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C485 Exam 2
Terms in this set (71)
1) What enzyme activities are required to metabolize an odd carbon unsaturated fatty acid and an even carbon unsaturated fatty acid.
1) Odd carbon chains require an isomerase
2) Even carbon chains require dehydrogenase then an isomerase
2) Calculate the energy yield from a C-10 saturated fatty acid. A C-12 fatty acid with an odd carbon double bond. A C-12 fatty acid with an even carbon double bond.
C10) 4 FA + 5 AcCoA -2 ATP = 64
C12O) 5 FA + 6 AcCoA - 2 ATP - QH2 = 76.5
C12E) 5 FA + 6 AcCoA - 2 ATP - NADH = 75.5
3) List the differences between FA synthesis and degradation.
1) Cytoplasm vs Mitochondria
2) locked intermediates vs Free CoA thioesters
3) One protein vs multiple enzymes
4) Uses NADPH vs Uses NADP+
5) Carbons from malonyl CoA vs carbons make AcCoA
4) What is an ACP? Describe its role in fatty acid synthesis.
an acyl carrier protein that contains a pantathene prosthetic group. Arm can reach all active sites and acts as foundation for growing FA
5) Describe the basic organization of a fatty acid synthase.
Homodimer enzyme that natively contains the functions needed for FA synthesis
6) What is the first committed step in fatty acid synthesis? Draw the mechanism.
formation of malonyl CoA from an acetyl CoA and AcCoA Carboxylase
7) Describe the requirements in building blocks, ATP and NADPH for the synthesis of palmitate.
7 HCO3, 8 AcCoA, 7 ATP, 14 NADPH
8) Outline the first round of fatty acid synthesis starting from AcCoA and malonyl CoA.
Bicarbonate is combined with AcCoA through the biotin AcCoA Carboxylase
9) Is there a direct mechanism for generation of AcCoA in the cytoplasm? If not, why might this be a problem? How do cells deal with this?
There is no direct mechanism which is a problem because AcCoA must be used for FA synthesis in the cytoplasm. Citrate is brought from the mitochondria and lysed in the cytoplasm to form AcCoA and OAA
10) Name and outline (show the reactions) the process used to solve the problem in question 10.
11) In what other ways does the generation of AcCoA in the cytoplasm address a problem of fatty acid biosynthesis.
the process forms 8 NADPH which accounts for some of the 14 needed for palmitate synthesis
12) Draw the structures of ketone bodies. Where are they synthesized and where are they predominantly used.
they are made in the liver and predominantly used in cardiac muscle but can be used by the brain under starvation conditions
13) Calculate the energy yield from beta-hydroxy butyrate. (You will have to do a little thinking here.)
oxidation of beta-hydroxy butyrate creates an NADH and a succinyl CoA which is broken down into 2 AcCoA however 1 GTP cannot be formed from succinyl CoA which brings total to 22.5-1= 21.5
14) Outline (structures) the process by which ketone bodies are made.
15) What are peroxisomes and what do they do? How is this process different from normal beta oxidation of fatty acids?
Peroxisomes degrade long fatty acids by using FADH2 to convert O2 into HOOH during the initial dehydrogenase reaction
16) Under what conditions would you expect ketone body formation? Why? Explain the statement - "fats burn in the flame of carbohydrates".
ketone bodies are formed from the AcCoA produced from FA degradation. Under starvation conditions, oxaloacetate is being used in gluconeogenesis and cannot be used to bring AcCoA into CAC
17) How does the brain adapt to starvation?
the brain can operate on up to 75% ketone bodies
18) How does the energy charge of a cell affect the regulation of FA synthesis. Describe how this takes place and the role of any hormones in this process.
Low energy turns off FA synthesis. AMP will bind AMPK which turns off AcCoA carboxylase
19) List the small molecules that activate FA synthesis and briefly say how they do this.
1) Citrate - activates carboxylase through polymerization
2) malonyl CoA - turns off Cat1 so synthesis and degradation arent happening simultaneously
20) List the small molecules that inhibit FA synthesis and briefly say how they do this.
1) epinephrine - activates AMPK which inactivates AcCoA carboxylase
2) Palmitoyl CoA - depolymerization
21) How does malonyl CoA affect FA metabolism? Explain the logic of this.
Malonyl CoA acts as the high energy molecule the drives the reaction towards completion. ATP used in the carboxylation of AcCoA to malonyl CoA is stored then released during decarboxylation
1) What is the first step in amino acid breakdown?
conversion of an AA to an alpha-keto-acid
What four basic roles do lipids play in the body?
1) energy storage
2) essential membrane component
3) essential membrane anchors
4) important hormone component
What is the basic structure of a triglyceride
glycerol with three fatty acids
What reaction do lipases catalyze? What special requirements do lipases have?
Lipases catalyze the removal of an FA group from an acyl glycerol. The require water to reduce a FA group
Diagram the process by which triglyceride particles are digested in the intestines. What essential molecules are present and what is their role? Where do they come from?
Bile acids dispose of FA as micelles. Bile acids are secreted by the liver and stored in the gall bladder until release into the small intestine.
Where are triglycerides reassembled and how are they disperse3d throughout the body.
triglycerides are reassembled in adipose tissue and muscle tissue. They are dispersed after being packaged into chylomicrons in intestinal epithelial cells and are then transported to the lymph system and circulatory system
Where are triglycerides stored? What signal gives rise to their mobilization? What molecules are activated and what is their role?
triglycerides are stored in muscle and adipose tissue. epinephrine and glucagon begin a similar signaling cascade to glycogen degradation. PKA becoming active phosphorylates perilipin which restructures the fat droplet and causes the ATGL coactivator release.
Outline the mobilization of fatty acids
TAG -- (ATGL) --> DAG
DAG -- (HSL) --> MAG
MAG -- (MGL) --> glycerol
How are poorly water soluble fatty acids transported to target tissues
serum albumin in the blood binds and transports FA and other hydrophobic molecules
what modification occurs to fatty acids before entering the mitochondria and explain how this reaction is driven to completion.
The conversion of ATP to AMP drives the addition of a high energy thioester to a fatty acid to form FACoA
How many protein activities are required for entry of a fatty acyl CoA molecule into the mitochondria
1) CAT1 creates s a carnitine bound FACoA in the cytosol
2) Translocase removes the FACoA from the carnitine in the matrix
3) CAT2 shuttles the free carnitine back across the membrane and a FACoA carnitine inside
What are the 4 steps to beta oxidation
Describe beta oxidation based on the energy output from QH2 and NADH
NADH generates 2.5 ATP and QH2 generates 1.5 ATP because NADH enters the ETC earlier. AcCoA generates 10 ATP total
what is the final product when the fatty acid has and odd number of carbons
propionyl CoA goes through a biotin dependent carboxylation. It then undegoes a mutase reaction to form succinyl CoA which can be converted to make OAA. OAA can enter the Krebs cycle
explain how a low carb diet might affect someone who is trying to maintain a daily workout routine
depleting glycogen stores will decrease potential exercise return overtime
What is the driving force of fatty acid elongation
carbon dioxide release after decarboxylation
Name two functions activated by insulin that directly affect glucose utilization
1) inactivation of glycogen synthase, activating glycogen synthesis
2) increase of glucose transporter proteins
How is the insulin signal terminated
Phosphatases desphosphorylate enzymes, inactivating previously active kinases
1) Was is meant by an enzymopathy? What is the major enzymopathy associated with the PPP? What are the consequences?
enzymopathy is the deficiency in the stability, amount or activity of an enzyme. G6PDH is the major enzymopathy of the PPP and it causes a lowered response to oxidative challenges due to a deficiency in NADPH/
2) What are the sources of NADPH in mammalian systems?
3) What is the structure of glutathione? How does glutathione protect erythrocytes from oxidative damage?
reduced Glutathione in combination with a peroxide and peroxidase will become oxidized by oxidizing agents
4) Describe the process that leads to hemolytic anemia. Why is this a particular problem in erythrocytes?
G6PDH causes glutathione deficiency which causes a lack of reducing power in the cell. During an oxidative challenge, hemoglobin sulfurs can become oxidized and polymerize
5) How is G6PDH regulated in mammalian systems? How does this regulation relate to regulation of GAPDH?
G6PDH is turned off during reducing conditions because NADPH will replace the NADP+ that creates the active dimer enzyme. GAPDH is turned off during oxidizing conditions due to sulfur bond dimerization in the active site
1a) How many forms (related by covalent modification) of phosphorylase are there? Describe how they are interconverted. Which statepredominates in the liver and in muscle?
PhosB is inactive in the muscle and PhosA is active in the liver. They are interconverted by Phosphorylase Kinase and Phosphatase
1b) How many states (related by conformational change) of phosphorylase are there? How are they interconverted? Be specific as to how this process occurs in different tissue types, given different isozymes of the enzyme.
In the liver, glucose binds PhosA and converts it from R to T. In the muscle, AMP binds PhosB to convert it from T to R
2) What is meant by processivity? Give an example of a processive enzyme involved in glycogen processing. Give an example not involved in glycogen processing.
Processivity is when an enzyme completes multiple rounds of catalysis without releasing the substrate. Glycogen synthase and polymerase are both examples
3) What are the general steps associated with signal transduction.
1) Signal Release
3) 2nd messenger in cell
4) activation of effector
4) What hormone(s) activate glycogen breakdown in the liver? In muscle?
Glucagon activates glycogen breakdown in the liver. Epinephrine activates glycogen breakdown in the muscle.
6) What is meant by reciprocal regulation? Give an example.
reciprocal regulation occurs when the upregulation of one metabolite is associated with the down regulation of another. PKA specifically turns on glycogen degradation and specifically turns off synthesis
7) Describe the processes that give rise to termination of the signal for glycogen breakdown in muscle.
1) A ligand dissociation
2) B arrestin binds and inhibits receptor
3) C terminus binds and inhibits receptor
4) GTPase activty of alpha subunit
5) cAMP --> AMP
6) Protein Phosphatase 1
8) What enzyme activities are required for glycogen synthesis? Describe what these enzymes do.
1) pyrophosphorylase forms UDP glucose
2) glycogenin self primes creating 10-20 residues
3) glycogen synthase elongates branches
4) branching enzymes move block of glucoses to form a-1,6 linkage
9) What hormone activates glycogen synthesis? How does this relate to the physiological role of the hormone?
Insulin activates glycogen synthase by turning glycogen synthase kinase off. Insulin is anabolic
10) Describe the receptor that is associated with the hormone in question 9.
Tyrosine Kinase dimer
11) Many steps in signal transduction involve activation of an enzyme. Give three examples of such activation. Why is it advantageous to include enzyme activation in a signal transduction pathway?
It is advantageous to have a signal transduction pathway because one enzyme can activate multiple turnover events.
1) adenylate cyclase activated by A-GTPase
2) PKA activated by cAMP
3) phosphorylase kinase activated by PKA
14) Describe the structure of glycogen. Use chemical structures as necessary.
tree branching with at least 4 spaces between branches. Tyrosine dimer forms base of extension
15) What enzyme activities are required for glycogen breakdown? Describe what these enzymes do.
1) phosphorylase cleaves bonds on non reducing end leaving 4 residue blunt ends before branch
2) transferase transfers 3 of remaining 4 to new branch
3) A-1,6-glucosidase removes 1,6 bond
16) Describe the differences in the biochemistry of glycogen breakdown in the muscle and liver. How do these differences relate to the physiological functions of muscle and liver?
Muscle is constitutively inactive and uses PhosB because it does not need constant ATP. Liver is constitutively active and uses PhosA to release glucose
17) The synthesis of UDP-glucose requires UTP and glucose-1-phosphate. What would be the advantages and disadvantages of performing the same reaction using UDP?
An advantage is not consuming 2 UTP which is the eq. of using 2 ATP. A disadvantage is that the reaction is reversible because a phosphate anhydride is consumed and formed
18) Phosphorylase uses Pi as a substrate. What is the advantage of this?
Inorganic phosphate is abundant in the cell which pushes the reaction towards product formation. Using Pi also cuts out the need for an ATP
19) Why does adenylate cyclase not use ADP as a substrate. How many ATP equivalents (i.e. single phosphate anhydride bonds) are required for the action of adenylate cyclase? Is the hydrolysis of cAMP functionally irreversible? If so why, and compare to the hydrolysis of a phosphate diester such as DNA.
2 phosphate anhydrides must be cleaved because there is a high energy strained phosphodiester product formed. cAMP is more irreversible due to formation of H2O and strained cyclic product
22) What post-translational modifications are associated with the signal cascades involved in regulation of glycogen utilization? How are these steps reversed
phosphorylation that gets reduced by phosphatases
Malonyl CoA formation
Fatty acid synthesis
Ketone body synthesis
Odd and even unsaturated fatty acids metabolism
odd carbon fatty acid degradation
Fatty acid degradation
animated glycogen degradation
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