Chapter 12: Bioenergetics and Regulation of Metabolism

Question 1

Biological Systems.

Answer 1

They’re considered open systems because they exchange both energy and matter with the environment. Energy is exchanged in the form of mechanical work when something is moved over a distance or is heat energy. Matter is exchanged through food consumption and elimination as well as respiration.

Question 2

Internal energy.

Answer 2

Some of all of the different interactions between and within atoms in the system; Vibration, rotation, linear motion, and stored chemical energies all contribute.

Question 3

Closed system.

Answer 3

Most biochemical studies are performed on the cellular subcellular level rather than the entire Organism. These systems are considered closed because there are no exchange of matter within the environment. Because the system’s closed, the changing internal energy can only come in the form of work or heat. This can be expressed mathematically through the first law of thermodynamics. Working thermodynamic refers to changing pressure and volume. These are constant in most living systems, so the quantity of interest in determining internal energy is heat.

Question 4

Bioenergetics

Answer 4

Term used to describe energy States and biological system.

Question 5

Entropy

Answer 5

Measure the degree of disorder or energy dispersion in the system. It carries the units of J/K.

Question 6

Enthalpy

Answer 6

Measure the overall change in heat of the system during a reaction.

Question 6

Free energy.

Answer 6

ΔG = ΔH - TΔS

Spontaneous reactions proceed in the forward direction, exhibit a net loss of free energy, and therefore have a negative ΔG. Non spontaneous reactions exhibit a net gain of energy and have the positive ΔG. Free energy approaches 0 as the reaction proceeds in equilibium.

Question 7

Physiological Conditions.

Answer 7

ΔG= ΔG ° + RTln(Q)

Standard free energy ΔG ° Is the energy that occurs at standard concentration of 1M, pressure of 1 ATM and temperature of 25°C. The modified standard state is that [H+]=10^-7 and the pH is 7. ΔG ° Is giving the special symbol ΔG °’ Indicating that it is standardized to neutral buffers used in biochemistry.

Question 8

Which is the preferred long term energy storage?

Answer 8

fat

Question 8

What does ATP stands for?

Answer 8

Adenosine triphosphate.

Question 8

A complete combustion of fat results in how much energy?

Answer 8

9 kcal/g

Question 9

Complete combustion of Carbohydrates?

Answer 9

3kcal/g

Question 10

How is ATP formed?

Answer 10

From substrate level phosphorylation as well as oxidative phosphorylation. Most of the ATP cells produced by mitochondrial ATP synthase. But some ATP is produced during glycolysis and the citric acid cycle. Is generated from ADP and Pi.

Question 11

How much energy does ATP provide?

Answer 11

30.5kJ/mol

Question 12

Difference between ATP, ADP and AMP

Answer 12

ATP is consumed either through Hydrolysis or the transfer of phosphate group to another molecule. If one phosphate group is removed, adenosine diphosphate (ADP) produce. If two phosphate groups are removed, adenosine monophosphate (AMP) is produced.

Question 13

What is more stable, ADP or ATP?

Answer 13

The negative charges on the phosphate groups experience repulsive forces within another in ADP and P molecules that form after hydrolysis are stabilized by resonance.

Question 13

Hydrolysis and coupling.

Answer 13

ATP hydrolysis is most likely to encounter in the context of coupled reactions. Many coupled reactions use ATP as an energy source. ATP cleavage is the transfer of high energy phosphate group from ATP to another molecule. Generally, this activates or inactivates the target molecule. With this phosphoryl group transfer, the overall free energy reaction will be determined by taking the sum of the free energies of the individual reactions.

Question 14

Half reactions.

Answer 14

Divide oxidation reduction reactions into their half reactions component to determine the number of electrons being transferred.

Question 15

Electron carriers.

Answer 15

High energy electron carriers, these are Soluble and include NADH, NADPH, FADH2, ubiquinone, cytochromes, and glutathione. As electrons are passed down the electron transport chain, they give up free energy to form proton motive force across the inner mitochondrial membrane. Membrane bound electron carriers embedded within the end of mitochondrial membrane.

Question 16

Flavoproteins

Answer 16

Container a modified vitamin B or riboflavin. They function as coenzymes for enzymes in the oxidation fatty acids, the decarboxylation of fire and the reduction of glutathione.

Question 16

Metabolic States.

Answer 16

Biochemist seeks a state of homeostasis, is a Physiological tendency towards a relative stable state that is maintained and adjusted, often with the expenditure of energy. It is different from equilibrium, which allows us to store potential energy.

Question 17

Postprandial (absorptive ) state.

Answer 17

It is also called the absorptive or well fed state. Occurs shortly after eating. These days marked by greater anabolism and full storage than catabolism. You generally last three to five hours after eating a meal. Just after eating, blood glucose level rise and stimulate the release of insulin. The three major target tissues for insulin are delivered muscle and adipose tissue. Insulin promotes glycogen synthesis in the liver and muscle. After the glycogen stores are filled, the liver converts excess glucose to fatty acids and triglycerides. Most of the energy needs of the liver and met by oxidation of excess amino acids. Nervous tissues and red blood cells are notably insensitive to insulin. Nervous tissue derives energy from oxidizing glucose to CO2 and water in both well fed and normal fasting stages. Red blood cells can only use glucose anaerobically.

Question 18

Post absorptive (fasting) state.

Answer 18

Glucagon, cortisol, epinephrine, non epinephrine, and growth hormones oppose the action of insulin. These remains are sometimes termed counterregulatory hormones because of their effects on skeletal muscle, adipose tissue and liver. In the liver, glycogen degradation and the release of glucose into the blood are simulated. Hepatic glucose genesis is also stimulated by Glucagon, but the response is lower than of glycogenolysis. Amino acids and fatty acids can provide the necessary carbon skeleton and make energy required for gluconeogenesis.

Question 18

Prolonged fasting, (Starvation)

Answer 18

levels of Glucagon and epinephrine are markedly elevated during starvation. There’s a rapid degradation of glycogen storages in the liver. After about 24 hours, gluconeogenesis is the predominant source of glucose for the body. Lipolysis is rapid, resulting in an excess ascetical aid that is used in the synthesis of ketone bodies. After several weeks of fasting, the brain derives approximately 2/3 of its energy from ketones and 1/3 from glucose. This shift from glucose to ketones as a major fuel reduces the quantity of amino acids that must be degraded to support gluconeogenesis, which spares proteins that are vital for function.

Question 19

Water soluble peptide hormones.

Answer 19

Able to rapidly adjust the metabolic process of cell via second messenger cascades.

Question 20

Fat soluble amino acid derivative hormones.

Answer 20

Like thyroid hormones and steroid hormones like cortisol enacts longer range effects by exerting regulatory actions at the transcriptional level. Hormones are regulated by feedback loops with other endocrine structures such as the hypothalamic pituitary axis.

Question 21

Insulin.

Answer 21

It’s a peptide hormone secreted by beta cells of the pancreatic islets of Langerhans. Glucose is absorbed by peripheral tissues via facilitated transport mechanism that utilize glucose transporter located in the cell membrane. The tissues that require insulin for effective uptake of glucose are adipose tissue and resting skeletal muscle.

Question 22

What happens when insulin increases?

Answer 22

Glucose and triacylglycerol uptake by fat cells. Lipoprotein lipase activity which clears VLDL, and chylomicrons from the blood. Triacylglycerol synthesis in adipose tissue.

Question 23

What is the normal glucose insulin in the blood?

Answer 23

5.6 mM

Question 23

What happens when insulin decreases?

Answer 23

Triacylglycerol breakdown in adipose tissue. Formation of ketone bodies by the liver.

Question 24

Glucagon.

Answer 24

Peptide hormone secreted by the alpha cells of the patriotic islets of Langerhans. The primary target for Glucagon action is the hepatocyte. Glucagon acts through second messengers to cause the following effects: Increase liver glycogenolysis. Glucagon activates glycogen phosphorylase and inactivates glycogen synthase. Increased liver glycogenesis. Logon promotes the conversion of pyruvate to phosphoenolpyruvate by pyruvate carboxylase and phosphoenolpyruvate carboxykinase. Increased liver ketogenesis and decreased lipogenesis.

Question 25

What types of amino acid promotes secretion of Glucagon?

Answer 25

Amino acid, especially basic amino acids like arginine, lysine, histidine.

Question 26

Functional relationship of Glucagon and insulin.

Answer 26

Enzymes that are phosphorylated by Glucagon are generally dephosphorylated by insulin; enzymes that are forced formulated by insulin are generally dephosphorylated by Glucagon.

Question 27

Glucocorticoids

Answer 27

They are from the adrenal cortex. Glucocorticoids, especially cortisol, are secreted with many forms of stress, including exercise, cold and emotional stress. Cortisol is a steroid hormone that promotes the mobilization of energy stores through the degradation and increased delivery of amino acids and increased lipolysis. Cortisol also elevates blood glucose levels, increasing glucose availability for neurons tissues through 2 mechanisms. First, cortisol inhibits glucose uptake in most tissues and increase hepatic output of glucose via gluconeogenesis, from amino acids. 2nd, cortisol has a permissive function that enhances the activity of Glucagon, epinephrine, and other catecholamines.

Question 28

What does adrenal cortex produce?

Answer 28

Sarod hormones like glucocorticoids, mineralocorticoids, and sex hormones.

Question 28

What does the adrenal medula produce?

Answer 28

Catecholamines.

Question 29

Catecholamines

Answer 29

Are secreted by the adrenal medula and include epinephrine and non epinephrine, also known as adrenaline and non adrenaline. Catecholamines increase the activity of the liver and muscle glycogen phosphorylase, thus promoting glycogenolysis. Catecholamines act on adipose tissue to increase lipolysis by increasing the activity of hormone sensitive lipase. Epinephrine also acts directly on target organs like the heart to increase the basal metabolic rate through the sympathetic nervous system.

Question 30

Thyroid hormones.

Answer 30

Thyroid hormones increase the basal metabolic rate, as evidenced by increased O2 consumption and heat production when they are secreted. The increasing metabolic rate produced by a dose of thyroxine T4 occurs after a latency of several hours but may last for several days, while triiodothyronine T3 produces a more rapid increase in metabolic rate and has a shorter duration of activity. T4 can be thought of as the precursor for T3. Thyroid hormones have their primary effect in lipid and carbohydrate metabolism. They accelerate cholesterol clearance from the plasma and increase the rate of glucose absorption from the small intestine. Insufficient thyroid hormone levels (hypothyroidism) can cause symptoms including cold intolerance, fatigue, weight gain, and depression as metabolism suffers. Excessive thyroid hormone levels (hyperthyroidism) can cause rapid weight loss, anxiety and fever.

Question 31

What does the muscle lack?

Answer 31

Glucose 6 phosphatase, which means that glucose cannot be released by skeletal muscle into the bloodstream. Instead, it is metabolized by the muscle tissue itself.

Question 32

Liver

Answer 32

Synthesize ketones when excess fatty acids are being oxidized. Hepatocytes responsible for the maintenance of blood glucose levels by glycogenolysis and glycogenesis in response to pancreatic hormone stimulation.

Question 33

Adipose tissue.

Answer 33

Stores lipids under the influence of isoline and release them under the influence of epinephrine. During fasting states, decrease levels of insulin. Increased epinephrine activate hormone sensitive lipase in fat cells, allowing fatty acids to be released into circulation.

Question 34

Skeletal muscle metabolism.

Answer 34

Resting muscle conserves carbohydrates and glycogen stores and uses free fatty acids from the bloodstream. Active muscle may use anaerobic metabolism, oxidative phosphorylation of glucose to Raphaelian from creatine phosphate, or fatty acid oxidation depending on fiber and type of exercise duration.

Question 35

Cardiac Muscle.

Answer 35

It uses fatty acid as the preferred fuel in the well fed state and fasting states.

Question 36

Brain

Answer 36

Fatty acids cannot cross the blood brain barrier and therefore not used at all as an energy source. The brain relies on blood glucose supply by either hepatic glycogenolysis or glycogenesis. Only doing prolonged fasting does the brain gain the capacity to use ketone bodies for energy.

Question 37

Respirometry.

Answer 37

Allows accurate measurement of the respiratory quotient, which differs depending on the fields being used by the Organism. Their respiratory quotient (RQ), can be major experimentally, and can be calculated as:
RQ=CO2 produced/O2 consumed

Question 38

Calorimeters

Answer 38

Can measure basal metabolic rate based on heat exchange with the environment.

Question 39

Body mass regulation.

Answer 39

The hormones leptin, ghrelin and orexin are as well as the receptors play a role in body mass. Long term changes in body mass result from changes in lipid storage. Changes in conception or activity must surpass a threshold to cause weight change. The threshold is lower for weight gain than for weight loss. Body mass can be measured and tracked using the body mass index (BMI):

BMI= mass/ height^2

Question 39

Leptin

Answer 39

Hormone secreted by a fat cell that decreases appetite by suppressing orexin production.

Question 40

Orexin

Answer 40

Increases appetite and is also involved in alertness and the sleep wake cycle.

Question 41

Ghrelin

Answer 41

Secreted by the stomach in response to signals of the impending mule, it increases the appetite and also stimulates secretion of orexin.

Question 42

Different metabolic processes occur in the mitochondria and cytosol of a cell:
Mitochondria

Answer 42

Contain many metabolic pathways, including:
Electron transport chain: Occurs in the mitochondrial membrane
Oxidative phosphorylation: Occurs in the inner mitochondrial membrane
Citric acid cycle: Occurs in the mitochondrial matrix
Beta oxidation: Occurs in the matrix
Some steps of amino acid breakdown: Occurs in the matrix

Question 43

Different metabolic processes occur in the mitochondria and cytosol of a cell:
Cytosol

Answer 43

Glycolysis: The first step of cellular respiration
Pentose phosphate pathway
Fatty acid biosynthesis
Glycogen synthesis
Some steps of amino acid breakdown
Protein synthesis and degradation
Stress response signaling
Carbon metabolism
Biosynthesis of secondary metabolites
Accumulation of enzymes for defense and detoxification