Cellular Homeostasis Flashcards
Describe GLUT 1
Ubiquitous Found in RBCs, brain, cornea, placenta, and transformed cells Unregulated Always saturated bc Km is 1mM High affinity
What is the normal concentration of glucose in plasma?
4-8 mM
Describe GLUT 2
Main transporter in liver and pancreas Lumen of small intestines Really low affinity Works independent of insulin unregulated Km 10 mM
Describe GLUT 3
Main transporter in neurons
unregulated
Km 1mM
Describe GLUT 4
Main transporter in skeletal muscle, adipose tissue and the heart.
REGULATED by insulin
Surface expression dependent on insulin
Km 5 mM, normally 50% saturated
What are the dietary sources of glucose?
fructose and galactose
Glucose
When glucose in the blood is used, a supply of glucose can come from _________ especially after overnight fasting.
Glycogenolysis
When glucose storage supply is depleted, where can glucose be derived?
Gluconeogenesis - De novo synthesis From non-carbohydrate sources: Glycerol Lactate Glucogenic amino acids TCA cycle intermediates
Child exhibits stunted growth, hepatomegaly, and bouts of hypoglycemia between meals but hyperglycemia and hypergalactosemia after a meal. What is the disorder?
Inherited deficiency of GLUT2 in the liver, pancreatic beta cells, and proximal renal tubules: Fanconi-Bickel Syndrome
Why does hyperglycemia and hypergalactosemia occur after a meal with a patient with Fanconi-Bickel syndrome?
Due to deficiency in GLUT 2 in the liver, glucose and galactose are not rapidly cleared from circulation after feeding
Why does hypoglycemia between meals presents in a patient with Fanconi-Bickel Syndrome?
Glucose generated during gluconeogenesis is not released from liver during fasting
Is insulin secretion high or low in a patient with Fanconi-Bickel Syndrome?
Low because pancreatic beta cells do not detect increase in glucose
Hepatomegaly occurs in Fanconi-bickel syndrome due to what?
accumulation of glycogen in liver
Dwarfism can present in patients with fanconi-bickel syndrome because of what?
Due to vitamin D-dependent hypophosphatemic rickets due to proximal tubular nephropathy
What is the treatment for fanconi-bickel syndrome?
Ingesting frequent small meals to ensure adequate caloric intake and avoidance of galactose
Vitamin D supplementation
How does glucose cause the release of insulin from pancreatic B cells?
Glucose is metabolized to form ATP
Rise of ATP closes K channels
Depolarization
Ca channels open
Ca influx causes release of insulin - rapid
CaM kinase activated
New insulin synthesized and slowly released
How is the Glucose Tolerance test administered?
Test used for Type 2 diabetes
Patient given known amounts of glucose
8-12 hour fasting period
Glucose levels measured in blood plasma before and at intervals after.
Determine how quickly glucose levels fall and homeostasis is regained
________ of erythrocyte membrane proteins defines an individual’s blood type.
Glycosylation: enzymatic attachment of a number and variety of sugars
Proteins that are degraded by extracellular proteolytic enzymes when needed are often secreted as _______.
zymogen
The mitochrondrial matrix is the site of what 4 processes?
B-oxidation of fatty acids
TCA cycle
Urea cycle
and storage of Ca
Describe how lupus erythematosus can be drug induced?
The body metabolizes certain drugs by acetylating them. This detoxifies or reduces the potency of drugs. Individuals that have genetic mutations in enzymes that carry out acetylation reactions show a slow rate of drug acetylation. Drugs have a longer half-life. The drugs are converted to by-products that are toxic to the body. The production of antinuclear antibodies are triggered.
*signs-muscle and bone pain, rash, inflammation of the lungs and heart, fever and fatigue
