Protein Structure

Question 1

What is the monomer of a protein

Answer 1

Amino acid

Question 2

When does a dipeptide form?

Answer 2

When two amino acids join together

Question 3

When does a polypeptide form?

Answer 3

When more than two amino acids join together

Question 4

What are proteins made up of?

Answer 4

One or more popypeptides

Question 5

Draw the structure of an amino acid

Answer 5

A carboxyl group joined to an amine group and an R group

Question 6

How are polypeptides formed + describe?

Answer 6

Condensation reaction

A molecule of water is released during the reaction

Question 7

Draw two amino acids undergoing a condensation reaction

Answer 7

…

Question 8

Describe the primary structure of a protein

Answer 8

The sequence of amino acids in a polypeptide chain - joined by peptide bonds

Question 9

Describe the secondary structure of a protein

Answer 9

Folding of the primary structure into an alpha helix or beta pleated sheet held together by hydrogen bonds

Question 10

Describe the tertiary structure of a protein

Answer 10

Folding into a 3D structure using:
Hydrogen bonds 
Disulfide bridges
Ionic bonds
Hydrophobic and hydrophilic interactions

Question 11

Describe the quaternary structure of a protein

Answer 11

Several popypeptides held together by bonds

Question 12

Describe ionic bonds

Answer 12

Attractions between negative and positive charges on different parts of the molecule

Question 13

Describe disulfide bridges

Answer 13

When two molecules of cysteine (amino acid) come close together, the sulfur atim in one systeine bonds to the sulfur in the other cysteine

Question 14

Describe hydrophobic and hydrophilic interactions

Answer 14

When hydrophobic groups are close they clump together so that hydrophilic groups are pushed to the outside - affects the final folding of the protein

Question 15

How does a proteins primary structure determine its 3D structure

Answer 15

Amino acid sequence determines what bonds will form and how the protein will fold which affects its properties

Question 16

What are globular proteins?

Answer 16

Round, compact proteins made up of multiple polypeptide chains

Question 17

What are the polypeptide chains like in globular proteins? + what does this mean?

Answer 17

They are coiled so that the hydrophobic parts face inwards and the hydrophilic parts face outwards allowing the protein to be soluble

Question 18

Give an example of a globular protein

Answer 18

Hameoglobin:
Made of 4 polypeptide chains
Iron-containing haem groups that carry oxygen in the blood

Question 19

What are fibrous proteins?

Answer 19

Long insoluble polypeptide chains that are tightly coiled to form a rope shale

Question 20

What are the polypeptide chains like in fibrous proteins?

Answer 20

Held together by lots of bonds eg. Hydrogen and disulfide making the protein strong

Question 21

Where are fibrous proteins found?

Answer 21

In supportive tissue

Question 22

Give an example of a fibrous protein

Answer 22

Collagen is a strong, fibrous protein that forms connective tissuw

Question 23

What do enzymes do?

Answer 23

Catalyse metabolic reactions on a cellular level (respiration) and on a body lebel (digestion)

Question 24

What is a catalyst?

Answer 24

A substance that speeds up a chemical reaction without being used up in the reaction itself

Question 25

What makes enzymes highly specific?

Answer 25

Tertiary structure

Question 26

What is the active site?

Answer 26

The part of the enzyme where the substrate molecules bind to

Question 27

How do enzymes speed up the rate of reaction?

Answer 27

They lower activation energy making the reactions happen at a lower temperature

Question 28

How does an enzyme-substrate compelx lower the activation energy x2

Answer 28

• if two substrates need joining, being attached to enzyme holds them closer together reducing repulsion between the molecules so can bond easier
• if enzyme catalsyses a breakdown reaction, active sites put a strain on bonds so substrate molecules breaks easier

Question 29

Describe the lock and key model

Answer 29

The substrate fits into the enzyme the way a key fits into a lock

Question 30

Describe the induced fit theory

Answer 30

The active site changes shape as the substrate binds

Question 31

What determined the active sites shape?

Answer 31

The tertiary strucutr ehich is determined by the primary structure

Question 32

What is the primary sturcture determined by?

Answer 32

A gene - if a mutation occurs then the tertiary structure could be altered