April 14, 2016 - Carbohydrate Metabolism

Question 1

Types of Carbohydrates

Answer 1

Sugars (small molecules of monosaccharides or disaccharides)

Starches (polysaccharides)

Question 2

D5W

Answer 2

5% dextrose (L-glucose) in water

Question 3

Lactulose

Answer 3

A non-digestible sugar used as medication.

100% remains in the GI tract, and through osmosis, draws water into the GI tract. It is used to treat constipation by giving you diarrhea.

Can also increase the colonic elimination of NH4+ for hepatic encephalopathy.

Question 4

Alpha 1-4 Bonds

Answer 4

Bonds connecting glucose monomers together.

Can be broken by amylase.

Question 5

Alpha 1-6 Bonds

Answer 5

Used as branch points off glocuse.

Question 6

Amylase

Answer 6

Can break down alpha 1-4 bonds in amylose and amylopectin but…

Cannot break a1-4 bonds

Cannot break a1-4 bonds next to a1-6 bonds

Cannot break a1-4 bonds that are terminal

Because it can’t break the terminal chains, no glucose monomers can be made.

Question 7

Sources of Amylase

Answer 7

Saliva (a little)

Pancreas (a lot)

Question 8

SGLT2 Inhibitor

Answer 8

Blocks SGLT2 in the kidney and prevents the uptake of glucose.

This causes you to pee a lot of sugar (followed by water). This can cause rapid weight loss and dehydration.

Question 9

SGLT

Answer 9

Sodium GLucose coTransporter

Uptakes one sodium and one glocuse into the cell.

This is why oral rehydration packets are so effective.

Question 10

GLUT1

Answer 10

Basic supply of all cells with glucose

Question 11

GLUT2

Answer 11

Low affinity for glucose (need a lot of glucose before they will uptake)

Found in the pancreas, liver, and intestines

Question 12

GLUT3

Answer 12

Has a high affinity for glucose (will uptake even at low levels).

Found in the brain

Question 13

GLUT4

Answer 13

Insulin sensitive transporters

Exercise sensitive transporters

Found in muscle and fat cells

Not expressed on the surface unless insulin or exercise is present. When this occurs, it can increase the glucose transport by a factor of 10-20.

Question 14

Pancreas Response to Glucose

Answer 14

High levels of glucose will stimulate GLUT2 in the pancreas and glucose will be transported into the cell. In the cell, glucose makes ATP which binds to potassium channels and closes them so the potassium stays inside, which will depolarize the membrane of the cell, allow calcium ions to enter, and secrete insulin.

Sulfonureas block the potassium ATP channel and keep potassium inside the cell all the time, which makes it easier to secrete insulin.

Question 15

Fate of Glucose Inside the Cell

Answer 15

Metabolized to make ATP

Stored as glycogen

Stored as triglycerides

Question 16

Glucose and Phosphate

Answer 16

Upon entry to the cell, glucose is bound to phosphate.

Because phosphate is charged and does not cross membranes easily, the glucose is trapped inside the cell.

This can also lead to refeeding syndrome where suddenly refeeding a patient can cause phosphate levels to bottom out, along with potassium levels, and the patient can go into cardiac arrest and die.

Question 17

Refeeding Syndrome

Answer 17

During starvation, phosphate levels become low.

When a person is re-fed quickly, the rush of glucose entering the cells bottoms out the phosphate level and there are no phosphates left to create ATP. This can lead to cardiac arrest and death.

Question 18

Lactic Acidosis

Answer 18

Occurs with anaerobic metabolism

An elevated lactate is a big red flag that something pathological is going on. Could be full or regional hypoperfusion

Question 19

Liver - Post Prandial

Answer 19

Glocuse enters the liver through the GLUT2 receptor where it is broken down through glycolysis to make ATP, stored as glycogen, and stored as triglycerides.

Question 20

Muscles - Post Prandial

Answer 20

Glucose enters through the GLUT4 transporter because of the insulin response.

Glocuse is used for ATP for energy, and is stored as glycogen.

(No storage as TGA)

Question 21

Fat - Post Prandial

Answer 21

Glocuse enters through the GLUT4 transporter because of the insulin secretion.

This is broken down into acetyl CoA which is further broken down into triglycerides for storage.

Question 22

Sympathetic System and Insulin

Answer 22

Beta-adrenergic stimulation increases insulin secretion

Alpha-adrenergic stimulation decreases insulin secretion

Question 23

Pancreatic Islet of Langerhans Cells

Answer 23

Alpha-cells = glucagon

Beta-cells = insulin

Delta-cells = somatostatin

F cells = pancreatic polypeptide

Question 24

Ketogenesis

Answer 24

The production of ketone bodies

These can be used by the brain for energy and ketone body production is increased in low insulin states

Commonly seen in starvation, or in Type 1 DM (even though you have enough sugar, your liver can’t shut down ketone production without insulin)