Start of Exam 2 Ch. 16 and 17

Glycogen is a branched carbohydrate polymer composed of  

Glycogen main chains are   glycosidic linkages, whereas at branch points
the linkage is  .

Glycogen serves as a source of stored glucose mainly in   and  

Glycogenolysis (breakdown of  ) in   results in the production of glucose,
which is released into blood, and eventually utilized by various other tissues

The major site of glucose consumption (75%) is  , through  .

In the liver, a glucokinase reaction occurs that makes Glucose + ATP into  . The Km for glucose is high with  unlike  .

The product of glycogenolysis ( ) in muscle is not available to other tissues, since muscle lacks the crucial enzyme  .

Animals use   (alpha or beta) for glycogen synthesis

Plants use   (alpha or beta) of glucose for cellulose biosynthesis and   for starch synthesis.

The Synthesis of glycogen from glucose is carried out by the enzyme  

Glycogen synthase utilizes an activated glucose monomer  , to extend the polymer
by  .

What type of reaction forms large glycogen polymers?

Glycogen = straight chain polymer of glucose with  

How is UDP-glucose made? What enzyme catalyzes this rxn?

What happens to the pyrophosphate that is formed?

What is significant about the pyrophosphate becoming 2 inorganic phosphates?

The energy of the phospho-glycosyl bond of UDP-glucose is utilized by glycogen synthase to
catalyze the incorporation of   into  

What is the primer in glycogen synthesis?

Glycogenin autocatalytically attaches  of a UDP-glucose (UDPG) to its  . From the first glucosyl residue   more glucosyl units are sequentially added using   to form an   attached to glycogenin.

The glucose   formed at the bgeinning of glycogen synthesis has shown to be needed as a primer in glycogen synthesis

UDP is   used in the formation of the polymer unit. It is a  

The alpha-1,6 branches in glycogen are synthesized by a (alpha -1-4)- (alpha-1-6)-glucan transferase commonly known as  

What does branching enzyme do?

The terminal fragment that branching enzymes uses must be a polymer at least   glucose long

Glycogen terminal with free hydroxyl on C4 is called the  

The glycogen terminal with free hydroxyl at the C-1 carbon is called the  

The degradation of glycogen (glycogenolysis) is catalyzed by 

Glycogen phosphorylase contains a   moiety covalently attached to the   residue of the enzyme which participates in the catalysis

What is the function of the PLP (vitamin B6) phosphate?

Where does the degredation of glycogen start?

How is the terminal residue at the reducing end cleaved?

How does glycogen phosphorylase break down glycogen units?

By phosphorolysis a single glucose residue is removed at a time to form  

How does alpha-amylase break down glucose (specific instance in the stomach and pancreas)?

What is the benefit of phosphorolytic cleavage?

At   before a branching point, phosphorylase stops cleaving the glycogen

Once the branch is down to four residues,  , (alpha -1-4)- (alpha-1-4)-glucantransferase activity) takes over.

First (alpha-1-4)- (alpha-1-4)-glucantransferase, domain activity transfers the  on to another branch. Then the   activity removes the last glucose residue from the branch by  

In muscle, what happens to the free glucose that is released?

Glucose 1-phosphate produced by the action of phosphorylase is converted into
  by the enzyme phosphoglucomutase.

Glucose 1-phosphate is
 a direct precursor for glycolysis

Phosphoglucomutase contains a  in the active site. The enzyme linked covalent phosphate is transferred to C-6 of glucose 1-phosphate, generating   as a transient intermediate. The phosphate on the C-1 is then transferred to the enzyme regenerating the phospho enzyme and releases  as a product.

In muscle the sole purpose of glycogenolysis is to breakdown glycogen, to form
 , which is converted into  

It is interesting to note that   is absent in muscle, therefore the only fate for the glucose 6-phosphate is to enter the glycolytic pathway for ATP production

In liver, the enzyme glucose 6-phosphatase releases , which enter the
bloodstream for maintaining  .

Regulation of an enzyme activity by an effector or a metabolite that binds to allosteric site is
called  

  is a compound other than the substrate that modulates
enzyme activity in allosteric regulation

During basal cellular needs, , controlled by metabolites, governs the glycogen breakdown, which is sufficient to provide the needed energy for various cell types. It does this by   and   regulation.

Glycogen phosphorylase (phosphorylase-b) is a homodimeric enzyme that has a  and  state. R state is stabalized by   and inhibited by   and  

During the resting state, the unmodified form (Phosphorylase-b), is
sufficient to generate   for entry into glycolysis, for the production of ATP,
both in liver and muscle, however during high energy demand,   is needed.

When blood sugar is low, alpha cells of pancrease secrete glucagon which causes activation of   which forms  , which binds to   and causes the formation of the   because of the removal of an R unit.

The active catalytic subunit (dimer) (C2) of PKA then activates  
by phosphorylating critical   residues. Now activated, it in turn
phosphorylates   converting into active  .

Epinephrine binds to its
receptor in muscle cell and activates the  

When epinephrine is released during flight or fight, glycogenolysis   and glucose-1-phosphate is produced and isomerized to  . It enters glycolysis after step 1 and so it  

Each stored glucosyl unit of glycogen would yield   as opposed to the free glucose which would yield a   ATP.

In hormonal regulation/insulin secretion, phosphorylase kinase activity is also affected by  

The binding of Ca2+to calmodulin like subunit, induces a conformational change, which in turn  

During glycogenolysis,   increase.

Glucagon (Signals  ,   in Liver)

Epinephrine Stimulates Glycogen  in
 and  

The signaling mechanism in glycogenolysis is mediated by secondary messengers  and  .

The action of epinephrine at alpha -adrenergic receptors is coupled through   that
activates  .

Activation of PLC leads to the hydrolysis of   into   and  

  binds to and activates protein kinase C (PKC) an enzyme that phosphorylates numerous
substrates, one of which is  

IP3 binds to receptors on the surface of the
endoplasmic reticulum leading to the  

The Ca2+ binds to the calmodulin like subunit of  , resulting in its activation. Ca2
+ also directly activates  similar to DAG.

Glycogenolysis is “turned off” by  

The activity of PP-1 must be closely regulated so that it does not  

Phosphorylase leads to activation of  , whereas phosphorylation in the case of   inactivates it, avoiding the futile cycle

Glycogen synthase is a consisting of  identical subunits

The activity of glycogen synthase is regulated by   residues in the subunit proteins.

Phosphorylation of glycogen synthase reduces its affinity toward its substrate  

In the non-phosphorylated state, glycogen synthase does not require   as an allosteric activator (  of glycogen synthase)

In the phosphorylated state, glycogen
synthase requires the allosteric activator,   (  of glycogen synthase).

The D form corresponds to the phosphorylated and (less active) form also termed as   and the I form corresponds to the non-phosphorylated, glucose 6-phosphate independent form termed as  

Phosphorylation of synthase occurs primarily in response to hormonal activation of 

One of the major kinases that phosphorylates glycogen synthase is
 ; the same enzyme that phosphorylates g 

What is an example of a enzyme that can phosphorylate glycogen its own?

What are the effects of ephinephrine binding to alpha-adrenergic receptors for the glycogen synthase?

Insulin in general is an   hormone, whereas glucagon is a
hormone that induces   events

What is Von Gierke's disease?

What would not be impacted by Von Gierke's disease? Why?

Pompe’s Disease

McArdles Disease

Cori’s Disease

Andersen’s Disease

Hers Disease

In Type 1 Diabetes, the   is very low, the liver is breaking down and
depleting the storage glycogen to make further increasing amounts of glucose.

Cataracts form in diabeteics why?

Glycoconjugates are formed in Type 1 Diabetes by the   of glucose
that forms linkages with many proteins either with the amino terminal residue or with reactive
lysines. This non-enzymatic glycation artificially damages many protein/enzyme activities

Type I diabetics due to low levels of insulin exhibit in the blood (i.e., High
Levels of  in the blood). Normally, lipoprotein lipase responds to insulin and converts TG of liver VLDL into   and  . In diabetes,   continues to circulate in blood.

In type 2 diabetes, the body is resistant to  
administration.

If there is a pancreatic tumor of the beta-cell region of pancreas, then the
hormone insulin is  . This means the insulin/ glucagon ratio is  . This leads to over uptake of glucose into cells resulting in  

3 difference between diabetes and hyperlipidemia

 = Increased Urination
 = Increased Thirst
 = Increased Hunger

What is the significance of metformin?

How is AbA1C formed?

What is glucose comverted to?