Transcript SURVEY OF BIOCHEMISTRY - School of Chemistry and …

SURVEY OF BIOCHEMISTRY
Glycogen
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What is Glycogen?
• Branched polymer of glucose
• Storage form of glucose
– Liver
• Maintenance of blood glucose levels, especially
during fasting
– Skeletal Muscle
• Fuel reserve for synthesis of ATP for muscle
contraction
Draw Structure
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Types of Polysaccharide Linkages
• What is an alpha 1->4 linkage?
• What is a beta 1->4 linkage?
• How are monosaccharides branched at
C6?
Illustrate
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Branched Structure of Glycogen
What is meant by
non-reducing vs.
reducing end?
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Reducing v. Nonreducing Sugars
• A reducing sugar has an anomeric C that
has NOT formed a glycosidic bond, such that
it can reduce oxidizing agents.
Recall what an
anomeric C is!
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Reducing v. Nonreducing Sugars
Glycogen has one
reducing end.
All other ends are
non-reducing.
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A Closer Look at Glycogen
• Today: Glycogen Breakdown
• Monday: Glycogen Synthesis
• Wednesday: Control of Glycogen Synthesis
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Three Enzymes Involved in
Glycogen Breakdown
• Glycogen Phosphorylase
– Produces Glucose 1-Phosphate
– Uses Pyridoxal 5’-Phosphate (cofactor)
• Glycogen Debranching Enzyme
– 2 Enzymatic functions
• Produces glucose
• Transfers branches onto main polymer chain
• Phosphoglucomutase
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Glycogen Phosphorylase
Glycogen phosphorylase uses the cofactor
pyridoxal 5’-phosphate to catalyze production of
glucose 1-phosphate from a terminal end of glycogen.
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Glycogen Phosphorylase
Mechanism
1. Formation of a ternary complex
Glycogen
+
Pi
+
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Glycogen Phosphorylase
Mechanism
2. Formation of an oxonium intermediate
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Glycogen Phosphorylase
Mechanism
3. Formation of glucose 1-phosphate
Glucose
1-Phosphate
+ Glycogenn-1
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Three Enzymes Involved in
Glycogen Breakdown
• Glycogen Phosphorylase
– Produces Glucose 1-Phosphate
– Uses Pyridoxal 5’-Phosphate (cofactor)
• Glycogen Debranching Enzyme
– 2 Enzymatic functions
• Produces glucose
• Transfers branches onto main polymer chain
• Phosphoglucomutase
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Glycogen Debranching Enzyme
Transferase
activity
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Phosphoglucomutase
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Glycogen Debranching Enzyme
Transferase
activity
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How To Study
• Learn all 10 steps of Glycolysis
– Substrates
– Products
– Enzymes
– Know general process by which
mechanisms occur
• Learn 3 enzyme activities used to
break down glycogen
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PRS
• What is the maximum number of
O2 molecules that hemoglobin
can bind?
1. One
2. Two
3. Three
4. Four
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PRS
• What is the product formed by the
activity of triose phosphate
isomerase in glycolysis?
1.
2.
3.
4.
Glucose 1-phosphate
Glucose 6-phosphate
Glyceraldehyde 3-phosphate
Pyruvate
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PRS
• How many ATP’s are produced after
the first stage (Steps 1-5) of
glycolysis?
1.
2.
3.
4.
None
One
Two
Four
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PRS
• Which of the following vitamins are
fat soluble?
1.
2.
3.
4.
Vitamin C
Vitamin A
Riboflavin
Folate
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PRS
•
1.
2.
3.
4.
B cells mature in the ________.
Thymus
Bone marrow
Muscle tissue
Myosin
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PRS
• Oxygen binding to myoglobin
results in what shaped curve?
1. Sigmoidal
2. Hyperbolic
3. Linear
4. Sinusoidal
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PRS
• Which of the following amino
acids is not in the catalytic triad
of serine proteases?
1. Ser
2. Thr
3. His
4. Asp
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PRS
•
1.
2.
3.
4.
What is Km?
The catalytic efficiency
The catalytic rate constant
1/2 Vmax
[S] at 1/2 Vmax
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