module 1: easy on the sugar

Question 1

Your doctor is concerned that you might be developing type 2 diabetes and wants to collect a fasting blood sample at 8 AM. Would the results be okay if you forgot and ate a Cinnabon when you woke up at 7 AM?
what are the three things you must know to answer this question?

Answer 1

1. why doctors prefer fasting blood samples
2. what is in a Cinnabon that might alter the laboratory results
3. how quickly could something be absorbed from a Cinnabon that would inappropriately convince your doctor that you have type 2 diabetes

Question 2

what is an oral glucose tolerance test?

Answer 2

sees how well your body handles a known amount of glucose after it has been ingested

• requires that a fasting sample be collected to serve as a baseline value

Question 3

Typically, fasting blood glucose concentrations are less than ___ mg/dl.

Answer 3

110

Question 4

what is the aim of the oral glucose tolerance test after you drink a liquid containing about 75 grams of glucose?

Answer 4

to determine how well this large bolus of glucose has been cleared from your bloodstream by 2 hours, as this gives the pancreas sufficient time secrete insulin into the bloodstream in response to the increase in blood glucose concentration

Question 5

what are the two approaches the glucose tolerance test may be performed:?

Answer 5

1. blood samples are collected 1 and 2 hours after the liquid has been consumed
2. only the 2-hour sample is collected

Question 6

what is the reason for collecting a blood sample after one hour? what should the result be?

Answer 6

to provide evidence that glucose was absorbed by the intestine, as this should result in an increase in blood glucose concentration to somewhere around 180 mg/dl.

Question 7

what values after two hours is the blood glucose at and what can that indicate?

Answer 7

blood glucose at 2 hours is below 140 mg/dl; values higher than 140 mg/dl at 2 hours are indicative of hyperglycemia

Question 8

what are villi?

Answer 8

lines the small intestine and is comprised of tiny finger-like projections

Question 9

what is the purpose of villi?

Answer 9

increases the surface area of the intestinal lining

Question 10

what surrounds the villus by capillaries and intestinal epithelial cells?

Answer 10

central arteriole

Question 11

what is the the surface of epithelial cells comprised of and define it

Answer 11

microvilli
- even tinier finger-like projections into the intestinal lumen

Question 12

why should the intestine have a huge surface area available?

Answer 12

to absorb nutrients as they pass along

Question 13

what is located deep to the intestinal epithelial cells?

Answer 13

interstitial space and then the capillary

Question 14

what is the path glucose follows to get absorbed by the intestine?

Answer 14

move from the intestinal lumen, through the intestinal epithelial cells and interstitial space, and then into the underlying capillary.

intestinal lumen –> intestinal epithelial cells and interstitial space –> underlying capillary

Question 15

what is facilitated diffusion?

Answer 15

molecule binds with a protein to facilitate diffusion down the concentration gradient

Question 16

why doesn’t facilitated diffusion occur with glucose?

Answer 16

• concentration of glucose inside the intestinal epithelial cells is pretty high (higher than inside the epithelial cells than in the intestinal lumen)
• glucose must move against its concentration gradient from the intestinal lumen into the epithelial cells to reach the blood because of its high concentration

Question 17

define the basolateral membrane

Answer 17

membrane between the epithelial cell and the interstitial space

Question 18

in the basolateral membrane, what is the key piece that allows glucose to be absorbed into the blood?

Answer 18

Na+/K+ ATPase

Question 19

Na+/K+ ATPase breaks the high energy bond in ATP to convert it to ___.

Answer 19

ADP

Question 20

overall, at what state does the Na+/K+ ATPase keep the intracellular concentration and how?

Answer 20

low
bc for every 3 Na+ ions the Na+/K+ ATPase pumps against its concentration gradient into the interstitial space, it pumps 2 K+ into the cell

Question 21

define primary active transport

Answer 21

process that uses the energy from ATP

Question 22

what transporter is embedded in the apical membrane that moves both glucose and Na+ from the intestinal lumen into the cell?

Answer 22

sodium-glucose linked transporter (SGLT1)

Question 23

how does SGLT1 transport glucose?

Answer 23

co-transports 2 Na+ and 1 glucose molecules from the lumen into the cell

moves glucose against its concentration gradient (i.e., from where it is in low concentration in the intestinal lumen to where it is in high concentration inside the cell) by coupling it with the energy associated with movement of Na+ down its concentration gradient (i.e., from where it is in high concentration in the intestinal lumen to where it is in low concentration inside the cell)

Question 24

does SGLT1 use ATP and what type of transport is it?

Answer 24

no
secondary active transport

Question 25

by using secondary active transport, where is the glucose getting transported from and to where?

Answer 25

from the intestinal lumen and into the epithelial cells.

Question 26

in the basolateral membrane, how can glucose get from inside the cell into the interstitial space and why?

Answer 26

facilitated diffusion via GLUT2 - can passively move from inside the cell to outside the cell bc concentration of glucose is higher inside the cell than it is in the interstitial space, movement of glucose doesn’t involve Na+, K+ or additional energy

Question 27

once glucose has entered the interstitial space, what does it have to do to finally enter the bloodstream?

Answer 27

diffuse down its concentration gradient through pores (fenestrations) between adjacent endothelial cells that comprise the capillary wall

Question 28

After drinking the test liquid that contains glucose, blood glucose concentrations typically start to increase by about __ minutes and reach their highest values between 150 and 180 mg/dl at __ minutes.

Answer 28

30 60

Question 29

how much sugar is in a cinnabon?

Answer 29

58 g

Question 30

why shouldn't you eat the cinnabon at 7 if your blood sample is taken at 8?

Answer 30

it is highly likely that your “fasting” blood glucose concentration would be well above the high end of the normal range (i.e., 110 mg/dl) at 8 AM if you gobbled down that Cinnabon at 7 AM. Furthermore, the value obtained at 60 minutes likely would exceed 180 mg/dl, as you would have consumed not only the 75 grams of sugar used for the test, but also the 58 grams in the Cinnabon. These results might cause your physician to start treating you with drugs that you don’t need