Title: Jack Sparrow Biochem / Biochemistry / Biochemistry Chapter 12
Tags: #JackSparrow::#B/B::#Biochemistry::#Chapter.12

Q: Biological systems are often considered [closed, open, or isolated systems?]
A: open
Extra: Think about it!  We definitely exchange energy with the environment and mass.  We're losing and gaining weight all the time.

Q: Why do we use heat to determine the energy change of cells?
A: As you recall, U = Q + W.
W only changes when the pressure and the volume of the cell change, which is basically never.
Heat on the other hand is getting messed with all the time because of the chemical reactions in the cell.
So, it just makes more sense to use heat.

Q: What is bioenergetics?
A: The study of energy states in biological systems.

Q: The more negative the Delta G of a biological reaction the more [favorable or unfavorable?] the reaction.
A: favorable

Q: Can we use Standard Thermodynamic properties to calculate the thermodynamics of biological systems?
A: No!  Remember, standard conditions are 25 degrees C, 1 M, and pressure of 1 atm.  The body is basically never in this state, and as such, the modified Delta G equation must be used in the body.

Q: Describe the relative energy richness of fats, ketones, proteins, and carbohydrates.
A: Ketones, proteins, and carbohydrates all have an energy densitry of 4kcal/g.
Fats on the other hand have an energy density of 9kcal/g.
This is why fats are our storage form of energy, they are dense and we can pack a lot of energy into a little bit of fat!

Q: Why does ATP make such a good energy molecule?
A: ATP is not too high energy, which means that the hydrolysis of its phosphate releases enough heat to drive most important reactions, but not a crazy high amount of heat where all the extra heat just gets wasted.

Q: How does ATP drive reactions forward?
A: ATP provides heat in the form of energy released when its phosphate is cleaved.  This free energy pushes nonfavorable reactions forwward.

Q: What is homeostasis?
A: Homeostasis is the physiologically tendency to push towards a balanced state as opposed to a large surplus or deficit of any type.

Q: What are the three main metabolic states?
A: 1.  Postprandial (well-fed) state.
2.  Postabsorptive (fasting) state.
3.  Starving state.

Q: Describe the metabolic changes associated with the Postprandial state.
A: This state is marked by greater anabolism than catabolism.  It is also marked by increased blood sugar, which leads to an increase in insulin.  Insulin leads to glycogen synthesis in the liver and muscle.  Once gylcogen stores are filled, excess glucose is further converted into fatty acids and triacylglycerols in the liver.  In the muscle, insulin stimulates the production of proteins from excess glucose.

Q: What are the two main insulin-insensitive tissue types?
A: 1.  Blood
2.  Nervous tissue

Q: What are counterregulatory hormones?
A: The counterregulatory hormones are a group of hormones that have the opposite effect of insulin on muscle, liver, and adipose tissue.  These hormones are Glucagon, Epinephrine, cortisol, and growth hormone.

Q: Describe the metabolic changes associated with the Postabsorptive state.
A: In the postabsorptive state, glycogen is degraded in the liver and released into the blood to fuel other tissues.  Gluconeogenesis in the liver also helps to make glucose for the body, albeit much more slowly and over time.
The release of amino acids from proteins and fatty acids from adipose tissue are both stimulated by the decrease in insulin and the presence of counterregulatory hormones.  Again, the point is to make glucose so these get shuttled to gluconeogenic pathways in the liver.

Q: Describe the metabolic changes associated with starving.
A: The major change in metabolism when you are starving is the focus on burning fats and the switch to the creation of ketone bodies.  Glucagon and catecholamine secretion is higher than ever due to the low level of sugar in the blood.

Q: What are the two forms of metabolism?
A: 1.  Catabolism
2.  Anabolism

Q: What is catabolism?
A: Breaking things down

Q: What is anabolism?
A: Building things up

Q: How does insulin affect different macromolecule metabolism?
A: For Carbohydrates, insulin increases uptake of glucose and increases carbohydrate metabolism.
For Proteins, insulin increases uptake of amino acids in the cells for use in protein synthesis.
For Fats, insulin increases triacylglycerol uptake and triacylglycerol synthesis in the liver and adipocytes.  Insulin also decreases the breakdown of fats and the formation of ketone bodies in the liver.

Q: How does Glucagon affect different macromolecule metabolism?
A: Glucagon is much more focused on liver cells than insulin.
Glucagon increases the breakdown of glycogen in the liver.  It also increases gluconeogensis, ketogenesis, and break down of fats in the liver for energy.

Q: What effect do the glucocorticoids have on metabolism?
A: Remember, cortisol's purpose is to increase blood glucose levels.  All these effects can rationalized just because they are all things that lead to more sugar in the blood.
Cortisol blocks uptake of sugar by cells.
Cortisol increases gluconeogenesis in the liver, especially the gluconeogenesis associated with breaking down proteins.

Q: What effects do catecholamines have on metabolism?
A: Remember, epinephrine and norepinephrine's purpose is to increase blood glucose levels.  All these effects can rationalized just because they are all things that lead to more sugar in the blood.
Epinephrine promotes the breakdown of glycogen.
Epinephrine also promotes the breakdown of fats.
Epinephrine also acts directly on target organs such as the heart to actually increase the basal metabolic rate.

Q: What effect do thyroid hormones have on metabolism?
A: Thyroid hormones are permissive hormones, which means they are basically kept at a constant level all of the time.  The presence of thyroid hormones increases the basal metabolic rate.
Specifically, Thyroxine (T4) increases metabolic rate after a latent period of several hours.  This increases lasts for a few days.
Triiodothyronine (T3) produces a rapid increase in metabolic rate that is short lived.

Describe the major differences in the fuel sources used by different tissues in times of feeding and fasting.

Q: What is respirometry?
A: Respirometry is a method that is used to determine how exactly a person's metabolism is operating.
This is accomplished by calculating the Respiratory Quotient for an individual or a specific tissue.  The Respiratory Quotients for Carbohydrates, Lipids, and amino acids are different, which means that you can use this number to determine what kind of metabolism is going on in a tissue.

Q: What is Basal Metabolic Rate?
A: Basal metabolicrate is the amount of energy used by an animal per unit of time while they are resting.  This is considered to be the basic amount of energy an animal needs to expend to live and exist.

Q: What are the main hunger and satiety hormones?
A: 1.  Ghrelin
2.  Orexin
3.  Leptin

Q: Describe Ghrelin
A: Ghrelin is secreted by the stomach in response to signals of an impending meal.  Ghrelin increases appetite and stimulates secretion of Orexin.

Q: Describe Orexin
A: Orexin is a hormone that further increases appetite.  It is also involved in alertness and the sleep-wake cycle.  Low blood sugar and ghrelin release are both stimulators of Orexin release.

Q: Describe Leptin
A: Leptin is a hormone secreted by fat cells that decreases appetite by suppressing orexin production.

Q: What are the RQ's for different fuel sources?
A: 1.  Carbohydrates - Around 1.0
2.  Lipids - Around 0.7
3.  Amino Acids - Around 0.8-0.9