module 3 protein function Flashcards
what is the geometry of the 2 Hb
tertramer of 2 subunits which are a2B
is Hb a monomer or polymer
polymer
is Mb is monomer or polymer
monomer
Hb and Mb are what is each other
they are anologues and paralogues
how many subunits does Hb have
4 subunits with a Fe2+ heme group
interpret this graph
- As the concentration of oxygen goes up more binding sites get filled
- Myoglobin fill rapids and get close to saturation
Haemoglobin is sigmoidal happens due to allosteric interactions which leads to cooperative bind
- Myoglobin fill rapids and get close to saturation
what are the 5 structural differences between Hb and Mb
Quaternary Structure:
Myoglobin: Myoglobin is a monomeric protein, meaning it consists of a single polypeptide chain.
Hemoglobin: Hemoglobin is a tetrameric protein, composed of four polypeptide subunits:
Heme Binding:
Myoglobin: Myoglobin contains a single heme group, which is the site where oxygen binds.
Hemoglobin: Hemoglobin contains four heme groups, one in each subunit, providing multiple binding sites for oxygen.
Binding Affinity:
Myoglobin: Myoglobin has a higher binding affinity for oxygen than hemoglobin. This high affinity allows myoglobin to store oxygen in muscle tissues, releasing it when oxygen levels are low.
Hemoglobin: Hemoglobin has a lower binding affinity for oxygen compared to myoglobin. This allows hemoglobin to efficiently transport oxygen from the lungs to tissues and release it where needed.
Tertiary Structure:
Myoglobin: Myoglobin has a single polypeptide chain folded into a compact globular structure.
Hemoglobin: Each subunit of hemoglobin has its own tertiary structure, and these subunits come together to form the quaternary structure of the protein.
Function:
Myoglobin: Myoglobin is primarily found in muscle tissues and is involved in storing oxygen for use during periods of low oxygen availability, such as during muscle contraction.
Hemoglobin: Hemoglobin is found in red blood cells and is responsible for transporting oxygen from the lungs to tissues throughout the body and carrying carbon dioxide from tissues back to the lungs for exhalation.
what are the 2 functions of Mb
1) Storage of oxygen
2) Release oxygen when rapidly contracting muscle needs energy (oxygen concentration drops
where is Mb abdunat in an organism
in muscle cells
describe the correlation of diving animals and Mb
- Mb concentration in muscles of diving mammals is 10x higher then others
- Mb in elephant seals is positively charges on its surface so the molecules repel each other and do not clump together at higher concentrations
oxygen is a what for Mb
a ligand!!!!
where does oxygen attach to in Hb and Mb
O2 binds to the Fe2+ which is attached to the binding site of the protein
what is the heme prosthetic group
a histidine residue
what is the equilibrium dissociation constant
what is biotin
Biotin is a vitamin and it must be provided in diets
the relationship between ligand binding affinity and the equilibrium dissociation constant Kd
The relationship between ligand binding affinity and the equilibrium dissociation constant (Kd) is crucial in understanding how tightly a ligand binds to its receptor or protein. Kd represents the concentration of the ligand at which half of the binding sites on the receptor are occupied.
what happens at higher and lower kd values and ligand binding
Lower Kd values indicate higher binding affinity, meaning the ligand binds tightly to the receptor, while higher Kd values indicate lower binding affinity, meaning the ligand binds less tightly.
Myoglobin’s Oxygen Binding:
- Heme Group with Iron (Fe)
- Histidine Residue (His) near heme
- Oxygen binds to iron, forms oxy-myoglobin
- Heme pocket shields oxygen
- High affinity for oxygen
- Heme Group: Iron in protoporphyrin ring
- Histidine Residue: Fifth ligand to iron
- Oxygen Binding: Induces conformational change
- Heme Pocket: Hydrophobic crevice
- High Affinity: Efficient oxygen storage and delivery
what is the t state of Hb and what does it mean
- T= tense state
-More interactions, more stable
Lower affinity for O2
what is the r state of Hb
- R= relaxed state
-Fewer interactions, more flexible
High affinity for O2
oxygen binding to the heme group triggers what
O2 binding triggers T–>R conformational change
Hemoglobin (Hb) Affinity States:
- Tense (T) State: Low Affinity
- Relaxed (R) State: High Affinity
- Oxygen Binding Induces Transition
Tense (T) State:
- Iron less accessible
- Stabilized interactions
- Low Affinity for Oxygen
Relaxed (R) State:
- Conformational change
- Straightened heme groups
- High Affinity for Oxygen
- Cooperative Binding
Oxygen Binding Induces Transition:
- From Tense (T) to Relaxed (R) State
Oxygen Binding to Hemoglobin (Hb):
- Heme Group
- Iron (Fe)
- Histidine (His) Residue
- Heme Group: Contains Iron (Fe)
- Iron Coordination: Histidine Residue (His)
- Oxygen Binding: Induces Conformational Change
- Tense (T) State: Low Affinity
- Relaxed (R) State: High Affinity
- Cooperative Binding
what does each term of the hill expression mean
- θ: Fractional saturation of binding sites
- n: Hill coefficient (cooperativity)
- Kd: Dissociation constant
- Positive cooperativity when n > 1
- Hyperbolic binding curve when n = 1
If nH >1 (eg Hb/O2
- Positive cooperativity
Binding at one site increases binding at other sites on other subunits
If nH=1
- Binding is not cooperative
Sites are independent
Is nH<1 (rare)
- Negative cooperativity
Binding at one site decreased binding at another site on another subunit
what is the end product of metabolism in tissues
H+ and Co2 are end products of metabolism in tissues
do H+ and CO2 compete with Oxygen for the binding of the heme group
no cunt they do not!!!!!!!
as O2 binds to Hb what happens to pH
pH increases as O2 binds to the heme groupn
Effect of pH on Hb Affinity for O2:
- Histidine Protonation
- Protein Structure Changes
- Bohr Effect
- Histidine Residues: Coordinate iron in heme
- Protonation: Alters charge distribution
- Tertiary Interactions: Salt bridges, stability
- Bohr Effect: Lower pH reduces O2 affinity
- Protonation destabilizes T state
- Facilitates O2 release in tissues
what is the bohr effect
- Bohr Effect: Lower pH reduces O2 affinity
what is BPG
BPG is derived from an intermediate in glucose metabolism
what is the relationship between BPG and Hb
BPG interacts with Hb at a separate site to the O2 binding site and affects O2 binding
where is BPG present
present in red blood cells
what is the mechanism for BPG binding to the central cavity
BPG binds to Hb and decreased the affinity of Hb for O2
§ HbBPG + O2 <–> HbO2 + BPG
* Hb has a single binding site for BPG at the central cavity which is larger in the T state then in the R state
* BPG binding to residues around the cavity stabilises the T state
Explain why BPG is important for oxygen release
(BPG) is important for oxygen release from hemoglobin because it stabilizes the T state of hemoglobin, decreases its affinity for oxygen, and promotes efficient oxygen unloading in tissues with high metabolic activity. This ensures that oxygen is delivered to cells where it is needed for cellular respiration and energy production.
Explain why higher BPG concentration is advantageous at high altitude
(BPG) at high altitudes are advantageous because they enhance oxygen unloading from hemoglobin, compensate for reduced oxygen availability, help adapt to hypoxic conditions, and regulate oxygen affinity, ensuring efficient oxygen delivery to tissues despite the challenging environmental conditions.
what is the Functional Effect of Carbon Monoxide (CO) Binding to Hb:
- CO binds to hemoglobin (Hb) with much higher affinity than oxygen (O2)
- Forms carboxyhemoglobin (COHb), reducing O2 transport
- Shifts oxygen dissociation curve to the left
- Decreases O2 release to tissues
- Causes tissue hypoxia and potentially lethal poisoning
Describe 3 broad areas for lipid functions and provide examples
- Storage
- Structure
Signals
- Structure
Define the term lipid
Lipids are organic molecules characterized by insolubility in water and solubility in nonpolar solvents.
- They serve essential functions including energy storage, membrane structure, and signaling.
what are the essential componets of a storage lipid
- Fatty acids are essential components of other important lipids
§ Waxes
§ Phospholipids
Triacyclglycerols
what are biological lipids used for
□ Energy storage
□ Structural components of biological membranes
Signals and cofactors
Fatty Acid Melting Points trends
Melting points increase with chain length and decrease with unsaturation.
Longer, saturated fatty acids have higher melting points due to stronger intermolecular forces. Unsaturated fatty acids with cis double bonds have lower melting points due to kinks in the chain.
Fatty Acid Solubility trends
Fatty acids are insoluble in water but soluble in nonpolar solvents. Solubility decreases with increasing chain length.
Longer hydrocarbon chains make fatty acids more hydrophobic, reducing solubility in water. Shorter chains and polar functional groups increase solubility in water to some extent.
Explain trends in melting temperatures of natural fats
Influenced by fatty acid composition, chain length, and degree of saturation.
- Saturated fatty acids have higher melting points due to stronger intermolecular forces.
- Longer fatty acid chains generally have higher melting points.
- Unsaturated fats have lower melting points due to double bonds introducing kinks in the chains.
- Natural fats contain a mixture of saturated and unsaturated fatty acids, influencing their melting temperatures.
identify an omega 3 fatty acid
Omega-3 Fatty Acids:
- Have a double bond at the third carbon from the methyl (omega) end of the fatty acid chain.
- Examples include α-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA).
- Found in fatty fish (such as salmon, mackerel, and sardines), flaxseeds, chia seeds, walnuts, and algae.
- 3rd carbon in the opposite direction of the carboxyl group
identify an omega 6 fatty acid
6th carbon from the oppoite end of the carboxyl group (COOH)
highlight the structure of triglycerides
they have a glycerol molecule with 3 OH groups that attach to 3 fatty acids via an ester link/bond. these can be the same fatty acid or they can be different
are triglycerides storage molecules
yes they are storage molecules
what are the biological functions of lipids (there are three)
Storage of energy
§ Reduced compounds: lots of available energy through oxidation
§ Hydrophobic nature: good packing
- Insulation from environment
§ Low thermal conductivity
§ High heat capacity (can adsorb heat)
§ Mechanical protection (can absorb shocks) - Water repellent
§ Hydrophobic nature keeps surfaces of the organism dry
§ Prevents excessive wetting
§ Prevents loss of water via evaporation
what are phospholipids
are defined by the phosphate group within their polar head
what are the 2 categories of phospholipids
1) Glycerophospholipids (based on the glycerol molecule)
2) Sphingolipids (bases on sphingosine)
what is a Glycerophospholipids
a Glycerophospholipids is a phospolipid where it has 2 fatty acids attach to a glycerol, however it has a phosphate group an an alochol group attach to where the third fatty acid would be
what is the range of charges on a Glycerophospholipids
ranges -4 to 0 in charge
what are Glycerophospholipids mainly used for
used in for structure and signalling
what is a Sphingolipids
a phospholipid where the glycerol is an L shape (where one of the fatty acids would be), one fatty acid attach to the glycerol through an ester bond and a phosphate group and a chlorine group bonded to the phosphate group
what are Sphingolipids used for
structure and signalling roles
