1D: Principles of Bioenergetics & Fuel Molecule Metabolism Flashcards
Endothermic Reactions
Require energy, nonspontaneous, positive heat flow (absorbed = feels cold), increase enthalpy, breaking chemical bonds
Exothermic Reactions
Release energy, can be spontaneous, high entropy, negative heat flow (lost = feels hot), decrease enthalpy, form chemical bonds
Free Energy Equation
dG = dH - TdS
Standard Free Energy Equation
dG = -RTlnK
dG less than 1
K>1, favors products, spontaneous
dG equal to 0
K=1, at equilibrium
dG greater than 1
K
Nonspontaneous Reaction Criteria
\+G = +H, -S \+G = +H, +S (low temp) \+G = -H, -S (high temp)
Spontaneous Reaction Criteria
- G = +H, +S (high temp)
- G = -H, +S
- G = -H, -S (low temp)
Spontaneous Reaction Criteria
- G = +H, +S (high temp)
- G = -H, +S
- G = -H, -S (low temp)
ATP Hydrolysis
ATP + H2O -> ADP + Pi
Exergonic (dG
ATP Group Transfer
When ATP is depleted during exercise, phosphate is transferred from phosphocreatine to ADP to replenish ATP
Oxidation Half Reaction
Loses electrons (uses solid)
Reduction Half Reaction
Gains electrons (produces solid)
Soluble Electron Carriers
Electrons transferred from one electron carrier to another; energy level decreases; energy is released
Ubiquinone (Q)
Lipid-soluble electron carrier; reduced to ubiquinol
Cytochrome c
Water-soluble electron carrier; contains Fe pigment
Quinone
Lipid-soluble carrier that shuttles electrons between large macromolecular complexes embedded in the membrane
Quinone
Lipid-soluble carrier that shuttles electrons between large macromolecular complexes embedded in the membrane
Flavoproteins
Derivatives of riboflavin; FAD and FMN; involves in bioluminescence, photosynthesis, DNA repair, apoptosis
Electron Transfer Flavoprotein
Function as a specific electron acceptor for primary dehydrogenases
Carbohydrate Formula
(CH2O)n; deoxy = hydrogen replacing -OH
Aldose
Sugar with an aldehyde group
Ketose
Sugar with a ketone group
Pyranose
Hexagonal ring
Furanose
Pentagonal ring
Common Sugars
Glucose, Galactose, Fructose
Absolute Configuration
D/L = based on chirality of the carbon atom furthest from the carbonyl group
Alpha/Beta = anomeric configuration
Alpha Anomer
Oxygens are cis to each other
Beta Anomer
Oxygens are trans to each other
Beta Anomer
Oxygens are trans to each other
Epimers
Diastereomers; different configuration at one of the chiral carbons
Anomers
Stereoisomers; different configuration at the same carbon
Hydrolysis of Glycoside Linkage
Done by enzymes (amylase = starch, glycosylase = nucleotide)
Hydrolysis of Glycoside Linkage
Done by enzymes (amylase = starch, glycosylase = nucleotide)
Monosaccharides
Colorless, water-soluble, crystalline solid
Mutarotation
Equilibrium between the alpha and beta anomer
Disaccharides
Simple polysaccharides, made via condensation reaction between two monosaccharides
Maltose
Glucose + Glucose (1->4 Linkage)
Sucrose
Glucose + Fructose (1->2 Linkage)
Lactose
Galactose + Glucose (1->4 Linkage)
Lactose
Galactose + Glucose (1->4 Linkage)
Polysaccharides
Long chains of repeating monosaccharide units connected by glycosidic links; Storage or Structural
Storage Polysaccharides
Starch and Glycogen
Structural Polysaccharides
Chitin and Cellulose
Starch
B 1->4 linkages
Cellulose
A 1->4 linkages
Cellulose
A 1->4 linkages
Glycolysis
Conversion of Glucose into 2 molecules of Pyruvate; produces 4 ATP molecules and 2 NADH; occurs in cytosol
Glycolysis Net Products
2 NADH 2 ATP
Glycolysis Enzymes
- Hexokinase
- Phosphoglucoisomerase
- PFK
- Aldolase
- GAP Dehydrogenase
- Phosphoglycerate Kinase
- Phosphoglycerate Mutase
- Enolase
- Pyruvate Kinase
Hexokinase
Glucose -> G6P
-ATP
Phosphoglucoisomerase
G6P -> F6P
PFK
F6P -> F1,6BP
-ATP
Aldolase
F1,6BP -> GAP or G3P
GAP Dehydrogenase (x2)
GAP -> 1,3BPG
-Pi
+NADH
Phosphoglycerate Kinase (x2)
1,3BPG -> 3PG
+ATP
Phosphoglycerate Mutase (x2)
3PG -> 2PG
Enolase (x2)
2PG -> PEP
+H2O
Pyruvate Kinase (x2)
PEP -> Pyruvate
+ATP
Glycolytic Feeder Pathways
Glycogenolysis, Starch Metabolism
-contribute glucose to the pathway
Fermentation
Anaerobic Glycolysis; converts sugars to acids, gases or alcohol; occurs in bacteria, yeast and o2 starved muscle cells
Fermentation
Anaerobic Glycolysis; converts sugars to acids, gases or alcohol; occurs in bacteria, yeast and O2 starved muscle cells; regenerates NAD to keep glycolysis going
Fermentation
Anaerobic Glycolysis; converts sugars to acids, gases or alcohol; occurs in bacteria, yeast and O2 starved muscle cells; regenerates NAD to keep glycolysis going
Fermentation Chemistry
Redox reaction, reduces pyruvate to oxidize NADH into NAD; 1 NAD per Pyruvate
Alcoholic Fermentation
Pyruvate reduced to Ethanol
Lactic Acid Fermentation
Pyruvate reduced to Lactate
Gluconeogenesis
Synthesis of Glucose from non-carbohydrate sources (pyruvate, lactate, glycerol); occurs in the liver
Gluconeogenesis Unique Enzymes
Pyruvate Carboxylase
PEP Carboxykinase
G6Pase
Pyruvate Carboxylase
Pyruvate -> Oxaloacetate
+HCO3
-ATP
PEP Carboxykinase
OAA -> PEP
-GTP + CO2
G6Pase
G6P -> Glucose
+H2O
-Pi
G6Pase
G6P -> Glucose
+H2O
-Pi
F1,6BP
Activates PFK,
high levels = glycolysis
low levels = gluconeogenesis
PPP Oxidative Phase
Generates NADPH
PPP Non-oxidative Phase
Generates 5C Sugar (Ribose-5-Phosphate)
PPP Non-oxidative Phase
Generates 5C Sugar (Ribose-5-Phosphate)
Net Products of Respiration
36 ATP
Net Products of Respiration
36 ATP
Regulation of Metabolic Pathways
Done through feedback inhibition, isozymes, enzymes concentrations, rapid effect or slow effects
Isozymes
Different enzymes that catalyze the same reaction
Regulation of Glycolysis
Irreversible steps: Hexokinase, PFK, Pyruvate Kinase
F2,6BP, AMP
F2,6BP
Potent Activator of PFK-1, synthesized when blood sugar is low and glucagon elevates cAMP
PEPCK Inhibitors
ADP
F1,6BP
Activates PFK,
high levels = glycolysis
low levels = gluconeogenesis
Glycogenolysis [Muscle]
Provides G6P for Glycolysis; Muscle lacks G6Pase
Glycogenolysis [Liver]
Creates free glucose to be released into the bloodstream for cellular uptake
Glycogenolysis Enzymes
Glycogen Phosphorylase
Phosphoglucomutase
Glycogen Debranching Enzyme
FBPase Activators
Citrate
Glycogenesis Enzymes
Hexokinase Phosphoglucomutase UDP-Glucose Phosphorylase Glycogenin Glycogen Synthase
Pyruvate Kinase Activators
F1,6BP
Glycogenin
Acts as a primer, converting glucose to glycogen; it is a glycosyltransferase
Pyruvate Carboxylase Activators
Acetyl CoA
Pyruvate Carboxylase Inhibitors
ADP
Protein Kinase A
Activated by epinephrine through adenylate cyclase activity; activated by calcium ions + cAMP
Inhibits Glycogen Synthase
Insulin
Stimulates glycolysis, glycogenesis, protein anabolism, lipogenesis
Glycogenolysis [Muscle]
Provides G6P for Glycolysis; Muscle lacks G6Pase
GLUT2
Transports dephosphorylated glucose into the bloodstream
Metabolic Control Analysis
Examines how the control of influx and concentrations of metabolites in a metabolic pathway distributed between different enzymes
Acetyl-CoA Production
Produced via Pyruvate Dehydrogenase Complex and Pyruvate Formate Lyase
Glycogenesis Enzymes
Hexokinase
Phosphoglucomutase
UDP-Glucose Phosphorylase
Glycogenin
UDP-Glucose Phosphorylase
Converts G1P to UDP-Glucose, forming pyrophosphate
Glycogenin
Acts as a primer, converting glucose to glycogen; it is a glycosyltransferase
Dihydrolipoyl Dehydrogenase (E3) (FAD, NAD+)
Restores the complex to its initial state producing NADH
Glycogen Phosphorylase
Phosphorylation activates; b form -> a form
Protein Kinase A
Activated by epinephrine through adenylate cyclase activity; activated by calcium ions + cAMP
Inhibits Glycogen Synthesis
Citric Acid Cycle Enzymes
- Citrate Synthase
- Aconitase
- Isocitrate Dehydrogenase
- Alpha-Ketoglutarate Dehydrogenase
- Succinyl-CoA Synthetase
- Succinic Dehydrogenase
- Fumarase
- Malate Dehydrogenase
Citrate Synthase
Acetyl-CoA + Oxaloacetate -> Citrate + CoA
GLUT2
Transports dephosphorylated glucose into the bloodstream
Metabolic Control Analysis
Examines how the control of influx and concentrations of metabolites in a metabolic pathway distributed between different enzymes
Alpha-Ketoglutarate Dehydrogenase
[NAD]
[CoA]
Alpha-Ketoglutarate -> Succinyl-CoA
+NADH
+CO2
+H
Acetyl-CoA Formation Reaction
[Pyruvate Dehydrogenase Complex]
Pyruvate + CoA + NAD+ –> Acetyl-CoA + NADH + H+ CO2
Pyruvate Dehydrogenase (E1) (Thiamine Pyrophosphate [TPP])
Attaches Acetyl Group to Sulfur Atom
Dihydrolipoyl Transacetylase (E2) (Lipoate, CoA)
Transfers Acetyl from Sulfur to CoA
Dihydrolipoyl Dehydrogenase (E3) (FAD, NAD+)
Restores the complex to its initial state producing NADH
Citric Acid Cycle Products [In Order]
Acetyl-CoA + Oxaloacetate -> Citrate -> Isocitrate -> Alpha-Ketoglutarate -> Succinyl-CoA -> Succinate -> Fumarate -> Malate -> Oxaloacetate
When is GTP Produced in the CAC?
From the Succinyl-CoA Dehydrogenase reaction
Citric Acid Cycle Enzymes
- Citrate Synthase
- Aconitase
- Isocitrate Dehydrogenase
- Alpha-Ketoglutarate Dehydrogenase
- Succinyl-CoA Synthetase
- Succinic Dehydrogenase
- Fumarase
- Malate Dehydrogenase
Regulation of Pyruvate Dehydrogenase
Activated by Ca, NAD+, CoA
Inhibited by high levels of Acetyl-CoA, NADH
Aconitase
[H2O]
Citrate -> Isocitrate
Isocitrate Dehydrogenase
[NAD]
Isocitrate -> alpha-ketoglutarate
+NADH
+CO2
Alpha-Ketoglutarate Dehydrogenase
[NAD]
[CoA]
Alpha-Ketoglutarate -> Succinyl-CoA
+NADH
+CO2
+H
Succinyl-CoA Synthetase
[GDP + Pi]
Succinyl-CoA -> Succinate
+GTP
+CoA
a-Ketoglutarate Dehydrogenase Regulation
Activated by Ca, AMP
Inhibited by NADH, Succinyl-CoA
Net Outcome of Respiration
2 ATP [Glycolysis]
2 NADH [Glycolysis] = 4 ATP
8 NADH [PyDh+CAC] = 24 ATP
2 FADH2 [CAC] = 4 ATP
Total = ~35
Characteristics of Lipids
Insoluble in water, soluble in nonpolar organic solves
i.e. Hydrophobic, Lipophilic
Citric Acid Cycle Products [In Order]
Acetyl-CoA + Oxaloacetate -> Citrate -> Isocitrate -> Alpha-Ketoglutarate -> Succinyl-CoA -> Succinate -> Fumarate -> Malate
When is GTP Produced in the CAC?
From the Succinyl-CoA Dehydrogenase reaction
CAC Mnemonic
Citrate Alone Is Often Kreb’s Starting Substrate For Making Oxaloacetate
Regulation of Pyruvate Dehydrogenase
Inhibited by high levels of Acetyl-CoA, NADH
Sphingophospholipids
Sphingolipids with a phosphodiester bond
Sphingomyelins
Contain phosphatidylcholine or phosphatidylethanolamine; component of the myelin sheath
Glycosphingolipids, Cerebrosides, Globosides
Sugar moieties attached instead of a phosphate group
Cerebrosides = monosaccharide connected to sphingosine
Globosides = disaccharide
Gangliosides = oligosaccharide (w/ N-acetylneuraminic acid)
Waxes
Long chain fatty acids esterified to long chain alcohols; used for protection against evaporation and parasites in plants and animals
a-Ketoglutarate Dehydrogenase Regulation
Activated by Ca, AMP
Inhibited by NADH, Succinyl-CoA
Net Outcome of Respiration
2 ATP [Glycolysis]
2 NADH [Glycolysis] = 4 ATP
8 NADH [PyDh+CAC] = 24 ATP
2 FADH2 [CAC] = 4 ATP
Total = ~35
Characteristics of Lipids
Insoluble in water, soluble in nonpolar organic solves
i.e. Hydrophobic, Lipophilic
Phospholipids
Amphipathic (hydrophilic head, hydrophobic tail)
Phosphodiester Linkage
Links the polar head to the tail; determines the function of the phospholipid
Sesquiterpenes
3 Isoprene Units
Sphingolipids
Contain a sphingosine backbone
Steroid Hormones
Have high affinity receptors, work at low concentrations, affect gene expression & metabolism; derived from cholesterol
Glucocorticoids [Cortisol], Mineralocorticoids [Aldosterone], Estrogen, Progesterone, Testerone
Sphingomyelins
Contain phosphatidylcholine or phosphatidylethanolamine; component of the myelin sheath
Prostaglandins
Autocrine & Paracrine Hormones that regulate cAMP levels; affect muscle contraction, body temperature, sleep-wake cycle and pain
Waxes
Long chain fatty acids esterified to long chain alcohols; used for protection against evaporation and parasites in plants and animals
Vitamin D [Cholecalciferol]
Metabolized to calcitriol; regulates calcium and phosphorus homeostasis; promotes bone formation; deficiency = rickets
Vitamin E [Tocopherols]
Biological antioxidants, destroy free radicals and prevent oxidative damage
Vitamin K [Phylloquinone & Menaquinone]
Formation of prothrombin (clotting factor)
Diterpene
4 Isoprene Units
Triterpene
6 Isoprene Units
Adipocytes
Animal cells that are used for storage of large triacylglycerol deposits
Saponification
The ester hydrolysis of triacylglycerols using a strong base
Lipase (Digestion)
Breaks down Triacylglycerols to fatty acids and monoglycerides through hydrolysis
Emulsifcation
Breaks down fat globules into emulsion droplets; increases the surface area for digestion
Colipase
A protein that binds to lipase at the surface of the emulsion droplets
Oxidation of Fatty Acids
Occurs in the Matrix of the Mitochondria; Ester Hydrolysis in the Cytosol
Vitamin E [Tocopherols]
Biological antioxidants, destroy free radicals and prevent oxidative damage
Vitamin K [Phylloquinone & Menaquinone]
Formation of prothrombin (clotting factor)
Why are triacylglycerols the preferred form of energy storage?
They are reduced and anhydrous which allow them to have a greater caloric yield; allows survival for about several weeks
They are not hydrated by the body and do not carry additional weight
Triacylglycerols
One glycerol attached to 3 fatty acids by ester bonds
Lipid Mobilization
Adipocytes -> Hormone-Sensitive Lipase
Lipoproteins -> Lipoprotein Lipase
Saponification
The ester hydrolysis of triacylglycerols using a strong base
Lipase
Breaks down Triacylglycerols to fatty acids and monoglycerides through hydrolysis
Emulsifcation
Breaks down fat globules into emulsion droplets; increases the surface area for digestion
Colipase
A protein that binds to lipase at the surface of the emulsion droplets
Chylomicrons
Packaged groups of lipoprotein particles that are transported into enterocytes
Apoproteins
Control interactions between lipoproteins
Cholesterol Metabolism
Obtained through dietary sources or de novo synthesis in the liver
Enzyme of Cholesterol Biosynthesis
HMG-CoA Reductase
Short Chain Fatty Acids
Absorbed across the intestine into the blood
CETP Enzyme
Catalyzes transition of IDL to LDL by transferring cholesteryl esters from HDL
Lipid Mobilization
Adipocytes -> Hormone-Sensitive Lipase
Lipoproteins -> Lipoprotein Lipase
Where are fatty acids synthesized?
In the cytoplasm from Acetyl-CoA transported out of the mitochondria
Chylomicrons
Transport mechanism for dietary TAG molecules and are transported via lymphatic system
Where are fatty acids oxidized?
In the mitochondria following transport by carnitine shuttle
Acetyl-CoA Shuttling
Citrate is shuttled across the mitochondrial membrane into the cytosol and is split by citrate lyase; Oxaloacetate is then returned to to the mitochondria to continue shuttling Acetyl-CoA
HDL
Reverse transport of cholesterol
Fatty Acid Synthase
Adds group to ACP and continuously extends the chain using NADPH
Cholesterol Metabolism
Obtained through dietary sources or de novo synthesis in the liver
Enzyme of Cholesterol Biosynthesis
HMG-CoA Reductase
LCAT Enzyme
Catalyzes formation of cholesteryl esters for transport with HDL
CETP Enzyme
Catalyzes transition of IDL to LDL by transferring cholesteryl esters from HDL
Process of Fatty Acid Synthesis
Activation -> Bond Formation -> Reduction -> Dehydration -> Reduction
-Repeated 8 times to form palmitic acid-
Carnitine Acyltransferase II
Converts Acylcarnitine back to Acyl-CoA
Beta-Oxidation Enzymes (Even)
- Fatty Acyl-CoA Dehydrogenase
- Enoyl-CoA Hydratase
- Thiolase
Where are fatty acids oxidized?
In the mitochondria following transport by carnitine shuttle
Beta-Oxidation Enzymes (Monounsaturated)
- Enoyl-CoA Isomerase
- Fatty Acyl-CoA Dehydrogenase
- Enoyl-CoA Hydratase
- Thiolase
Beta-Oxidation Enzymes (Polyunsaturated)
- Dienoyl-CoA Reductase
2. Enoyl-CoA Isomerase
Ketone Bodies
Acetoacetate, B-Hydroxybutyrate
Ketogenesis
Occurs in the MTC of Liver Cells when excess Acetyl-CoA accumulates; ketone bodies are used for energy
Fatty Acid Entry
Involves Carnitine Acyltransferase I; 2-12 Carbons diffuse into MTC, 14-20 carbons utilize Carnitine Shuttle
Carnitine Shuttle Enzymes
Carnitine Palmitoyltransferase I
Carnitine Acylcarnitine Translocase
Carnitine Acyltransferase II
HMG-CoA Lyase
HMG-CoA -> Acetoacetate -> B-Hydroxybutyrate
Ketolysis
Regenerates Acetyl-CoA for use as an energy source in peripheral tissues
Carnitine Acyltransferase II
Converts Acylcarnitine back to Acyl-CoA
Ketolysis in the Brain
Brain begins to use ketone bodies and derive up to two-thirds of its energy during prolonged starvation; Ketones are metabolized to Acetyl-CoA, Pyruvate Dehydrogenase is inhibited in the brain
Beta-Oxidation Enzymes (Odd)
- Propionyl-CoA Carboxylase
2. Methylmalonyl-CoA Mutase
Beta-Oxidation Enzymes (Monounsaturated)
Enoyl-CoA Isomerase
Beta-Oxidation Enzymes (Polyunsaturated)
Dienoyl-CoA Reductase
Non-Template Synthesis of Lipids
DHAP - > Phosphatidic Acid -> Diglyceride [+Acyl CoA] -> Triglyceride
Non-Template Synthesis of Polysaccharides
Hexokinase -> Phosphoglucomutase -> G1P UDP Transferase -> Glycogen Synthase
Ketogenesis Enzymes
HMG-CoA Synthase
HMG-CoA Lyase
Pyruvate Dehydrogenase Phosphotase
Activates PDH when ADP levels are high
Electron Transport Chain
Takes place on the matrix-facing surface of the inner mitochondrial membrane; creates a proton gradient that pumps protons into the ATP synthase in order to produce ATP
Complex I
[NADH-CoQ Oxidoreductase]
(4 Protons)
Transfers electrons from NADH -> FMN -> CoQ forming CoQH2
Complex II
[Succinate-CoQ Oxidoreductase]
(No Protons)
Transfers electrons from Succinate -> FAD -> CoQ forming CoQH2
Ketolysis in the Brain
Brain begins to use ketone bodies and derive up to two-thirds of its energy during prolonged starvation; Ketones are metabolized to Acetyl-CoA, Pyruvate Dehydrogenase is inhibited
Complex IV
[Cytochrome c oxidase]
(2 Protons)
Transfers electrons in the form of hydride ions from Cyt c to Oxygen forming Water
Transamination/Deamination
Loss of an amino acids amino group that allows the carbon skeleton to be used for energy
Malate-Aspartate Shuttle
Electrons transferred from NADH to Oxaloacetate, forming malate which crosses the inner mitochondrial membrane and transfers electrons to NAD+
Non-Template Synthesis of Lipids
DHAP - > Phosphatidic Acid -> Diglyceride [+Acyl CoA] -> Triglyceride
Flavoproteins
Function as specific electron acceptors for dehydrogenases
Cytochromes
Water soluble electron carries that contain iron pigments
Pyruvate Dehydrogenase Phosphotase
Activates PDH when ADP levels are high
Electron Transport Chain
Takes place on the matrix-facing surface of the inner mitochondrial membrane; creates a proton gradient that pumps protons into the ATP synthase in order to produce ATP
Chemiosmotic Coupling
Electron transfer is coupled to ATP synthesis via the proton electrochemical gradient
Complex II
[Succinate-CoQ Oxidoreductase]
(No Protons)
Transfers electrons from Succinate -> FAD -> CoQ forming CoQH2
Complex III
[CoQH2-cytochrome c Oxidoreductase]
(4 Protons)
Transfers electrons from CoQH2 -> Heme forming Cyt c
Complex IV
[Cytochrome c oxidase]
(2 Protons)
Transfers electrons in the form of hydride ions from Cyt c to Oxygen forming Water
F1 Portion of ATP Synthase
Uses energy released by the gradient to phosphorylate ADP into ATP
Malate-Aspartate Shuttle
Electrons transferred from NADH to Oxaloacetate, forming malate which crosses the inner mitochondrial membrane and transfers electrons to NAD+
NADPH
Reducing Agent that drives anabolic reactions
Flavoproteins
Function as specific electron acceptors for dehydrogenases
Cytochromes
Water soluble electron carries that contain iron pigments
Proton-Motive Force
Electrochemical gradient generated by the ETC across the inner mitochondrial membrane
MTC Intermembrane Space
Higher concentration of protons than the matrix; stores energy
Hormones that Regulate Metabolism
Insulin, Glucagon, Glucocorticoids (Cortisol), Catecholamines (Epinephrine and Norepinephrine), Thyroid Hormones
Uncoupling Reagents
Block oxidative phosphorylation by dissipating the electrochemical gradient
Glucagon Effects on Metabolism
- Increases rate of catabolic metabolism
- Increases blood glucose by stimulating gluconeogenesis, glycogenolysis
- Secreted by alpha cells of pancreas
Glucocorticoids Effects on Metabolism
Increase blood glucose in response to stress by mobilizing fat stores and inhibiting glucose uptake
-Increases the impact of glucagon and catecholamines
Catecholamines Effects on Metabolism
[Epinephrine and Norepinephrine]
Promotes glycogenolysis and increases basal metabolic rate through their sympathetic nervous system activity
Energetic Yield
- Glycolysis
- PDH
- CAC
Glycolysis [2 NADH + 2 ATP]
PDH [2 NADH]
CAC [6 NADH, 2 FADH2, 2 GTP]
NADH ATP Yield
2.5 ATP per NADH
FADH2 ATP Yield
1.5 ATP per NADH
Optimal ATP yield per Glucose
30-32 ATP
Postprandial State
Well fed, insulin secretion is high and anabolic metabolism is high
Postabsorptive State
Fasting, insulin secretion decreases while glucagon and catecholamine secretion increases; transition to catabolic metabolism
Hormones that Regulate Metabolism
Insulin, Glucagon, Glucocorticoids (Cortisol), Catecholamines, Thyroid Hormones
Brain & Nervous Tissue Metabolism
Consumes glucose mostly but in prolonged fasting, ketone bodies are used.
Glucagon Effects on Metabolism
- Increases rate of catabolic metabolism
- Increases blood glucose by stimulating gluconeogenesis, glycogenolysis
- Secreted by alpha cells of pancreas
Glucocorticoids Effects on Metabolism
Increase blood glucose in response to stress by mobilizing fat stores and inhibiting glucose uptake
-Increases the impact of glucagon and catecholamines
Catecholamines Effects on Metabolism
[Epinephrine and Norepinephrine]
Promotes glycogenolysis and increases basal metabolic rate through their sympathetic nervous system activity
Thyroid Hormones
[T3 & T4]
Modulates the impact of other metabolic hormones and have a direct impact on basal metabolic rate
-T3 is more potent than T4
Liver Metabolism
Responsible for maintenance of blood glucose levels by glycogenolysis and gluconeogenesis in response to pancreatic hormone activity; also processes lipids and cholesterol, bile, urea and toxins
Adipose Tissue Metabolism
Stores lipids under the influence of insulin and releases them under the influence of epinephrine
Skeletal Muscle Metabolism [Resting]
Conserves carbohydrates in glycogen stores and uses free fatty acids in the blood stream
Skeletal Muscle Metabolism [Active]
Anaerobic Metabolism, OXPHOS, Direct phosphorylation from creatine phosphate or beta oxidation
Cori Cycle
Lactate -> Gluconeogenesis -> Glucose
Between Liver & Muscle
Cardiac Muscle Metabolism
Uses fatty acid oxidation, uses creatine phosphate
Brain & Nervous Tissue Metabolism
Consumes glucose mostly but in prolonged fasting, ketone bodies are used.
Hormones that regulate body mass
Leptin, Ghrelin & Orexin
