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2.1.2 biological molecules > Proteins - globular and fibrous proteins > Flashcards

Proteins - globular and fibrous proteins Flashcards

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Organic Chemistry 101 flashcards
1
Q

what is a globular protein

A

molecules of a relatively spherical shape which are soluble in water and often have metabolic roles within the organism

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2
Q

how do globular proteins role up in a spherical shape

A

any hydrophobic R groups are turned inwards towards the centre of the molecule, while hydrophillic R groups are on the outside of the protein

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3
Q

why are globular proteins soluble in water

A

water molecules can easily cluster round and bind to them.

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4
Q

why is it important for globular proteins to be insoluble

A

its essential for regulating many of the processes necessary for life (chemical reactions, immunity and muscle contractions)

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5
Q

what are examples of globular proteins

A

enzymes, hormones

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6
Q

what is haemoglobin an example of

A

a globular, conjugated protein

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7
Q

what is a conjugated protein

A

globular proteins that contain a non protein component called a prosthetic group

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8
Q

what is different about simple proteins

A

they dont have prosthetic groups

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9
Q

what is a prosthetic group

A

a non protein component that forms a permanent part of a functioning molecule

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10
Q

give examples of prosthetic groups

A

lipids or carbohydrates combine with proteins forming lipoproteins or glycoproteins
metal ions and molecules derived from vitamins also form prosthetic groups.

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11
Q

what is the prosthetic group in haemoglobin

A

haem

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12
Q

what does haem contain

A

iron (II) ion - Fe2+

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13
Q

what is the primary structure of hameoglobin

A

contains a wide range of amino acids connected together in a specific sequence of peptide bonds

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14
Q

what is the secondary structure of haemoglobin

A

most of the amino acids in haemoglobin form alpha helices connected by short beta-pleated sheet segments

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15
Q

what is the tertiary structure of haemoglobin

A

each polypeptide chain with haemoglobin contains a haem prosthetic group making it a conjugated protein
hydrophobic R groups migrate to the centre of the structure
hydrophillic R groups migrate to the outside of the structure
contains ionic bonds but no disulfide bridges

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16
Q

what is the quaternary structure of haemoglobin

A

has 4 subunits (polypeptide chains). 2 alpha units and 2 beta units
each polypeptide chain has its own tertiary structure but when fitted together form a haemoglobin.

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17
Q

how is haemoglobin able to effectively tranport oxygen around the body

A

each chain contains a haem prosthetic group capable of carrying a single oxygen molecule. it can pick up oxygen in the lungs and transport it to cells that need it, where its released. when oxygen binds to iron, haemoglobin turns from purple to red

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18
Q

where is haemoglobin found

A

within red blood cells and plays a vital role in transporting oxygen and carbon dioxide around the body

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19
Q

give properties of haemoglobin

A

its very flexible and soluble in water

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20
Q

what is catalase

A

a globular conjugated protein
an enzyme that catalyses the breakdown of hydrogen peroxide

21
Q

describe the structure of catalase

A

a quaternary protein containing four haem prosthetic groups.

22
Q

what does the presence of the iron (II) ions in the prosthetic groups allow catalase to do

A

allow catalase to interact with hydrogen peroxide and speeds up its breakdown.

23
Q

what is hydrogen peroxide

A

a common byproduct of metabolism but is damaging to cells and cell components if allowed to accumulate.

24
Q

what is insulin

A

a globular protein but its not conjugated
its a hormone

25
Q

what is similiar about globular proteins

A

all globular proteins are compact and soluble in water as their hydrophobic R groups are kept away from the aqueous environment whilst the hydrophillic R groups are on the oustide of the protein

26
Q

what is insulin involved in

A

the regulation of blood glucose concentration.

27
Q

why must insulin be soluble

A

its a hormone that needs to be transported in the bloodstream. they have to fit into specific receptors on cell surface membranes to have their effect and therefore need to have precise shapes

28
Q

how many polypeptide chains does insulin have

A

two

29
Q

describe the structure of insulin

A

the A chains begins with a section of alpha helix and the B chain ends with a section of beta pleats. both chains fold in a tertiary structure and are joined by disulfide links. amino acids with hydrophillic R groups are on the oustide of the molecule making it soluble in water.

30
Q

what does insulin bind to

A

glycoprotein receptors on the outside of muscle and fat cells to increase their uptake of glucose from the blood and also increase their rate of consumption of glucose

31
Q

what are fibrous proteins

A

they have a relatively thin structure, insoluble in water and metabolically inactive often having a structural role within an organism

32
Q

what are fibrous proteins made up of

A

long insoluble molecules. this is due to the presence of a high proportion of amino acids with hydrophobic R groups in their primary structure.
they contain a limited range of amino acids usually with small R groups. the amino acid sequence in the primary structure is usually quite repetitive

33
Q

what does the repetitive sequence of amino acids in fibrous proteins allow them to form

A

to form fibres which have a structural function. this leads to very organised structures reflected in the roles they have. they tend to make strong, long molecules which aren’t folded into 3d shape

34
Q

where is keratin present

A

in hair, skins and nails

35
Q

what does keratin have a high proportion of

A

cysteine (contains sulfur)
this results in many strong disulfide bridges forming strong, inflexible and insoluble materials. the degree of disulfide bonds determines the flexibility - hair contains fewer bonds making it more flexible than nails.

36
Q

where does the unpleasant smell when hair or skin is burnt come from

A

due to the presence of relatively large amounts of sulfur in these proteins

37
Q

what does keratin provide

A

mechanical protection and an impermeable barrier to infection and being waterproof it prevents the entry of waterborne pollutants

38
Q

where is elastin found

A

in elastic fibres (along with small protein fibres).

39
Q

where are elastic fibres found

A

elastic fibres are present in the walls of blood vessels and in the alveoli of lungs - they give these structures the flexibility when needed but to also return to their normal size

40
Q

how do elastic fibres help blood vessels

A

helps them stretch to maintain pressure wave of blood as it passes through

41
Q

what is the primary structure of elastin

A

alternate hydrophobic and lysine rich areas

42
Q

what is the secondary and tertiary structure of elastin

A

polypeptide chain form soluble tropoelastin molecules that can stretch and recoil

43
Q

what is the quaternary structure of elastin

A

tropoelastin molecules aggregate to form large and insoluble elastin through interactions between the hydrophobic regions. this is stabilised throigh cross linking covalent bonds between lysine molecules. this gives flexibility so they can stretch and recoil without breaking

44
Q

what would happen if our skin had no elastin

A

skin can stretch around our bones and muscles because of elastin. without elastin, skin would not go back to normal after being pinched. elastin in our lungs allows them to inflate and deflate and in out bladder it helps it expand to hold urine

45
Q

what does collagen provide

A

mechanical strength in:
- in artery walls, a layer of collagen prevents the artery bursting when withstanding high pressure from blood being pumped by the heart
- tendons are made of collagen and connect muscles to bones, allowing them to pull on bones
- bones are made from collagen and reinforced with calcium phosphate making them hard
- cartilage and connective tissue are made from collagen

46
Q

what is collagen made of

A

has a number of different forms but all are made up of 3 polypeptides wound together in a long and strong rope structure. it has flexibility.

47
Q

what are some properties of collagen

A
  • great tensile strength
  • insoluble in water
  • forms long straight fibres as it has a high proportion of hydrophobic amino acids
  • flexible
48
Q

why is collagen strong

A

its made from a small range of amino acids making three polypeptide chains tightly wound around in a rope-like structure. it has hydrogen bonds between chains and crosslinking covalent bonds between ropes
the polypeptide chains overlap.

49
Q

does collagen have a quaternary structure

A

there is little tertiary structure but 3 chains give it a quaternary structure

2.1.2 biological molecules (11 decks)

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