proteins Flashcards

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1
Q

what are proteins made of?

A

carbon
hydrogen
oxygen
nitrogen
some sulfur

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2
Q

what are the functions of proteins?

A

enzymes that catalyse reactions
carrier/transport proteins
antibodies
structural support for cells
hormone transmit information
enable muscles to contract

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3
Q

what are proteins?

A

polymers made up of amino acid monomers

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4
Q

how many different naturally occurring amino acids are there?

A

20

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5
Q

what does an amino acid contain?

A

amino group
R functional/variable group
carboxyl group

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6
Q

what bond is in a protein?

A

peptide bond

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7
Q

what is the primary structure of a protein?

A

a sequence of amino acids bonded by peptide bonds
forms a polypeptide
has no functions

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8
Q

what is the secondary structure of a protein?

A

alpha helix or beta pleated sheat

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9
Q

what is an alpha helix?

A

chains of amino acids coiled
stabilised by hydrogen bonds between carboxyl and amino groups

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10
Q

what are beta pleated sheets?

A

parts of amino acid chain are folded and lie next to each other
held in place by hydrogen bonds

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11
Q

what is the tertiary structure of a protein?

A

chains become folded into a globular or fibrous shape
(include areas of helix and pleated sheet)

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12
Q

what are the bonds in a tertiary structure?

A

hydrogen bonds
ionic bonds
disulphide bonds

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13
Q

where are the hydrogen bonds in a tertiary structure?

A

between OH and R groups

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14
Q

where are the ionic bonds in a tertiary structure?

A

oppositely charged amino acids form bonds due to positive or negative R groups

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15
Q

where are the disulphide bonds in a tertiary structure?

A

amino acid cysteine contains sulfur
between two sulfur atoms in two cysteines which are close together

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16
Q

what are the functions of a protein in its tertiary structure?

A

enzymes
plasma/channel/carrier proteins

17
Q

what is the quaternary structure of a protein?

A

two or more polypeptide chains

18
Q

what is an example of a quaternary structure?

A

haemoglobin

19
Q

what happens if proteins unfold?

A

it will lose its 3 dimensional shape so will lose its function

20
Q

what can cause a protein to unfold?

A

shifts in temperature or ph
exposure to detergent/salts

21
Q

what happens in the primary and secondary structure of a globular protein?

A

chains of amino acids
alpha helix and bet pleated sheets held together by hydrogen bonds

22
Q

what happens in the tertiary structure of a globular protein?

A

folds into a precise globular 3D shape
hydrogen, ionic, disulphide bonds
hydrophobic and hydrophilic interactions

23
Q

what does haemoglobin contain (groups)?

A

contains prosthetic group (non-protein) called the haem group

24
Q

what way do the hydrophobic and hydrophilic group point in haemoglobin?

A

hydrophobic group points inwards
hydrophilic group points outwards
so it is soluble in water

25
Q

what is in haemoglobin?

A

2 alpha polypeptide chains and 2 beta polypeptide chains
each chain has prosthetic haem group containing iron ions

26
Q

what does iron ions in prosthetic haem group do in haemoglobin?

A

bind to oxygen molecules
(4 x O2 = 8 oxygen molecules)

27
Q

what is the function of haemoglobin?

A

haem group binds to oxygen in the lungs
transports oxygen to tissues where it is released and used by cells in aerobic respiration

28
Q

what are the different colours of haemoglobin?

A

haemoglobin (bluish red) + 4O2 –> oxyhaemoglobin (bright red)

29
Q

what are the conditions needed to make haemoglobin separate from oxygen?

A

low partial pressure of oxygen
high CO2 level and low pH to make it more efficient

30
Q

what is the primary and secondary stage of a fibrous protein (collagen)?

A

a polypeptide chain coils up into a left handed alpha helix
3 of these left-handed alpha helixes twist together to form a triple helix or collagen molecule

31
Q

what happens after triple helices/collagen molecules are formed?

A

triple helices/collagen molecules interact to form collagen fibrils (cross linked by covalent bonds)
collagen fibrils can make a collagen fibre

32
Q

what is the structure of a triple helix in a fibrous protein?

A

3 polypeptide chains twisted together
contains high proportion of amino acids alanine and proline
every third amino acid is glycine (smallest amino acids so allows chains to get close and form hydrogen bonds)

33
Q

what is the function of collagen?

A

gives strength to tendons, ligaments and bones

34
Q

how is collagen strong?

A

large number of hydrogen bonds between helices so molecules/fibres are very strong
strength is also increased by covalent crosslinks between collagen molecules