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proteins Flashcards

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1
Q

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

A

amino acid

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2
Q

how does a polypeptide become functional

A

it must be folded

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3
Q

what happens to a polypeptide if it is folded wrong?

A

it will be dysfunctional

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4
Q

list 6 functions of proteins

A

support, enzymes, transport, defense, contraction, regulation

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5
Q

explain how proteins are used for support

A

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

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6
Q

write a short note about enzymes

A

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

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7
Q

explain how proteins can be used in transport

A

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

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8
Q

what is the purpose of haemoglobin

A

transports oxygen

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9
Q

what is the purpose of myoglobin

A

transports oxygen to muscle

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10
Q

what is the purpose of transferrin

A

transports iron

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11
Q

how many polypeptide chains can a protein have

A

one or more

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12
Q

how many polypeptide chains does a red blood cell have

A

4 (with binding sites)

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13
Q

explain how proteins aid with defense

A

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

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14
Q

give 3 examples of protein contractions

A

muscle fibres, cilia, spindle fibres

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15
Q

what is actin and myosin

A

two protein filaments which aid muscle contraction (sliding action)

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16
Q

how do proteins help with regulation in the body

A

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

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17
Q

what bio-molecule is insulin made of?

A

protein (all hormones are proteins)

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18
Q

what is the monomer of protein?

A

amino acids

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19
Q

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

A

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

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20
Q

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)

A
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21
Q

how can the 20 distinct amino acids be distinguished?

A

by the R group/chain (variable side chain)

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22
Q

define hydrophobic and hydrophillic

A

hydrophobic- water hating, hydrophillic- water loving

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23
Q

what are the features of hydrophobic amino acids?

A

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

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24
Q

what are the features of hydrophillic amino acids?

A

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

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25
Q

what is a zwitterion?

A

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

26
Q

draw a zwitterion

A
27
Q

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

A

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

28
Q

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

A

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

29
Q

what is the isoelectric point (pI)

A

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

30
Q

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

A
  1. non-polar and aliphatic. 2. aromatic (generally nonpolar) 3. polar but uncharged. 4. neg charged. 5. pos charged
31
Q

what are the features of nonpolar alliphatic R groups

A

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

32
Q

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

A

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,

33
Q

what are some features of aromatic R groups

A

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

34
Q

features of positively charged R groups

A

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

35
Q

features of negatively charged R grouos

A

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

36
Q

what is a peptide bond + how is it formed?

A

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

37
Q

is the R chain involved in a condensation dehydration reaction?

A

no- the reaction is only between carboxyl and amino groups

38
Q

what sort of bond is a peptide bond

A

a covalent bond (electrons are shared)

39
Q

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

A

condensation dehydration reaction

40
Q

is the R side chain involved in a condensation dehydration reaction

A

no

41
Q

draw the formation of a peptide bond

A
42
Q

which groups do peptide bonds form between

A

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

43
Q

define polypeptide

A

the amino acid structure of a single chain

44
Q

define peptide

A

two or more amino acids joined together by peptide bonds

45
Q

what effect does the final shape have on a protein

A

it determines its function

46
Q

how many levels of structure are there in a protein?

A

4

47
Q

list the 4 protein structure levels

A

primary, secondary, tertiary, Quaternary

48
Q

what is the primary structure of a protein?

A

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

49
Q

what does every polypeptide begin and end with

A

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

50
Q

what is the secondary structure of a protein?

A

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

51
Q

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

A

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

52
Q

how do alpha helix proteins fold?

A

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

53
Q

explain how beta pleated sheets are folded

A

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

54
Q

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

A

the sequence of amino acids of the polypeptide

54
Q

can proteins have both beta and alpha foldings

A

yes- most have both

55
Q

explain what the tertiary structure of polypeptide is

A

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

56
Q

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

A

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

57
Q

what is the quaternary structure of a protein

A

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

58
Q

give an example of a protein that has a quaternary structure

A

haemoglobin- made of 4 subunits

59
Q

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

A

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

60
Q

can proteins renature

A

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

61
Q
A

s1 cell bio (8 decks)

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