Biomolecules

Question 1

What is the monomer of proteins

Answer 1

Amino acids

Question 2

What is the structure of amino acids?

Answer 2

A central carbon atom(a-carbon) covalently bonded to 4 groups

1. basic amine group (-NH2)
2. acidic carboxyl group (-COOH)
3. a hydrogen atom
4. a variable group, R group

Question 3

What are the properties of amino acids?

Answer 3

1. Non-polar (Hydrophobic)
   e.g glycine, valine, methionine
2. Polar (hydrophilic)
   e.g cysteine
3. Charged (hydrophilic)
   e.g glutamic acid

*charged ≠ polar

Question 4

How are the properties of amino acids affected by?

Answer 4

The R-group vary in size and charge and this gives the amino acid its unique chemical properties.

chem properties influence types of bonds btw amino acids -> how a protein folds-> affects its 3D configuration -> function

Question 5

In an aqueous solution, amino acids exist as …

Answer 5

zwitterions

• carries both negative and positive charges on different atoms but has total net charge of zero (electrically neutral) -> dipolar ion
• amphoteric

Question 6

In neutral aq solution, amino acids act as …

Answer 6

buffers , resisting small changes in pH when an acid or alkali is added by taking up or losing protons (H+)

Question 7

When amino acids bond to each other and form proteins, do they still act as buffers?

Answer 7

Buffering properties are still retained because of the basic and acidic R groups of individual amino acids.

Question 8

How is a polypeptide formed?

Answer 8

Amino acids are joined together via peptide bond to form polypeptide

Question 9

Describe the formation of the peptide bond

Answer 9

It is a covalent bond formed btw the amino group of one amino acid and the carboxyl group of another via a condensation reaction, with the loss of a water molecule, catalysed by peptidyl transferase

Question 10

Describe ionic bond

Answer 10

Bond (electrostatic attraction) formed btw basic and acidic R groups of amino acids

Question 11

Describe disulfide bond

Answer 11

It is a covalent bond (STRONG) formed between sulfhydryl groups (-SH)

• only amino acid cysteine contains -SH in its R group

Question 12

Describe hydrogen bond

Answer 12

It is a relatively weak, non-covalent bond between an electronegative atom (F,O,N) and a hydrogen atom attached to another electronegative atom.

Question 13

Describe hydrophobic interactions

Answer 13

Occur btw non-polar or hydrophobic R groups

-formed at the core of the proteins

Question 14

What are the types of bonds that hold a protein in shape?

Answer 14

1. hydrogen bonds
2. ionic bonds
3. disulfide bonds
4. hydrophobic interactions

Question 15

What is the feature of reducing sugars?

Answer 15

They contain free ketone/aldehyde groups