module 5 protein function

what are ligands?

anything that is bound to a protein. ( may be another protein, but can only be one molecule)

what are the functions of ligands?

regulate protein function.

describe ligand specificity, and what interactions play a major part of it.

specificity refers to the complimentary binding sites. shape, charge, hydrophobicity, and h bond potential. 

what is induced fit?

when the protein changes conformation due to the ligand binding. this change in structure also changed function.

explain how oxygen is a limiting source.

it has poor solubility in aq, solutions, amount of available binding limits the organisms size. w

why are transition metals used for oxygen delivery and storage?

because transition metals have a high affinity for oxygen but produce damaging free radicals. so the solution is a specialized heme group protein that harnesses the metals oxygen binding properties.

what is myoglobin? 

a monomeric protein that facilitates oxygen storage in PERIPHERAL tissues. 

how many bidning sites does myoglobin have?

1

myoglobin has a ___ affinity.

higher

what is hemoglobin?

a tetrameric protein found in red blood cells that trasnport oxygen from lungs to the periphery. 

how many binding sites does hemoglobin have?

4

hemoglobin has a ___ affininity

lower

what is a heme group?

a protophyrin ring bound to a single Fe2+ atom. that provides four coordinating interactions with the iron atom. the electron donating characteristics of nitrogen prevents conversion of Fe2+ to fe3+ making it a free radical.

do both Mb and Hb use heme rings?

yes

how many interactions does iron seek?

6

four from the heme ring

1 from the imidazole group of proximal histidine residue

1 from O2 binding.

why is carbon monoxide poisoning so deadly?

because carbon monoxide had a 200x greater affinity than O2 and because they represent almost the same shape, binding sites cannot decipher the difference. 

what does an oxygen saturation curve show us?

saturation by fraction and pressure.

what is P50?

3 torr

explain the coorperativity of Hb

because Hb has more than 1 binding site, once one does it makes subsequent O2 easier to bind. 

define an allosteric protein

have an inactive T form and an active R form

T and R are in____ ________

rapid equilibrium

what are effectors (modulators)

proteins that eiether stablize or inhibit the allosteric states

which state is stabilized by activators

the R state ( r is ready to go)

which state is stablized by ihibitors?

the T state.

what is a homotropic interaction?

when the ligand and modulator is the same moleculew

what is a heterotropic interaction?

when ligand and modulator are different.

what is 2,3 BPG

an heterotrophic allosteric inhibitor of Hb. carries five units of Neg. charge

what does 2,3 BPG do to Hb?

decreases Hb’s affinity for O2

fetal Hb has a higher affinity for oxygen because_____

it must pull oxygen from mom (adult Hb)

decreased affinty for 2,3 BPG results in _____

higher O2 affinity. and vice versa

describe high altitude adaptation.

at less oxygen, increased production of 2,3 BPG occurs decreasing Hb’s affinity for O2.

binding less in the lungs and releasing more into the periphery.

what is the bohr effect?

describes pH affect on Hb affinity for O2.

Hb has a lower affinity for O2 at descreased pH

which Hb state has a lower affinity for O2?

the T state has a lower affinity than R state.

Hbs affinity for O2 is regulated by what?

CO2 produced in tissues, both indirectly and directly