Intro to Cell Exam 2 w/ Moon

Identify enzymatic reactions of the Krebs (Citric Acid) Cycle Drag the labels to identify the enzymatic function of the indicated steps.

(Clockwise) (Starting at 12) Molecular rearrangement but not oxidation Oxidation/ decarboxylation Oxidation/ decarboxylation Substrate level phosphorylation Oxidation Molecular rearrangement but not oxidation Oxidation Addition of 2 carbon acetyl group to OAA

Drag the labels to identify each molecule in the cycle acting as an oxidizing agent and reducing agent respectively.

(Clockwise)(Starting at 1) reducing agent oxidizing agent reducing agent oxidizing agent reducing agent oxidizing agent reducing agent oxidizing agent

For the oxidation of pyruvate shown in Figure 9.9, which answer correctly identifies molecules involved in the positive (+) and negative (−) control of this reaction?

+: NAD+, CoA, and AMP −: Acetyl CoA, NADH, and ATP

All proteins are synthesized by ribosomes in the cell. Some ribosomes float freely in the cytosol, while others are bound to the surface of the endoplasmic reticulum. Most proteins made by free ribosomes function in the cytosol. Proteins made by bound ribosomes either function within the endomembrane system or pass through it and are secreted from the cell. Which of the following proteins are synthesized by bound ribosomes? Select all that apply.

-lysosomal enzyme -insulin -ER protiein (LIE)

Each of the four stages of cellular respiration occurs in a specific location inside or outside the mitochondria. These locations permit precise regulation and partitioning of cellular resources to optimize the utilization of cellular energy. Match each stage of cellular respiration with the cellular location in which it occurs. Labels may be used once, more than once, or not at all.

-stage---> location -glycolosis---> cytosol -acetyl CoA formation---> mitochondrial matrix -citric acid cycle--->mitochondrial matrix -oxidative phosphorylation--->inner mitochondrial membrane

Select each treatment description that accurately describes the functioning of 'inside-out' vesicles. Choose all that apply.

-will make ATP from ADP and Pi if transferred to a pH7 buffered solution after incubation in a pH4 buffered solution. -will become acidic inside when NADH is added.

Complete the following sentences about enzyme function: Enzymes speed reaction rates by ______ and lowering activation energy. Activation energies drop because enzymes stabilize _______. Enzyme specificity is a function of the active site's shape and the chemical properties of _______ at the active site.

1. orienting substrates; 2. the transition state; 3. R-groups

If ΔH = -60.0 kJ and ΔS = -0.400 kJ/K , the reaction is spontaneous below a certain temperature. Calculate that temperature. Express your answer numerically in kelvins.

150 K

Consider the two-step metabolic pathway: A—(enzyme 1)—>B—(enzyme 2)—>C How would inactivating enzyme 1 affect the concentrations of molecules A, B, and C relative to what they would be if the pathway were fully functional?

A would increase; B and C would decrease.

When the ATP to ADP+AMP ratio is low (indicating low energy charge) the excess _________ binds to an _______________ site on the enzyme and the binding causes a overall shape change that alters the active site in such as way that enhances the binding of substrate. The effect of this regulation speeds the production of the oxidative metabolism during times when the cell has inadequate number of energy carrier molecules available to fuel the endogonic biochemical work of the cell. Fill in the blanks with the correct terms separated by a comma

ADP, allosteric

If this represents an exergonic reaction, identify which of the five substances would have the highest-energy electrons.

AH2

Why is ATP production during cellular respiration characterized as indirect?

ATP is not produced directly by the ETC but instead via the proton gradient generated during electron transport through the ETC.

Which of the following results provided evidence of a nuclear localization signal in the nucleoplasmin protein?

After cleavage of the protein, only the tail segments appeared in the nucleus.

The Golgi apparatus has a polarity, or sidedness, to its structure and function. Which of the following statements correctly describes this polarity?

All of the listed responses correctly describe polarity characteristics of the Golgi function.

When the ATP to ADP+AMP ratio is high (indicating high energy charge) the excess ATP binds to an _______________ site on the enzyme and the binding causes a overall shape change that prevents the binding of substrates at the acitve site. The effect of this regulation slows the production of the oxidative metabolism during times when the cell has more than enough energy carrier molecules available to fuel the endogonic biochemical work of the cell. Fill in the blanks with the correct term.

Allosteric

Which answer best explains why aerobic respiration produces more ATP per mole of glucose than either anaerobic respiration or fermentation?

Among known electron acceptors, O2 is most electronegative.

Which is true of the metabolic pathway shown here? enzyme 1 enzyme 2 A ————————> B ————————> C enzyme 3 ————————> D

B is the product of enzyme 1 and the substrate for enzyme 2.

What do they have in common?

Both enzymes are regulated by feedback inhibition.

Which of the listed statements describes the results of the following reaction? C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy

C6H12O6 is oxidized and O2 is reduced.

From the equation ΔG = ΔH − TΔS, it can be concluded that __________. A) the capacity of a system to perform useful work is related to the total free energy of the system B) increasing the change in entropy of a system will increase the probability of spontaneous change C) increasing the temperature of a system will increase the probability of spontaneous change D) all of the other answer choices are true

D) all of the other answer choices are true

Which of the following is a statement of the first law of thermodynamics?

Energy cannot be created or destroyed.

Which of the following statements is a logical consequence of the second law of thermodynamics?

Every chemical reaction must increase the total entropy of the universe.

Glucose is taken up into cells through a carrier (transport) protein called a _________ transporter Type the correct term to fill the blank (use all capital letters for the acronym for this transporter).

GLUT

Immediately after Glucose enters the cell it is phosphorylated by the enzyme __________, which adds a phophate from ATP to Glucose to produce Glucose -6- phosphate and ______________. Enter the name of the enzyme followed by the second product separated with a comma. For example if the enzyme were catalase and the second product was FAD you would enter: catalase, FAD

Hexokinases, ADP

A new mutant has been discovered such that electrons from NADH are not passed to FMN but rather to Cyt b directly. What effect would this change have on the relative magnitude of the electrochemical proton gradient across the inner mitochondrial membrane?

It would reduce the gradient

For eukaryotic cells, which answer best describes the function of the indicated component?

Peroxisome: detox center

Pyruvate Processing either by a fermentation reaction or by entry to the Krebs cycle and subsequent oxidative phosphorylation, is essential to prevent glycolysis from grinding to a halt. The key need for pyruvate processing is to regenerate ________________.

NAD+

Considering the standard reduction potential (SRP), which of the following molecules is storing the most energy?

NADH (SRP -0.322 Volts)

Considering the standard reduction potential (SRP), which of the following molecules would be the strongest reducing agent?

NADH (SRP -0.322 Volts)

What would happen to NADH levels in a cell in the first few seconds after a drug has poisoned the enzyme that converts acetyl CoA to citrate?

NADH levels would decrease.

Can an enzyme make a nonspontaneous reaction occur spontaneously? Why or why not?

No, because enzymes do not affect the overall ΔG of a reaction.

A key enzyme in glycolysis, whose catalytic activity is controlled by feedback regulation is ____________________. This enzyme balances the need for energy with the production of ATP.

Phosphofructokinase

Use the figure shown above of Lineweaver-Burk Plots of a mutant enzyme and a normal enzyme. Remember that when genes are mutated (change in DNA sequence), leading to changes in amino acids in the primary sturcture of the protein, this often leads to changes in the overall shape of the protein. Consider that mutant enzymes with altered shapes almost aways have lower catalytic efficiency when compared to the normal enzyme (use this information to interpret the question below). Which plot represents the mutant enzyme and why?

The blue line represents the mutant enzyme since it has the higher slope and the higher Km

The transport of pyruvate into mitochondria depends on the proton-motive force across the inner mitochondrial membrane. How does pyruvate enter the mitochondrion?

active transport.

Which statement most accurately explains why ATP hydrolysis is highly exergonic?

There is a large drop in potential energy because charge repulsion is reduced, accompanied by a large increase in entropy.

When is the overall free energy change ΔG in a reaction most likely to be negative (meaning that the reaction is exergonic)?

When products have lower potential energy and higher entropy than reactants

Using what you have learned about changes in free energy, would you predict the ΔG value of catabolic reactions to be positive or negative? Catabolic reactions will often have:

a negative ΔG based on a decrease in enthalpy and increase in entropy

What about anabolic reactions? Anabolic reactions will often have:

a positive ΔG based on an increase in enthalpy and decrease in entropy

Which of the following intermediary metabolites enters the citric acid cycle and is formed, in part, by the removal of a carbon (CO2) from one molecule of pyruvate?

acetyl CoA

A series of enzymes catalyze the reaction X → Y → Z → A. Product A binds to the enzyme that converts X to Y at a position remote from its active site. This binding decreases the activity of the enzyme. With respect to the enzyme that converts X to Y, substance A functions as _____.

an allosteric inhibitor

The polymerization of amino acids into a protein is an example of _____.

an anabolic pathway

Canine phosphofructokinase (PFK) deficiency afflicts Springer spaniels, affecting an estimated 10% of the breed. Given its critical role in glycolysis, one implication of the genetic defect resulting in PFK deficiency in dogs is _____.

an intolerance for exercise

Considering the standard reduction potential (SRP), which of the following molecules would be the strongest oxidizing agent?

cytochrome a3 (SRP +0.624 Volts)

Enzymes speed up chemical reactions by ____.

decreasing the activation energy

Lysosomes that lack mannose-6-phosphate receptors _____.

do not receive enzyme shipments from the Golgi apparatus

Oxidation and reduction reactions are chemical processes that result in a gain or loss in _______________

electrons

When ATP is hydrolyzed into ADP and inorganic phosphate, _____.

free energy is released

The induced-fit model:

involves a conformational change in the shape of the enzyme.

Which of the following contains hydrolytic enzymes?

lysosome

During cellular respiration, acetyl CoA accumulates in which location?

mitochondrial matrix.

Which of the following mitochondrial activities would most likely be inhibited?

oxidative phosphorylation

Scientists can track the movement of proteins through the endomembrane system using an approach known as a pulse-chase experiment. This experiment involvesBased on these data, what is the most likely function of the cells in this experiment?

phagocytosis

As two electrons are passed from FMN to Fe-S proteins, FMN becomes ______________, whereas Fe-S protein becomes __________.

re-oxidized......reduced

If a metabolic poison irreversibly binds to cyt a, cyt a will become permanently ___________, whereas cyt a3 will be permanently _________.

reduced ...... oxidized

Wben an atom or molecule gains one or more electrons, it is said to be ______________ and is at a ____________ energy state.

reduced......higher

In their fermentation reaction shown below, pyruvate (pyruvic acid) is being _________ and NADH is being _______________

reduced......oxidized

When electrons from NADH are released onto FMN, FMN becomes _____________, and since Fe-S protein is a stronger _________ agent with a ___________ negative Standard Reduction Potential, it immediately accepts the electrons from FMN.

reduced......oxidizing agent......less

What can be said about an exothermic reaction with a negative entropy change? The reaction is:

spontaneous at low temperatures

What can be said about an endothermic reaction with a negative entropy change? The reaction is:

spontaneous in the reverse direction at all temperatures.

How many carbon atoms are fed into the Krebs (citric acid) cycle as a result of the oxidation of one molecule of pyruvate?

two