Bio 12 - Starvation And Malnutrition Flashcards
What fuels are used in the post-absorptive period?
Muscles, brain and other tissues use predominantly glucose.
When does gluconeogenesis begin in the post-absorptive period? When does it become fully active?
Begins 4 to 6 hours after the last meal. Fully active when glycogen stores are depleted (10 to 18 hours after last meal).
How does the pattern of fuel production and usage change in early starvation (24 hours after last meal)?
Whats produced: Glucose and fatty acids. Whats used: Brain uses predominantly glucose, muscles and other tissue predominantly use fatty acids but also some glucose.
How does the pattern of fuel production and usage change in intermediate starvation (48 hours after the last meal)?
Whats produced: Glucose, fatty acids, ketone bodies. Whats used: Brain uses predominantly glucose but also some ketone bodies, muscles and other tissue use predominantly fatty acids but also some ketone bodies.
What are the two main ketone bodies that are derived from fatty acids
Acetoacetate. Then, coupled with a NADH, gives Beta-hydroxybutyrate.
What is the rate-limiting enzyme for Ketogenesis?
HMG-CoA synthase.
Why do people with ketobetic acidosis as their main source of energy have a fruity smell to their breath?
Acetoacetate, one of the main ketone bodies used as energy from fatty acids, can spontaneously become acetone, which gives the fruity smell.
What does the test for ketone bodies in the urine actually detect?
Only acetoacetate. It does NOT test for beta-hydroxybutyrate (another main ketone body used as fuel).
What fuels are produced in the post-absorptive period?
Glucose (from hepatic glycogenolysis and gluconeogenesis). Fatty acids (from adipose tissue).
Why do we make ketone bodies when we are starving or on really low carb intake?
Oxaloacetate is depleted from making too much gluconeogenesis. The TCA cycle then shuts down, leaving only Acetyl-CoA to be converted into Ketone bodies.
What metabolic scenario favors the synthesis of ketone bodies?
When production of acetyl CoA from beta oxidation of fatty acids exceeds the oxidative capacity of the TCA cycle.
True or False? Ketone bodies can be used by all body tissues including the brain.
False. RBCs can ONLY use glucose.
What is the pattern of fuel production and utilization in prolonged starvation (5 days after last meal)?
Whats produced: Glucose, fatty acids, and ketone bodies. Whats used: Brain uses predominantly ketone bodies, muscles and other tissue predominantly use fatty acids but also some ketone bodies and small amounts of glucose.
Comparing an overnight fast to a 3-day fast, what percentage of energy comes from glucose and from ketone bodies?
Overnight: 90% glucose (2/3 from glycogen breakdown, 1/3 from gluconeogenesis), 5% ketone bodies, 5% fatty acids. 3 Day fast: 60% ketone bodies (1/2 from beta-hydroxybutyrate, 1/2 acetoacetate), 40% glucose (most from gluconeogenesis).
What does metabolization of alcohol create? What does the liver do in response to that? What happens to gluconeogenesis?
It creates NADH. Therefore the liver must regenerate NAD+ by converting pyruvate to lactate and Converting oxyloacetate to malate. When your liver is metabolizing ethanol, it can’t undergo gluconeogenesis, causing a severe fasting hypoglycemia in patients that consume a lot of alcohol in a fasting state.
