3.6/3.7 Proteins

Question 1

What is the protein structure consisted of?

Answer 1

one or more polypeptide chains folded in a 3D shape

Question 2

What is the primary structure of a protein?

Answer 2

Order of amino acids determined by genetic code

Question 3

What is the secondary structure of proteins?

Answer 3

alpha helix coil or beta pleated sheet

Question 4

What is the tertiary structure of proteins?

Answer 4

how a protein is further folded (globular shape - 3D)

Question 5

What is the quaternary structure?

Answer 5

more than one polypeptide chain, held together by bonds

Question 6

Where are hydrogen bonds formed?

Answer 6

they are formed between R groups, and are numerous and easily broken

Question 7

Where are disulphide bonds together?

Answer 7

formed between sulphur containing amino acids - found in skin/hair

Question 8

What are the properties of globular proteins?

Answer 8

Proteins rolled into a ball are globular, they are are soluble, used in metabolism and as enzymes.

Question 9

What are the main components of an alpha helix?

Answer 9

• Hydrogen bonds form between oxygen and hydrogen molecules brought into close proximity
• Help to stabilise a structure

Question 10

What are the main components of a beta pleated sheet?

Answer 10

• folds back upon itself many times forming anti-parallel chains
• forms hydrogen bonds
• stability

Question 11

What are hydrogen bonds?

Answer 11

Hydrogen and oxygen atoms from both the main chain and the R group may form hydrogen bonds

Question 12

What are Disulphide Bridges?

Answer 12

The R groups of two amino acids contain sulphur atoms, when in close proximity, form disulphide bridges

Question 13

What are Ionic bonds?

Answer 13

Many of the carboxylic acid and amino groups form charged groups in solution, oppositely charged groups form ionic bonds

Question 14

What are Hydrophobic interactions AKA covalent bonds?

Answer 14

many hydrophobic R groups tend to cluster towards the interior of the protein molecule forming hydrophobic interactions

Question 15

What are proteins?

Answer 15

• proteins can be enzymes, hormones and oxygen transporters (i.e. haemoglobin),
• 3D complex microscopic molecules,
• polymers called polypeptides
• made up of amino acid units

Question 16

Where can proteins be found in people?

Answer 16

bulk of skin, hair, nails/feathers (keratin), and cartilage (smoothness in joints)

Question 17

Where can amino acids be found?

Answer 17

seeds, nuts, pulses, beans, meat

Question 18

What is the structure for a protein?

Answer 18

. R
|
H2N——–C——–COOH
|
H

Question 19

What is the structure for a protein undergoing condensation?

Answer 19

. H R1 O H R2 O
| | || | | ||
N—-C- –C–condensation– N–C–C
| | | |
H H H OH

Question 20

What is the bond formed during a condensation reaction?

Answer 20

A Peptide bond

Question 21

What are two amino acids joined together called?

Answer 21

Dipeptide

Question 22

What are many amino acids joined together called?

Answer 22

Polypeptide

Question 23

What is the R group?

Answer 23

A variable unit, eg. hydrogen

Question 24

What is the amino acid group?

Answer 24

H2N (left)
- AKA Basic Group (neutralises acidic group)

Question 25

What is the carboxylic group?

Answer 25

COOH (right)
- AKA Acidic group (neutralises basic group)

Question 26

Where do excess amino acids go?

Answer 26

stored as NH2 (ammonium), released into urea

Question 27

What is the simplest amino acid that possesses hydrogen as its R group called?

Answer 27

Glycine - every third amino acid in a polypeptide chain

Question 28

What is the shape of an amino acid?

Answer 28

Tetrahedral shape, over 90 degree angles of the bonds between the atoms

Question 29

how many different naturally occuring amino acids are there?

Answer 29

20, that differ by virtue of the R group

Question 30

What R group does Alanine have?

Answer 30

CH3, one basic, one acidic group

Question 31

What amino acid has sulphur in its R group?

Answer 31

Cysteine/ Methionine

Question 32

What are the main components of collagen?

Answer 32

• Fibrous protein
• connective tissue
• triple helix
• flexibility
• Tropocollagen is formed when quaternary proteins have staggered ends which join together (strong polypeptide)

Question 33

What are the main components of elastin?

Answer 33

• Fibrous protein
• can expand/shrink when needed due to having elastic fibres which allow flexibility
• quaternary protein made from tropoelastin
• insoluble
• confers strength and elasticity to the skin, organs and tissues
• found in alveoli and walls of blood vessels
• strengthened by cross-linking covalent bonds

Question 34

What are the main components of Keratin?

Answer 34

• Fibrous protein
• has a lot of the sulphur containing amino acid, Cysteine
• many strong disulphide bonds
• strong, inflexible and insoluble
• degree of disulphide bonds determines flexibility
• quaternary structure

Question 35

What are the main components of Catalase?

Answer 35

• Conjugated protein
• enzyme (Active site)
• quaternary protein that catalyses reactions
• contains four haem prosthetic groups with iron 2 ions, allowing interaction with hydrogen peroxide (substrate) (toxic by-product of metabolism) and speeds up its breakdown
• antioxidant, present in all aerobic organisms
• 2H2O2 –> 2H2O + O2

Question 36

What are the main components of Haemoglobin?

Answer 36

• red, oxygen carrying pigment found in red blood cells (carries oxygen form lungs to all cells where it is released)
• quaternary protein made from four polypeptides
  (2 alpha, 2 beta subunits - each contains a prosthetic haem group which has iron 2 ions present and are able to combine reversibly with an oxygen molecule)
• found in muscle cells as myoglobin
• some amount of carbon dioxide is transported back via haemoglobin as carbaminohaemoglobin