Lecture Four: Glucose Absorption
_____ membrane is the one next to the lumen and the _______ membrane is the one next to like blood lol (in contact with basement membrane tho)
apical, basolateral
renal threshold: is the _______ of a substance dissolved in the blood above which the kidneys begin to _______ it into the urine
concentration, remove
Sodium absorption occurs in two stages. The first is via intestinal epithelial cells. Sodium passes into cells by ________ with glucose, (SGLT1 protein). Then sodium is pumped by active transport (sodium-potassium pump) through the ________ cell membrane into the extracellular space.
cotransport, basolateral
Glucose and sodium are ________ across the basolateral membrane by _________ diffusion.
cotransported, facilitated
Treatment for glucose/galactose malabsorption: removal of glucose & galactose from diet & use ______ as sort of carbohydrate. This uses facilitative transporter specific for _______
fructose, fructose
______ exits the cell across the basolateral membrane by facilitated diffusion mediated by the _____ transporter protein
glucose, GLUT
Renal glucose reabsorption: retrieval of filtered ______, preventing it from disappearing from the body through the ______.
glucose, urine
______: accumulation of glucose in urine
glucosuria
Facilitative glucose transporter mediates glucose exit across the basolateral membrane via passive diffusion down its __________
gradient
The Na/K pump sets up _____ ______
ion gradients
SGLT2 is a protein in humans that facilitates glucose reabsorption in the _______.
kidney
________ is the inside space of a tubular structure, such as an artery or intestine
lumen
Glucosuria occurs when transport _______ for _____ protein exceeded.
maximum, SGLT
The ability of glucose to enhance the absorption of Na+ (and thus Cl- and water) means simple sugar solution can be given to babies suffering from diarrhoea. Called _____ ______ ______
oral rehydration therapy
The movement of glucose across the epithelium creates ______ imbalance (which drives the absorption of water)
osmotic
The transport of Na+ and glucose across epithelium induces ______cellular Cl- and H2O fluxes
para
In a diarrheal illness, sodium-rich intestinal secretions are lost before they can be __________.
reabsorbed
If glucose is not _______ by the kidney, it appears in the _____
reabsorbed, urine
All filtered glucose is _______ until renal threshold is reached
reasorbed
_______ ____ reflects transport maximum of SGLT
renal threshold
SGLT proteins use energy from this downhill sodium gradient to transport glucose across the apical membrane of the cell against the glucose gradient. Thus the co-transporters are examples of ________ active transport.
secondary
Glucose/galactose malabsorption syndrome results in accumulation of glucose & galactose in lumen of _____ _______ - producing _____ imbalance (attracting water = severe diarrhoea)
small intestine, osmotic
The energy for glucose entry is supplied by the ______ gradient
sodium
Two ______ ions and one molecule of glucose (or galactose) are transported together across the cell membrane via the SGLT1 protein into epithelial cells
sodium
Na+ taken up via the _____ _______ ____ and exits via the basolateral _____ pump
sodium glucose symporter, Na/K
Without glucose, intestinal _____ is not absorbed. This is why oral rehydration salts include both ______ and glucose. Water molecules move into the epithelial cell to maintain _______ equilibrium. The resultant absorption of sodium and water can achieve rehydration.
sodium, sodium, osmotic
Common cause of glucosuria = diabetes mellitus (deficient insulin & blood sugar too high). Glucose _____ can not absorb glucose fast enough & glucose appears in urine.
symporter
The sodium glucose ______ uses the energy of the Na+ gradient to actively accumulate glucose above its concentration gradient
symporter
A ________ is an integral membrane protein that is involved in the transport of many differing types of molecules across the cell membrane. Molecules are transported across the cell membrane at the same time, and is, therefore, a type of _____transporter.
symporter, co
Both SGLT1 and SGLT2 are known as _________, since both sodium and glucose are transported in the same direction across the membrane.
symporters
____ ____ divide cells into apical and basolateral membrane domains
tight junctions
If glucose absorption impaired or saturated _________, glucose will appear in the urine
transporter
Glucose transport is a _ step process
2
Glucose/galactose malabsorption syndrome is caused by a mutation in sodium-dependent glucose (co-) transporter (_______) protein.
SGLT