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1.3 (biological molecules) Flashcards

proteins

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1
Q

proteins are polymers (and macromolecules) made of monomers called

A

amino acids

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2
Q

the sequence, type and number of the amino acids within a protein determines its shape and therefore its

A

function

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3
Q

proteins are extremely important in cells because they form all of the following:

A
  • enzymes
  • cell membrane proteins (eg. carrier)
  • hormones
  • immunoproteins (eg. immunoglobulins)
  • transport proteins (eg. haemoglobin)
  • structural proteins (eg. keratin, collagen)
  • contractile proteins (eg. myosin)
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4
Q

there are how many amino acids found in proteins common to all living organisms

A

20

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5
Q

the general structure of all amino acids is a central carbon atom bonded to:

A
  • an amine group: NH2
  • a carboxylic acid group: COOH
  • a hydrogen atom
  • an R group (which is how each amino acid differs and why amino acid properties differ e.g. whether they are acidic or basic or whether they are polar or non-polar)
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6
Q

in order to form a peptide bond a

A
  • hydroxyl (-OH) is lost from the carboxylic group of one amino acid
  • and a hydrogen atom is lost from the amine group of another amino acid
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7
Q

during the formation of a peptide bond the remaining carbon atom (with the double-bonded oxygen) from the first amino acid bonds to

A

the nitrogen atom of the second amino acid

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8
Q

the formation of a peptide bond is a condensation reaction so water is

A

released

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9
Q

dipeptides are formed by the condensation of

A

two amino acids

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10
Q

polypeptides are formed by the condensation of

A

many (3 or more) amino acids

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11
Q

during hydrolysis reactions of polypeptidds, the addition of water breaks

A
  • the peptide bonds
  • resulting in polypeptides being broken down to amino acids
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12
Q

amino acids are bonded together by covalent peptide bonds to form a dipeptide in a condensation reaction diagram

A
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13
Q

what are the four levels of structure in proteins

A
  • primary
  • secondary
  • tertiary
  • quaternary
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14
Q

three of the four levels of the structure in proteins are related to a single polypeptide chain and the fourth level relates to a protein that has

A

two or more polypeptide chains

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15
Q

the sequence of amino acids bonded by covalent peptide bonds is the

A

primary structure of a protein

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16
Q

primary structure of a protein is the sequence of

A

amino acids bonded by covalent peptide bonds

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17
Q

DNA of a cell determines which structure of a protein

A

primary structure

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18
Q

DNA of a cell determines the primary structure of a protein by instructing the cell to

A
  • add certain amino acids in specific quantities
  • in a certain sequence
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19
Q

DNA of a cell determines the primary structure of a protein by instructing the cell to add certain amino acids in specific quantities in a certain sequence, this affects the

A

shape and therefore the function of the protein

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20
Q

the primary structure is what for each protein

A
  • specific
  • (one alteration in the sequence of amino acids can affect the function of the protein)
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21
Q

the primary structure of a protein diagram

A

the three-letter abbreviations indicate the specific amino acid (there are 20 commonly found in cells of living organisms)

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22
Q

the secondary structure of a protein occurs when

A

the weak negatively charged nitrogen and oxygen atoms interact with the weak positively charged hydrogen atoms

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23
Q

the secondary structure of a protein occurs when the weak negatively charged nitrogen and oxygen atoms interact with the weak positively charged hydrogen atoms to form

A

hydrogen bonds

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24
Q

what are the bonds in the secondary structure of proteins

A

hydrogen

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25
Q

there are two shapes that can form within proteins due to the hydrogen bonds:

A
  • α-helix
  • β-pleated sheet
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26
Q

the α-helix shape occurs when the hydrogen bonds form between every

A
  • fourth peptide bond - (between the oxygen of the carboxyl group and the hydrogen of the amine group)
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27
Q

the β-pleated sheet shape forms when the protein

A

folds

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28
Q

the β-pleated sheet shape forms when the protein folds so that

A

two parts of the polypeptide chain are parallel to each other

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29
Q

the β-pleated sheet shape forms when the protein folds so that two parts of the polypeptide chain are parallel to each other enabling

A

hydrogen bonds to form between parallel peptide bonds

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30
Q

most fibrous proteins have which protein structures

A
  • secondary structures - (e.g. collagen and keratin)
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31
Q

the secondary structure only relates to hydrogen bonds forming between which two groups

A
  • amino group
  • carboxyl group (the ‘protein backbone’)
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32
Q

the hydrogen bonds in the secondary structure can be broken by what two things

A
  • high temperatures
  • pH changes
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33
Q

the secondary structure of a protein with the α-helix and β-pleated sheet shapes highlighted diagram

A

the magnified regions illustrate how the hydrogen bonds form between the peptide bonds

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34
Q

further conformational change of the secondary structure leads to additional bonds forming between the

A

R groups (side chains)

35
Q

in the tertiary structure the additional bonds between the R groups (side chains) are

A
  • hydrogen (these are between R groups)
  • isulphide (only occurs between cysteine amino acids)
  • ionic (occurs between charged R groups)
  • weak hydrophobic interactions (between non-polar R groups)
36
Q

the tertiary structure is common in what proteins

A

globular proteins

37
Q

quaternary structure occurs in proteins that have more than one

A
  • polypeptide chain working together as a functional macromolecule
  • for example haemoglobin
38
Q

each polypeptide chain in the quaternary structure is referred to as a what of the protein

A

subunit

39
Q

peptide bonds occure in which level

A
  • primary
  • secondary
  • tertiary
40
Q

hydrogen bonds occur in which levels

A
  • secondary (only between the amino and carboxyl groups)
  • tertiary (R groups + amino and carboxyl groups)
41
Q

disulphide bonds occur in which level

A

tertiary

42
Q

ionic bonds occur in which level

A

tertiary

43
Q

hydrophobic interactions occur in which level

A

tertiary

44
Q

remember that the hydrogen bonds in tertiary structures are between the R groups whereas in secondary structures the hydrogen bonds form between the

A

amino and carboxyl groups

45
Q

polypeptide chain will fold differently due to the

A
  • interactions (and hence the bonds that form)
  • between R groups
46
Q

each of the twenty amino acids that make up proteins has a unique

A

R group

47
Q

each of the twenty amino acids that make up proteins has a unique R group and therefore many different

A
  • interactions can occur
  • creating a vast range of protein configurations
  • and therefore functions
48
Q

within tertiary structured proteins are the following bonds

A
  • strong covalent disulfide
  • weak hydrophobic interactions
  • weak hydrogen
  • ionic
49
Q

disulfide bonds are strong

A
  • covalent bonds
  • that form between two cysteine R groups (as this is the only amino acid with an available sulfur atom in its R group)
50
Q

strong covalent disulfide bonds are the strongest within a protein, but occur less frequently, and help

A
  • stabilise the proteins
  • disulfide bridges
51
Q

disulfide bridges can be broken by

A

reduction

52
Q

disulfide bonds are common in proteins that are what from cells

A
  • secreted
  • eg. insulin
53
Q

ionic bonds form between

A
  • positively charged (amine group -NH3+)
  • and negatively charged (carboxylic acid -COO-) R groups
54
Q

ionic bonds are stronger than hydrogen bonds but they are not

A

common

55
Q

ionic bonds are broken by

A

pH changes

56
Q

hydrogen bonds form between

A

strongly polar R groups

57
Q

hydrogen are the weakest bonds that form but the most common as they form between a wide variety of

A

R groups

58
Q

hydrophobic interactions form between

A
  • non-polar (hydrophobic) R groups
  • within the interior of proteins
59
Q

globular proteins are

A
  • compact
  • roughly spherical (circular) in shape
  • soluble in water
60
Q

globular proteins form a spherical shape when folding into their tertiary structure because

A
  • their non-polar hydrophobic R groups are orientated towards the centre of the protein away from the aqueous surroundings and
  • their polar hydrophilic R groups orientate themselves on the outside of the protein
61
Q

this orientation enables globular proteins to be what in water

A

sluble

62
Q

this orientation enables globular proteins to be (generally) soluble in water as the water molecules can

A

surround the polar hydrophilic R groups

63
Q

the solubility of globular proteins in water means they play important physiological roles as they can be easily

A

transported around organisms

64
Q

the solubility of globular proteins in water means they play important physiological roles as they can be easily transported around organisms and be involved in

A

metabolic reactions

65
Q

the folding of the protein due to the interactions between the R groups results in globular proteins having

A

specific shapes

66
Q

the folding of the protein in globular proteins enables them to play physiological roles, for example, enzymes can

A

catalyse specific reactions

67
Q

the folding of the protein in globular proteins enables them to play physiological roles, for example, enzymes can catalyse specific reactions and immunoglobulins can

A

respond to specific antigens

68
Q

some globular proteins are conjugated proteins that contain a

A

a prosthetic group eg. haemoglobin which contains the prosthetic group called haem

69
Q

fibrous proteins are long strands of

A
  • polypeptide chains
  • that have cross-linkages due to hydrogen bonds
70
Q

fibrous proteins have little or no

A

tertiary structure

71
Q

due to the large number of hydrophobic R groups fibrous proteins are

A

insoluble in water

72
Q

fibrous proteins have a limited number of

A

amino acids with the sequence usually being highly repetitive

73
Q

the highly repetitive sequence creates very organised structures that are strong and this along with their insolubility property, makes fibrous proteins very suitable for

A
  • structural roles
  • for example, keratin that makes up hair, nails, horns and feathers and collagen which is a connective tissue found in skin, tendons and ligaments
74
Q

what is the shape of glodbular proteins

A

roughly circular

75
Q

what is the shape of fibrous proteins

A

long strands

76
Q

what is the amino acid sequence of globular proteins

A
  • irregular
  • wide range of R groups
77
Q

what is the amino acid sequence of fibrous proteins

A
  • repetitive
  • limited range of R groups
78
Q

function of globular proteins

A
  • physiological
  • functional
79
Q

function of fibrous preoteins

A

structural

80
Q

examples of globular proteins

A
  • haemogoblin
  • enzymes
  • insulin
  • immunogoblin
81
Q

examples of fibrous proteins

A
  • collagen
  • keratin
  • myosin
  • actin
  • fibrin
82
Q

solubility of globular proteins

A

generally soluble in water

83
Q

solubility of fibrous proteins

A

generally insoluble in water

84
Q

to distinguish between the two proteins, learn SAFES

A

(Shape, Amino acid sequence, Function, Examples and Solubility)

as biology (sme) (8 decks)

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