Exam 2 (L2-3)

Biochemistry 401 with Foley at Michigan State University

About this deck

By: Kara Brockhaus
Textbook: Biochemistry (Looseleaf)
Created: 2010-10-05
Size: 68 flashcards
Views: 23

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heme synthesis needs

• Formation of Protoporphyrin IX

Asymmetric ring structure

• Chelation of Iron

heme synthesis requires

•4 Mitochondrial enzymes •4 Cytosolic enzymes

Heme biosynthesis: reaction one ia a _____ between _____ and ____ to make ____

condensation rxn

Succinyl CoAand

Glycine to form δ-Aminolevulinate

what enzyme catalyzes rxn 1?

Aminolevulinate Synthase in the mitochondrial matrix

regulation of rxn one

(primarily neg. feedback)

1. transport of δ-Aminolevulinate in to mitochondrian is blocked by high heme concentration

2. translation: neg feedback by heme reduces translation of δ-Aminolevulinate

mRNA

reaction 2: dehydration rxn (steps)

1. transport to cytosol

2. 2 molecules of δ-Aminolevulinate condense to form each porphobilinogen molecule

products from rxn 2

8 molecules of δ-Aminolevulinate and 4 of porphobilinogen

rxn 3: condensation rxn

4 molecules of porphobilinogen condense head to

tail to form a linear tetrapyrrole molecule with

release of one ammonium ion for each methylene

bridge made.

what enzyme molecule catalyzes rxn 3

Porphobilinogen Deaminase

rxn 4 is known as _____ and does what?

cyclization

Synthesis of an asymmetric ring

Uroporphyrinogen III

what enzyme catalyzes rxn 4?

Uroporphyrinogen III

synthase. Note: this enzyme is also

known as Uroporphyrinogen III

Cosynthase

reactions after 4 do what?

form methyl and vinyl side chains,

and alter saturation of ring constituents, finally ending

with protoporphyrin IX. These reactions take place in the

mitochondrion. Finally, ferrous iron, Fe2+is chelated.

what enzyme helps Fe2+ chelate?

ferrochelatase

free iron is

toxic because can donate and accept electrons making it a catalyst

ferritin does what?

intracellular iron storage

transferrin

carries iron in the blood and Extracellular space

*can carry two Fe3+ ions

2 types of porpohyrias

1. acute intermittent

2. congenital erythropoietic

acute intermittent porphohyrais

(from rxn 3)

Porphobilinogen Deaminase

Deficiency -

Porphobilinogen and δ-

Aminolevulinate excess

what are symptoms of intermittent porphohyrais?

severe abdominal pain

neurological involvement

*think maddness of king george the 3rd

congenital erythropoietic porphohyrais

(from rxn 4) cosynthase deficiency

Uroporphyrinogen I, a

symmetric ring, is formed in addition to uroporphyrinogen III.

Uroporphyrinogen I has no use, this ring and its metabolites build up,

because they cannot be

used.

symptoms of erythropoietic porphohyrais

photosensitivity and red flourescent teeth

primary site of RBC scavengering

spleen

when heme is broken down in the spleen it happens in several steps to form:

1-urobilin and

1-stercobilin

where is

1-stercobilin

excreted?

feces (red-orange)

where is

1-urobilin excreted?

urine (yellow- orange)

the spleen does what to hemoglogin?

Hemoglobin protein components -globin chains

- are hydrolyzed to individual amino acids.

Iron is recycled.

heme oxygenase does what?

breaks the alpha methene bridge to release Fe2+

Products: Bilverdin, CO, H2O, NADP+

biliverdin reductase does what?

breaks the central methene bridge

Products: NADP+ and bilirubin

(e- donor is NADH)

*occurs in the spleen

what rxn is the limiting rxn?

rxn 1:

Condensation reaction between Succinyl CoA and Glycine to form delta-Aminolevulinate

builirubin is transported from the ____ but is poorly ____ and needs ____ to bind to it to move throughout the blood

*spleen
*soluble
*Serum Albumin

UDP - Glucuronide

activated acid derivative of glucose

Glucuronyl transferase is what kind of enzyme

liver

Glucuronyl transferase does what?

transfers two molecules of UDP - glucuronide to 2 propionate side chains of bulirubin
*(aka: Conjugated Bilirubin OR

Bilirubin Diglucuronide)

*does this so that it can travel in bile (makes it hydrophillic)

increased unconguated bilirubin results in

anemia
neonatal jaundice
resolution of large hematoma

BRUISE red - green - yellow means

heme - biliverdin - bilirubin

increased direct bilirubin

Liver disease:
bile obstruction
cirrhosis
hepatitis

most enzymes are

proteins

Some enzymes are protein and RNA in which the RNA is

catalytic

enzymes are

catalysts

primary function of an enzyme is to

increase the rate of reaction for a given reaction

enzymes are not

consumed in a reactoin

In an enzyme catalyzed reaction:

Concentrations of products at equilibrium are

unchanged from the uncatalyzed reaction

Enzymes stabilize the

transition state

enzymes decrease the _____

activation E and thus decreases time.

delta G =

Free energy difference between products and reactants: this dictates whether a reaction is spontaneous in the forward direction

• Dependent on the final energy difference of the products and reactants, not the path in between. • • Says nothing about the rate of a reaction.

delta G double dagger

Activation energy is the amount of energy needed to initiate the reaction

This affects the rate of reaction

- Enzymes effect only the rate of reaction, not the equilibrium.

cofactors are divided into two groups

metals: tightly bound, inorganic
coenzymes - small organic molecules

tightly bound cofactors are called

prosthetic groups

a cofactor can be a ____ for many diff enzymes that need it's chemical function

coenzyme

apoenzyme_cofactor =

holoenzyme

apoenzyme def

enzyme without its requiredcofactor

holoenzyme def

enzyme with its required cofactor

two methods of enzyme binding

lock and key

induced fit

Vmax:

the velocity of the enzyme when all enzyme binding sites said to be filled, saturated, with substrate. No matter how much additional substrate is added, the reaction will not proceed any faster. The enzyme is going at its maximum rate of speed.

Km =

the concentration of substrate at which half of all the possible enzyme binding sites are full.

the _____ the Km the more efficient the binding of the enzyme is for that substrate

lower

the _______ the Vmax the more efficient the enzyme and substrate are at producing the product.

higher

the lineweaver burk plot is a

double reciprocal plot

types of reversible inhibition

Competitive

Uncompetitive

Non-competitive

Mixed

Ki=

Measure of inhibitor potency

Kmapp =

Km in the presence of inhibitor

K max app =

Vmaxin the presence of inhibitor

competitive inhibitor:

Inhibitor competes with substrate for the active site. Addition of more substrate can overcome the effect of the inhibitor

noncompetitive inhibitor:

doesn't bind to active site

uncompetitve inhibitor:

Binds to an enzyme that is already bound with a substrate and decreases the eff of the enzyme

*diff from noncomp. Inhb. Bc noncomp binds the enzyme where this one binds the enzyme-substrate complex.

competetive inhib increases what?

Km app

In response to a non-competitive inhibitor

Km = Km app

Vmax> Vmaxapp

i response to uncompet. inhib:

Km>Km apparent, Vmax >Vmax apparent

About this deck

By: Kara Brockhaus
Textbook: Biochemistry (Looseleaf)
Created: 2010-10-05
Size: 68 flashcards
Views: 23

About StudyBlue

“I have been getting MUCH better grades on all my tests for school. Flash cards, notes, and quizzes are great on here. Thanks!”
Kathy