LG 1.6 Brain Metabolism Flashcards
What does the brain metabolize?
Glucose
What type of metabolism does the brain normally have?
Aerobic
What does the brain have Aerobic metabolism instead of anaerobic metabolism?
Aerobic metabolism yields 15 fold more energy than anaerobic.
What uses the most energy in the brain?
80% of ATP that is hydrolyzed in the brain powers the formation and maintenance of ionic gradients.
What type of diffusion do GLUT’s use?
Facilitated diffusion
What is the function of GLUT transporters?
Facilitate the movement of glucose through membranes by providing a channel. In the absence of a pore, glucose cannot get through a membrane.
What GLUT Transporter and what is the functioning concentration in the Liver?
GLUT 2, 300 mg/dL
What tissues use GLUT 4 and what is the normal functional concentration?
- Muscle and Adipose
- 90 mg/dL
What GLUT transporters does the brain have and what is the normal functioning concentration?
- GLUT 1 and GLUT 3
- 20 mg/dL
What cells in the brain use GLUT 1?
Blood Brain Barrier endotheilial cells (astrocyte)
What cells in the brain use GLUT 3?
Neuronal cell membranes (neuron)
What is the Michaelis-Menten enzyme kinetics?
-Mathematically describes the rate at which an enzyme catalyzes reactions.
What does the Michaelis constant stand for?
The Km value of an enzyme indicates the concentration of substrate which is sufficient for the rate of catalysis to be half of the maximum rate of catalysis.
What do astrocytes do with glucose?
Glycogen phosphorylase in astrocytes hydrolyze glycogen to glucose-6-phosphate.
What do astrocytes release for energy use for neurons?
Lactate
What are the only cells in the body that have glucose-6-phosphatase activity?
Only liver and kidney cells have glucose-6-phosphatase activity
What does the brain do during starvation mode?
The Brain can supplement its fuel supply by substituting ketone bodies for glucose. The brain can catabolize two of them, acetoacetate and b-hydroxybutarate, to supplement glucose in generating energy.
Where does most of the ketone bodies come from?
Draws upon fatty acids stores in adipose tissue that are released and converted into ketone bodies in the liver to supplement glucose in providing energy to the brain.
What transports free fatty acids in the blood?
Albumen
What process does the liver go through to produce glucose for the brain?
Gluconeogenesis to regenerate the glucose for the brain which tends to deplete citric acid cycle intermediates.
What is a precursor to make ketone bodies or cholesterol?
3-hydroxy-3-methyl glutaryl CoA
What is HMG-CoA reductase?
Reduces 3-hydroxy-3-methyl glutaryl CoA to Mevalonate, the modular building building block for cholesterol
What is HMG-CoA Lyase?
Lyses 3-hydroxy-3-methyl glutaryl CoA leading to ketone body synthesis.
