Overview of Metabolism and Glycolysis Flashcards
What is metabolism?
Metabolism refers a series of chemical reactions in which the product of one reaction is the substrate for the next reaction.
What is catabolism?
Catabolism refers to chemical reactions that result in the breakdown of more complex organic molecules into simpler substances, release energy (ATP) that is used to drive chemical reactions.
What is anabolism?
Anabolism refers to chemical reactions in which simpler substances are combined to form more complex, new, molecules, usually require energy (ATP).
What are NAD+ and NADP+?
Oxidizing agents
What are NADH and NADPH?
Reducing agents
What is the end product of glycolysis?
Pyruvate
What is the importance of ketone bodies?
They are important in starvation as they allow for the operation of neurons
What is glucose stored as in the body?
Glycogen
What is fat stored as in the body?
Triacylglycerol
What is the main molecule fed into the TCA cycle?
Acetyl Coenzyme A (AcCoA)
What is the common cause of lactose intolerance?
Lactose intolerance occurs in most adults as a result of decreased lactase enzyme production
In the fed state, what glucose pathways are occurring?
- Glycogenesis
- Pentose Phosphate Pathway
- Citric Acid Cycle
- Glycolysis
What hormone is important in balancing the glucose level in the fed state?
Insulin
In the fasting state, what glucose pathways are occurring?
- Glycogenolysis
- Gluconeogenesis
What hormones are important for the glucose balance in the fasting state?
Glucagon and Epinephrine
What is the main product of anaerobic respiration?
Lactate
What is the main product of aerobic respiration?
Pyruvate
What is glycogenesis?
Glycogenesis is the formation of glycogen from glucose (hyperglycemia – Insulin increased)
What is glycogenolysis?
Glycogenolysis is the break down of glycogen to glucose-1- phosphate and glucose in the liver and in the muscles by the enzyme glycogen phosphorylase (hypoglycemia – glucagon increased)
What is gluconeogenesis?
Gluconeogenesis results in the generation of glucose from non- carbohydrate carbon substrates such as pyruvate, lactate, glycerol, and glucogenic amino acids (hypoglycemia – glucagon increased)
What is glycolysis?
Glycolysis (means “splitting sugars
What is the sole form of metabolism in RBCs?
Glycolysis
What metabolism is found in neurons?
Citric Acid Cycle
What metabolism is found in adipose tissue?
Glycolysis but no TCA cycle
What glucose receptor is found in liver cells?
GLUT 2
What glucose receptor is found in skeletal muscle?
GLUT 4
In the fed state in the liver cell what is the process on glucose?
Insulin binds -> Glucose transport into cell via GLUT2 -> Glucokinase converts glucose into G6P
In the fasting state in the liver cell what is the process on glucose?
Glucagon binds -> G6Pase converts G6P into glucose -> Glucose transport out of cell via GLUT2
In the contracting state of a muscle cell what is the process on glucose?
Glucose transported into the cell via GLUT4 -> Hexokinase converts it into G6P -> G6P is turned into ATP via glycolysis
In the resting state of a muscle cell what is the process on glucose?
Glucose transported into the cell via GLUT4 -> Hexokinase converts it into G6P -> G6P is turned into glycogen
What are the main 3 enzymes in glycolysis that have irreversible reactions?
Hexokinase/Glucokinase
Phosphofructokinase
Pyruvate Kinase
What is allosteric regulation and what are the types?
Allosteric activation of inhibition of enzyme activity and it can be negative or positive
What are the types of enzyme regulation?
- Allosteric
- Phosphorylation
- Induction/Suppression of enzyme synthesis
What is the first step of glycolysis?
Conversion of glucose to G6P via hexokinase/glucokinase
What is the importance of the glucose -> G6P reaction?
G6P cannot leave the cell and the reaction is irreversible as G6P is impermeable to the membrane as it is too polar
Where is hexokinase found?
All cells
Where is glucokinase found?
Liver and pancreas cells
What regulates hexokinase?
It is allosterically inhibited by its product G6P.
Where is glucokinase in its active form and inactive form?
Active: Cytosol
Inactive: Nucleus
What will promote glucokinase activity?
Glucose does so by promoting glucokinase translocation into the cytosol
What will inhibit glucokinase activity?
Fructose-6-P will decrease glucokinase activity by promoting translocation into the nucleus
What will increase glucokinase synthesis?
Insulin
What has the higher glucose affinity, hexokinase or glucokinase?
Hexokinase
What converts Fructose-6-Phosphate to Fructose-2,6-Bisphosphate?
PFK-2
What converts Fructose-6-Phosphate to Fructose-1,6-Bisphosphate?
PFK-1
What regulates the activity of PFK-1?
The activity of PFK-1 is regulated by Fructose-2,6-Bisphosphate, the product of PFK-2
In the liver what is the effect of E and glucagon on PFK-2 and hepatic glycolysis?
Inhibitory
How does glucagon inhibit PFK-2?
Glucagon stimulates the formation of cAMP. cAMP activates protein kinase A. Protein kinase A phosphorylates PFK-2 and inhibits the production of fructose 2,6-bisP.
What is the effect of epinephrine and glucagon on hepatic glycolysis?
Inhibits
What is the effect of epinephrine and glucagon on muscular and cardiac glycolysis?
Stimulates. Epinephrine (but not glucagon) activates heart and skeletal muscle PFK-2 by inhibiting the phosphatase activity
What are some of the effects of glucagon and epinephrine?
- Inhibits PFK-2 which leads to decreased fructose-2,6-bisphosphate and decreases the activity of PFK-1
- Inhibits pyruvate kinase
How is NAD+ regenerated?
- Lactate dehydrogenase (Cytosolic reaction)
- Malate-aspartate shuttle (Cytosol and mitochondria)
- Glycerol-phosphate shuttle (Cytosol and mitochondria)
What is the function of lactate dehydrogenase?
LDH regulates pyruvate concentration by converting pyruvate to lactate and vice versa
What is the reaction of LDH in skeletal muscle?
In skeletal muscle, the LDH5 M4 ISOZYME prefers to catalyze the conversion of pyruvate to lactate; this allows for high bursts of energy.
What is the reaction of LDH in the cardiac muscle?
In heart muscle, the H4 ISOZYME prefers to catalyze the conversion of lactate to pyruvate; this allows for a sustained production of energy.
What is the function of pyruvate dehydrogenase?
Pyruvate dehydrogenase is a enzyme complex that converts pyruvate and coenzyme A to acetyl-CoA
How is pyruvate dehydrogenase regulated?
NADH and Ac-CoA, end-products of PDH reaction promote the phosphorylation and inhibition of this enzyme.
What do anaerobic conditions favor?
Anaerobic conditions favor the formation of lactate
What is the problem in Lactate Dehydrogenase Deficiency?
When lactate dehydrogenase levels are insufficient, the level of NAD+ becomes limiting during exercise and flux through the glyceraldehyde-3-P dehydrogenase reaction is inhibited.
What is the problem in galactosemia?
Deficiency in:
- galactokinase
OR
- galactose 1-phosphate uridyltransferase
What enzyme is implicated in fructose intolerance?
Aldolase B
