proteins

Question 1

what is the most basic form of a protein/ what is the monomer of protein

Answer 1

amino acid

Question 2

how does a polypeptide become functional

Answer 2

it must be folded

Question 3

what happens to a polypeptide if it is folded wrong?

Answer 3

it will be dysfunctional

Question 4

list 6 functions of proteins

Answer 4

support, enzymes, transport, defense, contraction, regulation

Question 5

explain how proteins are used for support

Answer 5

some proteins have a rigid structure and can be used in the cell/body for structural support, i.e keratin in hair or fibrin in clots

Question 6

write a short note about enzymes

Answer 6

biological catalysts, substrate -> product, active site/cleft, specific, globular

Question 7

explain how proteins can be used in transport

Answer 7

membrane proteins allow transport of substances in and out of the cell (aqueous substances cannot pass through the lipid bilayer and so pass through protein channels). carrier proteins can close around a molecule, flip, and release it to the other side of the cell membrane

Question 8

what is the purpose of haemoglobin

Answer 8

transports oxygen

Question 9

what is the purpose of myoglobin

Answer 9

transports oxygen to muscle

Question 10

what is the purpose of transferrin

Answer 10

transports iron

Question 11

how many polypeptide chains can a protein have

Answer 11

one or more

Question 12

how many polypeptide chains does a red blood cell have

Answer 12

4 (with binding sites)

Question 13

explain how proteins aid with defense

Answer 13

antibodies are proteins which can detect foreign cells/substances and alert the defense system

Question 14

give 3 examples of protein contractions

Answer 14

muscle fibres, cilia, spindle fibres

Question 15

what is actin and myosin

Answer 15

two protein filaments which aid muscle contraction (sliding action)

Question 16

how do proteins help with regulation in the body

Answer 16

hormones are inter-cellular messengers that influence the metabolism of cells, i.e insulin regulates blood glucose levels

Question 17

what bio-molecule is insulin made of?

Answer 17

protein (all hormones are proteins)

Question 18

what is the monomer of protein?

Answer 18

amino acids

Question 19

name the 4 groups the central carbon in an amino acid is bonded with

Answer 19

a hydrogen atom (-H), an amino group (NH2), a carboxyl group (COOH), a side chain (-R)

Question 20

draw the basic structure of an amino acid and include: a hydrogen atom (-H), an amino group (NH2), a carboxyl group (COOH), a side chain (-R)

Question 21

how can the 20 distinct amino acids be distinguished?

Answer 21

by the R group/chain (variable side chain)

Question 22

define hydrophobic and hydrophillic

Answer 22

hydrophobic- water hating, hydrophillic- water loving

Question 23

what are the features of hydrophobic amino acids?

Answer 23

repel aqueous environment, reside usually on the interior of proteins, do not ionise (ionic bond formation) or participate in hydrogen bonding

Question 24

what are the features of hydrophillic amino acids?

Answer 24

interact with aqueous environment, often involved in hydrogen bond formation, are found on the exterior surfaces of proteins

Question 25

what is a zwitterion?

Answer 25

an amino acid with no ionisable R group with a neutral electric charge and a pH of 7.4

Question 26

draw a zwitterion

Question 27

what happens if you increase the pH of a solution of an amino acid by adding hydroxide ions (OH-) to a zwitterion

Answer 27

the hydrogen ion is removed from the NH3+ group and water is formed

Question 28

what happens if you decrease the pH by adding an acid (H+) to a solution of an amino acid

Answer 28

the -COO- part of the zwitterion picks up a hydrogen ion and becomes positive

Question 29

what is the isoelectric point (pI)

Answer 29

when the net charge of an amino acid/protein is zero

Question 30

what are the 5 chemical classes of amino acid R groups?

Answer 30

1. non-polar and aliphatic. 2. aromatic (generally nonpolar) 3. polar but uncharged. 4. neg charged. 5. pos charged

Question 31

what are the features of nonpolar alliphatic R groups

Answer 31

the hydrocarbon groups are nonpolar and hydrophobic, usually located on the interior of the protein, no pos or neg poles are formed due to it being nonpolar

Question 32

what are the features of the polar + uncharged class of R groups

Answer 32

the hydrocarbon R groups are polar (electron distribution is uneven- they will interact with other elements in a solution) and hydrophillic. located on the exterior of the protein,

Question 33

what are some features of aromatic R groups

Answer 33

an amino acid which has an aromatic ring, are very hydrophobic

Question 34

features of positively charged R groups

Answer 34

are positively charged at physiological pH, are not in zwitterion formation, are hydrophillic

Question 35

features of negatively charged R grouos

Answer 35

have a negative charge, have carboxyl groups in R side chains, negatively charged at physiological pH, hydrophillic

Question 36

what is a peptide bond + how is it formed?

Answer 36

a covalent bond (sharing of electrons) formed between two amino acids when the a-carboxyl group of one and the a-amino group of the other undergo a condensation dehydration reaction losing a water molecule

Question 37

is the R chain involved in a condensation dehydration reaction?

Answer 37

no- the reaction is only between carboxyl and amino groups

Question 38

what sort of bond is a peptide bond

Answer 38

a covalent bond (electrons are shared)

Question 39

what is the reaction called that involves the creation of a peptide bond and the loss of a water molecule

Answer 39

condensation dehydration reaction

Question 40

is the R side chain involved in a condensation dehydration reaction

Answer 40

no

Question 41

draw the formation of a peptide bond

Question 42

which groups do peptide bonds form between

Answer 42

carboxyl group of one amino acid and the amino group of another

Question 43

define polypeptide

Answer 43

the amino acid structure of a single chain

Question 44

define peptide

Answer 44

two or more amino acids joined together by peptide bonds

Question 45

what effect does the final shape have on a protein

Answer 45

it determines its function

Question 46

how many levels of structure are there in a protein?

Answer 46

4

Question 47

list the 4 protein structure levels

Answer 47

primary, secondary, tertiary, Quaternary

Question 48

what is the primary structure of a protein?

Answer 48

the specific sequence of a amino acids joined together via peptide bonds

Question 49

what does every polypeptide begin and end with

Answer 49

free amino group (N-terminus) and ends with free carboxyl group (C-terminus)

Question 50

what is the secondary structure of a protein?

Answer 50

the local folding of chains into regular patterns (either alpha helix or beta pleated sheets)

Question 51

what bond is involved in alpha helix and beta pleated sheets?

Answer 51

hydrogen bonds- forms between the carbonyl O of one amino acid and the amino H of another

Question 52

how do alpha helix proteins fold?

Answer 52

hydrogen bonds form between the carbonyl C=O and amino N-H groups 4 amino acids down the chain. this pulls the polypeptide into a helical shape that resembles a coil

Question 53

explain how beta pleated sheets are folded

Answer 53

the polypeptide chain can either turn back on itself or,,, two or more segments of a polypeptide chain lines up next to each other forming a sheet like structure held together by hydrogen bonds that form between carbonyl and amino groups of backbone. the r groups extend above and below the sheet of the polypeptide

Question 54

what factor determines whether an alpha helix or beta pleated sheet is formed?

Answer 54

the sequence of amino acids of the polypeptide

Question 54

can proteins have both beta and alpha foldings

Answer 54

yes- most have both

Question 55

explain what the tertiary structure of polypeptide is

Answer 55

the folding and twisting that results in a final 3d shape of the polypeptide

Question 56

examples of some bonds that can be found in tertiary structure in proteins

Answer 56

hydrogen bonds, ionic bonds, covalent bonds, disulphide linkages, hydrophobic interactions

Question 57

what is the quaternary structure of a protein

Answer 57

when diff subunits (many polypeptide chains) come together they give the protein its quaternary structure

Question 58

give an example of a protein that has a quaternary structure

Answer 58

haemoglobin- made of 4 subunits

Question 59

what happens to a protein when it is exposed to a change in temperature or pH

Answer 59

the tertiary structure is lost- the protein unravels and is referred to as denatured (non-functional)

Question 60

can proteins renature

Answer 60

yes- if the denaturation was not too severe + if the condition is removed