proteins

Question 1

define polymer

Answer 1

a long chain of repeating units (monomers)

Question 2

what is a condensation reaction?

Answer 2

a condensation reaction joins two monomers together, and water is formed as a by-product

Question 3

what is a hydrolysis reaction?

Answer 3

a hydrolysis reaction breaks down (the covalent bonds between) polymers by adding water

Question 4

what is a polymer made from amino acids called?

Answer 4

a protein

Question 5

what is the bond that joins amino acids to form a protein?

Answer 5

peptide bond

Question 6

what happens to an amino acid in an acidic environment?

Answer 6

in an acidic environment there are excess H+ ions, so the amino acid will absorb H+ and become positive (NH2 -> NH3+)

Question 7

what are the features of a protein’s primary structure?

Answer 7

-the sequence of amino acids
-does not occur in nature
-only peptide bonds
-tells us the order of amino acids/how many there are in a chain

Question 8

what are the features of a protein’s secondary structure?

Answer 8

-forms due to hydrogen bonds between NH3+ and COO-
-primary structure folds into alpha helices and beta pleated sheets

Question 9

what are the features of a protein’s tertiary structure?

Answer 9

-further folding to produce a specific 3D shape
-contains disulfide bridges, ionic bonds, hydrogen bonds and hydrophobic interactions

Question 10

what are the features of a protein’s quaternary structure?

Answer 10

-not found in all proteins
-two or more polypeptide chains attached to each other

Question 11

where does a disulfide bridge occur?

Answer 11

between two R-groups that contain sulfur

Question 12

where does an ionic bond occur?

Answer 12

bewteen charged R-groups

Question 13

where does a hydrogen bond occur?

Answer 13

between polar R-groups

Question 14

where do hydrophobic interactions occur?

Answer 14

between non-polar R-groups

Question 15

order the bonds found in tertiary structures from strongest to weakest

Answer 15

strongest
disulfide bridge
ionic bond
hydrogen bond
hydrophobic interaction
weakest

Question 16

what is the structure of an amino acid?

Answer 16

structure:
‘R’
|
NH2—-C—-COOH
|
H

Question 17

what is the ‘R’ group?

Answer 17

also known as the variable group, it is different in every amino acid and causes different properties

Question 18

what is the amino group?

Answer 18

NH2

Question 19

what is the acid group?

Answer 19

COOH (carboxylic)

Question 20

what would happen to an amino acid in an acidic environment?

Answer 20

the amino group will absorb an H+ ion and become positive (NH3+)

Question 21

what would happen to an amino acid in an alkaline environment?

Answer 21

the acid group will lose an H+ ion and become negative (COO-)

Question 22

amino acid + amino acid = ?

Answer 22

dipeptide + water (condensation reaction)

Question 23

dipeptide + water = ?

Answer 23

2 amino acids (hydrolysis reaction)

Question 24

which bond joins two amino acids together?

Answer 24

peptide bond

Question 25

what is a zwitterion?

Answer 25

one with both a positive and negative charge on a molecule

Question 26

why are amino acids described as 'buffers'?

Answer 26

they prevent small changes in pH by accepting/donating H+ ions

Question 27

what is a prosthetic group?

Answer 27

any non-polypeptide incorporated into the structure

Question 28

what is the shape of a fibrous protein?

Answer 28

long, narrow fibres; often have repeated alpha helices or beta pleats

Question 29

what is the purpose of a fibrous protein?

Answer 29

structural- muscle, bones, hair, skin

Question 30

what is the amino acid sequence of a fibrous protein?

Answer 30

repeated sequence- to get the repetitive shape

Question 31

how durable are fibrous proteins?

Answer 31

very durable, less affected by changes in temperature/pH

Question 32

name some examples of fibrous proteins

Answer 32

collagen, keratin, silk

Question 33

are fibrous proteins soluble or insoluble?

Answer 33

insoluble

Question 34

what is the shape of globular proteins?

Answer 34

spherical, with no particular pattern

Question 35

what is the purpose of a globular protein?

Answer 35

metabolic- used in chemical reactions in the body

Question 36

what is the amino acid sequence of a globular protein?

Answer 36

irregular sequence- to get the irregular shape

Question 37

how durable are globular proteins?

Answer 37

low durability: more affected by changes in temp./pH

Question 38

name some examples of globular proteins

Answer 38

enzymes, hormones, antibodies, haemoglobin

Question 39

are globular proteins soluble or insoluble?

Answer 39

soluble in water

Question 40

where does protein trafficking take place?

Answer 40

1. nucleus 2. rough endoplasmic reticulum 3. golgi body 4. cell membrane 5. mitochondria

Question 41

what happens in the nucleus during protein trafficking?

Answer 41

1. the nucleolus produces ribosomes 2. DNA contains the instructions used to make proteins 3. mRNA is a copy of these instructions 4. mRNA leaves via the nuclear pore

Question 42

what happens in the rough endoplasmic reticulum during protein trafficking?

Answer 42

1. mRNA is converted into protein (primary structure) 2. protein leaves RER in a vesicle

Question 43

what happens in the golgi body during protein trafficking?

Answer 43

1. protein is 'modified' into secondary, tertiary and maybe quaternary structure 2. protein exits golgi body in a vesicle

Question 44

what happens in the cell membrane during protein trafficking?

Answer 44

some proteins are released from the cell (e.g. hormones + enzymes)

Question 45

how is the mitochondria involved in protein trafficking?

Answer 45

protein production, packaging and transport require lots of ATP

Question 46

what are glycoproteins?

Answer 46

modified proteins