Mod 10 Flashcards
(21 cards)
Why do we need energy
DNA replication, cell division, protein synthesis, maintaining a Na/K osmotic gradient, etc. (housekeeping activities)
Three macronutrients
- Carbs
- Lipids
- Proteins
Glucose for energy
reactions
Glycolysis:
glucose -> pyruvate
Pyruvate dehydrogenase rxn:
pyruvate -> acetylCoA
CA cycle:
acetylCoA -> CO2
Generates reducing equivalents NADH and FADH2, then converted to ATP through the ETC and oxidative phosphorylation
Fats for energy
- Triacylglycerols broken down to free glycerol and fatty acids
- Glycerol used in glycolysis
- Fatty acids are broken down to acetylCoA via beta oxidation
- AcetylCoA then feeds into CA cycle
Proteins for energy
- Broken down to their individual aas
- Feed into the above pathways depending on their aa
Brain preferred fuel
+ storage
glucose
accepts ketone bodies during starvation
doesn’t store anything
Muscle preferred fuel
+ storage
at rest fatty acids
during exercise glucose
Has its own carb reserves as glycogen and a very small amount of triacylglycerols
Heart preferred fuel
+ storage
fatty acids
doesn’t have energy reserves - relies on circulating fatty acids in our blood stream
Adipose tissue preferred fuel
+ storage
fatty acids
triacylglycerols
Liver preferred fuel
+ storage
any of the three
jack of all trades
glycogen (glucose), chylomicrons (fats)
Energy for muscle - at rest
fatty acids delivered to the muscle via the bloodstream from the adipose tissue at a constant supply
Energy for muscle - medium intensity activity
ATP demand increases, rate of ATP production from fat oxidation no longer enough to meet demand (beta-oxy and CA cycle are slow)
Body begins to rely more on the oxidation of glucose
Fatty acids continue to be supplied via the bloodstream, while the glucose is also being provided through the bloodstream (from the liver)
Energy for muscle - high intensity activity
Breakdown of glucose through glycolysis provides the greatest proportion of ATP and a high energy compound = creatine phosphate
The supply of glucose from the bloodstream (originating from the liver glycogen stores) is not able to keep up with the demand
Therefore, the muscle turns to its own local and immediate stores of glycogen for a rapid supply of glucose for glycolysis
High energy phosphate compound that buffers against low ATP during onset of exercise or high-intensity exercise
Enzyme creatine kinase catalyzes the transfer of a phosphate from creatine phosphate to to ADP to replenish dropped ATP levels
Made in our body and consumed when we eat meat
Lactate production during exercise
As energy intensity increases, shift from fat oxidation → glycolysis of glucose
NAD+ must be regenerated to allow glycolysis to continue during high-intensity exercise
Lactate cause muscle fatigue and cramping
Eventually lactate slows us down and we exhaust our creatine stores
Regulation of glucose metabolism
insulin
after meal = increased glucose
- Stimulates release of insulin from the pancreas
- Insulin signals uptake of glucose into the tissues (muscle and liver)
- Glucose stored as glycogen, excess glucose converted to fat and stored for long-term use
Regulation of glucose metabolism
glucagon
several hours after meal = blood glucose drops
- Pancreas releases counter regulatory hormone to insulin = glucagon
- Glucagon stimulates glycogen breakdown in the liver
Why does exercise help counter type II diabetes
- Occurs when there is insulin signalling dysfunction
- Muscle occupies ½ out body mass, consumes a significant amount of glucose
- So regular exercise can help maintain healthy glucose levels and prevent type II diabetes development
Starvation - what do our bodies do
Fasting for longer than ½ a day depletes our liver glycogen stores
use
1st: fatty acids
2nd: protein “reserves”
Fatty acid use during starvation
Fatty acids from adipose tissue can be taken up from the bloodstream by the liver and converted to ketone bodies
kb used by heart and brain
Protein use during starvation
Protein “reserves” in muscle mass will be broken down into aas
Glucogenic aas ⇒ converted to glucose
Ketogenic aas ⇒ converted to ketone bodies
