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9 Cards in this Set

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  • Back
List the alternative fates of Acetyl-CoA.

That is, how is Acetyl-CoA used by the body.
Acetyl CoA has 4 fates or paths of usage:
1) goes to Krebs to make energy -> ATP, H20, CO2
2) used in lipogenesis to fatty acids -> esterification to TAG
3) used in ketogenesis to make ketone bodies
4) used in cholesterologenesis to make cholesterols -> steroids
Compare the "preferred fuels" of liver, skeletal m., heart, adipose tissue and brain.
Brain -> fed state uses glucose , starvation uses ketone bodies and glucose
Liver -> aa, glucose, FA
Heart-> FA
Adipose tissue -> FA
Skeletal m. -> at rest uses FA and during exertion uses glucose
Identify the major DIETARY carbohydrates and the foods in which they are found.
Amylopectin ->rice, potato, corn, bread
Amylose -> rice, potato, corn, bread
Lactose-> milk, milk products
Fructose -> fruit, honey
Sucrose -> table sugar, desserts
Glucose ->fruit, honey, grapes
What are the enzymes in the brush borders of enterocytes that breakdown dietary carbohydrates?
Isomaltase/α-dextrinase breaks down Amylopectin into gluc, maltooligosaccharides

Maltooligosaccharides are broken down by glucoamylase into glucose

Maltase breaks down Amylose into glucose

Sucrase breaks down sucrose -> gluc & fruc

Lactase breaks down lactose -> gluc & galactose
Explain the consequences of consuming milk by an individual who has lactose intolerance (genetic deficiency of lactase).
In the prox. jejunum ther is no lactase to break down lactose at the β-1,4 glycos linkage to produce glucose and galactose to be transported by SGLT1 with Na.

Lactose stays in the intestinal lumen where it is osmotically active and isoosmotically retains water causing osmotic diarrhea.
Excess gas is caused by fermentation of the undigested, unabsorbed lactose to methane and hydrogen gas.
Identify the GLUTs that are responsible for
Na dependent glucose transport
Insulin dependent glucose transport
Insulin independent low affinity, high capacity transport in liver
Na dependent
SGLT1 -> gluc & galac w/ Na
Insulin dependent
GLUT4 (in muscle, heart, adipocytes)
Insulin independent, low aff, high capac
GLUT2 (liver, intestines, kidney)
GLUT3 in brain

FYI Fructose transporter is GLUT5 in sk. m, adipose tiss & RBC
Identify 3 Glycolytic rxns that are irreversible under physiological conditions

What are the enzymes that catalyze each of these rxns?
1) G converted by Hexo/Glucokinase to G-6-P -> 1 ATP consumed
2) F-6-P converted by PFK-1 to F-1,6-BP this is the committed step! I ATP consumed
3) PEP converted by Pyruvate kinase to Pyruvate -> produces 1 ATP for each pyruvate produced
Compare characteristics of Hexokinase and Glucokinase

What tissues?
Kinetic traits?
☆Hexokinase enzyme found in all cells
☆ low Km for glucose ~0.1mM -> sat @ low gluc. -> high affinity
☆ allosterically inhibited by its prod G-6-P feedback inhibition
☆always made and expressed in cytosol
✭ Glucokinase enzyme found in liver & pancreas
✭high Km for gluc ~7-10mM not saturated at physio gluc conc. -> low affinity
✭ Regulated by glucose which increases its activity by causing GK to move to cytosol.
✭F-6-P decreases activity by causing GK to move back to nucleus
✭GK is induced -> not made all the time -> induced by insulin
Compare the allosteric activitors and inhibitors of the 3 enzymes that catalyze the irreversible glycolytic rxn