BCHM 2 exam 2 unfinished flashcards

What are the two main things accomplished by the reactions where oxygen is consumed?

Regenerating all our redoxical factors1 . 2. Generating the proton gradient that drives ATP synthesis1

What is the net reaction carried out by Complex I of the electron transport chain

The oxidation of NADH2 . NADH gives up its electrons and reduces coenzyme Q3

What is the role of most of the redox cofactors in the electron transport system

To act like a molecular wire connecting the oxidation and reduction half reactions

What is an example of a redox cofactor that can do both two-electron and one-electron chemistry

Flavin mononucleotide (FMN)

What equation is used to calculate the free energy change (ΔG) from reduction potential (ΔE)

ΔG = -nFΔE6 , where n is the number of electrons transferred and F is the Faraday constant.

What is the P side of the mitochondrial membrane analogous to in bacteria

The periplasm .... It is the side with the higher positive charge

What happens to FADH2 generated in the succinate to fumarate step

FADH2 transfers its electrons along a molecular wire to ubiquinone . There is no proton pumping involved in this process (Complex II). The FADH2 is an intermediate and not really formed as a free cofactor

How many coenzyme Q cofactors does Complex III bind

Two13 : one molecule of reduced coenzyme Q and one molecule of oxidized coenzyme Q

What electron carrier does cytochrome C use14 ? How many electrons can it accept?

Heme . It can accept only one electron

What happens to the protons that were added to coenzyme Q during its reduction in Complexes I or II when it is reoxidized by Complex III?

They are released on the P side of the matrix

Why is the lipidated nature of coenzyme Q advantageous for electron transport

It allows for faster diffusion in two dimensions within the membrane compared to a three-dimensional search if it were soluble

What is the overall reaction of Complex IV

It goes from oxygen to water , taking half of an oxygen molecule

Approximately how many protons are pumped across the membrane per NADH that enters the electron transport chain ? Per succinate?

Approximately 10 protons per NADH18 and 6 protons per succinate . Succinate enters at Complex II, bypassing Complex I which pumps protons

What soluble protein is required to connect the membrane fractions of mitochondria to carry out electron transport chain reactions ? Where is it located ?

Cytochrome C . It is located in the periplasm or the P space (positive space) of the mitochondria

What are the two major pathways that regulate how glucose is initially utilized for energy production ?

Glycolysis and gluconeogenesis

Is the pentose phosphate pathway (PPP) truly a single pathway ...? What is it really ...?

No, the PPP isn't really a pathway .... It is a collection of multiple pathways that allow for the interconversion of 5-carbon and 6-carbon sugars

What are the two separate phases of the pentose phosphate pathway?

The oxidative phase and the non-oxidative phase

What is the role of the pentose phosphate pathway during DNA replication?

It can carry out this pathway to make five-carbon sugars, specifically ribose 5-phosphate, which can be used for DNA and RNA synthesis

What is a key role of NADPH produced in the pentose phosphate pathway, especially in non-replicating cells

Maintaining redox homeostasis inside the cell

How does NADP+ differ structurally from NAD+

NADP+ has a 2 prime phosphate on the adenine nucleotide portion

Is the oxidative phase of the pentose phosphate pathway reversible ? Why or why not?

No, it is unidirectional because of the loss of CO2

What are the two key types of reactions that occur in the non-oxidative phase of the pentose phosphate pathway to interconvert sugars

Reactions involving the enzymes transketolase and transaldolase . These enzymes transfer carbon units between sugar molecules

What size carbon unit does transketolase transfer?

Two-carbon units

The mechanism of transketolase is similar to which other enzyme?

Pyruvate decarboxylase

Besides its role in redox state, what is another main function of the pentose phosphate pathway?

It ties together the metabolism of five-carbon sugars with the metabolism of six-carbon sugars, allowing for their interconversion

The mechanism of transaldolase is very similar to which class of enzymes

Class 1 Aldolase

What is the overall effect on ATP yield in glycolysis if every glucose molecule first goes through the pentose phosphate pathway once before entering glycolysis

The ATP yield would be reduced because some of the carbons are diverted and potentially lost as CO2 in the oxidative phase. The subsequent non-oxidative rearrangements feed back into glycolysis, but the initial oxidative steps change the stoichiometry

How do cells regulate metabolism?

By altering the concentration or activity of the enzymes that catalyze the reactions

What does the Michaelis constant (KM) represent?

It is the concentration of substrate required to reach half saturation (1/2 Vmax) . It is also related to the rate of dissociation of the ES complex

In metabolic pathways, how does the KM of enzymes generally compare to the actual concentration of their metabolites ? Why is this significant?

Enzymes usually have KMs that are near or above the metabolite concentration . This means that changes in substrate concentration can significantly affect the enzyme's activity , allowing for responsiveness to metabolic needs.

What is cooperativity in enzymes

When the binding of a substrate at one active site on an enzyme affects the activity at other active sites

What are isozymes

Different enzymes that are encoded by different genes but catalyze the same reaction