measure of?

Answer 13

The strength of an acid is measure by Ka which is the acid dissociation constant

Question 14

What is pH a measure of?

Answer 14

pH is a measure of the amount of protons in a solution

Question 15

Make sure to know the formulas for calculating pH, Ka, pKa and the pH of a weak acid

Answer 15

Look in notes under intro to biochemistry 3

Question 16

What is a buffer and how do they work?

Answer 16

A buffer is a solution which controls the pH of a reaction mixture. At their pKa value, buffers tend to resist a change of pH on addition of moderate amounts of acid or base (relates to titration curves)

Question 17

What are zwitterions?

Answer 17

These are amino acids which don’t have charged side groups in neutral solutions

Question 18

What is the isoelectric point?

Answer 18

The isoelectric point is the pH at which a molecule as no net charge

Question 19

True or false: Proteins can acts as buffers

Answer 19

True

Question 20

True or False: Uncharged amino acids have 2 titratable groups meaning 2 pKa values

Answer 20

True