2B - Protein Structure

Question 1

What Are Proteins?
(2 Points)

Answer 1

~ Are polymers made from long chains of amino acids.
~ Are made up of one or more polypeptides.

Question 2

What Are Amino Acids ?
(2 Points)

Answer 2

~ Monomers of proteins.
~ They have different variable groups.

Question 3

What Determines The Shape Of The Protein?
(4 Points)

Answer 3

~ Sequence of amino acids.
~ Type of amino acids.
~ Shape of amino acids.
~ The shape of the protein is critical for its function.

Question 4

Proteins Are Extremely Important In Cells, Because They Form All Of The Following …
(6 Points)

Answer 4

~ Enzymes.
~ Cell membrane proteins.
~ Hormones.
~ Immunoproteins.
~ Transport proteins.
~ Structural proteins.

Question 5

Amino Acids Have The Same General Structure, Which Is?

Answer 5

~ Carboxyl group (-COOH).
~ Amino group (-NH2).
~ Carbon containing R group.

Question 6

When Amino Acids Join Together, What Bond Do They Form?

Answer 6

Peptide bond.

Question 7

What Do Peptide Bonds Form Between?

Answer 7

Between amino acids.

Question 8

What Are The Steps To Forming A Peptide Bond?
(4 Points)

Answer 8

1) A hydroxyl (-OH) is lost from the carboxylic group of one amino acid.

2) A hydrogen atom is lost from the amine group of another amino acid.

3) The remaining carbon atom from the first amino acid, bonds to the nitrogen atom of the second amino acid.

4) Water is released as this is a condensation reaction.

Question 9

How Are Dipeptides Formed?

Answer 9

By the condensation of 2 amino acids.

Question 10

How Are Polypeptides Formed?

Answer 10

By the condensation of 3 or more amino acids.

Question 11

What Happens During A Hydrolysis Reaction, With Regards To Peptide Bonds?

Answer 11

The addition of water breaks the peptide bonds resulting in polypeptides being broken down into amino acids.

Question 12

How Many Levels Are Involved In The Structure Of Proteins?

Answer 12

4.

Question 13

What Are The First 3 Levels Of The Protein Structure Related To?

Answer 13

A single polypeptide chain.

Question 14

What Is The 4th Level Of The Protein Structure Related To?

Answer 14

To a protein that has 2 or more polypeptide chains.

Question 15

Describe The Primary Structure Of The Protein
(3 Points)

Answer 15

~ The sequence / specific order of amino acids in a polypeptide chain, bonded by covalent peptide bonds.
~ DNA of the cell determines the primary structure of the protein.
~ Is specific for each protein.

Question 16

Describe The Secondary Structure Of The Protein
(2 Points)

Answer 16

~ The coiling of polypeptides into alpha-helices, or folding into beta-pleated sheets through hydrogen bonding.
~ This structure occurs when the weak negatively charged nitrogen and oxygen atoms interact with the weak positively charged hydrogen atoms to form hydrogen bonds.

Question 17

What Are The 2 Shapes Which Can Form Within Proteins Due To Hydrogen Bonds?

Answer 17

~ Alpha-helix.
~ Beta-pleated sheet.

Question 18

How Does The Alpha-Helix Shape Occur?
(2 Points)

Answer 18

~ When the hydrogen bonds form between every 4th peptide bond.
~ Between the oxygen of the carboxyl group and the hydrogen of the amine group.

Question 19

How Is The Beta-Pleated Sheet Formed?

Answer 19

When proteins fold so that two parts of the polypeptide chain are parallel to each other, enabling hydrogen bonds to form between parallel peptide bonds.

Question 20

How Can Hydrogen Bonds Be Broken?

Answer 20

~ High temperatures.
~ pH changes.

Question 21

Describe The Tertiary Structure Of The Protein
(3 Points)

Answer 21

~ Overall 3 dimensional shape of a polypeptide chain.
~ The further folding of the chain of amino acids.
~ Leads to additional bonds forming between R groups.

Question 22

Describe The Quaternary Structure Of The Protein
(2 Points)

Answer 22

~ Are proteins made from multiple polypeptide chains, held together by bonds and form the final 3D structure of the protein.
~ Shows us the position of prosthetic groups.

Question 23

What Are Proteins With Prosthetic Groups Called?

Answer 23

Conjugated proteins.

Question 24

What Bonds Hold The Primary Structure Together?

Answer 24

Peptide bonds between amino acids.

Question 25

What Bonds Hold The Secondary Structure Together?

Answer 25

Hydrogen bonds between polar Side groups, only between amino and carboxyl groups.

Question 26

What Bonds Hold The Tertiary Structure Together?
(4 Points)

Answer 26

~ Ionic bonds between oppositely charged side groups.
~ Hydrogen bonds between polar side groups.
~ Disulfide bonds.
~ Hydrophobic and hydrophilic interactions.

Question 27

What Bonds Hold The Quaternary Structure Together?
(5 Points)

Answer 27

~ Ionic bonds.
~ Hydrogen bonds.
~ Disulfide bonds.
~ Hydrophobic and hydrophilic interaction.
~ Peptide bonds.

Question 28

Give The Structure, Functions And Examples Of Globular Proteins

Answer 28

Structure:
~ Compact, spherical in shape and made up from multiple polypeptide chains.
~ Have a complex tertiary / quaternary structures.
~ Form a spherical shape when folding into their tertiary structure.
~ The folding of proteins due to the interactions between the R groups results in globular proteins having specific shapes.

Function:
~ The orientation of their R groups enables them to be soluble in water.
~ Their solubility in water means that they can play important physiological roles as they can be easily transported around organisms and be involved in metabolic reactions.

Examples:
~ Haemoglobin.
~ Myoglobin.
~ Amylase.
~ Insulin.

Question 29

Why Do Globular Proteins Form A Spherical Shape When Folding Into Their Tertiary Structure?
(2 Points)

Answer 29

~ Because their non-polar hydrophobic R groups are orientated towards the centre of the protein away from the aqueous surroundings.
~ Their polar hydrophilic R groups orientate themselves on the outside of the protein.

Question 30

Give The Structure, Functions And Examples Of Fibrous Proteins

Answer 30

Structure:
~ Long strands of polypeptide chains that are tightly coiled around each other and have cross-linkages due to hydrogen bonds.
~ These cross-linkages form microfibres for tensile strength.
~ Have little to no tertiary structure.
~ Have a limited number of amino acids with the sequence usually being highly repetitive.
~ The highly repetitive sequence creates very organised structures.

Function:
~ Due to a large number of hydrophobic R groups, they are insoluble in water.
~ Are strong which makes them suitable for structural roles.

Examples:
~ Keratin.
~ Elastin.
~ Collagen.