Shared Flashcard Set

Details

Boles - Biochem II - Quiz 4
Fatty Acid Catabolism and Lipid Biosynthesis
93
Biochemistry
Undergraduate 4
03/26/2013

Additional Biochemistry Flashcards

 


 

Cards

Term
Give two reasons why fatty acids are used as energy storage.
Definition
1. Fatty acids are reduced, so their oxidation yields the most energy possible.
2. Fatty acids are not hydrated, and can therefore be packed more efficiently.
Term
_________ are the major form of stored energy in the body.
Definition
Triglycerides
Term
Describe the general process by which hormones trigger the release of fatty acids from triglycerides.
Definition
Hormones bind to a receptor, causing the activation of adenyl cyclase. cAMP then stimulates a protein kinase cascade. These kinases activate triacylglycerol (TAG) lipase by phosphorylation. TAG lipase then promotes the release of fatty acids from TAGs.
Term
Dietary TAGs are released in the __________.
Definition
duodenum (first portion of the small intestine)
Term
__________ require bile salts that emulsify TAGs.
Definition
Pancreatic lipases
Term
____________ are carboxylic acid salts with hormone backbones.
Definition
Bile salts
Term
__________ are lipoprotein aggregates that are assembled in the intestinal wall.
Definition
Chylomicrons
Term
In the small intestine, fatty acids combine with bile salts in _____________ which deliver fatty acids to epithelial cells that cover the intestinal villi.
Definition
mixed micelles
Term
Fatty acids are degraded by repeated cycles of _________.
Definition
Beta oxidation
Term
Beta oxidation converts fatty acids into ____________.
Definition
acetate units (acetyl-CoA)
Term
____________ condenses fatty acids with CoA, with simultaneous hydrolysis of ATP to AMP and PPi.
Definition
Acyl-CoA synthetase
Term
True or False: The acyl-CoA synthetase reaction is energetically driven by the hydrolysis of pyrophosphate.
Definition
True
Term
Beta oxidation occurs in the ______.
Definition
mitochondrial matrix
Term
True or False: Long-chain fatty acids can be directly transported across the mitochondrial membrane.
Definition
False
Term
____________ are fatty acyl transporters.
Definition
Carnitines
Term
_____________ can be shuttled across the membrane by an acyl translocase.
Definition
o-acylcarnitine
Term
In general terms, list the steps of beta oxidation. (E.g. hydration, oxidation, etc.)
Definition
1. Oxidation
2. Hydration
3. Oxidation
4. Cleavage
5. Rinse and repeat
Term
Describe the first step of beta oxidation including reactant, enzyme, cofactors and product.
Definition
Fatty acyl-CoA --> trans-enoyl-CoA by acyl-coa dehydrogenase and reduction of FAD
Term
Describe the second step of beta oxidation, including reactant, enzyme, cofactor and product names.
Definition
trans-enoyl-coa --> beta-hydroxyacyl-CoA by enoyl-coa hydratase and addition of H2O
Term
Describe the third step of beta oxidation, including reactant, enzyme, cofactor and product names.
Definition
beta-hydroxyacyl-CoA --> beta-ketoacyl-CoA by hydroxyacyl-CoA dehydrogenase and NAD reduction
Term
Describe the fourth and final step of beta oxidation, including reactant, enzyme, cofactor and product names.
Definition
beta-ketoacyl-CoA --> shorter fatty acyl-CoA by thiolase and CoASH (causes release of acetyl-CoA)
Term
By how much does one cycle of beta-oxidation shorten a fatty acyl-CoA?
Definition
Two carbons
Term
True or False: VLCAD are membrane bound enzymes while LCAD, MCAD and SCAD are families of soluble enzymes.
Definition
True
Term
True or False: The two electrons removed during the beta oxidation cycle are delivered to the electron-transport chain in the form of reduced coenzyme Q (UQH2).
Definition
True
Term
Enoyl-CoA Dehydrogenase is also called __________.
Definition
Crotonase
Term
Complete beta-oxidation of palmitic acid yields how many ATPs?
Definition
106
Term
Large amounts of ______ is produced by beta-oxidation of fatty acids, which helps animals survive in arid conditions.
Definition
dietary/metabolic water
Term
Slow-twitch muscles are _________.
Definition
oxidative
Term
Fast-twitch muscles are __________.
Definition
glycolytic
Term
Beta-oxidation of odd-carbon fatty acids yields _____________.
Definition
propionyl-CoA
Term
True or False: A complex of four enzymes converts propionyl-CoA into succinyl-CoA.
Definition
False; three
Term
Succyinyl-CoA can be converted into _______ for transportation into the cytosol.
Definition
Malate
Term
Polyphenolic compounds found in chocolate, green tea and red wine are called ____________.
Definition
catechins
Term
__________ converts cis-acyl-CoA into trans-acyl-CoA so that it can be used by acyl-CoA dehydrogenase.
Definition
Enoyl-CoA isomerase
Term
_______________ converts trans-cis structures into a trans unsaturated fat.
Definition
2,4-Dienoyl-CoA reductase
Term
Branched fatty acids are degraded via ____________ oxidation.
Definition
alpha
Term
Name the three types of ketone bodies.
Definition
Acetone, acetoacetate and beta-hydroxybutyrate
Term
Synthesis of ketone bodies occurs in ________.
Definition
mitochondrial matrix
Term
True or False: Diabetics have an overabundance of glycolysis, which depletes their oxaloacetate levels, causing fat catabolism to go to ketone bodies rather than the TCA cycle.
Definition
True
Term
List the four major differences between the lipid catabolic and biosynthetic pathways.
Definition
1. In biosynth, lipids are linked to acyl carriers, as opposed to CoA.
2. Synth occurs in the cytosol instead of mitochondria.
3. Enzymes for synth are one polypeptide, the fatty acid synthase
4. Biosynth uses NADPH, while breakdown uses NADH
Term
The addition of two-carbon units to the growing fatty acid chains are driven by the decarboxylation of _____________.
Definition
malonyl-CoA
Term
True or False: Elongation reactions are repeated until the chain reaches 18 carbons in length.
Definition
False: 16 carbon (palmitic acid)
Term
Carboxylated acetyl-CoA
Definition
malonyl-CoA
Term
Three sources of acetyl-CoA in the cytosol
Definition
1. amino acid degradation
2. fatty acid oxidation
3. glycolysis (main source)
Term
Study the following diagram carefully. DO IT.
Definition
Term
True or False: The carboxylation of acetyl-CoA to form malonyl-CoA is the committed step in fatty acid biosynthesis.
Definition
True
Term
Acetyl-CoA carboxylase uses what three cofactors?
Definition
ATP, biotin and bicarbonate
Term
Name the three protein components of ACC.
Definition
1. biotin carboxyl carrier protein
2. biotin carboxylase
3. carboxyltransferase
Term
True or False: ACC is carefully regulated, being inhibited by citrate and activated by palmitoyl-CoA.
Definition
False: citrate favors active polymer while palmitoyl-CoA favors monomeric form
Term
True or False: Phosphorylated acetyl-CoA carboxylase is activated only by high levels of citrate, but is inhibited by low levels of palmitoyl-CoA.
Definition
True. The inverse holds true for its dephospho-form
Term
___________ carry the intermediates in fatty acid synthesis.
Definition
acyl carrier proteins
Term
True or False: In mammmals, fatty acid synthesis takes place in multienzyme complexes called fatty acid synthase II (FASII).
Definition
False; FASII is present in plants and bacteria. FASI is in mammals.
Term
True or False: When introducing double bonds into fatty acid chains, eukaryotes use an oxygen-dependent process.
Definition
True
Term
__________ is the precursor to omega-3 fatty acids.
Definition
Linolenic acid
Term
_____________ is the precursor to omega-6 fatty acids.
Definition
linoleic acid
Term
Omega-3 fatty acids are precursors to _________.
Definition
prostaglandins
Term
________ activates ACC/inhibits lipases.
Definition
glucagon
Term
___________ inhibits ACC/activates lipases.
Definition
insulin
Term
Fatty acyl-CoAs (activates or inhibits?) acetyl-CoA carboxylase.
Definition
inhibits
Term
Citrate (activates or inhibits?) acetyl-CoA carboxylase.
Definition
activates
Term
Malonyl-CoA blocks _______, thereby inhibiting beta-oxidation.
Definition
carnitine acyltransferase
Term
Study the following image carefully. DO IT.
Definition
Term
Study the following image carefully. DO IT.
Definition
Term
True or False: COX-1 is a common action site of many anti-inflammatory medications.
Definition
True; COX-2 is as well
Term
Where is the primary site of cholesterol synthesis in the body?
Definition
Liver
Term
The cholesterol biosynthetic pathway begins with the synthesis of ____________.
Definition

Mevalonate

 

Term

_________ is a precursor to bile salts and steroid hormones.

 

Definition

Cholesterol

Term
___________ is the rate-limiting step in cholesterol synthesis.
Definition
HMG-CoA reductase
Term
In general terms, what is the process of cholesterol synthesis?
Definition

1. Thiolase reaction converts acetyl-CoA into acetoacetyl-CoA

2. HMG-CoA is formed

3. HMG-CoA is converted to mavelonate using two NADPH

Term
What are the 3 mechanisms that regulate HMG-CoA reductase?
Definition

1. reversible phosphorylation

2. short half-life (degradation)

3. gene expression

Term
True or False: Statins lower serum cholesterol levels.
Definition
True
Term
______________ is a cluster of lipids with an apolipoprotein.
Definition
lipoprotein
Term

Name a few lipoprotein types.

 

Definition
LDL, VLDL, HDL, chylomicrons
Term
Lipoproteins are classified according to what?
Definition
their densities
Term
True or False: Lipoprotein lipases hydrolyze triglycerides from lipoproteins in the capillaries and tissues to make them smaller and increasing their density.
Definition
True story, bro
Term
________________ is the term given to a variety of inherited metabolic defects that lead to greatly elevated levels of serum cholesterol
Definition
familial hypercholesterolemia
Term
____________ is the branch point for either sex hormone or corticosteroid production.
Definition
progesterone
Term
True or False: Ketone bodies are formed from Acetyl-CoA in an ATP dependent reaction.
Definition
FAlse: no ATP required
Term
True or False: In mammals, fatty acid synthesis normally occurs in the mitochondria.
Definition
FAlse: cytosolic
Term
Which lipid form is transported across the inner mitochondrial membrane before beta-oxidation?
a. fatty acyl CoA
b. acetoacetyl CoA
c. o-acylcarnitine
d. L-carnitine
Definition
C. o-acylcarnitine
Term
Elevated levels of the 1st messenger ______ stimulates the conversion of TAGs stored in adipose cells to free fatty acids. This signal also results in phosphoylation of ACC, which inhibits fatty acid synthesis unless citrate levels are very high.
Definition
glucagon
Term
Which of the following enzymes delivers NADH to the electron transport system?
a. acyl-CoA dehydrogenase
b. hydroxyacyl-CoA dehydrogenase
c. thiolase
d. enoyl-CoA hydratase
Definition
B. hydroxyacyl-coa dehydrogenase
Term
True or False: Malonyl-CoA is not required for fatty acid synthesis since it can easily be made from Acetyl-CoA.
Definition
True
Term
Beta-oxidation of odd-carbon fatty acids yields ___________.
Definition
propionyl-CoA
Term
How is (glucose derived) acetyl-CoA made available for fatty acid biosynthesis?
Definition
Glucose is converted into pyruvate via glycolysis in the cytosol. Pyruvate is then translocated to the mito matrix and converted to either OAA or acetyl-CoA, condensed as citrate, and transported back out to the cytosol. From there, it can be converted back into OAA and acetyl-CoA and used for fatty acid synth. Malate can also be used in the shuttle allowing all pyruvate to be converted to acetyl-CoA.
Term
WHich of the following is the primary regulation step of fatty acid synthesis?
a. transportation of mitochondrial acetyl coa to the cytosol
b. carboxylation of the acetyl coa to form malonyl coa
c. assembly of the fatty acid chain
d. none of the above
Definition
b. formation of malonyl coa
Term
Each of the following is a hormonal regulator of fatty acid metabolism, except:
a. glucagon
b. epinephrine
c. insulin
d. none are regulators
e. all are regulators
Definition
e. all are regulators
Term
Which of the following blocks carnitine acyltransferase and thus inhibits beta-oxidation during lipid biosynthesis?
a. citrate
b. glucagon
c. insulin
d. malonyl-coa
Definition
d. malonyl-coa
Term
True or False: The phosphorylation of acetyl-CoA carboxylase regulates enzyme activity by introducing conformational changes within the protein that favor enzyme activity.
Definition
True
Term
Malonyl-CoA-acetyl-CoA-ACP transacylase (MAT) transfers the malonyl group of malonyl-CoA to ____________.
Definition
acyl carrier protein (ACP)
Term
What is the product of fatty acid synthesis?
Definition
palmitate
Term
True or FAlse: HMG-CoA reductase is the rate limiting step in cholesterol biosynthesis, and also the site of action of cholesterol reducing drugs.
Definition
True
Term
True or FAlse: The main function of LDL is to transport cholesterol to tissues.
Definition
true
Supporting users have an ad free experience!