BioChem Exam 2

Sort the following protein complexes of the electron transport chain according to whether they are involved in pumping protons across the inner mitochondrial membrane or not.

Pumps protons: 1,3,4

Stage 3 of the citric acid cycle

Reduction of oxygen to water Oxidation of NADH and FADH2 back to NAD+ and FAD Primary source of ATP production

What is the initial fate of an uncoated vesicle?

it fuses to the early endosome

The proximate (immediate) source of energy for oxidative phosphorylation is _____.

kinetic energy that is released as hydrogen ions diffuse down their concentration gradient

Where does glycolysis occur

cytosol

To determine whether isolated mitochondria exhibit respiratory control, one determines the ratio of rates of oxygen uptake in two different states. Which states?

step 3 divided by step 4

Where does oxidative phosphorylation occur?

inner mitochondrial membrane

Propionyl-CoA, the end product of β-oxidation of odd-chain fatty acids can enter the citric acid cycle after being converted to

succinyl-CoA

What protein does the term coated vesicle refer to?

the clathrin that forces the vesicle to invaginate

Calculate the standard free energy change for the reaction FADH2 + 1/2O2 → FAD + H2O given that the standard reduction potential for the reduction of oxygen to water is +0.82 V and for the reduction of FAD to FADH2 is +0.03 V.

-152kJ/mol

Functions of the photosystems The light reactions require the cooperation of two photosystems to power linear electron flow from water to NADP+

-Photosystem II oxidation of water reduction of electron transport chain between the two photosystems - Photosystem I reduction of NADP+ oxidation of electron transport chain between the two photosystems - Both light absorption reduction of primary electron acceptor

How do FAs of different carbon lengths cross into the mitochondrial matrix for oxidation? 1) Small FAs of 10 carbons or fewer can freely diffuse through the membrane. 2) Large FAs are cleaved into two smaller units that are actively transported across the membrane. 3) A membrane-bound transferase catalyzes the conversion of long-chain FAs to FA-carnitine esters, which are transported across the membrane via a specific carrier. 4) The breakdown of large FAs starts outside the matrix, allowing for smaller particles to pass easily through the membrane.

1 and 3

Which complexes of the electron transport system carry Fe-S clusters?

1,2,3

Which statements about complex IV are true?

1,2,3

Which of the four complexes pump protons out of the mitochondrial matrix?

1,3,4

Which regulatory effects are results of internalized cholesterol? 1) It activates acyl-CoA:cholesterol acyltransferase. 2) It increases endogenous cholesterol synthesis. 3) It downregulates the production of LDL receptors. 4) It inhibits HMG-CoA reductase.

1,3,4

Energetics of electron transport This diagram shows the basic pattern of electron transport through the four major protein complexes in the thylakoid membrane of a chloroplast.

1. no energy input required 2. energy input required 3. no energy input required 4. energy input required 5. no energy input required

If the birds relied on carbohydrate for this energy, how much additional weight would they have to start the flight with?

1.6 g 10g

Calculate the number of molecules of acetyl-SCoA derived from a saturated fatty acid with 22 carbon atoms.

11 molecules 110 ATPs 4 ATPs 148 ATPs

In cyclic photophosphorylation, it is estimated that two electrons must be passed through the cycle to pump enough protons to generate one ATP .

14.6%

Under conditions where ketone bodies are being produced in the liver, how many ATPs can be produced from a molecule of palmitic acid if all resulting molecules of acetyl-CoA are converted into β-hydroxybutyrate?

16 ATP

Match each compound with the complex it inhibits. 1. rotenone 2. CO 3. antimycin 4.cyanide 5.amytal A. complex 4 B. complex 3 C. complex 1

1:C; 2:A; 3:B; 4:A; 5:C

For each glucose that enters glycolysis, _____ acetyl CoA enter the citric acid cycle.

2

Calculate the number of ATPs generated from the metabolic oxidation of the four carbons of acetoacetyl-CoA to CO2.

20 ATP 20.5 ATP

Arrange the sequence of events that occur in complex I in their proper order.

3,2,1,4

In some instances, the levels of LDL cholesterol exceed the ability of the body to maintain homeostasis, and as a result, the excess material accumulates into fatty deposits that harden into plaques. Arrange in the correct order the sequence of events that leads to this condition, known as atherosclerosis: 1) The plaques harden, blocking the flow of blood in major arteries. 2) White blood cells become engorged with fatty deposits. 3) Excess LDL cholesterol accumulates in the interior of arterial walls. 4) Macrophages are drawn to this site.

3-4-2-1

Arrange the order of events in the fatty acid (FA) metabolism pathway in the correct order: 1) The modified FA is transported across the inner membrane of the mitochondrion. 2) Dehydration occurs to generate an α,β-unsaturated FA. 3) The free FA is converted to acetyl CoA ester. 4) Thiolytic cleavage occurs, releasing a molecule of acetyl CoA and a new FA with two fewer carbon atoms. 5) The FA CoA ester is converted to its carnitine ester. 6) Hydration occurs to yield a β-hydroxy ester. 7) The FA CoA ester is regenerated.

3-5-1-7-2-6-4

Based on the metabolism of such molecules, what quantity of a C−19 fatty acid would be required to produce 1 g of glucose? Considering that odd-chain fatty acids make up approximately 1% of the fat in our diet, what quantity of fatty acids would be needed to produce 1 g of glucose?

3.3g 330g

Calculate the number of ATPs generated by the complete metabolic oxidation of tripalmitin (tripalmitoylglycerol). Hydrolysis of the triacylglycerol occurs at the cell surface. Consider the energy yield from catabolism of glycerol, as well as from the fatty acids

336.5 ATP 6.6 ATP 5.3 ATP larger

From the ATP yield of palmitate oxidation, what is the metabolic efficiency of the biological oxidation, in terms of kilojoules saved as ATP per kilojoule released? (Ignore the cost of fatty acid activation.)

35.5%

What is the total number of ATP molecules that can be produced from the complete oxidation of one glucose molecule?

36

How many moles of glucose are required to provide the carbon for the synthesis of one mole of palmitate?

4 4.8

Arrange the sequence of events for the overall mitochondrial respiratory assembly in the correct order.

4,2,1,3

The β-oxidation of odd-numbered FAs presents a small problem in that once most of the oxidation has occurred, the last component is propionyl-CoA rather than acetyl CoA. This has one more carbon and as such cannot be utilized any further. Outline the events that control the metabolism of this unit in their proper order: 1) Methylmalonyl-CoA epimerase converts S-methylmalonyl-CoA to R-methylmalonyl-CoA. 2) Methylmalonyl-CoA mutase demethylates R-methylmalonyl-CoA to succinyl-CoA. 3) Propionyl-CoA carboxylase catalyzes the addition of CO2 to propionyl-CoA. 4) The odd-carbon FA is metabolized to propionyl-CoA.

4-3-1-2

Consider an ATP synthase complex with 12 "c" subunits in its F0 rotor (as illustrated in the molecular model of the E. coli enzyme in section II of the tutorial). How many protons must translocate through the F0 complex in order to generate 10 molecules of ATP?

40

Using Figure 16.9 on page 515 in the text, arrange the order of events for the internalization of LDL particles into cells: 1) A combination of cholesterol and apolipoprotein binds to LDL receptors and becomes internalized as endocytotic vesicles. 2) The environment of the endosome becomes acidic, which causes the LDL to dissociate from its receptor; additionally, the endosome fuses with a lysosome. 3) Several endocytotic vesicles fuse to form an endosome. 4) The LDL particle is degraded by the lysosome. 5) LDL receptors migrate to the cell surface and cluster in clathrin-coated pits.

5-1-3-2-4

For each glucose that enters glycolysis, _____ NADH + H+ are produced by the citric acid cycle.

6

How many tritium atoms (3H) are incorporated into palmitate when fatty acid synthesis is carried out in vitro with the following labeled substrate?

7

Which statement correctly describes how this increased demand would lead to an increased rate of ATP production?.

ATP levels would fall at first, decreasing..

Chloroplast membrane vesicles are equilibrated in a simple solution of pH 5. The solution is then adjusted to pH 8. Which of the following conclusions can be drawn from these experimental conditions?

ATP will not be produced...

Which of the following statements regarding the β-oxidation of FA is NOT correct?

Acyl-CoA dehydrogenase catalyzes the synthesis of a cis α,β-unsaturated CoA thioester.

Sort the following molecules based on whether or not they are biologically occurring ketone bodies.

Biological ketone bodies A. acetone C. B-hydroxybutyrate F. acetoacetate

How would anaerobic conditions (when no O2 is present) affect the rate of electron transport and ATP production during oxidative phosphorylation? (Note that you should not consider the effect on ATP synthesis in glycolysis or the citric acid cycle.)

Both electron transport and ATP synthesis would stop.

During electron transport, energy from _____ is used to pump hydrogen ions into the _____.

NADH and FADH2 ; intermembrane space

You identify a new pathway in yeast that converts glucose to pyruvate. The pathway consists of the following four steps:

C and D B and C

When pure reduced cytochrome c is added to carefully prepared mitochondria along with ADP, Pi, antimycin A, and oxygen, the cytochrome c becomes oxidized, and ATP is formed, with a P/O ratio approaching 1.0.

C to Ua to A to A3 to UBto O2 To block oxidation electron flow Because ADP is formed 2nd long equation 79.49kJ/mol

Which of the following statements about the lipoproteins given in the introduction are true?

Chylomicrons... Lipoproteins can... Lipoprotein densities vary... Lipoproteins vary...

Stage 1 of citric acid cycle

Conversion of pyruvate to acetyl-CoA Production of one molecule of CO2

Rank the following molecules by the number of ATP molecules they produce.

pyruvate, acetly CoA, NADH, FADH2, GTP

Label the steps of electron transport leading to oxidative phosphorylation where ATP is synthesized from ADP using the energy stored by the electron-transport chain.

Electron flow...; Protons return...; Protons release

Examine the molecular model of the partial structure of the yeast ATP synthase. Which part of the molecule spans the inner mitochondrial membrane?

F0 rotor

The chemiosmotic hypothesis states that the synthesis of ATP generates a proton gradient that leads to electron flow through an electron transport chain.

False

Which statement best explains why more ATP is made per molecule of NADH than per molecule of FADH2?

Fewer...

What would happen to the cell's rate of glucose utilization? during strenuous exercise

Glucose utilization would increase a lot.

Identify the complexes and mobile electron carriers that remain reduced and oxidized due to the following blocker/inhibitors. You can use the electron-transport chain labeled in part A to help answer this question.

I--Q C--4 3--c I--Q

Under anaerobic conditions (a lack of oxygen), the conversion of pyruvate to acetyl CoA stops.

In the absence...

Examine the F1 complex of the ATP synthase from bovine heart mitochondria. What prevents this F1 complex from rotating with the F0 c-ring complex?

It is bound by the stator...

Stage 2 of the citric acid cycle

Production of two molecules of CO2 Production of two molecules of C O 2 Joining of acetyl-CoA to oxaloacetate of citric acid cycle

Which of the following statements about complex II is NOT true?

The complex draws...

Briefly describe the mechanism(s) of these two types of photophosphorylation that explain all of these results.

The first reaction: Only PSI is involved-- The internal electron transport stimulates ATP synthesis-- The internal electron transport stimulates ATP synthesis-- Cyclic photophosphorylation-- Reduced NADPH is not produced-- Reduced NADPH is not produced-- O2 is not produced-- The electrons are transferred back into the electron transport chain.

Which statement about oxidative phosphorylation is NOT true?

The mechanisms of...

Which statement about uncouplers is NOT true?

They allow ATP...

How is receptor-mediated endocytosis (RME) different from pinocytosis and phagocytosis?

Unlike pinocytosis, RME is specific; unlike phagocytosis, RME is for small particles.

Sort the phrases into the appropriate bins depending on whether they describe exocytosis, endocytosis, or both.

a. decreases the surface area of the plasma membrane - Endocytosis b. requires fusion of vesicles with the plasma membrane - Exocytosis c. forms vesicles from inward folding of the plasma membrane - Endocytosis d. transported substances never physically cross the plasma membrane - Both e. increases the surface area of the plasma membrane - Exocytosis f. requires cellular energy - Both g. secretes large molecules out of the cell - Exocytosis

One pathway that appears to relate elevated cholesterol levels to atherosclerosis involves the oxidation of LDL. Which of the following are consequences of this process?

all

Which of the following are key discoveries of the experiments conducted by Brown and Goldstein? 1) Cholesterol is taken into cells through the action of a specific receptor. 2) The receptor for the LDL particle recognizes B-100 apolipoprotein. 3) The entire receptor complex, unlike hormones involved in signaling pathways, enters the cell via endocytosis. 4) Familial hypercholesterolemia patients have defective or deficient LDL receptors.

all

Which of the following enzymes are required for the oxidation of unsaturated FA?

all

Which of the following are part of the chemiosmotic coupling model?

all choices

Four electron carriers, a, b, c, and d, whose reduced and oxidized forms can be distinguished spectrophotometrically, are required for respiration in a bacterial electron-transport system. In the presence of substrates and oxygen, three different inhibitors block respiration, yielding the patterns of oxidation states shown below. What is the order of the carriers in the chain from substrates to O 2 , and where do the three inhibitors act?

c--b--a--d

The number of reactions, intermediates, and pathways of intermediary metabolism can at first seem overwhelming. However, these can all be simplified by viewing metabolism as a roadmap. This allows one to focus on the overall strategy, or one can focus on just a portion of the overall map. In this exercise, fill in the blanks to construct an overview of metabolism.

catabolism; release; anabolism; consumption; acetyl-CoA; citric acid cycle; oxidized; reduced;ETC; ATP

_______ is taken up by cells using receptor-mediated endocytosis, which involves the recognition of the B-100 apolipoprotein component of LDL.

cholesterol

Coenzyme Q carries electrons between which stages of the electron-transport chain?

complex 1 and complx III complex II and complex III

Chlorophylls, carotenes and xanthophylls absorb light in the visible part of the spectrum because they contain large ________ double-bond systems.

conjugated

Describe the probable effect in adipocytes of insulin-stimulated uptake of glucose into these cells. Match the words in the left column to the appropriate blanks in the sentences on the right. Make certain each sentence is complete before submitting your answer.

cytosol--pyruvate--mitochondrion--cytosol--citrate

What happens to your blood pH if you go into ketosis?

decreases

FAD is a stronger oxidant than NAD + ; FAD has a higher standard reduction potential than NAD + . Yet in the last reaction of the pyruvate dehydrogenase complex, FADH 2 bound to the E 3 subunit is oxidized by NAD + .

does no dissociate; enzyme; protein; negative; electrons; NAD+

The ATP yield from NADH transported across the mitochondrial inner membrane by the glycerol phosphate shuttle is the same as if the malate/aspartate shuttle were used.

false

True or false? The region of ATP synthase that catalyzes the production of ATP from ADP and inorganic phosphate spans the chloroplast membrane.

false

In the electron transport chain, protons are pumped from where to where in the mitochondria of eukaryotic cells?

from the mitochondrial matrix to the intermembrane space

Arrange the following steps or substances by where they appear in the process of glucose metabolism.

glycolysis, citric acid cycle, ETC, ATP synthase

Once of the processes linked to receptor-mediated endocytosis is transcytosis. When might this mechanism be useful?

in transporting antibodies from mother's milk from an infant's stomach into the bloodstream

What would be the effect on fatty acid synthesis of an increase in intramitochondrial oxaloacetate level? Briefly explain your answer.

increase stimulating

In what organelle of the cell does β oxidation of fatty acids take place?

mitochondria

where does the citric acid cycle occur

mitochondrial matrix

In order to function as an oxidative phosphorylation uncoupler, 2,4-dinitrophenol must act catalytically, not stoichiometrically.

mulltiple; deprotonating; the higher pH; proton; toxic

What is the trigger for the invagination of the vesicle?

occupied receptors accumulating in the coated pits

In cellular respiration, most ATP molecules are produced by _____.

oxidative phosphorylation

The final electron acceptor of cellular respiration is _____.

oxygen

Which term describes ATP production resulting from the capture of light energy by chlorophyll?

photophosphorylation

Electrons are transferred through the respiratory chain from reduced NADH or FADH2 to oxygen in small steps with each step in the pathway associated with a slightly more ________ reduction potential.

positive

According to the chemiosmotic hypothesis, what provides the energy that directly drives ATP synthesis?

proton gradient

Which of the following particles can pass through the ATP synthase channel?

protons

What is the source of energy that directly drives ATP synthase in its production of ATP?

protons diffusing through the F section of ATP synthase

The four stages of cellular respiration do not function independently. Instead, they are coupled together because one or more outputs from one stage functions as an input to another stage. The coupling works in both directions, as indicated by the arrows in the diagram below. In this activity, you will identify the compounds that couple the stages of cellular respiration.

pyruvate; NADH; NAD+; NADH; NAD+

Sort the labels into the correct bin according to the effect that gramicidin would have on each process.

remains the same: proton pumping rate, electron transport rate, rate of oxygen uptake. decreases or goes to zero: rate of ATP synthesis, size of protein gradient

On the graph, identify the state that might predominate in each stage of the trace indicated with a letter.

state 1--state 2--state 3--state 4--state 5

Which state probably predominates in heart muscle most of the time?

state 3

Which state probably predominates in resting skeletal muscle of a well-nourished animal?

state 4

Which state probably predominates in vivo in skeletal muscle fatigued from a long and strenuous workout?

state 5

In mitochondrial electron transport, what is the direct role of O2?

to function as the final electron acceptor in the electron transport chain

Proton gradient formation and ATP synthesis

top left pink: empty bottom left: site of H+ release top right pink: site of ATP synthesis left blue: H+ pumped across membrane middle blue: empty right blue: H+ diffuses across membrane

Briefly describe how cyclic AMP controls phospholipid synthesis.

triacylglycerol breakdown--activation--increase--increase

In the molecular model of the E. coli F0 rotor, the c-ring rotates as a direct result of __________.

twisting...

The rotation of the F0 rotor is driven by the proton gradient. Examine the F0 rotor of E. coli. The protons enter through the entry half-channel and are passed on to a(n) __________.

unprotonated...

Which of the following is NOT involved in the enzymatic inactivation of reactive oxygen species?

vitamin C