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Physiology > Energy Balance/Metabolism (Day 1) > Flashcards

Energy Balance/Metabolism (Day 1) Flashcards

1
Q

What is energy?

A

capacity to do work (chemical, transport, mechanical)

  • maintain ion gradients (ex. Na/K pump)
  • Maintenance and repair (ex. protein synthesis)
  • Movement (muscle contraction)
  • Reproduction
  • Lactation
  • Thermogenesis
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2
Q

What is metabolism?

A

overall energy economy in a cell or organism (ex. the sum total of all energy-obtaining and energy-consuming process –> metabolic rate)

  • catabolism
  • anabolism
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3
Q

Catabolism

A

part of metabolism
–>breakdown of macromolecules (fuels) to obtain usable energy –> ATP

big molecules –> small molecules + ATP

in aerobic organisms, the final common pathway whereby the chemical energy in fuel molecules is conserved as ATP is called RESPIRATION

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4
Q

Anabolism

A

part of metabolism
–> use of energy (ATP) to produce new macromolecules

small molecules + ATP –> big molecules

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5
Q

Respiration

A

a process of slow, controlled combustion (oxidation)

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6
Q

Krebs/Citric Acid Cycle

A

Rotary engine of metabolism

ALL macronutreints feed into a final, common pathway (glucose is basic metabolic fuel)

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7
Q

Energy content of food: Direct Calorimetry

A

1 Calorie = 1000 calories = 1 kcal = 2.184 kJ

amount of heat needed to raise temp of 1 liter of water by 1 degree C

yields “gross” energy of food

includes combustion of indigestible components (ex. fiber)

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8
Q

Gross Energy Content

A

adjusted for indigestible components and for any other relevant losses, then this modified value is used on food labels

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9
Q

Energy content of metabolic fuels

A

CHO: 4 kcal
PRO: 4 kcal
FAT: 9 kcal

–>PRO not usually used for energy, but preferably for protein synthesis

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10
Q

Energy Expenditure: indirect calorimetry

A 
since combustion (oxidation) of fuels to provide energy and use the use of that energy requires O2
--> then rate of O2 consumption can be used to measure metabolic rate
  • 1 liter O2 consumed per 4.5-5 kcal released from metabolized food
  • Metabolic rate (kcal/day) = L O2 consumed/day x 2.8kcal/L O2
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11
Q

BMR

A

minimal rate for maintaining life, aka SMR (12 hrs postabsorptive state, resting)

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12
Q

What influences metabolic rate?

A

Age: decreases with age

Sex

Lean muscle mass: as LMM increases so does MR

Diet: eating meal increases MR via thermal effect of food

Hormones: thyroid hormones, epinephrine, norepinephrine

Genetic Factors: poorly characterized

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13
Q

Metabolism recep

A

overall biochemical processes mediating disposition of macronutrients

oxidation for energy vs. biosynthesis vs. storage

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14
Q

Fed (absorptive) state

A

anabolic

fuels from food – oxidation –> ATP/storage

increase of blood glucose

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15
Q

Fasted (postabsorptive) state

A

catabolic

body stores – oxidation –> ATP

decrease of blood glucose

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16
Q

How is energy stored in the body? CHO

A

glycogen in liver and muscle vis glycogenesis – reverse process is glycogenolysis

17
Q

How is energy stored in the body? FAT

A

triglycerides in adipose

18
Q

What determines fed vs fasted state?

A

blood glucose levels –> ratio of insulin: glucagon (counter-regulatory hormones)

19
Q

Why is glucose so important?

A
  • major metabolic fuel for all tissues, obligatory fuel for RBCs, renal medulla, and under non-starvation conditions, the brain
  • sole food for muscle contraction under “fight or flight” conditions
  • provides anaplerotic precursors for citric acid (TCA) cycle –> an anaplerotic reaction is one which feeds intermediates into TCA cycle
  • provides carbon skeletons for synthesis of nonessential AA
  • provides carbon precursors for TG componenets (glycerol and FA)
20
Q

Fate/uses for glucose

A

precursor for DNA, RNA

ATP production

Glycogen (storage)

FA (stroage)

AA

21
Q

Fate of fuels: FED state, CHO

A

HIGH insulin, LOW glucagon

CHO:

  1. increases glucose uptake by cells form blood
  2. increased glucose utilization for ATP production
  3. increases glycogenesis in liver, muscle (storage as glycogen)
  4. increased lipgenesis in liver (conversion of glucose to FA)
22
Q

Fate of fuels: FED state, FAT

A

HIGH insulin, LOW glucagon

FAT: FA + glycerol — TG storage in adipose

23
Q

Fate of fuels: FED state, PRO

A

HIGH insulin, LOW glucagon

PRO: AA used strictly for PRO synthesis, any excess not used for PS are deaminated and carbon skeletons used for energy production for fat synthesis

24
Q

Fate of fuels: FASTED state, CHO

A

LOW insulin, HIGH glucagon

CHO:

  1. decreased glucose uptake by cells from blood
  2. decreased glucose utilization for ATP production
  3. decreased glycogenesis in liver, muscle (ex. decreased glycogen storage)
  4. decreased lipogenesis, increased lipolysis (liver)
  5. increased glycogenolysis in liver, muscle (increased breakdown of glycogen stores)
  6. increased gluconeogenesis
25
Q

Fate of fuels: FASTED state: FAT

A

LOW insulin, HIGH glucagon

FAT: TG –> FA + glycerol in adipose, FA + glycerol –> liver

26
Q

Fate of fuels: FASTED state, PRO

A

LOW insulin, HIGH glucagon

PRO: increased protein breakdown, AA carbon skeletons used for glucogeogenesis

27
Q

FED vs. FASTED

A

Fed: INSULIN: glucagon –> glucose utilization and storage as glycogen/fat

Fasted: Insulin: GLUCAGON –> breakdown of stored fat, glycogen and production of new glucose

28
Q

So, during fasting, where does the carbon needed for gluconeogenesis come from, if it can’t come from fat??

A

body protein

PRO –> AA –> c-skeletons –> glucose

29
Q

Nitrogen excretion: Urea cycle

A

PRO: nitrogen disposal problem, NH3, NH4 are toxic/require large amount of water for direct excretion (ex. fish)

Urea formation in liver - energetically costly, but avoids ammonia toxicity
–> AAs stripped of NH3, NH3 converted to less toxic formula and excreted

30
Q

What is needed to keep TCA cycle going?

A

GLUCOSE
If glucose is insufficient, the cycle slows –> less ATP produced (this has implications for fat use during fasting/starvation)

31
Q

Ketosis

A

incomplete oxidation of FA, due to combo of low levels of incoming glucose + high levels of incoming FA

–> brain uses detests for energy under starvation conditions

32
Q

Ketone Bodies

A

alternative source of energy for brain, but prolonged high systemic levels can be detrimental

at high plasma levels, kidney is unable to completely reabsorb KB –> net energy loss to body

KB are organic acids –> metabolic acidosis

Kidney can acidify urine to only pH 4.5-5, thus only about 1/2 of excreted KB are in acid form –> reminder but have a cation (ex. Na, K) –> ionic depletion

33
Q

Energy Stores

A

Ready reserves: work for seconds only
ex. creatine kinase, phosphocreatine, ATP

Long-term: work for minutes/months
ex. CHO, FAT, PRO

34
Q

Priorities during fasting/starvation

A
  1. Maintain blood glucose

2. conserve body protein

35
Q

Energy stored as fat

A

5: 1 compared to PRO
160: 1 compared to CHO

Physiology (29 decks)

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