NS 3310 1st Edition Lecture 7Outline of Past LectureI. Cholesterol Gallstone DiseaseII. Carbohydrates: Forms III. Carbohydrate DigestionOutline of Current LectureI. Review of Cholesterol Gallstone Disease: FXRII. Absorption of Glucose, Galactose, and FructoseIII. Glucose TransportersIV. Glycemic Response to CarbohydrateCurrent LectureI. Review of Cholesterol Gallstone Disease: FXR- If there is a high concentration of bile in the hepatocytes, FXR is activated. FXR goes to the nucleus and activates gene transcription of transporters while repressing CYP7A1. This reduces bile acid synthesis and increases export- If there is a low concentration of bile in the hepatocytes, FXR will not be activated because there is not enough bile (hormone) to activate it. CYP7A1 will be activated so there will be more bile acid synthesis and reduced export of bile acidII. Absorption of Glucose, Galactose and FructoseThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- Glucose and galactose require active transport to get into the cell. This is possible with the transporter SGLT1- In order for glucose and galactose to get into the blood, facilitated diffusion is necessary by the use of GLUT2- Fructose gets into the cell by facilitated diffusion using GLUT5 and into the blood by facilitated diffusion with GLUT2- Glucose absorption in enterocytes:-On brush border, SGLT1 transports glucose and galactose mediated by active transport. For active transport to work, the transporter requires sodium.-SGLT1 simultaneously transports sodium and glucose in same direction (it is a symporter); Na+ goes with its concentration gradient and glucose goes against it-Must bind Na+ in order to bind glucose-Once Na+ is released into the cell, affinity for glucose decreases and releases it into the cell as well-The sodium-potassium pump then pumps sodium out of the cell and potassium into thecell in order to maintain the concentration gradientIII. Glucose Transporters- Glucose transporters: GLUT isoforms-Integral transmembrane proteins-Undergo a conformational change upon binding the carbohydrate -Can reverse this change upon dissociation- Specificity of GLUTs-GLUT1: basic supply of glucose to cells-GLUT2: low-affinity transporter; glucose from enterocyte to blood; in hepatocytes and beta cells-GLUT3: high-affinity for brain and other glucose-dependent tissues-GLUT4: insulin sensitive, in muscle and adipose tissue-GLUT5: for fructoseIV. Glycemic Response to Carbohydrate- Glycemic index is the increase in blood glucose during 2-hour period after consumption of a certain amount of carbohydrate compared with equal carbohydrate from reference food-it is a way to classify carbohydrate based on the ability to change blood glucose