Protein Flashcards
How does Insulin work
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
What is the next step for glucose
Converted into Glycogen at the place where glycogenesis takes place
Describe the structure of insulin
By 2 polypeptide chain, by 4 S-S Bridges, with 2 between 2 chains and 2 within the peptide
What is the backbone of a chain formed by 3 amino acids
NCaCNCaCNCaC
What is the number of amino acids in a (i)protein (ii)peptide
(i)>100 (ii)<100
Leu-Cys-Pro shows what order of protein structure
Primary
What is a secondary structure
Local confrontmation of the backbone due to the interactions between atoms at the backbone
Name 2 commonly seen Secondary Structure
Alpha Helix, Beta Sheet
(i) What are the bonds stabilizing Alpha Helix and Beta Sheet
HYdrogen bond between O and H atom
(ii) Are the side chains pointing inwards or outwards in Alpha Helix
Outwards
(iii) What is the orientation of most Alpha Helices
Right-handed
What is the number of strand involved in each turn of Alpha helix
What is the size in Angstrong
3.6 amino acids
5.4Å (angstrom) per 360º turn
How many strands are involved in a Beta sheet
At least 2
Name the direction of the chains
Parallel or anti-parallel are ok
How do we described the zig-zag like appearance of Beta Sheet
Pleated
What contributes to a Tertiary structure
Name the 3 forces
Interactions between side chains
Hydrogen bond, VDW, electrostatic attraction
What contributes to a Quaternary Structure
Interactions between subunits
What is fibrous protein
What is their solubility in water
It has long, repetitive structures that enable structural role
And it is insoluble in water
What are the subunits of collagen. What is their orientation
3 left-handed Alpha-Helix
What is the orientation of collagen
A right-handed Super Helix
What is the recur in Collagen
Glycine-proline-hydroxyproline
When is hydroxyproline formed
Post-translational modification
Name the higher lvl structure that collagen joins to form
Fibrils
Describe and explain the appearance of fibrils
Striated as there are regular spaces between collagens
What is the chemical formula of Vitamin C
Sodium ascorbate
Why is Vitamin C required for the synthesis of collagen
To keep the Fe2+ ion reduced so that it can be the cofactor of prolyl 4-hydroxylase
What is the enzyme prolyl 4-hydrogenase for
Converting Proline to hydroxylproline
What is the component of Keratin and their orientation in the molecule
2 Alpha Helices to form a coiled coil structure
Name the higher level structures Keratin form
Protofilament–> Protofilbrils –>Intermediate filament
Name the force stabilizing the Keratin
S-S bridges between Cysteine amino acids
Does a RA/OA breaks the S-S bridges
RA
How to enhance the tensile strength of Keratin
Can microbes feed on Keratin. What are they
Increase the number of S-S bridges
Yes. Some infectious fungi
What is the solubilty of Globular Protein
Soluble in water
Name 2 oxygen-binding protein
Myoglobin and haemoglobin
Is the haem structure planar/3D
Briefly describe the structure
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
Is the myoglobin similar to the alpha/beta subunit of Hb
Beta
Where is the Myoglobin functioning
Muscles
How the Haemoglobin illustrates positive cooperativity
As it binds to more oxygen, the binding force becomes stronger and stronger
How can Hb exhibit the postitive cooperativity
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
What is the effect of Carbon monoxide binding on the haemoglobin
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
Name 2 differences between myoglobin and haemoglobin
Myoglobin has 1 subunit with 1 haem with Haemoglobin has 4 subunit and 4 haem
What are the proteins helping protein folding called.
What is it’s size, Does it use energy?
Name 1 example
Chaperstone(GroEL)
- Large protein complexes
- Often uses energy (ATP)
- Help fold proteins from its unfolded states
GroEL
Can a protein be stable at 2 states?
For lymphotacin, name the 2 forms
Do the 2 term co-exist
Yes
Chemokine form and Glycoaminoglycan-binding structure
Yes. In equilibrium
Name 1 type of improperly folding protein that can cause disease and infectious
Prion diseases. Like Bovine Spongyform encephalopathy, Kuru, Scrapie and CJD
In Bovine Spongyform Encephalopathy, what is the difference in structure of normal protein (PrPC) and abnormal
PrPc has Fully Helix structure
PrPsc has some beta sheets
Why mad cow disaese is infectious
The PrPSc can act as site of nucleation to convert more PrPc to PrPSC
What is the problem with Madcow disease improperly folded protein
It creates large fibres which aggregrate to form amyloid fibres in the brain
How is Alzemeir disease caused
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
Name 4 prion-related disease
CJD (Creutzfeldt-Jakob Disease)
Kuru
Bovine spongiform encephalopathy(BSE), aka Mad cow disease
Scrapie
What is the Lock-and-Key Model about
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
What is the Induced-Fit Model About
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
What is THE MICHAELIS-MENTEN EQUATION
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])
What is the Enzymatic reactions concerning 2 subtrates
What are the 2 types of the aforementioned reaction
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
