Biochem exam 3

Phosphatidic acid is an intermediate in both the synthesis of triacylglycerol and glycerophospholipids (membrane lipids). To convert phosphatidic acid to phosphatidylinositol, you would react phosphatidic acid with: A. CTP and then with inositol B. UTP and then with inositol C. CTP and then with inositol trisphosphate D. CDP and then with inositol trisphosphate E. UDP and then with inositol

A. CTP and then with inositol

What is not a function of glycerophospholipids? A. Component of biological membranes B. Component of plasma lipoproteins C. Component of lung surfactant D. Component of steroids E. Source of signaling molecules

A. Component of biological membranes

A lipoprotein associated with high incidence of coronary atherosclerosis is A. LDL B. VLDL C. IDL D. HDL

A. LDL

Fill in the blanks: Degradation of Sphingolipids primarily occurs in the A. ________ of the cell. The first step in degradation of sphingolipids occurs with the hydrolysis of the amide bond of sphingolipids producing sphingosine and free B. _________. Acid sphingosine kinase is used to C. __________ the substrate that is subsequently broke into hexadecanal and phosphoethanolamine using D._________ 1 phosphate lyase enzyme.

A. lysosome B. fatty acid C. phosphorylate D. sphingosine

To convert PA to phosphotidylcholine, you would remove phosphate and react DAG with A: ADP-Choline B: CDP-Choline C: UDP-Choline D: GDP-Choline

B: CDP-Choline

Which of the following step is a regulatory step of cholesterol biosynthesis? A: Formation of 3-hydroxy-3-methylglutaryl CoA B: Formation of mevalonate C: Formation of isoprenoid unit D: Formation of Iansterol

B: Formation of mevalonate

In the synthesis of membrane lipids, what is the function of SAM? A. To add phosphate groups to phosphatidylinositol B. To convert phosphatidylethanolamine into phosphatidylserine C. To convert phosphatidylethanolamine into phosphatidylcholine D. To convert phosphatidylcholine into phosphatidylinositol E. To convert phosphatidylserine into phosphatidylethanolamine

C. To convert phosphatidylethanolamine into phosphatidylcholine

The β-ketoacyl-ACP synthase cannot accommodate larger substrates; the reaction cycle ends with a ___ chain. A: 12 C B: 14 C C: 16 C D: 18 C

C: 16C

Essential FA(s) is/are: A: Linoleate B: Linolenate C: Both D: Neither

C: Both

Which of the following removes H₂O from β-hydroxyl ACP, creating a double bond? A: KS Domain B: MAT Domain C: DH Domain D: ER Domain

C: DH Domain

What is the role of lecithin-cholesterol acyltransferase (LCAT) in cholesterol metabolism and transport in the body? A: LCAT is an enzyme that converts malonyl CoA into palmitate B: LCAT is an enzyme that hydrolyzes FA from TAGs and cholesterols C: LCAT produces CE from C, and is transported from peripheral tissues to the liver. D: LCAT is an enzyme that incorporates acetyl-CoA into FA

C: LCAT produces CE from C, and transported from peripheral tissues to liver

In _____ cells dietary cholesterol is esterified and packaged into _______ for transport to the _________. A: Hepatic, HDL, Intestine B: Mucosal, Chylomicrons, Intestine C: Mucosal, Chylomicrons, Liver D: Mucosal, HDL, Intestine

C: Mucosal, Chylomicrons, Liver

Concerning the FAS complex, all fo the following are true EXCEPT A: Products include NADP+ and CoA B: Substrates include malonyl CoA C: Products include stearate (C18:0) and CO2 D: Substrates include NADPH

C: Products include stearate (C18:0) and CO2

In the synthesis of phosphatidylcholine from phosphotidylethanolamine, the methyl group donor is : A: methanol B: Choline C: S-adenosylmethione D: Serine

C: S-adenosylmethione

Conversion of acetyl co-A to malonyl co-A requires which of the following? A: NADPH B: H2O C: Folic Acid D: Biotin

D: Biotin

Write the net equation for the biosynthesis of palmitate in rat liver, starting from mitochondrial acetyl-CoA and cytosolic NADPH, ATP, and CO2.

8 Acetyl-CoA + 15ATP + 14NADPH + 9H2O →palmitate + 8CoA + 15ADP + 15Pi + 14NADP+ + 2H+

Acyl carrier protein and CoA have all of the following in common EXCEPT: A. Both incorporate ADP into their structure B. Both incorporate pantothenic acid into their structure C. Both have a functional SH group (thiol group) D. Both form thioester bonds with fatty acids E. Both form high-energy bonds with fatty acids

A. Both incorporate ADP into their structure

Phosphatidic acid phosphatase catalyzes the following reaction: A. Conversion Phosphatidic Acid to 1,2-diacylclycerol B. Conversion of glycerol to glycerol-3-phophsate C. Conversion of phosphatidylethanolamine to phosphatidylserine D. Conversion of CDP-choline to phosphatidylcholine

A. Conversion Phosphatidic Acid to 1,2-diacylclycerol

What is the role of citrate lyase in fatty acid synthesis? I. It catalyzes the formation of acetyl-CoA and oxaloacetate from citrate and coenzyme A. II. It converts ATP to ADP and phosphate. III. It converts ADP to ATP. IV. It catalyzes the formation of citrate and coenzyme A from acetyl-CoA and oxaloacetate. A. I and II B. I, III, and IV C. II, III, and IV D. I and IV E. I only

A. I and II

In the biosynthesis of complex lipids, components are assembled by transfer of the appropriate group from an activated donor. For example, the activated donor of acetyl groups is acetyl-CoA. For the following groups, the give the for of the activated donor. A. Phosphate B. Phosphethanolamine C. Fatty acyl D. D-glucosyl E. Methyl F. Two carbon group in fatty acid biosynthesis

A. Phosphate: ATP B. Phosphethanolamine: CDP-ethanolamine C. Fatty acyl: Acyl-CoA D. D-glucosyl: UDP-glucose E. Methyl: S-adenomethionine F. Two carbon group in fatty acid biosynthesis: Malonyl-CoA

True or False: The production of phosphatdylcholine occurs with the methylation of phosphatidylethanolamine using a SAM mediated protein A. True B. False

A. True

During fasting or exercise, fatty acids need to enter the mitochondria. All of the following will increase entry EXCEPT: A. insulin B. AMP C. increased active protein kinase A D. epinephrine E. glucagon in the liver

A. insulin

Fill in the blanks: Degradation of Sphingolipids primarily occurs in the A)____________ of the cell. The first step in degradation of sphingolipids occurs with the hydrolysis of the amide bond of sphingolipids producing sphingosine and free B)_____________. Acid sphingosine kinase is used to C.phosphorylate the substrate that is subsequently broke into hexadecanal and phosphoethanolamine using D.sphingosine 1 phosphate lyase enzyme.

A. lysosome B. fatty acid C. phosphorylate

ACP and CoA have all the following in common EXCEPT A: Both incorporate ADP into their structure B: Both incorporate pantothenic acid into their structure C: Both form thioester bonds with fatty acids D: Both form high-energy bonds with fatty acids

A: Both incorporate ADP into their structure

LONG-TERM REGULATION OF FA BIOSYNTHESIS involves A: Changes in gene expression B: Allosteric modulation C: Feedback inhibition

A: Changes in gene expression

\SREBP is attached to the ER and proteolytically cleaved to enter the ______________. A: Golgi B: Ribosome C: Nucleus D: Smooth ER

A: Golgi

Which of the following reduces β-keto group to β-hydroxyl A: KR Domain B: KS Domain C: DH Domain D: ER Domain

A: KR Domain

Higher activity of which of the following enzymes leads to increased synthesis of the precursors of glyceroneogenesis A: PEP carboxykinase B: Acyl Transferase C: Acyl-CoA synthase D: Phosphatidic Acid phosphatase

A: PEP carboxykinase

Enzyme that removes phosphate from phosphatidic acid ➜ 1,2 DAG. A: Phosphatidic Acid phosphatase B: Phosphatidic acid kinase C: PP1 D: None are correct

A: Phosphatidic Acid phosphatase

In adipose tissue, glyceroneogenesis couples with A: Reesterfication B: Esterfication C: Glycolysis D: Phosphorylation

A: Reesterfication

Which of these statements is true when cholesterol levels are low? A: SCAP binds to SREBP B: SREBP binds to SRE C: SCAP binds to SRE

A: SCAP binds to SREBP

C16-acyl-ACP is hydrolyzed by ___ to yield palmitic acid + free ACP. A: Thioesterase B: Thiokinase C: Thiolase D: CoA

A: Thioesterase

True or False: Activation of the polar head group for transfer to the Diacylglycerol occurs using a transferase and GTP nucleotide. A. True B. False

B. False

True or False: Cellular signaling can occurs when a phospholipase is activated using GTP. The purpose of a phospholipase is to cleave the amide bond of proteins, creating inactive proteins. A. True B. False

B. False

True or False: To produce the backbone for triacylglycerides and glycerophospholipids DHAP needs to be phosphorylated to produce glycer-3-phopshate A. True B. False

B. False

Fatty acid synthesis is dependent upon aggregation of dimers of acetyl-Co carboxylase to form polymers. This aggregation is slowed or prevented by: A. Insulin B. Glucagon C. Water D. Testosterone E. Sucrose

B. Glucagon

The structures which are known as 'foam' cells are actually: A. Soapy formations due to the reactions of fatty acids with alkali B. Macrophages which become filled with lipoprotein while attempting to clear injured endothelial cells of oxidized LDLs C. Microphages which become filled with lipoprotein while attempting to clear injured endothelial cells of oxidized cholesterol an cholesteryl esters D. Adipocytes E. Fatty hepatocytes

B. Macrophages which become filled with lipoprotein while attempting to clear injured endothelial cells of oxidized LDLs

Concerning the fatty acid synthase complex, all of the following are true EXCEPT: A. Products include NADP+ and CoA B. Products include stearate (C18:0) and CO2 C. SubstratesincludeacetylCoA D. Substrates include malonyl CoA E. Substrates include NADPH

B. Products include stearate (C18:0) and CO2

When the liver converts excess glucose into fatty acids, all of the following are true EXCEPT A. Glucose is converted by glycolysis into pyruvate in the cytosol B. Pyruvate is converted to acetyl CoA by pyruvate dehydrogenase in the cytosol C. Acetyl CoA and oxaloacetate form citrate that leaves the mitochondria D. Citrate lyase converts citrate, CoA and ATP into oxaloacetate, acetyl CoA, ADP and Pi E. The acetyl CoA is converted to palmitate and the oxaloacetate is converted to pyruvate

B. Pyruvate is converted to acetyl CoA by pyruvate dehydrogenase in the cytosol

If the DH subunit of FAS is mutated and cannot catalyze its proper reaction, which functional group would you expect to see on the C chain? A: ketone B: Alcohol C: Alkene D: Alkane

B: Alcohol

Sterol Regulatory Binding Protein binds to DNA at the sterol regulatory element to increase the expression of HMG CoA reductase, and synthesis of cholesterol. What happens when there is a presence of a high cellular concentration of cholesterol? A: Increases the proteolytic cleavage, release, and shuttling of SREBP into the nucleus. B: Decreases the proeolytic cleavage and release of SREBP from ER. C: Activates SREBP by inducing the conformational change D: Inhibit SREBP by competitively binding to DNA binding site of SREBP

B: Decreases the proeolytic cleavage and release of SREBP from ER.

Which of the following condenses acyl and malonyl groups? A: ACP B: KS Domain C: KR Domain D: TE Domain

B: KS Domain

The synthesis of both glycerophospholipids and TAGs involves: A: CDP-diacyglycerol B: Phosphatidic Acid C: Phosphoethanolamine D: Phosphatidate phosphatase

B: Phosphatidic Acid

When the liver converts excess glucose into fatty acids, all of the following are true EXCEPT A: Glucose is converted by glycolysis into pyruvate in the cytosol B: Pyruvate is converted to acetyl-CoA by PDH in the cytosol C: Citrate lyase converts citrate, CoA, and ATP into OAA, acetyl-CoA, ADP & Pi D; Acetyl-CoA is converted to palmitate and OAA is converted to pyruvate

B: Pyruvate is converted to acetyl-CoA by PDH in the cytosol

Which statement about the regulation of choelsterol synthesis is NOT true A. Insuline stimulates HMG-CoA reductase B. Dietary cholesterol has no effect on the synthesis of Cholesterol (liver) C. High intercellular cholesterol stimulates formation of Cholesterol esters D: Some metabolites or derivatives of cholesterol inhibits HMG-CoA reductase

B: dietary cholesterol has no effect on th synthesis of Choelster (liver)

Synthesis of Fatty Acids from Glucose After a person has ingested large amounts of sucrose, the body transforms the glucose and fructose that exceed caloric requirements to fatty acids for triacylglycerol synthesis. This fatty acid synthesis consumes acetyl-CoA, ATP, and NADPH. How do cells produce acetyl-CoA, ATP, and NADPH from glucose?

Both glucose and fructose are degraded to pyruvate in glycolysis. Pyruvate is converted to acetyl- CoA by the pyruvate dehydrogenase complex. Some of this acetyl-CoA enters the citric acid cycle, which produces reducing equivalents, NADH and NADPH. Mitochondrial electron transfer to O2 yields ATP.

Inactivation of lipid degradation enzymes identify possible lysosomal storage diseases. Some defects include enlarged organs and neurodegenerative concerns. What enzyme catalyzes the first step of the degradation of Ceramide? A. Sphingosine-1-phosphate lyase B. Acid sphingosine kinase C. Acid ceramidase D. Acid desmolase

C. Acid ceramidase

Which of the following enzyme is responsible for the conversion of cholesterol to cholesterol ester inside the cells? A. Lecithin Cholesterol Acyl Transferase B. Cholesterol Esterase C. Acyl CoA Cholesterol Acyl Transferase D. None of the options

C. Acyl CoA Cholesterol Acyl Transferase

Where does fatty acid synthesis take place in the cell? A. Mitochondria B. Ribosome C. Cytoplasm D. Lysosome

C. Cytoplasm

Which of the following are fatty acid synthase components? I. Malonyl CoA-ACP transacetylase. II. Beta-ketoacyl synthase. III. Beta-ketoacyl reductase. IV. Acetyl CoA-ACP transacetylase. Note: acyl carrier protein = ACP A. I and IV B. I, II, and III C. I, II, III and IV D. III and IV E. I and II

C. I, II, III and IV

Starting with an intermediate in glycolysis and acyl CoA, all of the following are intermediates in the synthesis of triacylglycerols EXCEPT: A. Glycerol-3-phosphate B. Monoacylglycerolphosphate C. Monoacylglycerol D. Diacylglycerol phosphate E. Diacylglycerol

C. Monoacylglycerol

Phosphotidylcholine is an integral part of the lipid membrane, specifically the outer leaflet. Which correctly identifies the path to synthesize the glycerophospholipids above? A. Activation of Choline with CTP catalyzed by CTP-choline cytidylyl transferase with subsequent transfer to phosphatidic acid. B. Choline activation using GTP catalyzed by GTP-coupling enzyme with subsequent transfer to diacylglycerol using CDP-choline-diacylglycerol phosphocholine transferase. C. Phosphorylation of choline head group followed by CTP activation and transfer to diacylglycerol using CDP-choline-diacylglycerol phosphocholine transferase. D. Attachment of choline to triacylglycerol using choline synthase.

C. Phosphorylation of choline head group followed by CTP activation and transfer to diacylglycerol using CDP-choline-diacylglycerol phosphocholine transferase.

When the liver converts excess glucose into fatty acids, all of the following are true EXCEPT: A. The control enzyme is acetyl CoA carboxylase B. The enzyme is activated by protein phosphatase C. Protein phosphatase is activated as a result of glucagon binding to liver cells D. The control enzyme converts ATP, CO2, and acetyl CoA into malonyl CoA, ADP, and Pi E. The concentrations of glucagon, epinephrine, or AMP are low because high concentrations would inhibit the control enzyme

C. Protein phosphatase is activated as a result of glucagon binding to liver cells

Dietary fats after absorption appear in the circulation as A. HDL B. VLDL C. LDL D. Chylomicron

D. Chylomicron

What is the rate-limiting step of fatty acid synthesis? A. Polymerization via fatty acid synthase B. Reduction of NADP+ during the reaction catalyzed by malic enzyme C. Acetyl-CoA Shuttling via the citrate D. Conversion of acetyl-CoA into malonyl-CoA via acetyl-CoA carboxylase

D. Conversion of acetyl-CoA into malonyl-CoA via acetyl-CoA carboxylase

A lipoprotein inversely related to the incidence of coronary arthrosclerosis is A. VLDL B. IDL C. LDL D. HDL

D. HDL

The lipoprotein with the fastest electrophoretic mobility and the lowest triglyceride content is A. Chylomicron B. VLDL C. IDL D. HDL

D. HDL

Drugs called statins are now used to decrease plasma cholesterol levels by inhibiting the rate-limiting step of cholesterol synthesis. This step is catalyzed by: A. Lipoprotein lipase B. β-ketothiolase C. Acyl carrier protein D. HMG-CoA reductase E. Transacylase

D. HMG-CoA reductase

In humans, a dietary essential fatty acid is A. Palmitic acid B. Stearicacid C. Oleicacid D. Linoleic acid

D. Linoleic acid

Which of the following is true about major lipoprotein metabolism pathways? A. In the endogenous pathway, circulating chylomicrons are transformed into remnants by lipoprotein lipase (LPL) B. The exogenous pathway involves progressive transformation of very low density lipoproteins (VLDLs), synthesized by the liver, into low density lipoproteins (LDLs) C. High density lipoprotein, HDL, transports cholesterol in tissues to the liver, where it is recognized the apolipoprotein B100 in hepatocytes D. Macrophages absorb oxidized low density lipoproteins (LDLs), thus transforming themselves into foam cells, an indicator for plaque build-up in atherosclerosis

D. Macrophages absorb oxidized low density lipoproteins (LDLs), thus transforming themselves into foam cells, an indicator for plaque build-up in atherosclerosis

Production of glycerol-3-phosphate can occur via two reactions. What are the two reactions? (pick all that apply) A. Activation by carboxylation B. Pick this for negative points C. De-phosphorylation of glycerol D. Reduction of DHAP E. Acyl Transfer F. Oxidation of DHAP G. Phosphorylation of glycerol

D. Reduction of DHAP G. Phosphorylation of glycerol

All of the following statements about essential fatty acids are true EXCEPT: A. They can not be synthesized by humans cells B. They are essential for the synthesis of some prostaglandins and other eicosanoids C. They contain omega-3 or omega-6 double bonds D. They contain at least 4 double bonds E. They are linoleic and linolenic acid

D. They contain at least 4 double bonds

All of the following are complex lipids, except? A: Phosphatidic Acid B: Cerebroside C: Cardiolipin D: Cholesterol

D: Cholesterol

VLDL is synthesized in _______________ and secreted in the _____________. A: ER, intestines B: Intestines, blood C: Nucleus, cytosol D: Liver, blood

D: Liver, blood

Which of the following transfers malonyl group from co-A to ACP? A: ACP domain B: KR domain C: KS domain D: MAT domain

D: MAT domain

Farber's Diesease is a deficiency in the enzyme acid ceramidase. Which is the product NOT created due to the disease? A: Ceramide B: Sphinganine C: Ganglioside D: Sphingosine

D: Sphingosine

Phosphatidic acid is an intermediate in both the synthesis of triacylglycerol and glycerophospholipids (membrane lipids). To convert phosphatidic acid to phosphatidyl choline, you would remove the phosphate and react diacylglycerol with: A. ADP-choline B. UDP-choline C. TDP-choline D. GDP-choline E. CDP choline

E. CDP choline

All of the following are glycerophospholipids that are typically found in the cell membrane EXCEPT: A. Phosphatidylcholine (lecithin) B. Phosphatidylethanolamine C. Phosphatidylserine D. Phosphatidylinositol E. Diphosphatidylglycerol (cardiolipin)

E. Diphosphatidylglycerol (cardiolipin)

Where does the desaturation of fatty acids take place in humans? A. Cytosol B. Nucleus C. Mitochondria D. VLDL E. Endoplasmic reticulum

E. Endoplasmic reticulum

Where does the elongation of most fatty acids take place? A. Cytosol B. Mitochondria C. Nucleus D. VLDL E. Endoplasmic reticulum

E. Endoplasmic reticulum

The fatty acids produced by the fatty acid synthase complex are not substrates for beta-oxidation because: A. They are immediately activated to palmitoyl CoA B. Acetyl CoA, one substrate for the fatty acid synthase complex, inhibits carnitine:palmitoyltransferase-2 C. High NADPH, a requirement for fatty acid synthesis, inhibits beta-oxidation D. High glucagon causes phosphorylation of acetyl CoA carboxylase whenever fatty acid synthase is active E. The product of the control step for fatty acid synthesis also inhibits carnitine:palmitoyltransferase-1

E. The product of the control step for fatty acid synthesis also inhibits carnitine:palmitoyltransferase-1

Prostaglandins, and the related compounds thromboxanes and ____, are collectively known as eicosanoids.

Leukotrienes

Explain: Many of the LSDs discussed in lecture include hepatomegaly. What would be the underlying reason for this observed symptom?

Many of the LSD are associated with a deficiency in the enzymes that breakdown lipids. This is an example of the inability to mediate an abundance of a substrate and the effects of the build up excess lipids in the lysosome, which leads to enlarged livers due to excess lipids present in the lysosome.

A young rat maintained on a diet deficient in methionine fails to thrive unless choline is included in the diet. Explain.

Methionine deficiency reduces the level of adoMet, which is required for de novo synthesis of phosphatidylcholine. The salvage pathway does not employ adoMet, but uses available choline. Thus phosphatidylcholine can be synthesized even when the diet is deficient in methionine, as long as choline is available.

Provide an explanation: A biochemist adds uniformly labeled [14C] acetyl-CoA to a soluble liver fraction, which yields palmitate uniformly labeled with 14C.

The 16 carbons of palmitate are derived from 8 acetyl groups of 8 acetyl-CoA molecules. The 14C-labeled acetyl-CoA gives rise to malonyl-CoA labeled at C-1 and C-2.

Fill in the blanks to answer the "Why, When, and Where?" metabolic questions about FAS.

The main purpose of fatty acid synthesis, which takes place in the CYTOPLASM of cells, is to create long chain fatty acids. Specifically, when ACETYL-CoA (the starting molecule) is plentiful, it is converted to CITRATE and transported outside the mitochondria where is converted into acetyl-CoA in the cytosol. Acetyl-CoA is irreversibly reacted to make the elongation unit, MALONYL-CoA necessary for fatty acid biosynthesis

Provide an explanation: In a second experiment, the biochemist adds a trace of uniformly labeled [14C] acetyl-CoA in the presence of an excess of unlabeled malonyl-CoA to a soluble liver fraction, which yields palmitate labeled with 14C only in C-15 and C-16

The metabolic pool of malonyl-CoA, the source of all palmitate carbons except C-16 and C- 15, does not become labeled with small amounts of 14C-labeled acetyl-CoA. Hence, only [15,16-14C] palmitate is formed