Fuel Metabolism
Terms
undefined, object
copy deck
- What are the 2 major goals of metabolism
-
1)extract energy and reducing power from environment
2)synthesize building blocks needed to make more complex polymeric macromolecules - What are the characteristics of catabolic pathways
-
1)generally oxidative
2)breaking covalent bonds
3)result in release of energy - What are the characteristics of anabolic pathways
-
1)generally redective
2)bond formation
3)consume energy - What are some examples of oxidative catabolic pathways
- glycolysis, FA oxidation
- What are some examples of non-oxidative catabolic pathways
- glycogenolysis, hydrolysis of TGs to FAs
- What is the universal carrier of acyl groups
- Coenzyme A
- What is the major function of skeletal muscle
- mechanical work
- Describe white muscle fibers in terms of their contraction speed, duration, capacity, aerobic oxidation and what they use as fuel
- high contraction speed, limited duration, high capacity, limited aerobic oxidation (low mitochondrial content), use glycogen and glucose with lactate formation
- Describe red muscle fibers in terms of their contraction speed and oxidative capacity
- slow contraction speed, high oxidative capacity
- Describe the heart in terms of contraction and oxidative capactiy
- continuous contraction, high oxidative capacity
- Rank white, red, and heart muscle fibers in terms of mitochondrial content from lowest to highest
- white<red<heart
- What is the main general role of the liver?
- biosynthetic and detoxifying organ
- Is the liver rich in mitochondria and poor in microsomal systems?
- No, it is rich in both
- Name 6 specific functions of the liver
- stores glucose as glycogen, de novo glucose synthesis, urea synthesis, ketone synthesis, assembles lipoproteins, coordinator of fuel homeostasis
- What are is the major work done by the brain and nerve?
- ion pumping to maintain membrane potential for electrical activity
- Describe the brain and nerve in terms of glycolytic and oxidative capacity?
- High capacity of both.
- What is the major and minor fuel source of the brain and nerve? What can they not use as a fuel source?
- glucose, ketone bodies, FAs
- What is the function of adipose tissue?
- Storage, mobilization and synthesis of TGs
- What is the major precursor of alpha-glycerol phosphate for tryglyceride synthesis?
- glucose
- What is the major function of the kidney?
- fluid homeostasis: osmotic work, high rate of active transport, acid and base balace
- What does the kidney use as fuel?
- FAs, lactate, ketones
- What are 2 minor functions of the kidney?
- ammonia synthesis, gluconeogenesis
- What is the main pathway of energy in RBCs and why?
- anaerobic glycolysis b/c no mitochondria
- Why do RBCs make 2,3 BPG?
- regulate O2 affinity of hb
- Rank the order of fat, protein, and glucose stores in the tissue of a normal adult.
- glucose<protein<fat
- Rank the order of fat and glucose stores in the extracellular fluid of a normal adult.
- glucose<fat
- What is more important in the body in terms of fuel metabolism after a meal? Replenishing glycogen stores or making fat
- repleneshing glycogen stores
- What are the 3 stages of energy extraction? How much energy is gained in each stage?
-
1)degrade macromolecule into building blocks, no useful energy gained
2)convert building blocks into common inermediate (Acetyl-CoA), small energy gained
3) terminal oxidation of acetyla-coA to CO2 and H2O, most energy gained - What 5 pathways occur in the cytosol?
- glycolysis, PPP, FA synthesis, Nucleotide synthesis, protein synthesis
- What 4 pathways occur in the mitochondria?
- CAC, Oxidative phosphorylation, B-oxidation of FA, ketogenesis/ketone oxidation
- What 3 pathways use both cytosolic and mitochondrial enzymes?
- gluconeogenesis, urea synthesis, steroid hormone synthesis
- What 4 pathways take place on SER?
- TG synthesis, phospho/glycolipd synthesis, cholesterol synthesis, hydroxylation/detoxification reactions (p450)
- One or more of what 3 properties is usually true for a highly regulated enzyme?
-
1)catalyze irreversible rxns
2)catalyze rate limiting step
3)catalyze committed step - What is a committed step?
- first step that is committed solely to the formation of the product
- What are 7 ways to regulate enzymes?
-
1)change abundance
2)alter pool size of sustrate
3)cooperativity
4)organization of enzymes into larger catalytic units
5)isoenzymes
6)altering kinetic properties of Enzymes with allosteric effectors
6)Regulation by covalent modification - What are 2 ways to change the abundance of an enzyme?
-
1)induction/repression of enzyme synthesis (transription level mostly)
2)degradation rate - What is the difference amongy a macromolecular complex, multifunctional protein, and metabolon? Give an example of each.
- metabolon are a group of enzymes in a pathway located in close proximity but not tightly organized like macromolecular complex. CAD protein in pyrimidine synthesis is used for multifxnal complex.
- What are the types of covalent modifications of enzymes?
- phosphorylation(reversible), proteolytic cleave(irreversible)
- what products are usually allosteric effectors?
- end productos of pathways, metabolites that reflect energy status
- Does proteolytic cleavage of an enzyme usually activate or inactivate cascade systems?
- activate
- What rxn does the enzyme myokinase/adenylate catalyze? Where is it most found?
- ADP-->ATP+AMP...muscle myfibril
- What is the reaction for energy charge?
- (ATP+0.5ADP)/(ATP+ADP+AMP)
- When E.C. begins to fall, what happens?
- catabolic pathways are activated and anabolic pathways are inhibited.
- T or F, the more negative the redox potential, the greater the tendency to lose electrons?
- True.
- T or F, the more negative the redox potential, the greater the tendency to gain electrons?
- False.
- T or F. A positive value for delta Eo indicates an exergonic reaction.
- True.
- T or F. A positive value for delta Eo indicates an endergonic reaction.
- False.
- NAD/NADH pair participate in the transfer of what?
- H:-...hydride ion
- FAD/FADH2 pair participate in the transfer of what?
- 2 hydrogen atoms
- Describe in general dehydrogenases?
- catalyze the transfer of H from substrate to coenzyme acceptor.
- What are the 2 major classes of dehydrogenases?
- Those requiring nicotinamide coenzymes and those requiring flavin coenzymes.
- What are nicotinamide coenzymes made from?
- niacin and tryptophan
- what is the difference between NAD+ and NADP+
- NAD+ is mainly in catabolic pathways that are mainly oxidative, NADPH is mainly in biosynthetic anabolic pathways usually reductive in nature. NAD/NADH concentrated in mitochondria while NADP/NADPH is in the cytosol
- NAD-->NADH +H+ reactions help what types of reactions?
- oxidation of alcohol to aldehyde or keto- groups
- What is pellegra and how do you get it?
- niacin deficiency, dermititis, diarrhea, and dementia
- Where does flavin come from?
- riboflavin
- where is the semiquinone intermediate found?
- Before transfer of second hydrogen in FAD/FADH2 rxns.
- FAD-->FADH2 rxns help what types of reactions?
- oxidation that creates carbon-carbon double bonds
- what are oxidases?
- catalyze transfer of electrons from an organic substrate to molecular oxygen via an intermediate carrier bound to the enzye tightly which is usually either metal ions or flavin nucleotides
- oxidases using metal ions usally end up with what product? what about those using flavin nucleotides?
- H2, H2O2
- What are the major ROS?
- O2-,H2O2,OH*
- what does superoxide dismutase do?
- 2O2- + 2H+ -->H2O2+O2
- what are the three SOD isozymes and where are they located?
- Cu/Zn SOD(cytosolic), MnSOD (mitochondrial), ec SOD (extracellular)
- What are two sources of H2O2?
- formation by SOD, formation of H2O2 via oxidase-catalyzed ractions (fad dependent oxidases)
- What does peroxidase do?
- H2O2 + AH2-->2H2O+O2
- What does catalase do?
- 2H2O2-->2H20+O2
- how is most H2O2 destroyed in the body?
- localized and destroyed in peroxisomes
- why is H2O2 dangerous and where does it cause the most damage?
- strong oxidizing agent...membranes
- What enzyme in the citric acid cycle is not in the matrix?
- succinate dehydrogenase
- What is succinyl-CoA used in?
- heme synthesis
- What is OAA used in?
- glucose synthesis.
- What is citrate used in?
- FA synthesis
- What are ketoacids (OAA,alpha ketoglutarate) used in?
- nonessential amino acid synthesis
- what is malate used in?
- gluconeogenesis
- What does the accumulation of ATP, which indicates an energy rich state, do to the citric acid cycle?
- Inhibits the cycle distal of citrate synthesis...accumulatation of citrate gets used in FA synthesis
- What part of the CAC effects PFK-1, acetyl-CoA carboxylase, pyruvate carboxylase...and how does it effect these parts?
- citrate inhibits PFK-1 and activates acetyl-CoA carboxylase (first step fatty acid synthesis. acetyl-coA activates pyruvate carboxylase (inital step for gluconeogenesis)
- What's the overall reaction for the CAC?
-
Acetyl~CoA + 3 NAD+ + FAD + GDP + Pi + 2H2O -->
2CO2 + 3NADH + FADH2 + GTP + 2H+ + CoASH