MD 1 - Energy Balance Flashcards
What is a positive energy balance?
When energy intake is greater than energy output
Results in an increase in body weight over time
What is negative energy balance?
When energy output is greater than energy intake
Reduces body weight over time
What macromolecules get converted to what monomers?
Carbohydrates to monosaccharides (glucose, fructose, galactose)
Proteins to amino acids
Lipids to fatty acids
Micronutrients are freed from macromolecules
What is primarily absorbed in the stomach?
Alcohol - 20% of total amount
Water - minor amount
What is primarily absorbed in the small intestine?
Calcium, magnesium & other micronutrients Glucose Amino acids Fatty acids Vitamins Water - 70% to 90% of total Alcohol - 80% of total Bile acids
What is absorbed in the large intestine?
Sodium Potassium Some fatty acids Gases Water - 10-30% of total
What is digestion?
Process of breaking down foods components into the molecules that are absorbed by enterocytes.
Macronutrients are digested into monomers, micronutrients are freed from macromolecules.
What is absorption?
Transport of monomers and micronutrients from the lumen of the GIT through enterocytes, into the blood or lymph circulation for delivery to cells.
There are 4 types of absorption.
What are the 4 types of absorption?
- Passive
• Moves down the concentration gradient
• Substrate concentration dependent - Facilitated
• Requires a carrier protein; saturable
• Moves down the concentration gradient - Active
• Requires energy (ATP)+ Na+
• Can transport against the concentration gradient - Endocytosis
• The cell wall engulfs a substance by surrounding it with the cell membrane
Process of converting macronutrients to usable energy for the body
- Digestion - breakdown of macromolecules (protein, carbohydrates, lipids, alcohol) to monomers (amino acids, monosaccharides - glucose, galactose, fructose, fatty acids, acetaldehyde)
- Conversion of monomers to acetyl-CoA
- Metabolism of acetyl-CoA through the citric acid cycle to produce ATP for energy and CO2
Process of converting alcohol to usable energy for the body
Alcohol is not digested or absorbed rapidly
Ethanol undergoes a series of conversion pathways to produce a transitionary molecule, acetaldehyde, which is then converted to acetyl-CoA that will then enter the citric acid cycle to produce ATP energy and CO2
What processes take place when there’s an excess of acetyl-CoA?
When excess energy is consumed, acteyl-CoA pools up and 3 processes can occur to reverse this production
- Lipogenesis - which makes fatty acids that gets converted to lipids to be stored in the body
- Gluconeogenesis - Deamination of amino acids (N grp removed from amino acid) - the C-backbone is used to make new glucose
- Monosaccharides get stored as glycogen in the muscle and liver. This storage is for emergency use when rapid glucose is needed.
How is ATP produced from glucose?
- Anaerobic respiration - NO oxygen
- One glucose molecule via glycolysis produces 2 pyruvate molecules => this conversion produces 2 molecules of ATP.
- Aerobic respiration - Oxygen present
- One glucose molecule via glycolysis produces 2 pyruvate molecules - produces 2 ATP
- When oxygen is present pyruvate molecules get converted into acteyl-coa => s acetyl-CoA enters into Krebs cycle/citric acid cycle - produces 2 molecules of ATP in the mitochondria.
- E- are carried via 6x NADH and 2x FADH2 to the electron transport chain in the mitochondria where with the presence of oxygen another 28 ATP molecules are produced with 6x H2O
How is ATP produced from fatty acids?
Lipids are consumed via the diet that is catabolised into fatty acids.
Fatty acids from the diet and floating in the bloodstream enter into the mitochondria to undergo beta oxidation
Beta oxidation cuts off 2 carbon molecules from the fatty acids to form acetyl-coa
Acetyl-CoA enters into the citric acid cycle to produce ATP
What occurs when there’s a build up of Acetyl-CoA during ATP production from fatty acids?
Ketone bodies get produced
These ketone bodies will float around in the bloodstream and will be taken up by tissues which will turn the ketone bodies back into ATP
Alternatively, the ketone bodies will convert back to acetyl-CoA and go back through the citric acid cycle to produce ATP.
How is ATP and glucose produced from amino acids?
- Glucogenic amino acids (alanine, glycine, cysteine, serine, threonine) are deaminated to produce pyruvate that’s converted to acetyl-CoA which enters the citric acid to produce ATP
- Fatty acids from the beta oxidation process (when dietary protein is consumed it will have lipids if animal source) and ketogenic amino acids (leucine, lysine, isoleucine, phenylalanine, tryptophan, tyrosine) - are deaminated to produce acetyl-CoA that then enters the citric acid to produce ATP
- Gluconeogenesis occurs with deaminated glucogenic amino acids (asparagine, arginine, aspartic acid, histidine, glutamic acid, glutamine, isoleucine, methionine, proline, valine, phenylalanine) going via citric acid cycle, exiting as oxaloacetate then converting to new glucose.
- The deaminated C-backbone can enter the citric acid cycle at any level to get the energy pathway going.
***** Deamination of the amino acid will ALWAYS occur - the Nitrogen (N) group is removed from the molecule, leaving the C-backbone to undergo 4 possible processes above
What does energy metabolism look like during the fed-state of energy metabolism?
Post-prandial metabolism is about anabolism - that’s influenced by insulin.
It promotes up-regulation of relevant enzymes for that allow plenty of fuel for the brain, nervous system and the muscles:
• Glycogen synthesis (glycogenesis)
• Fat synthesis (lipogenesis)
• Protein synthesis (gene expression => mRNA translation into functional protein)
• Urea synthesis (from deamination of amino acid carbon skeleton use)
• Insulin is the hormone primarily involved in the post-prandial state
What’s the energy metabolism during post-prandial fasting of 0-6hrs?
- Glycogen from liver => glucose => energy needs satisfied
- Protein from lean body mass cells => amino acids => converted to glucose => contribute a little bit to energy needs (GLUCONEOGENESIS)
- *** NOT favoured pathways - either no production of glucose or takes too long to produce glucose:
a. Fat from adipose stores => fatty acids => ketone bodies => contribute a little bit to energy needs
b. Fat from adipose stores => fatty acids => contribute a little bit to energy needs
c. Fat from adipose stores => glycerol => glucose => contribute a little bit to energy needs
