Bioenergetics and Regulation of Metabolism Flashcards

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1
Q

Biological systems are consider (open/closed) systems?

A

Open

bc they can exchange both energy and matter with the environment

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2
Q

Internal energy in closed system

A

The sum of all of the different interactions btw and within atoms in a system

-vibration, rotation, linear motion, and stored chemical energies all contribute

ΔU = Q - W

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3
Q

Bioenergetics

A

Term used to describe energy states in biological systems

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4
Q

Enthalpy (ΔH)

A

the overall change in heat of a system during a reaction

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5
Q

At constant pressure and volume, ___ and ___ are equal

A

ΔH and Q

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6
Q

Entropy (ΔS)

A

Measures the degree of disorder or energy dispersion in a system

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7
Q

Gibbs free energy equation

A

ΔG = ΔH - TΔS

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8
Q

Negative ΔG is a ____ rxn

A

Spontaneous

no net loss of free energy

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9
Q

Positive ΔG is a _____ rxn

A

Nonspontaneous

net gain in energy

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10
Q

ΔG and ΔG° relation equation

A

ΔG = ΔG° + RT ln (Q)

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11
Q

modified standard state

A

[H+] = 10^-7 M

pH = 7

  • used for biochemical reactions bc a 1M concentration would give a PH of 0 which is too acidic for the body

-given the symbol ΔG°‘

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12
Q

Fats are more energy dense and therefore usually preferred for

A

long-term energy storage

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13
Q

ATP structure

A
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14
Q

ATP

A

Mid-level energy carrier

-formed from substrate-level phosphorylation and oxidative phosphorylation

-consists of an adenosine molecule attached to 3 phosphate groups

-usually formed from ADP + Pi with an energy input

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15
Q

Why do we want to use a mid level energy carrier (ATP) instead of a high level?

A

Think about wallet

-if you could never get change back, what dollar would you want most of?

-single dollar bills

-same with this: ATP cannot get back the “leftover” free energy after a reaction so it’s best to use a carrier with smaller free energy

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16
Q

ATP is consumed from either

A

Hydrolysis or the transfer of a phosphate group to another molecule

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17
Q

adenosine monophosphate (AMP)

A

a low-energy compound that results from the removal of two phosphate groups from ATP

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18
Q

ATP hydrolysis is most likely to be encountered in the context of

A

Coupled reactions

ex: movement of sodium and potassium against their electrochemical gradients is harnessed from hydrolysis of ATP

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19
Q

ATP cleavage

A

the transfer of a high-energy phosphate group from ATP to another molecule

-usually activates or inactivated the target molecule

-bc of the phosphoryl group transfers, the overall free energy of the reaction will be determined by taking the sum of the free energies of the individual reactions

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20
Q

phosphoryl group transfers

A
  • the overall energy of the rxn is determined by taking the sum of the free energies of the overall rxns
  • ATP can provide a phosphate group as a reactant
  • ex: in the phosphorylation of glucose in the early stages of glycolysis, ATP donates a phosphate group to form G6P
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21
Q

ATP is used to fuel ________ reactions or to _______

A

Energetically unfavorable reactions

activate or inactive other molecules

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22
Q

Spontaneous reactions have a _____ electromotive force (E)

A

Positive

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23
Q

high energy electron carriers

A

NADH, NADPH, FADH2, ubiquinone, cytochromes, glutathione

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24
Q

Membrane bound electron carriers

A

-embedded within the inner mitochondrial membrane

-ex: FMN, which is bonded to complex I of the ETC and can also act as a soluble electron carrier

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25
Q

Flavoproteins

A

-contain a modified vitamin B2 (riboflavin).

-nucleic acid derivatives (FAD or FMN)

-electron carriers notably in mitochondria and chloroplasts

-coenzymes for the oxidation of fatty acids, decarboxylation of pyruvate, and reduction of glutathione

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26
Q

Postprandial state

A

-aka absorptive or well-fed state

-Occurs shortly after eating; generally lasts 3-5 hrs

-Nutrients move from the gut to hepatic portal vein to the liver, where they are stored or distributed to other tissues

-Increases insulin levels

-more anabolism than catabolism

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27
Q

Anabolism

A

Synthesis of biomolecules

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28
Q

Catabolism

A

Breakdown of biomolecules for energy

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29
Q

An increase in insulin in postprandial state causes

A

Promotes glycogen synthesis in liver and muscles
—–after stores are filled -> liver converts excess glucose to fatty acids and tricylglycerols

-promotes tricylglycerols synthesis in adipose tissue and protein synthesis in muscle

30
Q

Two types of cells are insensitive to insulin :

A

Nervous tissue and red blood cells

31
Q

Nervous system derives energy from :

A

Oxidizing glucose to CO2 and water in both well-fed and fasting states

-only changes in prolonged fasting

32
Q

Red blood cells derive energy from :

A

Only can used glucose anaerobically for all their energy needs regardless of metabolic state

32
Q

Metabolic profile of postprandial state

A
33
Q

postabsorptive (fasting) state

A

Glucagon, cortisol, epinephrine, norepinephrine, and growth hormone oppose insulin

-action is opposite of insulins

-in liver—> glycogen degradation and the release of glucose into blood are stimulated (glycogenolysis)

-gluconeogenesis is also stimulated by glucagon but responds slower than glycogenolysis

-release of amino acids from skeletal muscle and fatty acids from adipose tissue is stimulated by decrease in insulin and increase in epinephrine

34
Q

prolonged fasting (starvation)

A
  • levels of glucagon & epinephrine are markedly elevated
  • increased levels of glucagon relative to insulin result in rapid degradation of glycogen stores in the liver
  • after 24 hours, gluconeogenesis is the predominant source of glucose for the body
  • lipolysis is rapid resulting in excess acetyl-CoA that is used in the synthesis of ketone bodies
  • once levels of fatty acids & ketones are high enough in the blood, muscle tissue will utilize fatty acids as the major fuel & the brain will adapt to using ketones for energy

-cells that have few, if any mitochondria, like RBCs, continue to be dependent on glucose for their energy

35
Q

after several weeks of fasting, the brain derives approx. ____ energy from ketones and ____ from glucose

A

2/3 energy from ketones & 1/3 from glucose

  • the shift from glucose to ketones as the major fuel reduces the amount of essential amino acids that must be degraded to support gluconeogenesis, which spares proteins that are vital for other functions
36
Q

water-soluble peptide hormones

A
  • able to rapidly adjust the metabolic processes of cells via second messenger cascades
  • ex: insulin
37
Q

fat-soluble amino acid-derivative hormones and steroid hormones

A
  • enact longer-range effects by exerting regulatory actions at the transcriptional level
  • hormone levels are regulated by feedback loops w/ other endocrine structures (HPA-axis), or by the biomolecule upon which they act (insulin causes a decrease in blood glucose, which removes the trigger for continued insulin release)
  • ex: thyroid hormones -> fat-soluble
    Cortisol -> steroid
38
Q

Insulin

A

A peptide hormone produced and secreted by the β cells of the pancreatic islets of Langerhans

-key player in uptake and storage of glucose

39
Q

Tissues in which glucose uptake is not affected by insulin include:

A

-nervous tissue
-kidney tubules
-intestinal mucosa
-RBC
- β-cells of the pancreas

40
Q

Relationship of glucagon and insulin in metabolism

A
41
Q

Glucocorticoids

A

Responsible for part of the stress response

-secreted from adrenal cortex

-especially cortisol, are secreated with many forms of stress (exercise, cold, and emotional stress )

42
Q

Cortisol

A

stress hormone

-promotes the mobilization of energy stores through the degradation and increase delivery of amino acids and increased lipolysis

-elevates blood glucose level -> inc avaoliabiloyt for nervous tissue through 2 mechanism

43
Q

2 mechanism through will cortisol increase blood glucose levels

A

1) cortisol inhibits glucose uptake in most tissues and increases hepatic output of glucose via gluconeogenesis ( particularly from amino acids)

2) cortisol has a permissive function that enhanced the activity of glucagon, epinephrine, and other catecholamines

44
Q

Catecholamines

A

secreted by the adrenal medulla

-Include: epinephrine and norepinephrine

-increase the activity of liver and muscle glycogen phosphorylase >- promotes glucogenolysis -> increasing the rate at which the liver can release glucose into the blood

-glycogenolysis also increases in the muscle

—–But, bc muscle lacks glucose 6 phosphatase —> glucose cannot be released by skeletal muscle into the blood stream -> glucose is metabolized by the muscle itself

-act on adipose tissue to increase lipolysis by increasing the activity of hormone sensitive lipase

45
Q

Structure of adrenal catecholamines

A
46
Q

Thyroid hormone

A

Levels are relatively constant , rather than changing with metabolic state

-increases the basal metabolic rate

-increases O2 consumption and heat is produced when secreted

47
Q

Thyroid hormone structures /types:

A

Thyroxine (T4)

triiodothyronine (T3)

-subscript number refers to the number of iodine atoms in hormone

48
Q

Thyroxine (T4)

A

Increase in metabolic rate occurs after a latency of several hours but may last for several days

49
Q

Triiodothyronine (T3)

A
  • produces a more rapid increase in metabolic rate & has a shorter duration of activity
50
Q

Preferred Fuels in the Well-Fed and Fasting States

A
51
Q

Two major roles of the liver in fuel metabolism are:

A

To maintain a constant level of blood glucose under a wide range of conditions

to synthesize ketones when excess fatty acids are being oxidized

52
Q

Liver : well fed state

A

After meal: liver extracts excess glucose and uses it to replenish it’s glycogen stores

—any glucose remaining in liver is then converted to acetyl-CoA and used for fatty acid synthesis

—fatty acids are converted to triacylglycerols and released into the blood as VLDL

—liver derives most of it’s energy from the oxidation of excess amino acids

53
Q

Liver : between meals or prolonged fast

A

Released glucose into the blood

the increase in glucagon during fasting promotes both glycogen degradation and gluconeogenesis

-preferred fuel: fatty acids

54
Q

Adipose tissue : after meal

A

After meal: elevated insulin stimulates glucose uptake by tissue

-insulin triggers fatty acid release from VLDL and chylomicrons

-fatty acids released from lipoproteins are taken up by adipose tissue and re-esterified to triacylglycerols for storage

-insulin also suppresses release of fatty acids from adipose tissue

-main fuel: glucose

55
Q

Adipose tissue: btw meals or prolonged fast

A

Decreased levels of insulin and increased epinephrine activate hormone-sensitive lipase in fat cells

-this allows fatty acids to be released into circulation

main fuel: fatty acids

56
Q

Skeletal muscle : resting muscle : after meal

A

Major fuel: glucose
body’s major consumer of fuel

Insulin promotes glucose uptake in muscle which replenishes glycogen stores and amino acids used for protein synthesis

-both glucose and amino acids can be used for energy

57
Q

Resting Skeletal muscle: between meals/ prolonged fast

A

Uses fatty acids derived from free fatty acids circulating in the blood

ketone bodies may also be used

58
Q

Active Skeletal muscle primary fuel

A

Depends on the magnitude and duration of exercise as well as the major fibers involved

-creatine phosphate: short lived source of energy (2-7 sec) , transfers a phosphate group to ADP to form ATP

-short bursts of high intensity exercise are also supported by anaerobic glycolysis drawing on stores glycogen

-high intensity , continuous exercise: oxidation of glucose and fatty acids

-after 1-3 hours of exercise: oxidation of fatty acids

59
Q

Cardiac muscle

A

Prefer fatty acid as major fuel well fed or fasting

-prolonged fasting: also use ketones

-similar to skeletal muscles during extended periods of exercise

60
Q

Brain and fuel

A

Major fuel : glucose during well fed and prolonged fasting state

can use ketones during prolonged fasting

-blood glucose levels are tightly regulated to maintain sufficient amount for brain

-fatty acids can’t cross blood-brain barrier—> cannot be used as fuel at all

-btw meals—> relies on glycogenolysis and glyconeogenesis for glucose

61
Q

respirometry

A
  • allows accurate measurement of the respiratory quotient, which differs depending on the fuels being used by the organism
62
Q

Respiratory Quotient (RQ)

A

RQ = CO2 produced / O2 consumed

changes under conditions of high stress, starvation, and exercise

63
Q

Calorimeters

A

measure basal metabolic rate based on heat exchange with the environment

although, usually just use age, weight, height, and gender to estimate basal metabolic rate

64
Q

Body mass is determined by

A

Water, carbs, proteins, and lipids

(nucleic acids dint significantly contribute)

-lipids are primary factor in gradual change of body mass over time

65
Q

A calorie excess will cause

A

An increase in body mass until equilibrium btw the basal metabolic rate and exhibiting intake

66
Q

Larger changes much be made to (gain/lose) weight

A

Lose

67
Q

Ghrelin

A

Secreted by the stomach in response to signals of a soon meal (like smelling cookies)

-sight, sound, taste, and smell all act as signals for it’s release

-increases appetitive and also stimulates secretion of Orexin

68
Q

Orexin

A

-further increases appetite

-released in response to ghrelin

-involved in the alertness and sleep wake cycle

-hypoglycemia also triggers this to be released

69
Q

Leptin

A

Hormone secreted by fat cells that decrease appetite by suppressing Orexin production

70
Q

Body mass index (BMI)

A

a measure of body weight relative to height

BMI = mass/ (height)^2

mass = kg
height = meters

normal is btw 18.5 to 25

over 30 = obese