Biochem 3 Exam Review

Front 1

What is the pathway by which lypolysis is triggered?

Back 1

Glucagon/catecholamines--> cAMP--> Protein kinase A--> lipases--> lypolysis--> release of FA to bloodstream

Front 2

In the liver, where does TG synthesis occur? What triggers TG synthesis?

Back 2

In the cytosol. The AcCoA needs to be transported as citrate into the cytosol, where it can be converted back to AcCoA. This is stimulated by insulin in the fed state.

Front 3

What effect does insulin have on proteins and amino acids?

Back 3

Insulin stimulates synthesis of proteins from amino acids.

Front 4

What stimulates the proliferation of GLUT4 receptors in muscle and adipose cells?

Back 4

Insulin binds to receptors of the cell membrane and causes the deployment of GLUT4 receptors from their storage vesicles.

Front 5

True or false: adipose tissue can synthesize TG's from glycerol.

Back 5

False. Adipose tissue can only synthesize TG's from Glycerol 3P.

Front 6

What are TG's made of?

Back 6

Glycerol 3-P (from glucose) and FACoA (from FA's).

Front 7

What three pathways in the liver are activated by insulin?

Back 7

Glycolysis
Glycogenesis
Fatty acid synthesis

Front 8

What four pathways in the liver are inhibited by insulin?

Back 8

-Glycogenolysis
-Gluconeogenesis
-Fatty acid oxidation
-Ketone body formation

Front 9

What 2 processes in adipose tissue are stimulated by insulin? HINT: to build TG's!

Back 9

-Deployment of GLUT4 transporters to get glucose into the cell
-Secretion of LPL (lipoprotein lipase) to break down chylomicrons and get FA's into the cell

Front 10

What process in adipose tissue is inhibited by insulin?

Back 10

-Lypolysis is inhibited by supressing hormone sensitive lipase

Front 11

What four pathways in mucle are activated by insulin?

Back 11

-Glycolysis
-Glycogenesis
-GLUT4 deployment to get glucose into the cell
-Protein synthesis from amino acids

Front 12

What process in muscle tissue is inhibited by insulin?

Back 12

Protein breakdown

Front 13

At what end of glycogen does a new glucosyl add?

Back 13

-At non-reducing terminus

Front 14

What is the key enzyme in glycogen synthesis? What causes it to be activated?

Back 14

-Glycogen synthase
-Active when insulin is present. Active in unphosphorylated form (catecholamines and glucagon cause cascade for phosphorylation).

Front 15

What is the key enzyme in glycogenolysis? What causes it to be activated?

Back 15

-Glycogen phosphorylase
-Activated by presence of glucagon--> cAMP--> protein kinase A--> phosphorylated (activated) glycogen phosphorylase!

Front 16

What is the enzyme in the liver that allows it to export glucose?

Back 16

Glucose 6-phosphatase.

Front 17

What 3 things initiate glucogenolysis in a muscle cell?

Back 17

-Epinephrine--> cAMP--> Protein kinase A--> activated glycogen phosphorylase
-Ca2+ --> activated glycogen phosphorylase
-AMP--> activated glycogen phosphorylase

Front 18

How many ATP do you get from glycolysis of G-1-P (from glycogenolysis)?

Back 18

3ATP/G-1-P
-Normal glycolysis yields 2 ATP (2in, 4out) but if you enter the cycle with a G-P, then you have to put less ATP it (1in, 4out).

Front 19

How does glycogen degradation proceed?

Back 19

-Phosphorylase takes residues off the main strand (alpha-1,4 linkages) and residues off the branch (alpha-1,6 linkage) until the branch is down to 4 residues.
-Three residues from the branch are transferred to the main strand, leaving a single residue on the branch with an alpha-1,6 linkage.
-An alpha-1,6 glucosidase takes off the last residue on the branch while phosphorylase continues down the main strand.

Front 20

What is the thermodynamic trick to building glycogen?

Back 20

Use UDP-glucose to drive the reaction. Hydrolysis of pyrophosphate makes it favorable.

Front 21

How does glycogen synthesis proceed?

Back 21

-Starts with a primer (made by glycogenin)
-Glycogen synthase adds residues with alpha-1,4 linkages.
-Another enzyme, 4,6 transferase, transfers 7 residue blocks onto a branch.

Front 22

What initiates glycogenesis? How does it do it? (2 ways)

Back 22

-Insulin
-Activates phosphatases to get rid of glycogen phosphorylase and help glycogen synthase.
-Deploys GLUT4 receptors to get more glucose into the cell to build glycogen.

Front 23

What activates phosphatases?

Back 23

Insulin activates phosphatases

(Catecholamines activate kinases)

Front 24

What activates kinases?

Back 24

Catecholamines and glucagon activate kinases

(Insulin activates phosphatases)

Front 25

What cofactor is frequently required for carboxylations? (eg carboxylation of pyruvate to oxaloacetate)

Back 25

Biotin

Front 26

What cofactor is frequently required for difficult decarboxylations? (eg alpha-decarboxylation of pyruvate to AcCoA

Back 26

Thiamine

Front 27

What are 4 fates of pyruvate?

Back 27

-AcCoA
-OAA
-Lactate
-Alanine

Front 28

When gluconeogenesis is occuring, what process is likely occuring as well? (Think about those triggered by glucagon via cAMP)

Back 28

-Ketone body synthesis (increased FA's from lipolysis)
-Incidentally, PEP is no longer being converted to pyruvate and pyruvate is no longer being converted to AcCoA. Fatty acids are powering the TCA cycle AND producing ketone bodies.

Front 29

What enzyme is defective in Von Gierke's disease?

Back 29

Glucose 6-phosphatase. Can't get glucose out of the liver

Front 30

What enzyme is defective in Pompe's disease?

Back 30

alpha-1,4 glucosidase. Can't use glycogen stores at all.

Front 31

What enzyme is defective in McArdles disease?

Back 31

Phosphorylase. Can't use glycogen.