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Proteins 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?

25
How does a change in pH effect the LDL protein?
Once the endosome's pH drops to 5, the LDL can no longer bind releasing the cholesterol to the lysosome
26
What do the peptide bonds between amino acids not allow?
Rotation
27
Where can rotation occur in a peptide chain?
Around the alpha carbon
28
What stabilises secondary structures?
Hydrogen bonds
29
On which amino acid and carboxyl group is the alpha helix shape stabilized?
Every 4th amino acid
30
What two ways can beta sheets be arranged?
Parallel and anti-parallel
31
How many amino acids are usually required to form a turn?
4
32
What is the tertiary structure?
3D folding of secondary structure, hydrophobic residues are buried while hydrophilic residues are exposed outwards
33
What are the three types of tertiary structure?
alpha-helical, beta-sheets and a mixture of both
34
What forces stabilise tertiary structure?
Disulfide bonds, hydrogen bonds, ionic interactions, van der waals forces, hydrophobic interactions
35
What is a protein called that has more than one sub-unit?
Oligomeric protein
36
What is the structure of haemoglobin?
A symmetrical assembly of 2 alpha globin and 2 beta globin, each has a haem molecule attatched
37
What is haem?
A porphyrin ring with coordinated Fe atom
38
What happens when an oxygen bind the haem?
It changes shape from domed to planer, allowing more oxygen to bind easier
39
What causes sickle cell anaemia?
Caused by a glutamic acid being swapped to a valine
40
What happens to the binding of oxygen at higher pHs?
It has a higher affinity
41
What is the difference between adult and foetal haemoglobin?
Foetal haemoglobin has two gamma sub units instead of two beta sub units
42
What do the two gamma subunits allow in foetal haemoglobin?
Greater affinity for oxygen
43
What is the structure of collagen?
Tropocollagen helix, microfibril, fibril, fiber
44
Why is glycine vital for the formation of collagen?
It has a small side chain allowing for tight turns in the tropocollagen
45
Why is proline vital for the structure of tropocollagen?
Imposes left handed twists in the helix and provides a stabilising force, can also form hydroxyproline to form hydrogen bonds
46
How do you assemble tropocollagen?
Small left handed twists to form procollagen, the loose ends are chopped off to form tropocollagen
47
What is the quater-stagger model?
The molecules in collagen fibre are stitched together by covalent-crosslinks
48
How is collagen fibre formed?
Lysine- aldehyde derivative (lysyl oxidase)-aldol condensation prodect (allysine)
49
What is the medical term for brittle bone disease?
osteogenesis imperfecta
50
What causes osteogenesis imperfecta?
Glycine being replaced by cysteine residue meaning the tropocollagen cannot pack together properly
51
What are the symptoms of scurvy?
Dry skin, gum disorders
52
What causes scurvy?
Lack of proline hydroxylation
53
What are the symptoms of Ehlers-danloss syndrome?
Loose skin, hypermobile joints
54
What are the causes of ehlers-danloss syndrome?
Lack of procollagen peptidase or lysyl oxidase
55
Where does collagen get its strength?
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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