biochem ch17, 21, 19 clicker questions

which is not a major source of fatty acid fuels in vertebrates? 1. conversion in the liver of excess dietary amino acids to fats 2. conversion in the liver of excess dietary carbohydrates to fats 3. fats stored in adipocytes 4. fatty acids in the diet

1. conversion in the liver of excess dietary amino acids to fats although vertebrates do have pathways to convert aa to fats, this is not a significant source of fatty acid fuels

What is the potential ATP yield from complete oxidation of the coenzyme A derivative of stearic acid (18:0)

122 (22 from b oxidation, 100 from CAC)

what is the final product of the FAS 1 systems?

16:0

Succinate dehydrogenase is dysfunctional in a species of garden slug. While its metabolism is compromised on a number of levels, it can still undergo oxidative phosphorylation. What is the maximal P/O ratio for these organisms if NADH is used as an electron source

2.5 if 10 protons are pumped out per NADH and 4 must flow in to produce 1 ATP

Calculate the free-energy change for the creation of an electrochemical gradient by a proton pump if the pH of the matrix is 0.75 units more alkaline than that of the intermembrane space, the transmembrane difference in electrical potential is 0.20 V, and the temperature is 37 °C

24 kJ/mol ∆G = 2.3RT ∆pH + ZF ∆ψ = 2.3(0.008315 kJ/mol • K)(310 K)(0.75) +(+1)(96.5 kJ/V • mol)(0.20 V) = 19.3 kJ/mol + 4.45 kJ/mol = 24 kJ/mo

How many electrons would enter Complex I from complete oxidation of myristic acid, 14:0

54. Myristic acid undergoes 6 rounds of β oxidation, producing 7 acetyl-CoA and 6 NADH (1 NADH per round). Each acetyl-CoA yields 3 NADH in the citric acid cycle. 6 NADH + (7 acetyl-CoA×3 NADH/acetyl-CoA) = 27 NADH Each NADH molecule donates 2 electrons to Complex I. 27 NADH×2e−/NADH = 54e−

How is oxidative phosphorylation inhibited during anaerobicconditions?

A lack of terminal electron acceptor blocks the electron-transfer chain ADP levels decrease. A buildup of glycolytic products (pyruvic acid, lactic acid)lowers pH. Inhibitory protein IF1 becomes functionally dimeric under acidic conditions and binds the ATP synthase inhibiting it.

Which statement is false about Complex III? A. It holds ubiquinone on the matrix side of the inner mitochondrial membrane throughout the redox process. B. Its functional unit consists of two dimers made up of cytochrome b, cytochrome c1, and the Rieske iron-sulfur protein. C. It couples the oxidation of two molecules of reduced ubiquinone (QH2) with the reduction of two molecules of cytochrome c. D. It catalyzes the net movement of two protons from the N side to the P side of the inner mitochondrial membrane.

A. It holds ubiquinone on the matrix side of the inner mitochondrial membrane throughout the redox process. The two cytochrome b monomers surround a cavern in the middle of the membrane in which ubiquinone is free to move from the matrix side of the membrane (site QN on one monomer) to the intermembrane space (site QP on the other monomer) as it shuttles electrons and protons across the inner mitochondrial membrane.

Which statement regarding regulation of acetyl-CoA carboxylase is false? A. Phosphorylation activates acetyl-CoA carboxylase B. Acetyl-CoA carboxylase catalyzes the rate-limiting step of fatty acid biosynthesis. C. Citrate allosterically activates acetyl-CoA carboxylase .D. Active acetyl-CoA carboxylase polymerizes into long filaments.

A. Phosphorylation activates acetyl-CoA carboxylase. Phosphorylation, triggered by the hormones glucagon and epinephrine or by high [AMP], inactivates the enzyme and reduces its sensitivity to activation by citrate, thereby slowing fatty acid synthesis.

Which statement regarding ATP synthase is false? A. The γ subunit is stationary as the αβ dimers rotate around it. B. Protons flow through the a and c subunits .C. When the F1 domain is isolated, it functions as an ATPase. D. It is considered to have an Fo domain and an F1 domain.

A. The γ subunit is stationary as the αβ dimers rotate around it. The streaming of protons throughout the F0 pore causes the c ring and the attached y subunit to rotate about the long axis of y, which is perpendicular to the plane of the membrane. The y subunit passes through the center of the α3β3 spheroid, which is held stationary relative to the membrane surface

Which statement regarding mutations in mitochondrial DNA is false A. Type 1 diabetes is due to dysfunctional β-cell mitochondria resulting from mutations in the mitochondrial tRNA genes. B. Impaired ATP production due to mutations in mitochondrial genes can result in human diseases. C. Mutations in mitochondrial genes accumulate through the life of an organism. D. An individual cell may have mitochondria that are not genetically identical to each other

A. Type 1 diabetes is due to dysfunctional β-cell mitochondria resulting from mutations in the mitochondrial tRNA genes. Type 2, not type 1, diabetes mellitus is common in individuals with mutations in the mitochondrial tRNA Lys or tRNA Leu genes (although such cases make up a very small fraction of all cases of diabetes)

Linoleate is an essential fatty acid in humans because humans cannot

A. desaturate a fatty acid beyond Δ9. Mammalian hepatocytes can readily introduce double bonds at the 9 position of fatty acids but cannot introduce additional double bonds between C-10 and the methyl-terminal end. Thus mammals cannot synthesize the omega-6 family precursor linoleate, 18:2(Δ9,12), nor the omega-3 family precursor α-linolenate, 18:3(Δ9,12,15)

Which molecule is part of an important mass-action ratio in most cells and is a modulator of the three major ATP-producing pathways? A. ADP B. NAD+ C. AMP D. acetate E. NADH

ADP The mass-action ratio of the ATP-ADP system is [ATP]/([ADP][Pi ]). With more ADP available for oxidative phosphorylation, the rate of respiration increases, causing regeneration of ATP. This continues until the mass-action ratio returns to its normal high level, at which point respiration slows again.

Which molecule is produced in high concentration as a result of both enhanced gluconeogenesis during starvation and in untreated diabetes, which has the same fate under those two conditions

Acetyl-CoA The CAC is severely slowed under both conditions, and acetyl-CoA concentrations increase, leading to acetoacetate formation (ketone bodies)

Which statement about familial hypercholesterolemia (FH) is false? A. Affected individuals have a mutation in the LDL receptor. B. Affected individuals have very high blood levels of LDL and of the cholesterol it carries. C. Affected individuals are at much greater risk of developing atherosclerosis. D. Affected individuals accumulate cholesterol in lysosomes of liver, brain, and lung

Affected individuals accumulate cholesterol in lysosomes of liver, brain, and lung. Lysosomal accumulation of cholesterol is characteristic of Niemann-Pick type-C (NPC), not FH.

Which statement is false about fat oxidation in hibernating bears? A. The energy of fat oxidation allows bears to maintain a body temperature close to normal. B. Amino groups released during fat oxidation can be used to make amino acids. C. Fat oxidation releases water, which replenishes water lost in breathing. D. Degradation of triacylglycerols provides a substrate for gluconeogenesis.

B. Amino groups released during fat oxidation can be used to make amino acids Fat metabolism provides bears with energy, water, and glucose precursors, but not amino groups. Urea formed during breakdown of amino acids is reabsorbed in the kidneys and recycled, with the amino groups reused to make new amino acids for maintaining body proteins

Which statement is true regarding the reactions of ketone body metabolism? A. The enzymes that catalyze biosynthesis of ketone bodies are found in the cytosol of hepatocytes. B. NADH is produced by catabolism of D-β-hydroxybutyrate. C. Conversion of 2 acetyl-CoA to acetoacetyl-CoA is accompanied by hydrolysis of ATP to AMP and PPi. D. The liver lacks thiolase and therefore cannot use ketone bodies as fuel.

B. NADH is produced by catabolism of D‐β‐hydroxybutyrate. The oxidation of D‐β‐hydroxybutyrate to acetoacetateby D‐β‐hydroxybutyrate dehydrogenase reduces NAD+ to NADH.

Which statement regarding peroxisomal β oxidation is false? A. Peroxisomal β oxidation occurs in the liver of mammals. B. The acetyl-CoA produced is largely consumed by the peroxisomal citric acid cycle. C. It produces hydrogen peroxide. D. The reactions are similar to those of mitochondrial β oxidation

B. The acetyl-CoA produced is largely consumed by the peroxisomal CAC Peroxisomes, which lack the enzymes of the CAC, export the acetyl-CoA that they produce

Which statement does NOT describe a feature of theeicosanoids? A. They are ultimately derived from dietary linoleate. B. The thromboxanes are all made from α-linolenate, and the leukotrienes are all made from arachidonate. C. PGH2 synthase (which is irreversibly inhibited by aspirin) catalyzes conversion of arachidonate to prostaglandin H2. D. Some eicosanoids are produced from docosahexaenoic acid

B. The thromboxanes are all made from α-linolenate, and the leukotrienes are all made from arachidonate. Thromboxanes with three double bonds (series 3 TX) and leukotrienes with five double bonds (series 5 LT) are all derived from eicosapentaenoic acid (EPA), which is a derivative of α-linolenate. Conversely, thromboxanes with two double bonds (series 2 TX) and leukotrienes with four double bonds (series 4 LT) are all derived from arachidonate.

Which electron carrier or prosthetic group would NOT function after site-directed mutagenesis substituted Pro for Cys in succinate dehydrogenase? A. cytochrome c B. iron-sulfur center C. flavin adenine dinucleotide D. ubiquinone E. FMN

B. iron-sulfur center Subunits A and B contain three iron-sulfur (2Fe-2S) centers, in which the iron is present in association with the sulfur atoms of Cys residues in the protein.

Calculate the standard free-energy change for the transfer of two electrons from FADH2 through the respiratory chain to molecular oxygen (E′° for FAD/FADH2 is 0.050 V in succinate dehydrogenase and E′° for O2/H2O is 0.816 V)

B. −150 kJ/mol ∆E′° = E′° (electron acceptor) − E′° (electron donor) = 0.816 V − 0.050 V = 0.766 V ∆G′° = −nF ∆E′° = −2(96.5 kJ/V • mol)(0.766 V) = −150 kJ/mol

Which statement is true about heteroplasmic cells (and tissues) in which some of the mitochondria have a gene mutation? A. All of the cells (and tissues) will have the mutant phenotype .B. All of the cells (and tissues) will have the wild-type phenotype. C. Cells (and tissues) containing mostly wild-type mitochondria will have the wild-type phenotype. D. Cells (and tissues) containing mostly wild-type mitochondria will have the mutant phenotype

C. Cells (and tissues) containing mostly wild-type mitochondria will have the wild-type phenotype. Cells (and tissues) containing mostly wild-type mitochondria are essentially normal. Other heteroplasmic cells have intermediate phenotypes, some almost normal, others (with a high proportion of mutant mitochondria)abnormal

Which statement is false about the cytochrome electron carriers? A. Cytochromes a, b, and c are distinguished by differences in their light-absorption spectra. B. Soluble cytochrome c associates with the outer surface of the inner membrane through electrostatic interactions. C. The heme of cytochrome c is tightly, but not covalently, bound to its associated protein. D. Cytochromes a and b are integral proteins of the inner mitochondrial membrane.

C. The heme of cytochrome c is tightly, but not covalently, bound to its associated protein The hemes of a and b cytochromes are tightly, but not covalently, bound to their associated proteins; the hemes of c-type cytochromes are covalently attached through Cys residues

which statement regarding the proton motive force is false A. It is a result of electron flow through the respiratory chain. B. It is used by ATP synthase to synthesize ATP. C. It results from an [H+] gradient across the outer mitochondrial membrane. D. It is both chemical and electrical potential energy.

C. it results from an [H+] gradient across the outer mitochondrial membrane. The proton-motive force results from an [H+] gradient across the inner, not the outer, mitochondrial membrane.

four steps of fatty acid synthesis

Condensation, Reduction. Dehydration, Reduction step 1: condenses activated acyl group and 2 Cs from malonyl-CoA to form a B-keto product step 2: reduces B-keto product to an alcohol step 3: eliminates H2O to form a double bond step 4: reduces double bond to form the corresponding saturated fatty acyl group

Which statement regarding uncoupling protein 1 (UCP1) is false? A. It is found in brown adipose tissue. B. It forms proton-conducting pores in the inner mitochondrial membrane. C. It provides a path for protons to return to the matrix without passing through the FoF1 complex. D. It allows for ATP generation in addition to heat formation

D. It allows for ATP generation in addition to heat formation UCP1, an uncoupling protein in the mitochondria of brown adipose tissue, causes the E conserved by proton pumping to be dissipated as heat by providing an alternative route for protons to reenter the mitochondrial matrix, Because he protons passing through UCP1 bypass the F0F1 complex, ATP is not generated

Which statement is false about Complex I? A. It consists of more than 40 different polypeptide chains. B. It has an FMN-containing flavoprotein C. It catalyzes the transfer of a hydride from NADH and a proton from the matrix to ubiquinone (Q). D. Its activity makes the matrix more positively charged.

D. Its activity makes the matrix more positively charged. Complex I transfers four protons from the matrix to the intermembrane space. The loss of positively charged protons makes the matrix more negative.

Which enzyme would NOT be expected to contribute electron carriers to oxidative phosphorylation? A. alcohol dehydrogenase B. malate dehydrogenase C. succinate dehydrogenase D. glucose 6-phosphate dehydrogenase E. glyceraldehyde 3-phosphate dehydrogenase

D. glucose 6-phosphate dehydrogenase Glucose 6-phosphate dehydrogenase produces NADPH, which does not contribute electrons to the respiratory chain.

Which statement about liver X receptor (LXR) is true? A. LXR is a nuclear transcription factor. B. LXR is activated by binding of oxysterol. C. LXR forms a heterodimer with retinoid X receptor (RXR). D. LXR binds the LXR response element and promotes expression of the ABCA1 gene .E. All of the statements are true.

E. All of the statements are true. When bound to an oxysterol ligand, LXRs form heterodimers with a second type of nuclear receptor, the retinoid X receptors (RXR), and the LXRRXR dimer activates transcription from a set of genes, including those for the ATP-binding cassette (ABC) transportersABCA1 and ABCG1

What is the sequence of electron carriers that transfers electrons from fatty acyl coA to the mitochondrial respiratory chain?

FADH2 ETF ETF: ubiquinone oxidoreductase Ubiquinone each molecule of FADH2 formed during oxidation of the fatty acyl-CoA donates a pair of electrons to the ETF. electrons move from ETF to a second flavoprotein, ETF: ubiquinone oxidoreductase, and through ubiquinone into the mitochondrial respiratory chain

Which statement about isopentenyl pyrophosphate is false? A. It is an intermediate in cholesterol biosynthesis. B. It is the activated precursor of vitamins A, E, and K. C. It is the activated precursor of ubiquinone and plastoquinone D. It is the activated precursor of sphingomyelin

It is the activated precursor of sphingomyelin. Sphingomyelin is a derivative of ceramide, not isopentenyl pyrophosphate

Why is the formation of mevalonate considered the committed step, and rate-limiting step, in cholesterol synthesis

Mevalonate's formation requires 2 NADPH, and the next three steps each require ATP. Mevalonate is thermodynamically expensive to make, and together with the next three steps, this sequence of reactions is irreversible.

Which product from oxidation of fatty acids cannot feed into the CAC

NADP+ The acetyl-CoA resulting from all the β-oxidation pathways, the succinyl Co-A formed by the oxidation of odd-number fatty acids, and the succinate resulting from the oxidation of polyunsaturated fatty acids can all feed into the citric acid cycle. However, the NADP+ resulting from the reductase step in the oxidation of polyunsaturated fatty acids cannot enter the citric acid cycle

what is the reducing equivalent necessary for fatty acid synthesis?

NADPH in B oxidation, NAD+ and FAD serve as electron acceptors.

Which additional reactant is required for oxidation of polyunsaturated fatty acids compared with saturated fatty acids?

NADPH. enzyme 2,4-dienoyl-CoA reductase is NADPH dependent

what is the primary metabolic source of the reducing power required for fatty acid synthesis and desaturation?

Pentose phosphate pathway NADPH is generated by the oxidative phase of the the PPP

Why are reactive oxygen species (ROS) generated

Stray electrons bind to oxygen, creating a free radical oxygen species. Some intermediates in the electron-transfer system, such as the partially reduced ubisemiquinone (•QH), can react directly with oxygen to form the superoxide radical (•O2−)as an intermediate. The superoxide radical forms when a single electron is passed to O2 in the reaction: O2 + e− → •O2−

An important theme in Biochemistry is interaction among metabolic pathways. Which pathway would obviously be MOST affected by increased β oxidation of fatty acids?

The CAC. In the 2nd stage of fatty acid oxidation, the acetyl groups of acetyl-CoA are oxidized to CO2 in the citric acid cycle, which also takes place in the mitochondrial matrix.

Malonyl-CoA decarboxylase inhibition is an important treatment for ischemic tissues (as in heart attacks). Why

The process of β oxidation requires O2 to generate energy, so preventing degradation of malonyl-CoA allows inhibition of fatty acid import into mitochondria. Recall malonyl-CoA blocks B-oxidation by inhibiting carnitine acyltransferase 1 of the carnitine shuttle

Which statement does NOT describe a function associated with mitochondria? A. In brown adipocytes, electron transport is uncoupled from ATP synthesis. B. They make xenobiotic compounds more soluble for excretion. C. They release cytochrome c in the process of apoptosis. D. They are responsible for the production of steroid hormones by cytochrome P-450 enzymes.

They make xenobiotic compounds more soluble for excretion The P-450 enzymes that make hydrophobic compounds, including xenobiotics, more soluble are found in the endoplasmic reticulum of hepatocytes. These enzymes catalyze reactions similar to the mitochondrial P-450 reactions

in hypoxic cells

a subunit of Complex IV is replaced with another subunit optimized for activity under hypoxic conditions. One means of preventing reactive oxygen species formation is the replacement of one subunit of Complex IV, known as COX4-1, with another subunit, COX4-2, that is better suited to hypoxic conditions

What enzymatic step is considered to be the rate-limiting step of fatty acid biosynthesis

acetyl-CoA carboxylase The carboxylation of acetyl-CoA to malonyl-CoA by acetyl-CoA carboxylase is the rate-limiting step in the biosynthesis of fatty acids. Thus this enzyme is an important site of regulation

what does apolipoprotein C-II do

activates lipoprotein lipase activity on chylomicrons. in the blood, chylomicrons pick up apolipoprotein C-II from high density lipoprotein particles and are carried to muscle and adipose tissues. in the capillaries of these tissues, the extracellular enzyme lipoprotein lipase, activated by apoC-II, hydrolyzes triacylglycerols to free fatty acids and monoacylglycerols

Acyl-CoA synthetase adds coenzyme A to acyl chains for the construction of certain phospholipids. Each reaction requires ATP, but AMP + Pi are products. What is the likely reaction mechanism?

adenylation , which attaches an AMP molecule to the substrate, assists in making the overall reaction more thermodynamically favorable

which reaction mechanism has sufficient total E yield to add coenzyme A to fatty acids but required two enzymes?

adenylation. the rxn catalyzed by a fatty acyl-CoA synthetase involved a fatty acyl-adenylate intermediate. The formation of a fatty acyl-CoA is made more favorable by the hydrolysis of 2 high E bonds in ATP; the pyrophosphate formed in the activation rxn is immediately hydrolyzed by inorganic pyrophosphatase, which pulls the preceding activation reaction in the direction of fatty acyl-CoA formation

In cholesterol biosynthesis

all of the carbons originate in acetyl-CoA The structure of this 27-carbon compound suggests a complex biosynthetic pathway, but all of its carbon atoms are provided by a single precursor — acetate.

Wehre is the acetyl-CoA added to FAS incorporated into the growing fatty acid?

at the free end each condensation step occurs at the free end of the growing fatty acid (farthest from the attachment to FAS)

which statement is false regarding the processing of dietary lipids in vegetables? a. dietary lipids are emulsified by bile salts in the intestine b. triacylglycerols in mixed micelles in the intestine diffuse into cells in the intestinal mucosa c. ultimately, dietary lipids are oxidized as fuel by muscles or stored as triacylglycerols in adipose tissue d. dietary lipids are packaged in lipoprotein aggregates known as chylomicrons, which are then exported to the lymph system

b. triacylglycerols in mixed micelles in the intestine diffuse into cells of the intestinal mucosa water soluble lipases in the intestine convert triacylglycerols monoacylglycerols, diacylglycerols, and free fatty acids. these products of lipase action diffuse or are transported into the epithelial cells lining the intestinal surface (the intestinal mucosa), where they are reconverted to triacylglycerol's

Cellular uptake of LDL by the LDLR results in which homeostatic mechanism

binding of LDL-derived cholesterol by sterol cleavage activated protein (SCAP) A complex of three proteins — Insig, SCAP, and SREBP —sense cholesterol levels and trigger increased synthesis or degradation of HMG-CoA reductase in response

What specific lipid is a critical component of the inner mitochondrial membrane, necessary for function of the electron transfer chain?

cardiolipin Cardiolipin consists of two diacylglycerols joined through a common head group. In eukaryotes, cardiolipin is a relatively uncommon phospholipid, found almost exclusively in the inner membranes of mitochondria. Cardiolipin is essential for the function of some mitochondrial enzymes

Which subcellular compartment has the highest ratio of [NADPH]/[NADP+] in photosynthetic plant cells? a. mitochondria b. chloroplasts c. endoplasmic reticulum d. cytosol

chloroplasts NADPH is produced in chloroplasts by the light-dependent reactions of photosynthesis. Thus in the photosynthetic cells of plants, fatty acid synthesis occurs in the chloroplast stroma, rather than in the cytosol.

Which lipoprotein is the largest and least dense? A. chylomicron B. VLDL C. LDL D. HDL

chylomicron, have high proportion of triacylglycerols

In the exogenous lipid transport pathway:

chylomicrons transport lipids from intestine to tissues. In the exogenous pathway, dietary lipids are packaged into chylomicrons, which are lipoprotein particles made up of triacylglycerols, cholesterol, and proteins

what are perilipins?

coat proteins of lipid droplets expose the lipids stored in a lipid droplet to the hormone-sensitive lipase (HSL)

Which compound is NOT an electron carrier involved in the respiratory chain? A. NADH B. iron-sulfur proteins C. cytochromes D. coenzyme A

coenzyme A

Which complex does NOT transport H+ from the mitochondrial matrix to the intermembrane space

complex 2 electron transfer through complex 2 is not accompanied by proton pumping across the inner membrane, although the QH2 produced by succinate oxidation will be used by complex 3 to drive proton transfer

Which electron-carrier complex in the respiratory chain oxidizes ubiquinone

complex 3 carries electrons from reduced ubiquinone to cytochrome C

why is the net production of ATP from palmitate oxidation 106 ATP and not 108 ATP?

conversion of palmitate to palmitoyl Co-A consumes the equivalent of 2 ATP

electron transfer chain generates ATP by

creating a proton motive force The flow of electrons through Complexes I, III, and IV results in the pumping of protons across the inner mitochondrial membrane, making the matrix alkaline relative to the intermembrane space. This proton gradient provides the energy, in the form of the proton-motive force, for ATP synthesis from ADP and Pi

A derivative of a common medication was developed, and it appears to decrease the concentration of prostaglandins while decreasing pain and fever associated with certain illnesses. What enzyme is likely inhibited by this drug

cyclooxygenase 2, it synthesizes those prostaglandins responsible for causing pain and inflammation, as well as fever

Which compound is NOT a direct source of electrons for the respiratory chain A. cytosolic NADH B. dihydroorotate dehydrogenase C. glycerol 3-phosphate dehydrogenase D. FADH2

cytosolic NADH The inner mitochondrial membrane is not permeable to NADH. Thus special shuttle systems carry reducing equivalents from cytosolic NADH into mitochondria by an indirect route

reactions of mitochondrial B oxidation do NOT include a. hydratase b. thiolase c. dehydrogenase d. oxidase

d. oxidase. The 4 enzymes of mitochondrial B oxidation are 1. acyl-CoA dehydrogenase 2. enoyl-CoA hydratse 3. B-hydroxyacyl-CoA dehydrogenase 4. acyl-CoA acetyltransferase (thiolase)

the human mitochondrial genome

encodes 37 genes, 13 of which code for polypeptide chains

What is the cellular location for fatty acid elongation and desaturation in both plant and animal cells

endoplasmic reticulum

Which process is NOT a fate or role of cellular diacylglycerol? A. synthesis of glycerophospholipids B. synthesis of triglycerides C. functions as a second messenger D. synthesis of phosphatidic acid E. functions as an allosteric regulator of lipid metabolism

functions as an allosteric regulator of lipid metabolism Diacylglycerol does not allosterically regulate enzymes of lipid metabolism. It is a substrate or intermediate in the biosynthesis of diacylglycerol 3-phosphate (phosphatidic acid), triacylglycerols, and glycerophospholipids. Also, recall from Chapter 10 that diacylglycerol functions as a second messenger, which along with Ca2+ can activate protein kinase C

which factor would stimulate movement of fatty acids to muscle and the lover when blood glucose levels fall?

glucagon low levels of glucose in the blood trigger the release of glucagon. binding of this hormone to a G protein- coupled receptor on the adipocyte plasma membrane triggers the mobilization of stored triacylglycerol

Mitochondria produce a lot of acetate due to fatty acid oxidation and other pathways. Acetate is required for fatty acid synthesis in the cytosol. What transporter does NOT function in the acetate shuttle to move both acetate and the reducing equivalents of NADH across the mitochondrial membranes? A. pyruvate B. malate-α-ketoglutarate C. glutamate-aspartate D. citrate E. All of these operate in the acetate shuttle

glutamate-aspartate The glutamate-aspartate transporter is part of the malate-aspartate shuttle, which conveys reducing equivalents from cytosolic NADH into the mitochondrial matrix

which molecule can be produced rapidly from glycerol in only 3 steps, allowing an interaction between carbohydrate and lipid metabolism ?

glyceraldehyde 3- phosphate the glycerol released by lipase action is phosphorylated by glycerol kinase, and the resulting glycerol 3-phosphate is oxidized to dihydroxyacetone phosphate. the glycolytic enzyme triose phosphate isomerase converts this compound to glyceraldehyde 3-phosphase, which is oxidized via glycolysis.

Glyceroneogenesis produces:

glycerol 3-phosphate from pyruvate. Glyceroneogenesis is a shortened version of gluconeogenesis, from pyruvate to DHAP, followed by conversion of the DHAP to glycerol 3-phosphate

The B subunits of ATP synthase

have 3 distinct conformations The F1 complex has three nonequivalent adenine nucleotide-binding sites, one for each pair of α and βsubunits. At any given moment, one of these sites is in the β-ATP conformation (which binds ATP tightly), a second is in the β-ADP (loose-binding) conformation, and a third is in the β-empty (very loose-binding) conformation.

Which ion, atom, or molecule constitutes one reducing equivalent?

hydrogen atom (H+ + e−) The term reducing equivalent is used to designate a single electron equivalent transferred in an oxidation-reduction reaction. A proton cannot act as a reducing equivalent because it has no electrons. A hydrogen atom acts as one reducing equivalent. A hydride ion or NADH molecule acts as two reducing equivalents.

where does B oxidation occur?

in the mitochondrial matrix

With each rotation of 120°, the γ subunit of FoF1 comes into contact with a different β subunit, forcing that β subunit

into the B empty conformation because this conformation has very low affinity for ATP, the newly synthesized ATP leaves the enzyme surface

Where is the carboxyl group added to acetyl-CoA to make malonyl-CoA incorporated into the palmitic acid by FAS?

it is not incorporated into the growing fatty acid The carboxyl group of malonyl-CoA is lost as CO2 during the condensation step. Coupling the condensation to the decarboxylation of the malonyl group renders the overall process highly exergonic.

Starvation and uncontrolled diabetes mellitus can both result in:

ketosis, implying that the body of a person with uncontrolled diabetes mellitus is acting metabolically as though it is starving. When the insulin level is insufficient, extrahepatic tissues cannot take up glucose efficiently from the blood. Fatty acid oxidation increases, but the resulting acetyl-CoA cannot pass through the citric acid cycle because cycle intermediates have been drawn off for use as substrates in gluconeogenesis. The accumulation of acetyl-CoA accelerates the formation of ketone bodies

Which of these dehydrogenase enzymes is NOT found in the mitochondrial matrix A.malate dehydrogenase B. glutamate dehydrogenase C. acyl-CoA dehydrogenase D. lactate dehydrogenase

lactate dehydrogenase The mitochondrial matrix contains enzymes of the citric acid cycle (malate dehydrogenase), the β-oxidation pathway (acyl-CoA dehydrogenase), and amino acid oxidation (glutamate dehydrogenase). The enzymes of glycolysis and fermentation (lactate dehydrogenase) are located in the cytosol

Which factor is NOT associated with β oxidation of fatty acids with an odd number of carbons? A. malonyl-CoA as in intermediate B. a rare example in humans of an enzyme that requires a vitamin B12-derived cofactor C. repeated cycles of β oxidation until a three-carbon fragment remains D. a citric acid cycle intermediate as the end product

malonyl-CoA as an intermediate he intermediates in the B oxidation of ODD number fatty acids are D- and L-methyl malonyl-CoA.

The second cycle of the fatty acid synthesis cycle begins with the condensation of

malonyl-CoA with a butyryl group bound to ACP The first cycle produces a four-carbon (butyryl) saturated fatty acyl-ACP. In the second round, condensation occurs as the butyryl group, acting like the acetyl group in the first cycle, is linked to two carbons of the malonyl-ACP group with concurrent loss of CO2.

The simultaneous activation of β oxidation and fatty acid synthesis in the same cells is a futile cycle. No biological work is accomplished. Which molecule prevents this futile cycle by preventing fatty acid transport through a membrane

malonyl-CoA. this is the first intermediate in fatty acid synthesis and inhibits CAT1, assuring that fatty acid oxidation and synthesis do not occur at the same time

Which order of electron carriers is CORRECT for both fatty acid desaturation and oxidative phosphorylation, a relatively common biochemical strategy

nicotinamide, flavin, iron In the desaturation of fatty acids in vertebrates, electrons from NADPH reduce FAD to FADH2 in the flavoprotein Cyt b5 reductase. Electrons from FADH2 then reduce Fe3+ to Fe2+ in the cytochrome Cyt b5.

What is the advantage of fatty acid synthase (FAS) being a complex?

no diffusion of products/ substrates between rxns (increasing efficiency) conservation of E no release of growing hydrophobic product/substrate to the aqueous environment

Regulation of cholesterol biosynthesis:

occurs in the short term primarily by regulating HMG-CoA reductase Short-term (minute-to-minute) regulation increases or decreases the activity of existing HMG-CoA reductase by reversible covalent alteration (phosphorylation) in response to the AMP concentration. In the longer term, the number of molecules of HMG-CoA reductase is increased or decreased in response to cellular concentrations of cholesterol

The equation for palmitate synthesis by fatty acid synthase is:Acetyl-CoA + 7 malonyl-CoA + 14NADPH + 14H+ --> palmitate + 7CO2 + 8CoA + 14NADP+ + 6H2O Why are only six waters produced by palmitate synthesis, not seven?

one water is used (by thioesterase) to liberate palmitate from the synthase

Shuttles are used to transport reducing equivalents and molecules, which themselves have no specific transporter, through the inner mitochondrial membrane. Which molecule CANNOT move through the membrane directly? A. pyruvate B. malate C. glutamate D. α-ketoglutarate E. oxaloacetate

oxaloacetate In the matrix, malate passes two reducing equivalents to NAD+, and the resulting NADH is oxidized by the respiratory chain. The oxaloacetate formed from malate cannot pass directly into the cytosol and must first be transaminated to aspartate, which can leave via the glutamate-aspartate shuttle

Which of these is NOT one the three primary forms in which cholesterol is exported from the liver? A. oxysterols B. bile acids C. biliary cholesterol D. cholesteryl esters

oxysterols The liver forms small quantities of oxysterols, such as 25-hydroxycholesterol, which act as regulators of cholesterol synthesis

Which of these is NOT a stage in the synthesis oftriacylglycerols? A. reaction of two fatty acyl-CoAs with glycerol 3-phosphate to form phosphatidic acid B. removal of a phosphate to form diacylglycerol C. phosphorylation of a monoacylglycerol to form lysophosphatidic acid D. reaction with a third fatty acyl-CoA to form a triacylglycerol

phosphorylation of the monoacylglycerol to form lysophosphatidic acid Acylation of the two free hydroxyl groups of L-glycerol 3-phosphate by two molecules of fatty acyl-CoA yields phosphatidic acid. Hydrolysis of phosphatidic acid by phosphatidic acid phosphatase forms a 1,2-diacylglycerol.Transesterification of the diacylglycerol with a third fatty acyl-CoA produces a triacylglycerol

The overall reaction to convert palmitoyl-CoA to 8 acetyl-CoA:

produces 7 NADH and 7 FADH2 Palmitoyl-CoA, the coenzyme A derivative of palmitate (16:0) undergoes 7 rounds of B oxidation, with each round producing 1 NADH via the acyl-CoA dehydrogenase reaction and 1 FADH2 via the B- hydroxyacyl-CoA dehydrogenase reaction

Which factor is NOT associated with biosynthesis of palmitate? A. consumption of a total of 8 acetyl-CoA B. production of 14 NADP+ C. production of 8 H2O D. hydrolysis of 7 ATP

production of 8 H2O palmitate biosynthesis consumes 1 acetyl-CoA and 7 malonyl-CoA (each derived from the carboxylation of an acetyl-CoA). This requires an energy investment of 7 ATP and 14 NADPH and produces 6 H2O.

Which factor is NOT associated with acetyl-CoA carboxylase? A. production of malonyl-CoA B. biotin cofactor C. catalysis of an irreversible reaction D. production of oxaloacetate

production of oxaloacetate The formation of malonyl-CoA from acetyl-CoA is an irreversible process, catalyzed by acetyl-CoA carboxylase, which requires a biotin cofactor. Oxaloacetate is produced by malate dehydrogenase in the mitochondrial matrix or by citrate lyase in the cytosol

HDL particles are the densest lipoprotein because they contain the highest fraction of

proteins

what is the major energy barrier for ATP synthase

release or ATP from the enzyme in a typical enzyme catalyzed rxn, reaching the transitions state between substrate and product is the major energy barrier to overcome. in the rxn catalyzed by ATP synthase, release of ATP from the enzyme, not formation of ATP, is the major energy barrier

Acetone resulting from ketone body production is:

removed from the body by exhalation.

The chemiosmotic model:

requires that mitochondrial ATP synthesis and electron flow through the respiratory chain be obligately coupled. The chemiosmotic model, proposed by Peter Mitchell, is the paradigm for energy coupling. Here, "coupling" refers to the obligate connection between mitochondrial ATP synthesis and electron flow through the respiratory chain.

The addition of oligomycin, an inhibitor of ATP synthase, to mitochondria suspended in a buffered medium blocks both ATP synthesis and respiration. What would happen if 2,4-dinitrophenol (DNP) were also added to this suspension?

respiration would resume without ATP synthesis DNP uncouples respiration from ATP synthesis by entering the matrix in the protonated form and releasing a proton , thus dissipating the proton gradient. this allows respiration to continue without ATP synthesis

Which factor does NOT contribute to formation of atherosclerotic plaques A. high levels of LDL in the blood B. conversion of macrophages to foam cells C. scar tissue from damaged smooth muscle tissue D. reverse cholesterol transport

reverse cholesterol transport Reverse cholesterol transport protects against atherosclerosis by transporting excess cholesterol in extrahepatic tissues back to the liver as HDL.

In adipose tissue:

some triacylglycerol synthesis occurs, even during starvation Approximately 75% of all fatty acids released by triacylglycerol breakdown (lipolysis) are reesterified to form triacylglycerols, rather than used for fuel. This ratio persists even under starvation conditions.

Membrane sphingolipids are:

synthesized by first reacting palmitoyl-CoA with serine. The biosynthesis of sphingolipids takes place in four stages. The first stage is the synthesis of the 18-carbon amine sphinganine from palmitoyl-CoA and serine

The antidiabetic drugs rosiglitazone (Avandia) and pioglitazone (Actos) decrease

the release of free fatty acid from adipose tissue into the blood Thiazolidinediones increase sensitivity to insulin and increase the expression of PEP carboxykinase in adipose tissue. The resulting increase in glyceroneogenesis increases the resynthesis of triacylglycerol and reduces the release of free fatty acid from adipose tissue into the blood.

How many acetyl-CoA molecules does it take to synthesize one molecule of mevalonate

three. Acetyl-CoA acetyl transferase catalyzes the condensation of two acetyl-CoA molecules to form acetoacetyl-CoA. Next, HMG-CoA synthase catalyzes the condensation of a third acetyl-CoA with acetoacetyl-CoA to form β-hydroxy-β-methylglutaryl-CoA (HMG-CoA). Finally, HMG-CoA reductase reduces HMG-CoA to mevalonate.

How is production of reactive oxygen species (ROS)controlled?

through increased ADP content in the matrix through an increase in the NAD+/NADH ratio with expression of superoxide dismutase with expression of glutathione peroxidase The formation of ROS is favored when mitochondria are not making ATP (for lack of ADP or O2) and when there isa high NADH/NAD+ ratio in the matrix. ROS produced in mitochondria are inactivated by a set of protective enzymes, including superoxide dismutase and glutathione peroxidase.

Why is the glycerol 3-phosphate shuttle necessary foroxidative phosphorylation in the brain?

to bring reducing equivalents of NADH into the mitochondrial matrix NADH dehydrogenase (complex 1) of the inner mitochondrial membrane can accept electrons only from NADH in the matrix; however, the inner membrane is not permeable to NADH. Thus special shuttle systems carry reducing equivalents from cytosolic NADH into mitochondria by an indirect route

Why is the malate-aspartate shuttle necessary for oxidative phosphorylation in the liver?

to bring the reducing equivalents of NADH into the mitochondrial matrix NADH dehydrogenase (complex 1) of the inner mitochondrial membrane can accept electrons only from NADH in the matrix; however, the inner membrane is not permeable to NADH. Thus special shuttle systems carry reducing equivalents from cytosolic NADH into mitochondria by an indirect route

why does B oxidation occur in the mitochondrial matrix?

toallow coordinated regulation with fatty acid synthesis, to coordinate production of acetyl-CoA with the introduction into the CAC, to compartmentalize, and because necessary oxidative enzymes are present. the mitochondrial matrix contains all the enzymes necessary for the B oxidation pathway and the CAC. If B oxidation occurred in the cytosol, the simultaneous synthesis and degradation of fatty acids could occur, resulting in a wasteful and futile cycle

the regulation of B oxidation occurs both by

transcriptional regulation and by regulating transport of fatty acids into mitochondria. the first intermediate in fatty acid synthesis inhibits CAT1, assuring that fatty acid oxidation and fatty acid synthesis do not occur simultaneously. Two of the enzymes of oxidation are also regulated by metabolites that signal energy sufficiency. Additionally, transcriptional regulation can change the number of molecules of the enzymes of fatty acid oxidation on a longer time scale - minutes to hours

fatty acid synthase 1 of mammals

uses malonyl-CoA to add 2 Cs to a growing fatty acyl chain

The B oxidation of polyunsaturated fats

uses the same enzymes as β oxidation of saturated fatty acids, with the addition of an isomerase and a reductase

how do fatty acids get into the mitochondrial matrix?

via carnitine palmitoyltransferase. in a transesterification catalyzed by carnitine acyltransferase 1, CAT1 in the outer mitochondrial membrane, the fatty acyl-CoA is transiently attached to the hydroxyl group of carnitine to form fatty acyl-carnitine. the fatty acyl carnitine ester then diffuses across the intermembrane space and enters the matrix by passive transport through the acyl-carnitine/ carnitine cotransporter of the inner mitochondrial membrane

Cholesterol is NOT converted to:

vitamin A Cholesterol and vitamin A are both derivatives of Δ3-isopentyl pyrophosphate. Bile salts, steroid hormones,and cholesteryl ester all derive from cholesterol