oxygen:

conc is usually expressed as pO2

conc can be 1mmHg inside cells

is transported to cells from lung by Hb

conc is 155mmHg in the air we breath

is transported from the lungs to cells by myoglobin

conc is usually expressed as pO2

conc can be 1mmHg inside cells

is transported to cells from lung by Hb

conc is 155mmHg in the air we breath

the distal histidine:

sterically blocks the formation of haem-o2-haem sandwhiches

is at the side of the haem group where oxygen binds

decreases the strength of binding CO2

becomes protonated upon oxygen binding

decreases the strength of binding CO

sterically blocks the formation of haem-o2-haem sandwhiches

is at the side of the haem group where oxygen binds

decreases the strength of binding CO

in Mb-O2 binding:

the saturation curve is sigmoid in shape

it is weaker then Hb-O2 binding

the p50 is 2.75mmHg

the saturation curve is hyperbolic in shape

p50 is 26.6 mmHg

the p50 is 2.75mmHg

the saturation curve is hyperbolic in shape

in Hb-O2 binding the p50 of 26.6 mmHg:

is the typical PP in the mitochondria

is the typical pp in the lungs

represents the KD

represents the O2 conc at which 50% of sites are filled

represents the P50

represents the O2 conc at which 50% of sites are filled

represents the P50

in Hb, the allosteric regulators:

compete with O2 for the iron bindin site

protons, weaken O2 affinity

2,3 BPG strenghthens O2 affinity

CO2 binds non-covalently

all three weaken o2 affinity

protons, weaken O2 affinity

all three weaken o2 affinity

in the Bohr effect:

protons bind to His E7

protons bind to His F8

Protons bind to Cys residues

Protons bind to His 146

Acidification results in better unloading of o2

Protons bind to His 146

Acidification results in better unloading of o2

Retinol or Vitamin A acts as:

a fatty acid

a steroid hormone

a component of the night vision system

an anti-oxidant

an anti-coagulant

a steroid hormone

a component of the night vision system

an anti-oxidant

Retinol Binding Protein:

holds the hydrophobic retinol residues in the hydrophobic pocket

Is synthesised in the liver

Is itself bound to a larger protein, transthyretin

Holds the hydrophilic retinol in hydrophilic pocket

Binds two molecules of retinol

holds the hydrophobic retinol residues in the hydrophobic pocket

Is synthesised in the liver

Is itself bound to a larger protein, transthyretin

Enzymes:

shift equilibrium in postions to favour product formation

Allow reactions that could otherwise not take place

Always consist only of protein

Increase reaction rates

Enzymes:

Promote forward reaction rates more than backward reaction rates

Alter the total free energy change of a reaction

Decrease the activation energy of a reaction

Increase the activation energy of a reaction

The 8 electrostatic bonds in deoxyHb:

Involve His at the C-Termini at the alpha subunits

Includes ones between alpha subunits

Includes ones between beta subunits

Are all broken in oxyHb

Involve His at the C Termini of beta subunits

Includes ones between alpha subunits

Are all broken in oxyHb

Involve His at the C Termini of beta subunits

Mb:

is an extra cellular protein of Mr 17000

Has helical regions terminated by His residues

Contains RH alpha helices

Is an intracellular protein of 17000

Contains LF alpha helices

is an intracellular protein of Mr 17000

Contains RH alpha helices

Based on the common nomencalture of enzymes, which of the following proteins is most likely to be the name of a protease (an enzyme that breaks peptide bonds within proteins)

Pepton

Luciferase

Actinidin

Catalase

Polypeptide Synthase

How do enzymes help to form transition states?

they > temperature of reactants

formation of non-covalent bonds between enzyme and substrates

they prevent the backward conversion of products to substrates

They bring substrates together in the active site which increases the likelihood of a reaction taking place

They alter the overall energy difference between the substrate and product molecules

formation of non-covalent bonds between enzyme and substrates

They bring substrates together in the active site which increases the likelihood of a reaction taking place