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MCAT Biochem > Biochem #12 > Flashcards

Biochem #12 Flashcards

1
Q

biological systems can be _____

A

open or closed

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2
Q

open system

A

exchange both energy and matter with the environment.
 Energy is exchanged as mechanical work or heat energy.
 Matter is exchanged through food consumption and elimination and respiration.

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3
Q

closed system

A

what biological studies are oftentimes done on: no exchange of matter with the environment.

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4
Q

internal energy

A

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

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5
Q

bioenergetics

A

describes energy states in biological systems.

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6
Q

free energy (deltaG)

A

tell us about chemical reactions and predict if they will be favorable.

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7
Q

enthalpy (delta H)

A

measures the overall change in heat of a system during a reaction.
 At constant T and P, deltaH and Q are equal.

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8
Q

entropy (delta S)

A

measure the degree of disorder or energy dispersion in a system.

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9
Q

delta G and spontaneity

A

negative delta G, Keq > 1

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10
Q

Hormonal controls are ____, such as the modification of the enzymes of glycogen metabolism by insulin and glucagon.

A

covalent

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11
Q

Adipose tissue and resting skeletal muscle require ____ for glucose uptake. Active skeletal muscle uses creatine phosphate and glycogen (regulated by epinephrine and AMP) to maintain its energy requirements.

A

insulin

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12
Q

The brain uses_______ exclusively and therefore is very sensitive to oxygen levels.

A

aerobic metabolism of glucose

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13
Q

what occurs during a prolonged fast

A

Prolonged fast: enzyme phosphorylation and dephosphorylation, then glycogen storage is haulted, then ketone bodies are used by the brain and proteins are broken down as an energy source.

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14
Q

No work is performed in a ____ because pressure and volume remain constant.

A

closed biological system

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15
Q

compare standard free energy to modified standard state

A

o Standard free energy (ΔG˚) is the energy change that occurs at 1 M, 1 atm, and temperature of 25 C.
o Modified standard state (ΔG˚’): pH is 7, [H+] = 10-7
 General trend:
• Reactions with more products will have a more negative delta G, while reactions with more reactants will have a more positive deltaG.

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16
Q

compare the energies of breaking down fats and sugars

A

fats are much more energy rich than carbohydrates

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17
Q

how is ATP formed?

A

Formed from substrate level phosphorylation and oxidative phosphorylation.

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18
Q

why is it beneficial that ATP is a mid-level energy carrier?

A

It is a mid-level energy carrier which is beneficial because ATP cannot get back the ‘leftover’ free energy after a reaction. If it carried more energy than it would be wasting more with each reaction.

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19
Q

ATP provides around ______ of energy

A

30 kJ/mol

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20
Q

what are the two conditions in which ATP is formed?

A

o ATP is generated from ADP and Pi via an exergonic reaction or electrochemical gradient

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21
Q

how is ATP broken down?

A

o ATP is consumed through hydrolysis or the transfer of a phosphate group to another chemical.

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22
Q

compare ATP to AMP and ADP

A

o Adenosine diphosphate (ADP): one phosphate group is removed
o Adenosine monophosphate (AMP): two phosphate groups are removed

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23
Q

ATP hydrolysis

A

o ATP hydrolysis involved in coupling reactions

 Couple the breakdown of ATP with an endergonic reaction.

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24
Q

ATP cleavage

A

: the transfer of a high-energy phosphate group from ATP to another molecule. Will activate or deactivate a molecule.
 Phosphoryl group transfers: the overall of the free energy of the reaction will be determined by taking the sum of the free energy of the reaction.

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25
what is the value of the electromotive force for spontaneous reactions?
+ | deltaG is negative though
26
what are some of the high energy electron carriers?
o High-energy electron carriers: NADH, NADPH, FADH2, ubiquinone, cytochromes, and glutathione. Can be both soluble and membrane bound
27
flavoproteins
contain a modified vitamin B2 (riboflavin) o Nucleic acid derivatives. o Common ones: FMN and FAD o Function as coenzymes.
28
homeostasis
a physiological tendency toward a relatively stable state that is maintained and adjusted, often with the expenditure of energy. o Most compounds in the body are actually maintained at a homeostatic level that is different from equilibrium (allows us to store potential energy).
29
what does having the resting potential not at equilibrium allow us to do?
it allows us to store energy
30
postprandial state
absorptive state, well-fed state o Greater anabolism than catabolism. o Generally, lasts 3-5 hours after a meal. o Nutrients flood in. o Just after eating, blood glucose levels rise and stimulate the release of insulin.  Targets of insulin are the liver, muscle, and adipose tissue.  Glycogen synthesis in the liver and muscle.  Liver converts excess glucose to fatty acids and triacylglycerols.  Insulin promotes triacylglycerol synthesis in adipose tissue and protein synthesis in muscle. o After a meal, most of the energy needs of the liver are met by the oxidation of amino acids. o Nervous tissue and red blood cells are insensitive to insulin.  Nervous tissues: derive energy from oxidizing glucose to Co2 and water • Changes in prolonged fasting only  Red blood cells: can only use glucose anaerobically for all energy needs regardless of metabolic state.
31
After a meal, most of the energy needs of the liver are met by the oxidation of ____
amino acids.
32
what tissue and cells are insensitive to insulin?
o Nervous tissue and red blood cells are insensitive to insulin.  Nervous tissues: derive energy from oxidizing glucose to Co2 and water • Changes in prolonged fasting only  Red blood cells: can only use glucose anaerobically for all energy needs regardless of metabolic state.
33
counterregulatory hormones
Glucagon, cortisol, epinephrine, norepinephrine, and growth hormone oppose the actions of insulin.
34
postabsorbative state
fasting state o Counterregulatory hormones: Glucagon, cortisol, epinephrine, norepinephrine, and growth hormone oppose the actions of insulin. o Liver: glycogen degradation and release of glucose into the blood.  Gluconeogenesis (takes longer to occur than glycogenolysis). o Epinephrine: release of amino acids from skeletal muscle and fatty acids from adipose tissue.  These go to liver to aid gluconeogenesis.
35
where does gluconeogenesis mainly occur?
mainly occurs in the liver
36
prolonged fasting
starvation o Levels of glucagon and epinephrine are elevated during starvation. o Liver: Rapid degradation of glycogen stores in the liver.  Gluconeogenesis becomes primary source of glucose for the body after 24 hours. o Excess lipolysis, results in excess acetyl-CoA that is used in the synthesis of ketone bodies. o Muscles use fatty acids and brain uses ketone bodies for energy. o After extended fasting, the brain gets 2/3 of its energy from ketone bodies which allows proteins to not be degraded and not take away from other functions. (amino acids are used for gluconeogenesis)
37
peptide hormones
Ex insulin: able to rapidly adjust the metabolic processes of cells via second messenger cascades
38
fat soluble
Ex: thyroid hormones and steroid hormones like cortisol: enact longer-range effects by exerting regulatory actions at the transcriptional level.
39
hormones are used in the body to _______ (metabolism)
• Hormones are used to coordinate metabolism across the entire organism.
40
peptide hormone vs. fat soluble hormones actions
peptide: second messenger cascade (bind at cell membrane) | fat soluble: can directly affect transcription and translation (act inside the cell, can pass through cell membrane)
41
what is insulin secreted by?
peptide hormone secreted by beta cells of the pancreatic islets of Langerhans.
42
tissues that do not need insulin for glucose uptake are those that _____
must still be able to absorb glucose even when the concentration is low
43
insulin affect in the liver
• Increases glycogen synthesis in the liver. * Triacylglycerol synthesis in adipose tissue and the liver from acetyl-CoA * Decreases formation of ketone bodies in the liver.
44
insulin affect in muscle
used as extra fuel to burn during exercise or can be stored as glycogen.  Increases amino acid uptake by muscle cells, increases protein synthesis.
45
insulin affect in adipose tissue
* Glucose and triacylglycerol uptake by fat cells. * Lipoprotein lipase activity (clears VLDL and chylomicrons from blood) * Triacylglycerol synthesis in adipose tissue and the liver from acetyl-CoA * Decreases formation of ketone bodies in the liver.
46
what specifically triggers insulin release
Insulin is released when intracellular ATP levels are high in Beta cells in the pancreas.
47
glucagon
: peptide hormone secreted by alpha cells of the pancreatic islets of Langerhans  Primary target is the hepatocyte. • Increased liver glycogen breakdown. • Increased liver gluconeogenesis. • Increased liver ketogenesis and decreased lipogenesis • Increased lipolysis in the liver (not in adipocytes).
48
hyperglycemia
too much sugar in the blood
49
hypoglycemia
too little sugar in the blood
50
glucagon and insulin interplay
 Oppose each other with respect to pathways of energy metabolism.  Use phosphorylation and dephosphorylation.
51
glucocorticoids
o From the adrenal cortex, part of stress response. o To fuel fight or flight, glucose is released from the liver and fatty acids are released from adipocytes. o Ex: cortisol:  Increased lipolysis  Increased delivery of amino acids  Elevates blood glucose levels
52
catecholamines
o From the adrenal medulla, include epinephrine (adrenaline) and norepinephrine (noradrenaline) o Increase the activity of glycogen phosphorylase and increase glycogenolysis.  Glucose output in liver o Glycogenolysis is increased in skeletal muscle but cannot be released into blood due to lack of glucose-6-phosphatase so the muscle uses it. o Increase lipolysis in adipose tissue.
53
thyroid hormones
o Kept relatively consistent, long term changes can cause problems o Increase the basal metabolic rate, increased O2 consumption and heat production when they are secreted. o Latency of several hours: dose of thyroxine (T4)  Last several days o Triiodothyronine (T3): more rapid increase in metabolic rate and lasts for shorter duration of activity. o Accelerate cholesterol clearance from the plasma and increase the rate of glucose absorption in the small intestine. o Epinephrine requires thyroid hormones to be active.
54
overall role of liver during metabolism
o Two Major Roles:  Maintain a constant level of blood glucose  Synthesize ketones when excess fatty acids are being oxidized o After a meal, takes glucose from portal blood and converts to glycogen and fatty acid synthesis.  Fatty acids are converted to triacylglycerols and released into the blood as VLDL o In well-fed state, gets its energy from oxidation of excess amino acids.
55
overall role of adipose tissue during metabolism
o Fed: glucose uptake, fatty acid release from VLDL and chylomicrons (taken up by adipose tissue) and stored. o Insulin suppresses release of fatty acids. o Hormone-sensitive lipase: during fasting state, decreased levels of insulin and increased epinephrine activate it which allows fatty acids to be released.
56
overall role of skeletal muscle during metabolism `
o Resting Muscle  Major fuels are glucose and fatty acids.  Fed: glucose uptake, replenish glycogen stores and amino acids for protein synthesis.  Fast: uses fatty acids derived from free fatty acids in bloodstream and ketone bodes. o Active Muscle  Creatine phosphate: short-lived source of energy, forms ATP.  Short bursts of exercise can use glycogen stores.  Moderate high intensity: oxidation of glucose and fatty acids. • 1-3 hours of this intensity, glycogen stores are depleted and rely on oxidation of fatty acids.
57
cardiac muscle
o Prefer fatty acids for fuel, even in well-fed state. | o If ketones are present during fasting, they can be used.
58
brain
o Needs continuous glucose supply from the bloodstream. o Fatty acids cannot cross the blood bran barrier so they cannot be used. o Only during prolonged fasting does the brain gain the capacity to use ketone bodies for energy. o No storage molecules like glycogen or adipose cells in the brain.
59
what can be measured in the blood to determine metabolic control?
o Glucose, thyroid hormones, thyroid stimulating hormone, insulin, glucagon, oxygen, and CO2 can all be measured in the blood to determine metabolic control.
60
respirometry
allows accurate measurement of the respiratory quotient (RQ), which differs depending on the fuels being burned by the organism.
61
calorimeters
measure basal metabolic rate (BMR) based on heat exchange with the environment.  Uses big chambers. Simpler, can be estimated using age, weight, height, and gender.
62
respiratory quotient for different fuel sources
* Carbs: 1 * Lipids: 0.7 * Resting individual: 0.8
63
what is the main factor for gradual change of body mass over time?
o Lipids stored in adipocytes are the main factor for gradual change of body mass over time.  If energy consumed is greater than energy expenditure over a significant period of time, then fat stores accumulate, increase in weight.  As individuals increase in mass, basal metabolic rate (the amount of energy required for one sedentary day) also increases.  Body mass increases until caloric intake = base metabolic rate  This effect has a threshold that differs between individuals. • Compensations occur.  Larger changes must be made to lose weight than to gain it.
64
what play a role in weight control?
o Diet (energy intake) and exercise (energy expenditure), genetics, socioeconomic status, and geography all play key roles in weight control.
65
ghrelin
secreted by the stomach in response to signals of an impending meal.  Stimulates secretion of orexin: further increases appetite and is involved in the sleep-wake cycle.
66
leptin
secreted by fat cells that decreases appetite by suppressing orexin production.
67
body mass index
used to measure and track body mass.  Normal BMI is 18.5 to 25  Obese: over 30 takes into account height and weight
68
at constant pressure and volume, heat is _______ enthalpy
equal to
69
in general, proteins with prosthetic groups containing ______ are particularly well suited for the transport of electrons
iron-sulfur
70
glutathione is an _____
antioxidant
71
what is NADPH involved in?
PPP, lipid biosynthesis, bleach formation, oxidative stress, photosynthesis
72
the body is not in equilibrium but rather ______
homeostasis
73
what two cells are insensitive to insulin?
RBC and nervous tissue
74
in the postabsorbative state, does glycogenolysis or gluconeogensis occur quicker?
glycogenolysis
75
In which tissues is glucose uptake not affected by insulin levels?
kidney tubules, nervous tissue, red blood cells, Beta cells of the pancreas, intestinal mucosa
76
why do some tissues not respond to insulin?
they must still be able to absorb glucose even when glucose concentration is low (do not need the insulin trigger to do so)
77
what is interesting about fat metabolism when insulin levels are high?
increases lipoprotein lipase activity which clears chylomicron and VLDL from the blood stream
78
what types of cells release insulin and glucagon in the panceas?
pancreatic islets of langerhans
79
hyperglycemia
increased plasma glucose
80
where are glucocorticoids released from
adrenal cortex
81
what type of hormone is cortisol
steroid hormone
82
what happens to glucose that is produced through glycogenolysis in the skeletal muscle?
it is used by the cell because skeletal muscle cells do not have glucose-6-phosphatase.
83
T3 hormone is ______
triiodothyronine
84
T4 hormone is ____
thyroxine
85
T3 vs. T4 hormone
T3: takes longer to induce a change in metabolic rate but lasts longer T4: produces a more rapid increase in metabolic rate but has a shorter duration of activity
86
in the well-fed state, the liver derives most of its energy from _____
the oxidation of excess amino acids
87
cardiac myocytes prefer ____ as their major fuel
fatty acids
88
what is the primary factor in the gradual change of body mass over time?
lipids stored in adipocyte
89
what does increasing body mass do to metabolic rate?
increases it
90
what are some ways to assess metabolism?
chemical analysis: look at specific metabolic substrates, products, and enzymes calorimetry: looks at basal metabolic rate respirometry: provides basic info on fuel sources caloric analysis at constant weight: food and exercise logs
91
in the resting state, what is skeletal muscle's main energy source?
fatty acids
92
ghrelin activates ____
leptin
93
which organ is most sensitive to oxygen deprivation?
the brain
94
RQ values of carbs, AA, and lipids
carbs: 1.0 AA: 0.8-0.9 lipids: 0.7

MCAT Biochem (12 decks)

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