Cellular Homeostasis

Question 1

Describe GLUT 1

Answer 1

Ubiquitous
Found in RBCs, brain, cornea, placenta, and transformed cells
Unregulated
Always saturated bc Km is 1mM
High affinity

Question 2

What is the normal concentration of glucose in plasma?

Answer 2

4-8 mM

Question 3

Describe GLUT 2

Answer 3

Main transporter in liver and pancreas
Lumen of small intestines
Really low affinity
Works independent of insulin
unregulated
Km 10 mM

Question 4

Describe GLUT 3

Answer 4

Main transporter in neurons
unregulated
Km 1mM

Question 5

Describe GLUT 4

Answer 5

Main transporter in skeletal muscle, adipose tissue and the heart.
REGULATED by insulin
Surface expression dependent on insulin
Km 5 mM, normally 50% saturated

Question 6

What are the dietary sources of glucose?

Answer 6

fructose and galactose

Glucose

Question 7

When glucose in the blood is used, a supply of glucose can come from _________ especially after overnight fasting.

Answer 7

Glycogenolysis

Question 8

When glucose storage supply is depleted, where can glucose be derived?

Answer 8

Gluconeogenesis - De novo synthesis
From non-carbohydrate sources:
Glycerol
Lactate
Glucogenic amino acids 
TCA cycle intermediates

Question 9

Child exhibits stunted growth, hepatomegaly, and bouts of hypoglycemia between meals but hyperglycemia and hypergalactosemia after a meal. What is the disorder?

Answer 9

Inherited deficiency of GLUT2 in the liver, pancreatic beta cells, and proximal renal tubules: Fanconi-Bickel Syndrome

Question 10

Why does hyperglycemia and hypergalactosemia occur after a meal with a patient with Fanconi-Bickel syndrome?

Answer 10

Due to deficiency in GLUT 2 in the liver, glucose and galactose are not rapidly cleared from circulation after feeding

Question 11

Why does hypoglycemia between meals presents in a patient with Fanconi-Bickel Syndrome?

Answer 11

Glucose generated during gluconeogenesis is not released from liver during fasting

Question 12

Is insulin secretion high or low in a patient with Fanconi-Bickel Syndrome?

Answer 12

Low because pancreatic beta cells do not detect increase in glucose

Question 13

Hepatomegaly occurs in Fanconi-bickel syndrome due to what?

Answer 13

accumulation of glycogen in liver

Question 14

Dwarfism can present in patients with fanconi-bickel syndrome because of what?

Answer 14

Due to vitamin D-dependent hypophosphatemic rickets due to proximal tubular nephropathy

Question 15

What is the treatment for fanconi-bickel syndrome?

Answer 15

Ingesting frequent small meals to ensure adequate caloric intake and avoidance of galactose
Vitamin D supplementation

Question 16

How does glucose cause the release of insulin from pancreatic B cells?

Answer 16

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

Question 17

How is the Glucose Tolerance test administered?

Answer 17

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

Question 18

________ of erythrocyte membrane proteins defines an individual’s blood type.

Answer 18

Glycosylation: enzymatic attachment of a number and variety of sugars

Question 19

Proteins that are degraded by extracellular proteolytic enzymes when needed are often secreted as _______.

Answer 19

zymogen

Question 20

The mitochrondrial matrix is the site of what 4 processes?

Answer 20

B-oxidation of fatty acids
TCA cycle
Urea cycle
and storage of Ca

Question 21

Describe how lupus erythematosus can be drug induced?

Answer 21

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