Carbohydrate Metabolism and Regulation Flashcards
amylose and amylopectins are examples of:
starches/polysaccharides
the most important dietary hexose monosaccharides
glucose, fructose and galactose
D-glucose is also called:
dextrose
IV solutions that contain dextrose are called D followed by a number (the % solution)
D5W = 5% dextrose (glucose) in water
D5NS = 5% dextrose in normal saline
sucrose components
glucose and fructose
lactose
galactose and glucose
lactulose
galactose and fructose
__ is a non-digestible sugar used as medication It stays in the GI tract 100%
- Through osmosis, draws water into the GI tract
- Is used to treat constipation (by giving you diarrhea)
Lactulose is a non-digestible sugar used as medication It stays in the GI tract 100%
- Through osmosis, draws water into the GI tract
- Is used to treat constipation (by giving you diarrhea)
-
It can also increase colonic elimination of NH+4 treatment of hepatic encephalopathy (brain dysfunction
in liver disease)
bonds in amylose
straight 1-4 bonds, no branches
bonds in amylopectin
1-4 connecting bonds, and 1-6 branching bones
amylase enzymes can break down the 1-4 bonds in amylose and amylopectin, but they cannot break the 1-6 bonds, or the 1-4 bonds near. 1-6 bonds, or the terminal 1-4 bonds. therefore, NO GLUCOSE MONOMERS are liberated from thea ctivity of amylase on starch. instead, what are amylase’s products?
- maltose
- alpha limit dextrins
common disaccharidase deficiency that makes someone intolerant to dairy
lactase deficinecy– aka lactose intolerance. lactose enters colon and carries water with it by osmostic forces. without lactase to break lactose down to galactose and glucose, it stays in the bolon and can cause diarrhea and cramping
Note on glucosidases:
- αglucosidase inhibitors are drugs that inhibit these
enzymes and therefore reduce absorption of glucose - these drugs are sometimes used in diabetes
- exchange higher sugar levels for diarrhea
three absorbable sugars
glucose, fructose and galactose
which protein transporters allow simple sugars (glucose, fructose and galactose) to cross cell membranes
GLUT; glucose transporter
and SGLT: sodium glucose transporter
outline the absorption of CHO process in the gut
- glucose is tranported into enterocytes against a concentration gradient
- therefore, it requires active transport
- glucose or galactose are transported via SGLT1, which requires Na+ as co-transport (sodium moves down a concentration gradient)
- fructose is transported via GLUT 5.
- all 3 sugars are passively transported out of the enterocytes to the blood via GLUT2
glucose is tranported into enterocytes __ a concentration gradient
- therefore, it requires __ transport
- glucose or galactose are transported via __, which requires __+ as co-transport (sodium moves down a concentration gradient)
- fructose is transported via __.
- all 3 sugars are __ transported out of the enterocytes to the blood via ___
glucose is tranported into enterocytes against a concentration gradient
- therefore, it requires active transport
- glucose or galactose are transported via SGLT1, which requires Na+ as co-transport (sodium moves down a concentration gradient)
- fructose is transported via GLUT 5.
- all 3 sugars are passively transported out of the enterocytes to the blood via GLUT2
How does SGLT2 inhibitors affect glucose absorption? where does it act?
works on the kidney
- SGLT2 inhibitors block the receptors. blocking this tranpsort in the collecting duct of the nephron prevents glucose reabsorption. more is peed out to address hyperglycemic issues
- can cause you to pee a lot of sugar, then followed by water.
- can cause rapid weight loss and dehydration
- sugar in urine = infections
- can cause ketoacdisosis.
why is sugar water better for treating diarrhea compared to straight up normall water?
adding sugar and salt can facilitatae uptake of water by activating the SGLT and GLUT channes.
outline the affinity for glucose and describe the general characteristics of GLUT1-4 receptors
GLUT1: basic supply of all cells with glucose
GLUT2: LOW affinity; glucose will only go through this transporter when the glucose levels are very high. seen in the pancreas, liver and intestine
GLUT3: HIGH affinity, glucose will pass through all the time, even inf tehre are low levels of eceptors. located in tissues that always need glucose liek the brain.
GLUT4: insulin senstiive, exercise sensitive, found in MUSCLE and FAT
main location of GLUT4 receptors
muscles and fat. they are insulin and exercise sensitive
main location of GLUT 3 receptors
brain. GLUT3 has high affinity for glucose, so it is locavted in tissues that always need glucose
GLUT2 plays a vital role ot “sense” blood glucose levels, this is important in the pancreas. GLUT2 is ___ affinity.
low affinity. therefore, transport will only occur with high levels of glucose. the low affinity property is the key to its sensing function
outline the steps of the pancreatic repsonse to high glucose. which receptor is involved?
- high glucose in the blood
- glucose moves through cell through GLUT2
- increase in glucose causes an increase in ATP.
- ATP binds to the K+ channel, and the Katp channel closes.
- with no K+ channel open ,there is more K+ in the cell
- the membrane depolarizes
- Ca2+ enters
- Insulin is secreted
what receptor does sulfoneureas act on?
they bind to Katp channels,
two stimuli that causes GLUT4 receptrs on fat and muscle to move glucose into the cell
- insulin
- exercise.
- insulin binds to the insulin receptor, causing signalling through the PI3 kinase. GLUT4 is originally in the cell, but with PI3 signally, they fuse to the cell membrane, allowing glucose to now move into the cell.
what mechanism allows glucose to get trapped into the cell once it moves through the GLUT transporters
upon cell entry, phosphate is bound to glucose. phosphate is charged and therefore does not cross membranes easily. this traps the glucose inside the cell and prepares it for getting destroyed(for energy) or for storage.
how is phosphate involved in refeeding syndrome?
in previously-starving people, they can develop hypophosphatemia because glucose is convereted to glucose-6-phosphate rapidly, causing low phosphate, impairing ATP production. the body becomes free-phosphate depleted.
glycolsis– glucose turns to:
2 molecules of pyruvate
note; there are different types of glycogen storage diseases, which prevents storage of glucose
first step of lipogenesis from carbs
glucose –> 2 pyruvates –> 2 acetyl coA– this happens in the liver
glut2 is a low sensitivity transporter and is lovated on the __ and the ___
pacnreas and liver. glucose only shuttles across when levels are high. therefore, the liver only takes up significant glucose when levels are high in the blood
note; muscle and fat cells only undergo glycogen synthesis and lipogenesis when there is glucose abundance ( post prandial)
outline the neural insulin regulation
- vagus nerve is the major parasympathetic player. Acetylcholine stimulation on muscarinic receptors increases insulin secretion
- sympathetic system is also important; Beta-adrenergic stimulation increases insulin secretion. Alpha adrenergic stimulation decreases insulin secretion. important in exercise.
sympathetic insulin regulation: __-adrenergic stimulation increases insulin secretion. __ adrenergic stimulation decreases insulin secretion
Beta-adrenergic stimulation increases insulin secretion. Alpha adrenergic stimulation decreases insulin secretion
Vagus nerve parasympathetin insulin regulation: __ stimulation on __ receptors
increases insulin secretion
acetylcholine stimulation on muscarinic receptors
increases insulin secretion
outline the secretory products of alpha, beta, D cell, and F cells of the Islets of Langerhanas
glucose is transported into liver via ___ receptor.
proinsulin is degraded into:
via GLUT 2 receptor. proinsulin is degraded to insulin and C-peptide
regulation note
Overall, insulin in an anabolic hormone. Outline 4 building processes it stimulates
- glucose to glycogen
- glucose to ATP
- glucose to triglycerides
- amino acids to protein
glucagon is released by ___ cells in the pancreas when there is ___ blood glucose
released from alpha cells stimulated by low blood glucose. it is a catabolic hormone
the main actions of glucagon are in the ___
are in the liver.
- only at extremely high levels seen in ketoacidosis or sepsis will you see glucagon effects in muscle or fat cells.
main ketone bodies
- acetoacetic acid
- beta hydroxybutyric acid
T/F FFAs can be used by the brain
false. they must be turned into a ketone body. therefore, ketone body production is important for maintaining ATP production in the brain. Ketone body production is increased in low insulin states; starvation or Type I DM
is epinephrine catabolic or anabolic?
it functions in a similar manner as glucagon. increases blood glucose, is also catabolic
3 compounds that reduces glucose, and 4 compounds that increases glucose
reduce glucose: insulin, incretins, exercise
increase glucose: glucagon, epinephrine, growth hormone, cortisol
fill in this table of the organ and transporter characteristics
