Carbohydrate Metabolism and Regulation

Question 1

amylose and amylopectins are examples of:

Answer 1

starches/polysaccharides

Question 2

the most important dietary hexose monosaccharides

Answer 2

glucose, fructose and galactose

Question 3

D-glucose is also called:

Answer 3

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

Question 4

sucrose components

Answer 4

glucose and fructose

Question 5

lactose

Answer 5

galactose and glucose

Question 6

lactulose

Answer 6

galactose and fructose

Question 7

__ 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)

Answer 7

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)

Question 8

bonds in amylose

Answer 8

straight 1-4 bonds, no branches

Question 9

bonds in amylopectin

Answer 9

1-4 connecting bonds, and 1-6 branching bones

Question 10

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?

Answer 10

1. maltose
2. alpha limit dextrins

Question 11

common disaccharidase deficiency that makes someone intolerant to dairy

Answer 11

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

Question 12

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

Question 13

three absorbable sugars

Answer 13

glucose, fructose and galactose

Question 14

which protein transporters allow simple sugars (glucose, fructose and galactose) to cross cell membranes

Answer 14

GLUT; glucose transporter

and SGLT: sodium glucose transporter

Question 15

outline the absorption of CHO process in the gut

Answer 15

• 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

Question 16

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 ___

Answer 16

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

Question 17

How does SGLT2 inhibitors affect glucose absorption? where does it act?

Answer 17

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.

Question 18

why is sugar water better for treating diarrhea compared to straight up normall water?

Answer 18

adding sugar and salt can facilitatae uptake of water by activating the SGLT and GLUT channes.

Question 19

outline the affinity for glucose and describe the general characteristics of GLUT1-4 receptors

Answer 19

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

Question 20

main location of GLUT4 receptors

Answer 20

muscles and fat. they are insulin and exercise sensitive

Question 21

main location of GLUT 3 receptors

Answer 21

brain. GLUT3 has high affinity for glucose, so it is locavted in tissues that always need glucose

Question 22

GLUT2 plays a vital role ot “sense” blood glucose levels, this is important in the pancreas. GLUT2 is ___ affinity.

Answer 22

low affinity. therefore, transport will only occur with high levels of glucose. the low affinity property is the key to its sensing function

Question 23

outline the steps of the pancreatic repsonse to high glucose. which receptor is involved?

Answer 23

1. high glucose in the blood
2. glucose moves through cell through GLUT2
3. increase in glucose causes an increase in ATP.
4. ATP binds to the K+ channel, and the Katp channel closes.
5. with no K+ channel open ,there is more K+ in the cell
6. the membrane depolarizes
7. Ca2+ enters
8. Insulin is secreted

Question 24

what receptor does sulfoneureas act on?

Answer 24

they bind to Katp channels,

Question 25

two stimuli that causes GLUT4 receptrs on fat and muscle to move glucose into the cell

Answer 25

1. insulin
2. 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.

Question 26

what mechanism allows glucose to get trapped into the cell once it moves through the GLUT transporters

Answer 26

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.

Question 27

how is phosphate involved in refeeding syndrome?

Answer 27

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.

Question 28

glycolsis– glucose turns to:

Answer 28

2 molecules of pyruvate

Question 29

Question 30

note; there are different types of glycogen storage diseases, which prevents storage of glucose

Question 31

first step of lipogenesis from carbs

Answer 31

glucose –> 2 pyruvates –> 2 acetyl coA– this happens in the liver

Question 32

glut2 is a low sensitivity transporter and is lovated on the __ and the ___

Answer 32

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

Question 33

note; muscle and fat cells only undergo glycogen synthesis and lipogenesis when there is glucose abundance ( post prandial)

Question 34

outline the neural insulin regulation

Answer 34

1. vagus nerve is the major parasympathetic player. Acetylcholine stimulation on muscarinic receptors increases insulin secretion
2. sympathetic system is also important; Beta-adrenergic stimulation increases insulin secretion. Alpha adrenergic stimulation decreases insulin secretion. important in exercise.

Question 35

sympathetic insulin regulation: __-adrenergic stimulation increases insulin secretion. __ adrenergic stimulation decreases insulin secretion

Answer 35

Beta-adrenergic stimulation increases insulin secretion. Alpha adrenergic stimulation decreases insulin secretion

Question 36

Vagus nerve parasympathetin insulin regulation: __ stimulation on __ receptors
increases insulin secretion

Answer 36

acetylcholine stimulation on muscarinic receptors
increases insulin secretion

Question 37

Question 38

outline the secretory products of alpha, beta, D cell, and F cells of the Islets of Langerhanas

Answer 38

Question 39

glucose is transported into liver via ___ receptor.

proinsulin is degraded into:

Answer 39

via GLUT 2 receptor. proinsulin is degraded to insulin and C-peptide

Question 40

regulation note

Question 41

Overall, insulin in an anabolic hormone. Outline 4 building processes it stimulates

Answer 41

1. glucose to glycogen
2. glucose to ATP
3. glucose to triglycerides
4. amino acids to protein

Question 42

glucagon is released by ___ cells in the pancreas when there is ___ blood glucose

Answer 42

released from alpha cells stimulated by low blood glucose. it is a catabolic hormone

Question 44

the main actions of glucagon are in the ___

Answer 44

are in the liver.

• only at extremely high levels seen in ketoacidosis or sepsis will you see glucagon effects in muscle or fat cells.

Question 45

main ketone bodies

Answer 45

1. acetoacetic acid
2. beta hydroxybutyric acid

Question 46

T/F FFAs can be used by the brain

Answer 46

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

Question 47

is epinephrine catabolic or anabolic?

Answer 47

it functions in a similar manner as glucagon. increases blood glucose, is also catabolic

Question 48

3 compounds that reduces glucose, and 4 compounds that increases glucose

Answer 48

reduce glucose: insulin, incretins, exercise

increase glucose: glucagon, epinephrine, growth hormone, cortisol

Question 49

fill in this table of the organ and transporter characteristics

Answer 49