Bioenergetics and Regulation of Metabolism Flashcards
Chapter Outline
1. Thermodynamics and bioenergetics
I. Biological Systems
II. Enthalpy, entropy, and free energy
III. Physiological conditions
2. The role of ATP
I. ATP as an energy carrier
II. Hydrolysis and coupling
III. Phosphoryl group transfer
3. Biologial oxidation and reduction
I. Half reactions
II. Electron carriers
A. Flavoproteins
4. Metabolic States
I. Postprandial/absorptive state
II. Postabsorptive/fasting state
III. Prolonged fasting/Starvation
5. Hormonal Regulation of metabolism
I. Insulin & glucagon
II. Glucocorticoids
III. Catecholamines
IV. Thyroid hormones
6. Tissue specific metabolism
I. Liver
II. Adipose tissue
III. Seletal muscle
IV. Cardiac muscle
V. Brain
7. Integrative Metabolism
I. Analysis of metabolism
II. Regulation of body massThermodynamics Systems Involved in Biology
- Open Systems
I. Systems that involve exchange of
1. Energy
I. Mechanical work
II. Heat
2. Matter
I. Food ingestion
II. Food Elimination
III. Respiration
II. Systems involved in organisms as a whole - Closed Systems
I. Systems that involve exchange of
1. Energy
I. Work
II. Heat
In closed systems, internal energy can be easily measured
Internal Energy
U
Sum of all of the interactions b/w and within a cell
examples:
1. rotation
2. linear motion
3. vibration
Formula:
Delta U = Q - W
Work in Thermodynamics
work=−PΔV
involve change in pressure and volume
Bioenergetics
Concept that describes changes in energy states of biological systems
Gibs Free Energy; Enthalpy; Entropy
1: Gibbs free energy: ΔG:
I. measure of spontaneity of a chemical rxn in
a biological system
2. Enthalpy: ΔH:
I. measure of change in heat during a rxn
3. Entropy: ΔS:
I. measure of disorder and energy dispersal
of a rxn
Formula that relates ΔG, ΔH, & ΔS
ΔG= ΔH - TΔS
ΔG Under Standard Vs. Nonstandard Conditions
- Nonstandard: ΔG= ΔH - TΔS
- Standard: ΔG= ΔG* + RT* ln (Q)
* *************
1. R= universal gas constant
2. Q=reaction quotient
3. T= temperature
ATP
- Name:
I. Adenosine Triphosphate - Identity:
I. Energy currency in the body
II. Provides 30kj/mol of energy - Generating pathways:
I. Substrate level phosphorylation
II. Hydrolysis
III. Oxidative phosphorylation
IV. Glycolysis [minor]
V. Citric acid cycle [indirect-from GTP] - Significance
I. Contains high-Energy p-bond that can be cleaved
and transferred to
1. provide energy for
1. coupled rxns
2. unfavorable, energy costing rxns
2. activate or deactivate enzymes
ATP synthesis is a continuous recycling process of ADP and P*
Coupled Rxns
2 reactions taking place simultaneously with one reaction providing the energy source for the other reaction
Hydrolysis
Break down of a molecular bond using water as a reactant
Half Reactions
Separated oxidation or reduction part of a reaction useful for keeping track of electron movements
Electron Carriers
I. Identity:
I. Molecules that carry electrons to ETC and that
lose their energy to the proton motive force to
contribute to ATP production through oxidative
phosphorylation
II. Types:
1. Soluble
1. NADH
2. NADPH
3. FADH2
4. cytochrome
5. glutathione
2. inner-Mitochondrial-membrane-bound
1. flavoprotein
I. contain modified Vit B2 or riboflavin
II. Types:
A. FMN [flavin mononucleotide]
I. contains cluster of Fe-S
II. bonds to ETC’s complex I
III. nucleic acid derivative
B. FDN [flavin dinucleotide]
III. Function
1. electron carriers in
1. Mitochondria
2. Chloroplast
2. activators of modified riboflavins
3. coenzymes for enzymes involved in
1. beta-oxidation
2. pyruvate decarboxylation
3. glutathione reduction
Metabolic States
- Postprandial/Absorptive State
I. 3-5 hrs following a meal
II. Rate of anabolism > rate of catabolism
III. Insulin secretion is high - Postabsorptive
I. 5-17 hrs after a meal
II. Release of counterregulatory hormones
III. Marked by
1. Glycogenolysis
2. Hepatic gluconeogenesis
I. uses
1. amino acids from muscles
2. fatty acids from adipose
tissues - Prolonged fasting [starvation]
I. Markedly high levels of
1. glucagon
2. epinephrine
II. High levels of
1. Hepatic gluconeogensis
A. for cells with few mitochondria
*ex: red blood cells
2. Beta-oxidation
A. for muscle consumption
3. Ketone synthesis
A. for brain consumption
**After weeks of starvation, brain cells procure 2/3 of their energy from ketone bodies and 1/3 from glucose produced through gluconeogenesis
Target Tissues for Insulin
- Liver
- Muscles
- Adipose Tissue
Processes Following Food Intake
- Digestion
- Nutrient uptake to the liver through the hepatic portal vein
- Insulin release
- Glycogen synthesis in liver and muscles
- Triacylglycerol synthesis in adipose tissues after glycogen stores have been filled
- Protein synthesis in muscles
- Glucose entry into muscles and adipose tissues
Cell Types Insensitive to Insulin
- Nervous Tissues
1. Drive energy by oxidizing glucose to CO2
and H2O
unless in the starvation state* - Erythrocytes
1. drive their energy through anaerobic
glycolysis regardless of metabolic state - Kidney tubules
- Intestinal mucosa
- Pancreatic Beta-Cells
Counterregulatory Hormones
- Glucagon
- Cortisol
- Epinephrine
- Norepinephrine
- Growth hormone
Hormones that oppose action of insulin*
Hormonal Regulation of Metabolism
- Insulin
I. Peptide hormone
II. secreted by pancreatic B-cells of langerhans
III. acts via facilitated diffusion & 2nd messengers
IV. Affect muscle and adipose tissues
V. Effect:
1. increases glucose & amino acid uptake
2. increases glycogen storage
3. increases glucose and fat metabolism - Glucagon
I. Peptide hormone
II. secreted by pancreatic alpha-cells
III. act via 2nd messengers
IV. Target hepatocytes
V. Effects:
1. increase the following hepatic pathways:
1. glycogenolysis
2. gluconeogenesis
3. ketogenesis
4. lipolysis
2. decrease hepatic lipogenesis
VI. Regulators:
1. stimulator:
A. hypoglycemia
2. basic amino acids: lysine, arginine
3. protein-rich meal
2. inhibitor:
A. hyperglycemia - Glucocorticoids
I. Steroid hormones released in response to stress
II. released from adrenal cortex
III. Target hepatocytes
IV. Effects:
1. Contribute to stress response
I. release of cortisol
2. Mobilize fat and protein energy stores;
breakdown & deliver amino acids and
lipids to the liver for gluconeogenesis
3. Inhibit glucose reuptake by
I. muscles
II. fat
III. lymphoid tissues
4. promote hyperglycemia by promoting
I. catecholamines
II. glucagon
III. epinephrine - Catecholamines
I. Epinephrine/Adrenaline &
Norepinephrine/noreadrenaline
II. Secreted by adrenal medulla
III. Target
1. hepatocytes
I. increase glycogenolysis
2. skeletal muscle cells
I. increase glycogenolysis for the
muscle cell metabolism
3. adipose tissues
I. increase lipolysis of adipose tissues
by increasing activity of hormone-
sensitive lipase
4. cardiac tissues
I. increase basal metabolic rate of
heart through epinephrine
release/sympathetic NS regulation
associated w/ adrenaline rush - Thyroid Hormone
I. Nucleic Acid-derivative Hormone
II. Secreted by the thyroid gland & Hypothalamus
III. Types:
I. T3
1. stimulating hormone of T4
2. quick yet short-living effect
II. T4
1. hormone stimulated by T3
2. latent yet long-lasting effect
relatively constant levels at all times
IV. Effects
I. increase basal metabolic rate of
1. carbohydrates
2. lipids
II. increase glucose absorption rate from
intestine
III. clear cholesterol from the plasma
Various Categories of Hormones
- Water Soluble Peptide Hormones
1. insulin
2. act quickly via second messenger cascade - Steroid Hormones
1. cortisol
2. slow to exert effect b/c of transcriptional
regulation - Amino-Acid Derivative Hormones
1. thyroid hormone
2. slow to exert effect b/c of transcription
regulation involvement
Steroid Hormones
- glucocorticoids
- mineralocorticoids
- sex hormones
Hormones Released by Adrenal Cortex & Adrenal Medulla
- Adrenal Cortex:
I. Steroid hormones - Adrenal Medulla:
I. Catecholamines
Deiodonase
Enzyme that converts T4 to T3 by removing an iodone from T4
Major Sites of Metabolic Activity in the Body
- Brain
- Cardiac tissue
- Skeletal tissue
- Adipose Tissue
- Liver
Liver-Specific Metabolism
I. Functions
1. Maintenance of constant blood glucose levels
I. Well-fed state
1. glycogenesis
2. fatty-acid synthesis
i. from excess blood glucose
that is converted to acetyl-
CoA
ii. get released in blood asVLDL
2. Post-absorptive & fasting states
1. glycogenolysis
2. gluconeogenesis
i. contributing reactants:
1. lactate from anaerobic
glycolysis
2. glycerol from
triacylglycerol
3. ketogenic amino-acids
**Following a meal, amino acid metabolism provide hepatic energy*********
2. Ketogenesis during periods of excess beta-
oxidation
Adipose Tissue Metabolism
I. Well-fed state
1. increased glucose uptake
2. fatty acid uptake from
VLDL/Chylomicrons and its re-
esterification in triacylglycerol storages
2. Fasting State
1. fatty acid release from adipose tissues
into circulation following epinephrine
activation of hormone sensitive lipase
Skeletal Muscle Metabolism
I. Resting Muscle
1. Well-fed state
1. muscular glucose uptake
2. Muscular amino acid uptake for
protein synthesis
3. Glycogenesis
4. glycolysis and beta-oxidation
2. Fasting State
1. oxidation of circulating free-fatty
acids for energy
3. Prolonged Fasting State
1. oxidation of ketone bodies
II. Active Muscle
1. short-bursts of high intensity exercise
1. oxidation of glycogen stores
A. anaerobic glycolysis
2. beta-oxidation of triacylglycerol store
3. creatine phosphate
2. High-intensity, continuous exercise
1. glycogen stores deplete
2. beta-oxidation continues
rate of exercise declines at rate that
can be supported by beta-oxidation
Cardiac Muscle Metabolism
- Well-fed state
1. fatty-acid oxidation - Prolonged fasting-state
1. fatty acid oxidation
2. ketone body metabolism
In cases of cardiac illnesses like CHF, glucose oxidation increases and B-oxidation falls****
Otherwise, the heart always prefers beta-oxidation***
Brain Metabolism
- Well-fed State
1. Glucose only
* Fatty acid does not cross brain’s blood barrier*** - Fasting State
1. glucose from
1. glycogenolysis
2. gluconeogenesis - Prolonged-Fasting State
1. 1/3 glucose
2. 2/3 ketone bodies
when hypothalamus senses hypoglycemia, it triggers glucagon and epinephrine release**
Basal Metabolic Rate or BMR
The amount of energy required for one sedentary day
- measured by calorimetry
- predicted by
1. age
2. gender
3. weight
4. height
Factors Responsible for Weight Control
- Diet
- Exercise
- Socioeconomic Status
- Geography
- Genetics
Hormones that Regulate Hunger and Satiety
- Ghrelin
1. secreted by:
I. stomach
2. stimulators:
I. sight
II. taste
III. sound
IV. smell of food- Functions
I. increase appetite
II. stimulate orexin release
- Functions
- Orexin
- Stimulators:
I. hypothalamus signal
II. ghrelin release - Functions
I. sleep-wake cycle
II. increases alertness
III. increases appetite
- Stimulators:
- Leptin
1. Secreted by:
I. adipocytes- Functions:
I. decreases appetite
II. suppresses orexin production
- Functions:
Body Mass Index
1. Formula:
Mass/Height^2
2. Range of values
1. normal 18.5-20
2. overweight: 20-25
3. Obese: >30Respirometry
Device that allows accurate measurement of respiratory quotient
Respiratory Quotient
Formula:
RQ= CO2 produced / O2 consumed
***varies depending on
1. Type of fuel used
2. Starvation
3. Exercise
4. Stress
Types & levels
1. RQ of carbs: 1
2. RQ of lipids: 0.7
3. RQ in resting individuals: 0.8
i. significance:
1. consumption of both carbs & lipidsCalorimetry
Device that measures BMR
pg 420
