Membrane transport Flashcards
Structure of GLUT Transporter
12 transmembrane alpha helices
Type of transport GLUT carries out
Facilitated diffusion
High affinity GLUT transporter
GLUT 1,3,4
Low affinity GLUT transporter
GLUT 2,5
Where is GLUT-1 found?
RBC, blood-brain barrier, kidney
Where is GLUT-3 found?
neurons, brain
Hereditary GLUT-1 deficiency
metabolic encephalopathy
- At birth, microcephaly and seizures
- individuals mature and have ataxia, delayed psychomotor development, movement disorders, impaired speech
Where is GLUT-2 found?
intestinal mucosal cells
hepatocytes
pancreatic beta cells
renal tubular cells
Job of GLUT-2 in intestinal mucosal cells
release dietary monosaccharides into portal vein
Job of GLUT-2 in hepatocytes
facilitate glucose uptake from blood into hepatocytes at high blood glucose levels after a meal, also release glucose into blood during fasting
Job of GLUT-2 in pancreatic beta cells
measure high blood glucose levels, leading to high ATP and release of insulin
Job of GLUT-2 in renal tubular cells
re-uptake of glucose
Where is GLUT-4 found?
fat cell, skeletal muscle and heart
Relationship between insulin and GLUT-4
Insulin mobilize transport of GLUT-4 from intracellular pool to plasma membrane. Once GLUT-4 is aligned in plasma membrane, it allows the influx of blood glucose into cell.
How does insulin injection might lead to hypoglycemia?
Due to Rapid uptake of blood glucose into skeletal muscle and fat cell via mobilized GLUT-4
What can stimulate mobilization of GLUT-4?
Insulin and vigorous exercise
Where is GLUT-5 found?
intestinal mucosal cell on luminal side of intestinal membrane
seminal vesicle
Role of GLUT-5
transports mainly dietary fructose and dietary glucose only at very high level of glucose concentration
Role of GLUT-5 especially in seminal vesicle
for release of fructose into semen.
use blood glucose to form fructose to supply the energy metabolism of sperm cells.
What type of transport is SGLT?
Secondary active transport
Role of SGLT-1
Symporter that transport sodium ions and glucose or sodium ions and galactose into intestinal mucosal cells
Role of SGLT-2
Found in kidney and transports sodium ions and glucose for re-uptake
In eukaryotes, what molecules use ABC transporters?
lipids or lipid-related compound.
Example of ABC Transporter
Liver release bile salts, cholesterol and conjugated bilirubin into the bile ducts using ABC transport
What type of transport is CFTR?
special ABC-transporter, but considered as facilitated diffusion because chloride ions flow with the gradient from inside to outside of cell.
Symptoms of Cystic fibrosis
salty skin for newborn poor growth and low weight recurrent lung infecion chronic pancreatitis Steatorrhea Male infertility
How is the release of water to extracellular surfaces dependent on CFTR function?
In a typical epithelial cell, chloride ions are first accumulated inside the cell. Then, chloride ions are released into extracellular lumen through CFTR. Then sodium ions from interstitial fluid binds with Cl in the lumen to form sodium chloride with attracts water.
Where is CFTR present?
epithelial cells of airway ducts pancreatic ducts reproductive ducts skin
What is different between CFTR in skin and other places?
CFTR in epithelial cells of sweat secretory duct when opened, chloride ion flow with the gradient into epithelial cells from the duct lumen, being used as re-uptake of chloride ions by epithelial cells. (sweat formed in coil has higher conc of NaCl than those in epithelial cell)
