Metabolism Review Slides: Glycolysis Flashcards
Why are NAD+ and NADP+ so important?
They are the most important electron carriers. They are needed as oxidizing agents
What are the fuel preferences of the liver?
Fatty acids, glucose and amino acids
What are the fuel preferences of skeletal muscle?
At rest: fatty acids
Exertion: glucose
What are the fuel preferences of the brain?
Fed state: glucose
Starvation: ketone bodies/glucose
What are the fuel preferences of adipose tissue?
Fatty acids
What are the fuel preferences of heart muscle?
Fatty acids, but it will pretty much use anything
How does the liver use energy during fasting?
The liver expends energy through the metabolism of fatty acids in order to make glucose.
Fatty acid oxidation in the liver provides most of the ATP needed for gluconeogenesis
What is the driving force for the coordination of metabolism?
Provide the normal range of glucose necessary for the brain
When does the brain lose its requirement for glucose?
Never
The majority (76%) of our caloric stores are in which form?
Fat
What is the second most abundant form of energy stored in our bodies?
Protein- at 23%
Fasting glucose blood levels must be maintained above what concentration? What happens if it falls below?
Fasting blood glucose must be maintained above 60mg/100mL.
Acute hypoglycemia causes neurological problems, coma and death
Fasting blood glucose levels above what concentration is considered hyperglycemia? What are complications associated with hyperglycemia?
110mg/100mL
Multiple problems, including increased oxidative stress within cells, increased intracellular lipids, lipotoxicity. This ultimately leads to type 2 diabetes mellitus
Glucagon and epinephrine stimulate what two metabolic processes?
Glucagon and epinephrine stimulate glycogenolysis and gluconeogenesis
Insulin stimulates what two metabolic processes?
Insulin stimulates glycogenesis and glycolysis
What three enzymes catalyzes irreversible reactions in glycolysis?
Hexokinase/glucokinase: glucose –> glucose-6-phosphate
Phosphofructokinase-1: Fructose-6-phosphate –> Fructose-1,6-bisphosphate
Pyruvate Kinase: PEP –> pyruvate
Describe the three different “stages” of glycolylsis
Priming: ATP investment- 2 ATP invested
Splitting: Fructose-1,6-bisphosphate (6 carbon) split into two 3 carbon molecules
Oxidoreduction phosphorylation stage: ATP earnings- 4 total
Why is glucose “committed” to glycolysis after phosphorylation by hexokinase?
Glucose can exit the cell through a glucose transporter (GLUT2).
Glucose-6-phosphate is more polar, and therefore can no longer exit the cell. It is “trapped” and ready for further metabolism
Discuss the differences in location of hexokinase vs. glucokinase
Hexokinase is present in all cell types.
Glucokinase is present in the liver (for glycolysis) and pancreas (as a glucose- sensing enzyme in the pancreas)
Discuss the inhibition of hexokinase vs. glucokinase
Hexokinase is inhibited allosterically by its product (glucose-6-phosphate)
Glucokinase is inhibited via translocation into the nucleus, promoted by fructose-6-phosphate ( a downstream product)
Discuss the stimulation of hexokinase vs glucokinase
Hexokinase is constitutively active.
Glucokinase is inducible; enzyme synthesis is induced by insulin. Activity is also increased by glucose, which promotes translocation from the nucleus to the cytosol.