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Physiology (MPP 3202) > Ch. 19 Energy Balance/Metabolism (Day 1) > Flashcards

Ch. 19 Energy Balance/Metabolism (Day 1) Flashcards

1
Q

What is energy?

A

Capacity to do work

Types:
–chemical, transport, mechanical

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2
Q

What are the 2 major users of energy that our cells have?

A

Maintain ion gradients
–e.g. Na+/K+ pump

Maintenance (e.g. turnover) and repair
–e.g. protein synthesis

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3
Q

What are all the users of energy that our cells have?

A

Maintain ion gradients
–e.g. Na+/K+ pump

Maintenance (e.g. turnover) and repair
–e.g. protein synthesis

Movement (muscle contraction)

Reproduction

Lactation

Thermogenesis

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4
Q

What is metabolism?

A

Overall energy economy in a cell or organism

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5
Q

What is metabolic rate (MR)?

A

Sum total of all energy-obtaining and energy-consuming processes

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6
Q

Catabolism

A

Breakdown of macromolecules (fuels) to obtain usable energy –> ATP

big molecules –> small molecules + ATP

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7
Q

Anabolism

A

Use of energy (ATP) to produce new macromolecules

small molecules + ATP –> big molecules

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8
Q

Energy balance

A

Energy stored + energy intake minus energy expenditure

Energy expenditure: work + heat

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9
Q

Energy balance is a ____ ____ in which energy demand is balanced with energy supply.

A

Steady state

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10
Q

The turnover rate of the ATP cycle is equivalent to ____ ____.

A

Metabolic Rate

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11
Q

Flux through ATP demand pathways is ____ by flux through ATP supply pathways.

A

balanced

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12
Q

Catabolism in Anaerobic Organisms…

A

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

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13
Q

Respiration is a process of slow, controlled ____, and we gain energy at various stages along the way.

A

Combustion (oxidation)

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14
Q

All the macronutrients feed into a final, common pathway in ____. (Catabolism or Anabolism)?

A

Catabolism

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15
Q

____ is the basic metabolic fuel.

A

Glucose

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16
Q

The TCA Cycle is the rotary engine of ____.

A

Metabolism

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17
Q

Energy content of food

A

Direct calorimetry

1 Calorie = 1,000 calories = 1 kcal = 4.184 kJ

Amount of heat needed to raise temperature of 1 liter of water by 1ºC = 1 Calorie

Yields “gross” energy of food

Includes combustion of indigestible components
–e.g. fiber, so energy content of some foods wasn’t accurate

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18
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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19
Q

W.O. Atwater, USDA (1900)

A

obtained gross energy values from various foods, applied corrections for digestibility, energy losses in urine; published series of tables of foodstuff energy contents

Several variations on Atwater’s general system, but his basic approach remains basis for current food labeling policies, despite some significant problems

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20
Q

What are the energy contents of the following metabolic fuels: CHO, PRO, and fat?

A

CHO: 4kcal (16.7kJ)/g
PRO: 4kcal (16.7kJ)/g
Fat: 9kcal (37.7kJ)/g

21
Q

Under normal, well-fed conditions, protein is NOT used for energy, but is preferentially used for ____ ____.

A

Protein synthesis.

However, this can change under certain conditions, e.g. fasting, starvation, prolonged exercise

22
Q

Energy Expenditure: Indirect Calorimetry

A

Since combustion (oxidation) of fuels to provide energy, and the use of that derived energy requires OXYGEN, then the rate of OXYGEN CONSUMPTION can be used to measure metabolic rate

1 liter O2 consumed per 4.5-5.0 kcal released from metabolized food

Metabolic rate (kcal/day) = liter O2 consumed/day * 4.8 kcal/L O2

23
Q

Basal Metabolic Rate (BMR)

A

Minimal rate for maintaining life, aka SMR (12 hours post absorptive state, resting)

24
Q

What influences metabolic rate?

A

Age: as age increases, MR decreases

Sex: female MR = 0.9 * male MR

Lean muscle mass (LMM): as LMM increases, MR increases

Activity level: as physical activity increases, MR increases

Diet: eating meal increases MR via thermic effect of food (aka “heat increment, HI”) - heat loss due to processes of uptake/assimilation/processing of nutrients - varies w/ nutrient - protein has highest HI

Hormones: thyroid hormones, epinephrine, norepinephrine

Genetic factors: poorly characterized

25
Q

Metabolism: Recap

A

Overall biochemical processes mediating disposition of macronutrients (PRO, CHO, fat)

Oxidation for energy vs. biosynthesis vs. storage

Catabolism: large molecules –> small molecules –> ATP generation

Anabolism: small molecules + ATP –> large molecules

26
Q

Fed (absorptive) state

A

Anabolic, fuels from food – oxidation –> ATP and storage

27
Q

Fasted (post absorptive) state

A

Catabolic, body stores – oxidation –> ATP

28
Q

How is energy stored in the body?

A

CHO: glycogen in liver and muscle via glycogenesis - reverse process is glycogenolysis

Fat: triglycerides in adipose

29
Q

Under normal conditions, what determines whether metabolism goes in the direction of anabolism vs. catabolism?

A

Feeding determines anabolism

Fasting determines catabolism

30
Q

What determines fed vs fasted state?

A

Blood glucose levels

Ratio of insulin:glucagon (counter-regulatory hormones)

Decreased blood glucose levels = fasting

Increased blood glucose levels = fed

31
Q

In regards to metabolism, what is periphery?

A

Everything except the liver

32
Q

Why is glucose so important?

A

Major metabolic fuel for all tissues, obligatory fuel for RBC’s, renal medulla, and under non-starvation conditions, the brain
–glucose is only fuel that supports anabolic metabolism

Sole fuel for muscle contraction “fight or flight” conditions

Provides anapldrotic precursors for TCA cycle
–an anapleurotic reaction is one which feeds intermediates into TCA cycle

Provides carbon skeletons for synthesis of nonessential AA’s
–20AA’s: 8 essential (come from diet only), 12 made in body

Provides carbon precursors for triglycerides (TG) components (glycerol and fatty acids)

33
Q

What is glucose used for?

A

Precursor for DNA and RNA

AA’s

Fatty acids (FA) (storage)

Glycogen (storage)

ATP production

34
Q

Fate of fuels: Fed State (HIGH INSULIN, low glucagon)

A

CHO:

  • 1) increased glucose uptake by cells from blood
  • 2) increased glucose utilization for ATP production
  • 3) increased glycogenesis in liver, muscle (storage as glycogen)
  • 4) increased lipogenesis in liver (conversion of glucose to FA)

Fat: FA + glycerol –> TG storage in adipose

PRO: AA’s used strictly for protein synthesis (P.S.); any excess not used for P.S. are deaminated and carbon skeletons are used for energy production or fat synthesis

35
Q

Fate of fuels: Fasted State (low insulin, HIGH GLUCAGON)

A

CHO:

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

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

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

36
Q

Fed State

A

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

37
Q

Fasted State

A

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

body protein –> AA –> ATP, glucose

38
Q

One-way reaction between pyruvate and ____ ____ = no net carbon flux from fat –> glucose

A

Acetyl CoA

39
Q

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

A

Body protein

40
Q

Nitrogen Excretion: Urea Cycle

A

Protein: nitrogen disposal problem - NH3, NH4+ are toxic, require large volume of water for direct excretion (e.g. fish, amphibians)

Urea formation in liver - energetically costly, but avoids ammonia toxicity

AA’s stripped of ammonia, ammonia converted to less toxic formula –> excreted

41
Q

What is needed to keep the TCA cycle going?

A

Glucose

If glucose insufficient, cycle slows up –> less ATP produced - this has implications for fat use during fasting/starvation

42
Q

Oxaloacetic Acid (OAA)

A

Combines w/ Acetyl CoA for TCA cycle

43
Q

Ketosis

A

Incomplete oxidation of FA - due to combination of low levels of incoming glucose + high levels of incoming FA

  • No glucose coming in
  • Breakdown of FA mobilized from adipose results in high levels of Acetyl CoA
  • OAA diverted towards gluconeogenesis instead of combing w/ Acetyl CoA –> depletes TCA cycle of intermediates, so it slows down
44
Q

Can the brain use ketosis for energy?

A

Yes, but under conditions such as starvation

45
Q

Ketone Bodies: An Alternate Source of Energy for the Brain

A

Prolonged high systemic levels of them can be detrimental

At high plasma levels, kidney unable to completely reabsorb k.b. –> net energy loss to body

k.b.’s are organic –> metabolic acidosis

kidney can acidify urine to only pH of 4.5-5.0 (pK of k.b.), thus only about 50% of excreted k.b. are in acid form –> the remainder must be accompanied by a cation, e.g. Na+/K+ –> ionic depletion

46
Q

Energy Stores

A

Ready reserve: phosphocreatine and ATP
–lasts for seconds

Long-term: CHO, PRO, and fat

  • -glycogen, protein, triacylglycerol
  • -lasts minutes to months
47
Q

What are the priorities during fasting/starvation?

A

1) maintain blood glucose

2) conserve body protein
- -no storage depot for protein b/c we use it

48
Q

The majority of our energy reserve is stored as?

A

Fat

About 200x more energy stored as fat than CHO

49
Q

Energy stored as fat

A

> 5:1 compared w/ protein

> 160:1 compared w/ CHO

Physiology (MPP 3202) (32 decks)

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