Proteins

Question 1

Features and structures of fibrous proteins

Answer 1

• formed from long insoluble molecules, due to high proportion of hydrophobic R-group amino acids
• small amino acid range, with small R groups
• repetitive primary structure amino acid sequence
• make strong, long, complex molecules which AREN’T folded into 3D shapes

Question 2

Examples of fibrous proteins

Answer 2

• elastin
• keratin
• collagen

Question 3

Function of elastin

Answer 3

• found in elastic fibres within vessel walls and alveoli
• flexible- allows expansion and return
• quaternary protein made of stretchy molecules or tropoelastin

Question 4

Features of keratin

Answer 4

• present in hair, skin, nails
• large proportion of sulphur containing amino acids, resulting in strong, inflexible, insoluble materials
• degree of bonds determines flexibility
• unpleasant smell when burnt

Question 5

structure of collagen, where found

Answer 5

• connective tissue found in skin, tendons, ligaments
• made of 3 polypeptides wound in a long, rope like structure

Question 6

Structure of globular proteins

Answer 6

• compact
• water soluble
• roughly spherical
• form when proteins fold into tertiary structures, and R groups kept away from aqueous environment

Question 7

Examples of globular proteins

Answer 7

insulin

Question 8

function of insulin

Answer 8

• hormone involved with blood glucose concentration
• solubility and shape required

Question 9

Structure of conjugated proteins

Answer 9

• globular proteins that contain a prosthetic group (a non protein component)
• prosthetic groups lipids or carbs= glycoprotein, lipoprotein

Question 10

Examples of conjugated proteins

Answer 10

• Haemoglobin
• Catalase

Question 11

Function and structure of haemoglobin

Answer 11

• oxygen carrying pigment in RBC
• quaternary protein made of 4 polypeptides
• 4 subunits, each containing a prosthetic haem group

Question 12

What is catalase

Answer 12

• quaternary
• enzyme= hydrogen peroxide breakdown

Question 13

What is a peptide

Answer 13

• polymers made up of amino acid monomers

Question 14

What do proteins consist of

Answer 14

• carbon, hydrogen, oxygen and nitrogen elements only
• 1 polypeptide arranged as a complex macromolecule

Question 15

Amino acids- what is an R group, how many amino acids are there

Answer 15

-R group= variable groups, relative position and type determines the amino acid
- 20 different amino acids

Question 16

How do amino acids join

Answer 16

• amine and carboxylic acid groups react
• the hydroxyl in the carboxylic acid group of 1 amino acid reacts with the hydrogen in the amine group of another amino acid

Question 17

What is a peptide bond

Answer 17

• forms between 2 amino acids when they join
• condensation reaction
• results in a dipeptide

Question 18

What is a polypeptide

Answer 18

• when many amino acids are joined
• catalysed by enzyme peptidyl transferase

Question 19

How is a protein formed

Answer 19

• different R groups interact with each other forming different types of bond which lead to long polypeptide chains folding into complex proteins

Question 20

What is the primary structure of a protein

Answer 20

• the sequence in which the amino acids join
• contained within DNA
• Peptide bonds only

Question 21

What is the secondary structure of a protein

Answer 21

• O, N, H atoms of amino acids interact
• H bonds can form within an amino acid chain- pull it into a coil shape, ALPHA HELIX
• Polypeptide chains can lie parallel to each other, patterns of each acid causes pleats= BETA PLEATED SHEET
• secondary structure result of hydrogen bonds

Question 22

What is the tertiary structure of a protein

Answer 22

• folding of the protein into its final shape
• coiling/ folding brings different R groups closer to interact
• interactions produce a variety of complex shaped proteins with specialised characteristics and functions

Question 23

What are the interactions between R groups

Answer 23

• hydrophilic/ phobic reactions
• hydrogen bonds
• ionic bonds
• disulfide bonds

Question 24

What is the quaternary structure of a protein

Answer 24

• results from association of 2+ individual, different protein molecules (subunits)

Question 25

What enzyme breaks down peptide bonds into amino acids, type of reaction

Answer 25

• proteases
• hydrolysis (requires water)