Proteins

Question 1

list all 8 protein functions:

Answer 1

• enzymes
• defence
• storage
• transport
• hormonal
• receptor
• movement
• structural

Question 2

how much dry mass do proteins account for:

Answer 2

50%

Question 3

enzymes:

Answer 3

• accelerate chemical reactions

- lock and key mechanism

Question 4

defensive:

Answer 4

eg. antibodies help inactivate and destroy bacteria and viruses
- recognise pathogens and target them

Question 5

storage:

Answer 5

• store amino acids
• eg. casein protein of milk is major source of amino acids for baby mammals
• ovalbumin protein for egg white, amino acid source for developing embryo

Question 6

transport:

Answer 6

transport substance

• haemoglobin: iron-containing protein
• carries molecules

Question 7

hormonal:

Answer 7

• allows different components (organs or tissues) of an organism to communicate
  eg. insulin, causes other tissues to take in glucose, to regulate blood sugar levels

Question 8

receptor:

Answer 8

signals response to stimuli

- receptors in nerve cell detecting molecules

Question 9

movement:

Answer 9

flagella, cilia and muscle

• proteins actin and myosin responsible for contraction of muscles
• motor proteins for cilia and flagella responsible for contraction of muscles

Question 10

structural:

Answer 10

• support
• keratin protein in hair, skin, feathers
• collagen and elastin proteins provide framework in animal connective tissues

Question 11

polypeptides:

Answer 11

polymers built from 20 amino acids (charged, hydrophobic, hydrophilic)

• unique linear sequence of amino acids
• proteins have one or more polypeptides
• 10 to 1000 amino acids in length
• amino acids linked by peptide bonds

Question 12

amino acids:

Answer 12

organic molecules, carboxyl and amino groups

- amino acids differ in properties due to R groups (side chains)

Question 13

peptide bonds:

Answer 13

to join amino acids together

- carboxyl (COOH) and amino (NH2( groups form peptide bonds, loses water in process

Question 14

functional protein consists of:

Answer 14

1 or more polypeptides twisted and folded into 3D structure

- sequence of amino acids determines structure of protein

Question 15

structure of protein determines? and what else affects function

Answer 15

its function,

• only some amino acids are exposed on surface of protein,
• physical and chemical properties of these also affect function

Question 16

types of structural models

Answer 16

• space filling
• ribbon
• wire frame

Question 17

primary structure:

Answer 17

unique sequence of amino acids

- determined by DNA

Question 18

secondary structure:

Answer 18

coils and folds from hydrogen bonds btw amino acids in polypeptide

• alpha helix (coil)
• beta pleated sheet (fold)

Question 19

list 4 chemical bonds:

Answer 19

• hydrogen bonds
• van der Waals interactions
• ionic bonds
• disulphide bonds

Question 20

hydrogen bonds:

Answer 20

H atom + electronegative atom (eg. O or N)

Question 21

van der Waals interactions:

Answer 21

uneven distrubution of electrons, dynamic positive/negative charge, allows weak bonding btw molecules

Question 22

ionic bonds:

Answer 22

btw cation (positive) and anion (negative)

Question 23

disulphide bonds:

Answer 23

covalent bond btw two sulphur atoms

Question 24

tertiary structure:

Answer 24

interactions btw R groups

• H bonds, ionic, hydrophobic, van der Waals interactions
• strong disulphide bridges may reinforce protein structure

Question 25

quaternary structure:

Answer 25

two or more polypeptide chains forming one macromolecule

Question 26

chaperones:

Answer 26

chaperone proteins (chaperonins) aid in correct folding of protein
- cap and hollow cylinder provide safe space for proper folding

Question 27

protein structure: other conditions

Answer 27

physical and chemical can also affect protein structure
- pH
- salt conc.
- temperature
- environment
causes protein to unfold
- loss of native protein structure cause denaturation
- denatured protein in biologically inactive

Question 28

eg. of denaturation

Answer 28

protein thermal denaturation (irreversible) egg white cooking, albumen denatures - cross links

Question 29

eg. sickle cell haemoglobin

Answer 29

normal structure: proteins don’t associate with one another and carries O2 full capacity

vs sickle cell:
- proteins combine into fibre, greatly reducing oxygen carrying capabilities

Question 30

eg. diseases from irregular protein folding

Answer 30

• Alzheimers
• Parkinson’s
• Huntington’s