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MBBS IASM > Protein > Flashcards

Protein Flashcards

1
Q

How does Insulin work

A

It causes confrontmation change in the insulin receptor and bring more glucose transporter to the cell membrane to facillate Glucose Uptake to increase the uptake of glucose by liver and muscle

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2
Q

What is the next step for glucose

A

Converted into Glycogen at the place where glycogenesis takes place

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3
Q

Describe the structure of insulin

A

By 2 polypeptide chain, by 4 S-S Bridges, with 2 between 2 chains and 2 within the peptide

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4
Q

What is the backbone of a chain formed by 3 amino acids

A

NCaCNCaCNCaC

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5
Q

What is the number of amino acids in a (i)protein (ii)peptide

A

(i)>100 (ii)<100

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6
Q

Leu-Cys-Pro shows what order of protein structure

A

Primary

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7
Q

What is a secondary structure

A

Local confrontmation of the backbone due to the interactions between atoms at the backbone

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8
Q

Name 2 commonly seen Secondary Structure

A

Alpha Helix, Beta Sheet

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9
Q

(i) What are the bonds stabilizing Alpha Helix and Beta Sheet

A

HYdrogen bond between O and H atom

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10
Q

(ii) Are the side chains pointing inwards or outwards in Alpha Helix

A

Outwards

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11
Q

(iii) What is the orientation of most Alpha Helices

A

Right-handed

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12
Q

What is the number of strand involved in each turn of Alpha helix

What is the size in Angstrong

A

3.6 amino acids

5.4Å (angstrom) per 360º turn

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13
Q

How many strands are involved in a Beta sheet

A

At least 2

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14
Q

Name the direction of the chains

A

Parallel or anti-parallel are ok

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15
Q

How do we described the zig-zag like appearance of Beta Sheet

A

Pleated

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16
Q

What contributes to a Tertiary structure

Name the 3 forces

A

Interactions between side chains

Hydrogen bond, VDW, electrostatic attraction

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17
Q

What contributes to a Quaternary Structure

A

Interactions between subunits

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18
Q

What is fibrous protein

What is their solubility in water

A

It has long, repetitive structures that enable structural role

And it is insoluble in water

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19
Q

What are the subunits of collagen. What is their orientation

A

3 left-handed Alpha-Helix

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20
Q

What is the orientation of collagen

A

A right-handed Super Helix

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21
Q

What is the recur in Collagen

A

Glycine-proline-hydroxyproline

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22
Q

When is hydroxyproline formed

A

Post-translational modification

23
Q

Name the higher lvl structure that collagen joins to form

A

Fibrils

24
Q

Describe and explain the appearance of fibrils

A

Striated as there are regular spaces between collagens

25
Q

What is the chemical formula of Vitamin C

A

Sodium ascorbate

26
Q

Why is Vitamin C required for the synthesis of collagen

A

To keep the Fe2+ ion reduced so that it can be the cofactor of prolyl 4-hydroxylase

27
Q

What is the enzyme prolyl 4-hydrogenase for

A

Converting Proline to hydroxylproline

28
Q

What is the component of Keratin and their orientation in the molecule

A

2 Alpha Helices to form a coiled coil structure

29
Q

Name the higher level structures Keratin form

A

Protofilament–> Protofilbrils –>Intermediate filament

30
Q

Name the force stabilizing the Keratin

A

S-S bridges between Cysteine amino acids

31
Q

Does a RA/OA breaks the S-S bridges

A

RA

32
Q

How to enhance the tensile strength of Keratin

Can microbes feed on Keratin. What are they

A

Increase the number of S-S bridges

Yes. Some infectious fungi

33
Q

What is the solubilty of Globular Protein

A

Soluble in water

34
Q

Name 2 oxygen-binding protein

A

Myoglobin and haemoglobin

35
Q

Is the haem structure planar/3D

Briefly describe the structure

A

Planar

  • Consists of a porphyrin ring and crown like structure with nitrogen
  • Nitrogens interact with central Fe2+ of haemoglobin/myoglobin
  • Histidine in backbone of myoglobin (and haemoglobin)
  • Distal histidine stabilises oxygen at that position
  • Oxygen ligand interacts with the distal E7 histidine
36
Q

Is the myoglobin similar to the alpha/beta subunit of Hb

A

Beta

37
Q

Where is the Myoglobin functioning

A

Muscles

38
Q

How the Haemoglobin illustrates positive cooperativity

A

As it binds to more oxygen, the binding force becomes stronger and stronger

39
Q

How can Hb exhibit the postitive cooperativity

A

Binding of oxygen to haem increases oxygen affinity by inducing structural changes

in the adjacent globin chains, turning the haemoglobin from a Tense state to a Relaed
shape. This positive cooperativity within haemoglobin is responsible for a
sigmoidal-shaped oxygen dissociation curve

40
Q

What is the effect of Carbon monoxide binding on the haemoglobin

A

The binding of one CO molecule to haemoglobin increases the affinity of the other binding spots for oxygen, leading to a left shift in the dissociation curve. This shift
prevents oxygen unloading in peripheral tissue and therefore the oxygen
concentration of the tissue is much lower than normal

41
Q

Name 2 differences between myoglobin and haemoglobin

A

Myoglobin has 1 subunit with 1 haem with Haemoglobin has 4 subunit and 4 haem

42
Q

What are the proteins helping protein folding called.

What is it’s size, Does it use energy?

Name 1 example

A

Chaperstone(GroEL)

  • Large protein complexes
  • Often uses energy (ATP)
  • Help fold proteins from its unfolded states

GroEL

43
Q

Can a protein be stable at 2 states?

For lymphotacin, name the 2 forms

Do the 2 term co-exist

A

Yes

Chemokine form and Glycoaminoglycan-binding structure

Yes. In equilibrium

44
Q

Name 1 type of improperly folding protein that can cause disease and infectious

A

Prion diseases. Like Bovine Spongyform encephalopathy, Kuru, Scrapie and CJD

45
Q

In Bovine Spongyform Encephalopathy, what is the difference in structure of normal protein (PrPC) and abnormal

A

PrPc has Fully Helix structure
PrPsc has some beta sheets

46
Q

Why mad cow disaese is infectious

A

The PrPSc can act as site of nucleation to convert more PrPc to PrPSC

47
Q

What is the problem with Madcow disease improperly folded protein

A

It creates large fibres which aggregrate to form amyloid fibres in the brain

48
Q

How is Alzemeir disease caused

A

The Amyloid-Beta peptide self-associates into fibrils then into amyloid plaque.

The improper form has more Beta sheets than the original amyloid precursor protein(APP), leading to aggregation.

The amyloid protein itself is normal but the acculmulation is toxic to the brain

49
Q

Name 4 prion-related disease

A

CJD (Creutzfeldt-Jakob Disease)

Kuru

Bovine spongiform encephalopathy(BSE), aka Mad cow disease

Scrapie

50
Q

What is the Lock-and-Key Model about

A

The amino acid resifdue of the binding site are arranged in a complementary 3D surface that recognize the Subtrate

The subtrate is bound via VDW, hydrogen bond and Electrostatic interaction

51
Q

What is the Induced-Fit Model About

A

Induced-fit model
- The substrate binding site is not a rigid pocket
- It is a dynamic surface with flexible 3D structure
- As the substrate binds, the side chains of the amino acids in the active site will reposition to
interact with the substrate for the reaction to occur
- E.g. glucose binding of hexokinase:
- With the binding of glucose, the active site cleft of hexokinase closes
- It is one of the largest induced fits known

52
Q

What is THE MICHAELIS-MENTEN EQUATION

A

Vi= Initial Velocity

V max= maximal velocity reached when infinite amount of subtrate was present

Km (Michaelis Constant) is the concentration required to reach V max

High Km = low affinity

[S]= concentration of subtrate

Vi = V max [S]/ (Km +[S])

53
Q

What is the Enzymatic reactions concerning 2 subtrates

What are the 2 types of the aforementioned reaction

A

BISUBSTRATE ENZYMATIC REACTIONS

Sequential reactions (single displacement reaction):
- Ordered: one substrate must bind first, before the second substrate can bind and a reaction can
occur
- Random order: no requirement of which substrate has to bind first for reaction to occur

54
Q
A

MBBS IASM (24 decks)

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