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Molecules > Proteins > Flashcards

Proteins Flashcards

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Organic Chemistry 101 flashcards
1
Q

What do proteins do?

A

Provide structure, transport molecules, defend against infection, biological catalysts, regulation of genes

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2
Q

What does haemoglobin do?

A

Carry oxygen

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3
Q

How many protein sub units make up haemoglobin?

A

4

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4
Q

What is haem an example of?

A

A prosthetic group

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5
Q

What is the function of the LDL and LDL receptor?

A

Transport cholesterol molecules and co-ordinate their uptake into cells

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6
Q

What protein wraps around the LDL molecule?

A

Apolipoprotein B

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7
Q

What genetic disease causes too much cholesterol in the blood?

A

Hypercholesterolemia

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8
Q

What is the structure of an antibody?

A

Two identical heavy chains and two identical light chains linked by disulphide bonds

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9
Q

What is the function of a lysozyme?

A

Catalyses the cutting of polysaccharide chains

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10
Q

What shape is a lysozyme?

A

Kidney bean

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11
Q

What is the lac Repressor?

A

Controls the production of proteins metabolising lactose in bacteria, when not present it binds and represses the production of those genes

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12
Q

What is the primary structure of a protein?

A

The sequence of amino acids

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13
Q

What is the secondary structure of a protein?

A

Alpha helix, beta sheets or bend/loop

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14
Q

What is the tertiary structure of a protein?

A

The folding of the protein caused by the intermolecular forces

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15
Q

What is the quaternary structure of a protein?

A

Whether the protein has subunits

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16
Q

What determines the classification of amino acids?

A

The R-group

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17
Q

What are the different classifications of amino acids?

A

Hydrophilic

Hydrophobic

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18
Q

What can the hydrophilic amino acids be split into?

A

Basic
Acidic
Polar

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19
Q

What three amino acids fall under a special classification?

A

Cysteine, glycine and proline

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20
Q

What is special about cysteine?

A

Can form disulphide bridges

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21
Q

What is special about glycine?

A

Smallest amino acid so can fit into tight spaces

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22
Q

What is special about proline?

A

The side chain can bend around and react with the amide group creating a kink in the chain

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23
Q

What formula allows you to find the pH of an amino acid side chain?

A

pH=pKa + log[A-]/[HA]

24
Q

What shape does a dissociation of an amino acid create in a graph?

A

Sigmoidal

25
Q

How does a change in pH effect the LDL protein?

A

Once the endosome’s pH drops to 5, the LDL can no longer bind releasing the cholesterol to the lysosome

26
Q

What do the peptide bonds between amino acids not allow?

A

Rotation

27
Q

Where can rotation occur in a peptide chain?

A

Around the alpha carbon

28
Q

What stabilises secondary structures?

A

Hydrogen bonds

29
Q

On which amino acid and carboxyl group is the alpha helix shape stabilized?

A

Every 4th amino acid

30
Q

What two ways can beta sheets be arranged?

A

Parallel and anti-parallel

31
Q

How many amino acids are usually required to form a turn?

A

4

32
Q

What is the tertiary structure?

A

3D folding of secondary structure, hydrophobic residues are buried while hydrophilic residues are exposed outwards

33
Q

What are the three types of tertiary structure?

A

alpha-helical, beta-sheets and a mixture of both

34
Q

What forces stabilise tertiary structure?

A

Disulfide bonds, hydrogen bonds, ionic interactions, van der waals forces, hydrophobic interactions

35
Q

What is a protein called that has more than one sub-unit?

A

Oligomeric protein

36
Q

What is the structure of haemoglobin?

A

A symmetrical assembly of 2 alpha globin and 2 beta globin, each has a haem molecule attatched

37
Q

What is haem?

A

A porphyrin ring with coordinated Fe atom

38
Q

What happens when an oxygen bind the haem?

A

It changes shape from domed to planer, allowing more oxygen to bind easier

39
Q

What causes sickle cell anaemia?

A

Caused by a glutamic acid being swapped to a valine

40
Q

What happens to the binding of oxygen at higher pHs?

A

It has a higher affinity

41
Q

What is the difference between adult and foetal haemoglobin?

A

Foetal haemoglobin has two gamma sub units instead of two beta sub units

42
Q

What do the two gamma subunits allow in foetal haemoglobin?

A

Greater affinity for oxygen

43
Q

What is the structure of collagen?

A

Tropocollagen helix, microfibril, fibril, fiber

44
Q

Why is glycine vital for the formation of collagen?

A

It has a small side chain allowing for tight turns in the tropocollagen

45
Q

Why is proline vital for the structure of tropocollagen?

A

Imposes left handed twists in the helix and provides a stabilising force, can also form hydroxyproline to form hydrogen bonds

46
Q

How do you assemble tropocollagen?

A

Small left handed twists to form procollagen, the loose ends are chopped off to form tropocollagen

47
Q

What is the quater-stagger model?

A

The molecules in collagen fibre are stitched together by covalent-crosslinks

48
Q

How is collagen fibre formed?

A

Lysine- aldehyde derivative (lysyl oxidase)-aldol condensation prodect (allysine)

49
Q

What is the medical term for brittle bone disease?

A

osteogenesis imperfecta

50
Q

What causes osteogenesis imperfecta?

A

Glycine being replaced by cysteine residue meaning the tropocollagen cannot pack together properly

51
Q

What are the symptoms of scurvy?

A

Dry skin, gum disorders

52
Q

What causes scurvy?

A

Lack of proline hydroxylation

53
Q

What are the symptoms of Ehlers-danloss syndrome?

A

Loose skin, hypermobile joints

54
Q

What are the causes of ehlers-danloss syndrome?

A

Lack of procollagen peptidase or lysyl oxidase

55
Q

Where does collagen get its strength?

A

Close packing of subunits- Glycine ever 3rd residue

Opposing twists of subunits and super helix- high proline content

Hydrogen bonding- hydroxyproline

Cross-linking-lysine-derived aldehydes

Molecules (4 decks)

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