5. Energy Balance and Body Composition Flashcards
Where and how do endocrine hormones act? Where are they secreted?
- Act systematically
- Generally slow and long lasting
- Secreted into the blood stream and circulate throughout the body
Where and how do exocrine hormones act? Where are they secreted?
- Act locally
- Direct and fast acting
- Secreted into ducts
List the main anabolic hormones.
- Insulin
- Growth hormones
- IGF-1
- Testosterone and estrogen
List the main catabolic hormones.
- Glucagon
- Cortisol
- Adranaline/epinephrine
What does the fate of ingested nutrients depend on?
- Energy state of the body
- Amount and type of nutrient already present and available in the body
What are the major pathways for converting food to energy?
- Glycolysis
- TCA cycle
- ETC
Briefly summarize glycolysis.
Converts 1 glucose –> 2 pyruvate + high energy molecules
What are the products of the TCA cycle?
High-energy molecules and CO2
What happens in the electron transport chain?
High-energy moleules are used to produce ATP
What organ gets first access to many of the body’s nutrients? What does it do w/ them?
Liver
- takes what it needs for energy
- converts macronutriends to what the body and brain need according to the signals present
In terms of the energy state of the body, what is a key factor that helps determine the metabolic fate of macronutrients?
ATP:ADP ratio
What substrate CAN’T the liver use for fuel? Why not? What happens to this substrate?
Ketones
- Can produce ketones for use as fuel by other tissues
- Has little ability to enzymatically break down ketones for energy in its own cells
What tissues and organs are most important for maintaining energy homeostasis?
- Liver
- Muscle
- Adipose tissue
What type(s) of fuel is used by RBCs?
Only glucose
What type(s) of fuel is/are used by the brain?
- Primarily glucose
- Ketones when in a starving state
What type(s) of fuel is/are used by skeletal muscles and the heart?
Just about everything
What type(s) of fuel is/are used by adipose tissue?
Glucose and fat
What type of metabolites does the Krebs/TCA cycle have inputs and outputs for?
- Monosaccharide metabolites
- Fatty acid metabolites
- AA metabolites
What are the 3 primary energy-requiring cellular processes?
- Membrane transport
- Synthesis of molecules
- Mechanical work
What makes up an ATP molecule?
- Nucleotide adenosine
- Tail consisting of 3 phosphates
What is the net amount of ATP produced when a glucose molecule is oxidized? Through what process does this occur?
Aerobic cellular respiration
32-36 net ATP
How much ATP is produced when a 16 carbon fatty acid is oxidized? Through what process does this occur?
- Beta-oxidation
- 131 ATP
Why does beta oxidation produce more ATP than aerobic cellular respiration?
Energy is released (ATP is produced) when carbon-hydrogen bonds are broke
Fatty acids have more carbon-hydrogen bonds than glucose
How many beta-oxidation cycles are in a 16 carbon fatty acid? Why?
7 b/c 2 usable carbons are left remaining after the 7th beta-oxidation cycle
What are the 2 main energy-producing stages in fatty acid metabolism?
- Beta-oxidation
- Krebs cycle
What are the products of each beta oxidation cycle of a 16 carbon fatty acid?
- 1 NADH
- 1 FADH2
In the Krebs Cycle, what does each acetyl-CoA produce?
- 3 NADH
- 1 FADH2
- 1 ATP
What are fatty acids NOT easily converted to?
Glucose
What substrates can be converted into pyruvate? Which cannot? What are these substrates converted into?
- Proteins, carbs, and glycerol can
- Fat cannot –> converted into Acetyl-CoA
What is the significance of being able to be converted to pyruvate?
Can be converted into Acetyl-CoA
Is the conversion of pyruvate to acetyl-CoA a reversible or irreversible rxn?
Irreversible
What are the 2 most important intermediates of metabolism?
- Acetyl Co-A
- Pyruvate
What is the “link reaction”? Why was it named this? What enzyme does this rxn usually catalyze?
- Energy-releasing conversion of pyruvate to acetyl Co-A
- Forms an important link b/t the metabolic pathways of glycolysis and the TCA cycle
- This rxn usually catalyzes the same enzyme pyruvate dehydrogenase
What processes is acetyl-CoA involved in?
- Forms citrate in TCA cycle
- Used for energy production
- Gluconeogenesis
- Fatty acid precursors
What are the roles of the liver in metabolism?
- Key processor and distributor of nutrients
- Glycogenesis and glycogenolysis
- Protein synthesis, catabolism, conversion to other compounds
- Lipoprotein synthesis
How can a liver become damaged? Consequence?
- Fatty liver from a poor diet, hepatitis, too much alcohol, or meds
- Not be able to perform its metabolic functions properly
What is the body’s one main hormone that deals w/ nutrient storage?
Insulin
Why is excess fat unhealthy?
- When cell and organs get filled w/ fat, they can no longer function properly
- Too much fat can cause cells to put out inflammatory signals, which increase the risk for certain chronic diseases
- Excess weight puts stress on joints, causing peeps to be less active
What are the stages of the fed-fast cycle? How long does each last?
- Fed state: first 3 hrs after meal ingestion
- Postabsorptive/early fasting state 3-(12-18) hrs after meal
- Fasting state 18 hrs - 2 days w/o additional food intake
- Starvation/long-term fast: fully adapted to deprivation that can last several weeks
How long can you survive without water?
3 days
How long can you go without food? Depending on what?
3-4 weeks depending on how much fat you have stored in your body
What happens to metabolism during the fed state?
Metabolism is shifted towards anabolism and storage
What is the main hormone increased or activated after a meal?
Insulin
What are the main hormones increased or activated during a fast?
- Glucagon
- Epinephrine
- Cortisol
What do incretin hormones do? When are they activated?
- Cause an increase in insulin secretion and inhibit glucagon secretion
- Activated after a meal
What are the functions of insulin?
- Stimulates the uptake of glucose, fatty acids, and AAs by muscle and adipose tissue
- Promotes storage of carbs, lipids, protein by increasing the activity of enzymes that catalyze the synthesis of glycogen, lipids, and protein
- Inhibits expression or activity of enzymes that catalyze the catabolism of glycogen, lipids and proteins
What is hyperinsulinemia? Where is it primarily seen? Consequences?
-A state of having too much insulin
-Primarily seen in muscle and adipose tissue
-Muscle loses ability to stimulate glucose uptake
adipose tissue no longer inhibits FFAs
-Increased blood glucose and FFA
What is the primary tissue for glucose uptake?
Skeletal muscle
What can help muscles take up glucose in a non-insulin dependent manner?
Exercise
In a person w/ hyperinsulinemia, what organs retain insulin sensitivity? How?
- Liver and kidney
- Not GLUT4 dependent –> use GLUT 2 transporters to uptake glucose
What is the criteria for metabolic syndrome?
Patient has at least 3 of the following 5 conditions:
- Elevated waist circumference
- Elevated triacylglycerols
- Reduced HDL
- Elevated BP
- Elevated fasting glucose
What is the primary treatment for all of the risk factors of metabolic syndrome?
Weight loss
What is the significance of central adipose?
Very metabolically active tissue that puts out a lot of inflammatory molecules
What is body mass index? Downfall? Equation?
Measure of adiposity, but does not measure body fat
BMI = weight/height^2
How is anthropometry used to measure body composition?
Calipers used as a tool to measure skin folds
What is densitometry? How is it used to measure body composition?
- Underwater weighing
- Equations used to estimate bone density and ratio of lean:fat mass
How is the air-displacement (bod pod) method used to measure body composition?
Determines body volume
How does absorptiometry measure body composition?
Uses dual energy X-rays to measure bone density
How does computerized tomography measure body composition?
Creates images of cross sections of body
List the different methods of measuring body composition.
- Anthropometry
- Densitometry
- Air-displacement (bod pod)
- Bioelectrical impedance analysis
- Absorptiometry
- Computerized tomography
What are the gender references for body composition? What distinguishes males from females?
- Male: less fat, more muscle and bone mass
- Female: more fat, less muscle and bone mass
Define energy balance.
Energy intake - energy output
What defines an energy imbalance?
Weight gain or loss
What defines energy intake?
Sum of energy provided by all the food and beverages consumed and derived from the oxidation/breakdown of carbs, protein, fat, alcohols
What defines energy output?
Absorption, metabolism, and storage of nutrients in the food we eat and the energy we spend as we sustain life
What are calories?
Basic unit in nutrition that is used to measure energy in kcals
What is a kcal?
Amount of heat necesary to increase the temp of 1 g of water 1 °C
What is bomb calorimetry? How does it work?
- Method used to measure the energy/calories in food
- 1 g of dried food is combusted and the heat released is measured
How much heat does 1 g of carbs release? Protein? Fat? Alcohol?
- Protein, carbs = 4 cal/g
- Alcohol = 7 cal/g
- Fat = 9 cal/g
What does direct calorimetry measure?
Dissipation of heat from the body
What does indirect calorimetry measure?
Measures consumption of O2 and expiration of CO2
List the ways of assessing energy expenditure.
- Direct calorimetry
- Indirect calorimetry
- Harris-Benedict Equation
What is basal metabolic rate? What % of daily energy output does this account for?
- Amount of calories necessary for homeostasis (energy expenditure for sustaining life)
- ~60-70% of daily energy output
What is the equation for resting energy expenditure? What % of daily energy output does each component account for?
BMR + thermic effect of food + activity
- TEF ~5-10%
- Activity ~20-30%
What is considered a “healthy” BMI range?
19-24
What does the Harris-Benedict equation estimate?
Basal metabolic rate
What BMI range is considered underweight?
What BMI range is considered overweight?
25-29.9
What BMI range is considered obese?
> 30
