Study Chapter 17 Flash Cards

 
Pile Management Card
Chapter 17

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anomer
-differ in configuration at C1 (alpha or beta)
epimers
-differ by only the configuration of a single -OH other than at C1
How dietary starch/glycogen and intracellular glycogen is broken down
-dietary starch/glycogen is first broken down in mouth and then in intestines by hydrolysis of alpha (1-->4) linkages

starch/glycogen ---> oligosaccacharides ---> glucose

-intracellular glycogen is broken down by glycogen phosphorylase into glucose-1-phosphate
-phosphoglucomutase converts G-1-P to G-6-P enters glycolysis
Fate of lactate produced in muscles
-exported from muscles
-carried to liver by blood
-converted to pyruvate
-oxidized by TCA cycle or reconverted to glucose thru gluconeogenesis
alcoholic fermentation
-under anaereobic a=conditions in yeast
-NAD+ is regenerated
-produces EtOH and CO2 in 2 rxns:
1. pyruvate decarboxylase (contains TPP)
2. alcohol dehydrogenase
homolactic fermentation
-occurs when muscle very active
-O2 has been depleted
-lactate dehydrogenase oxidizes NADH via pyruvate to yield NAD+ and lactate
2 types of anaerobic replenishment
1. Lactic acid fermentation (in muscle with no O2)
2. Alcoholic fermentation (in yeast with no O2)

-both regenerate NAD+
Regeneration of NAD+ anaerobically
-NAD+ is replenished by the reduction of pyruvate
-no O2
-must resolve glycolysis with no net oxidation of carbon fuel compounds
-called "fermentation"
-lactic acid fermentation
-alcoholic fermentation
Regeneration of NAD+ aerobically
-NADH passed into mito for re-oxidation
-respiratory chain: NADH reduces O2 to H2O via e- transfer and oxidative phosphorylation
-in muscle
Problem with NADH
Coenzyme NAD+ is limiting, and must be regenerated from NADH
Overall rxn of glycolysis
glucose + 2 ADP + 2 Pi + 2 NAD+ --> 2 pyruvate + 2 ATP + 2 NADH + 2 H+ + 2 H2O
How does a partial deficiency of hexokinase affect ability of RBCs to transport oxygen?
-lower [glycolytic intermediates] b/c hexokinase catalyzes 1st rxn
-lower 2,3-BPG []
-increased Hb oxygen affinity
-person doesn't get as much O2
How 2,3 BPG influences O2 transport
-2,3 BPG specifically binds to deoxy Hb
-RBCs synthesize and degrade 2,3 BPG via detour from glycolysis
Fundamental difference b/w Class I and II Aldolases
-Class I mechanism in notes
-Class II mechanism does not form Schiff base
-instead, a divalent Zn+2 or Fe+2 polarizes the carbonyl oxygen to stabilize enolate intermediate
Class II Aldolase
-in fungi, plants
-no Schiff base
-Zn+2 or Fe+2 polarize carbonyl oxygen of substrate to stabilize enolate intermediate
Class I Aldolase
-in animals and plants
-mechanism in notes
-
*How does hexokinase prevent wasteful hydrolysis of ATP?
-HK catalyzes the transfer of a phosphate group from ATP to glucose to yield GP6, but not to water to yield ADP and Pi
-water can fit in active site!
-glucose induces large conformational change in HK
-like closing jaws on glucose
-places ATP closely to proper -OH of glucose and excludes H2O from the active site
-substrate-induced conformational change in HK is responsible for the enzyme's specificity
-undergo conformational changes upon binding their substrates
*Why is Mg+2 absolutely required for kinases?
Mg+2 functions to shield - charged groups of ATP, making the phosphorous atom more accessible for nucleophilic attack of the -OH of glucose.
*2 major differences between hexokinase and glucokinase
1. HK is non-specific (catalyzes D-glucose, D-fructose, D-mannose) Its Km is 10-20 microM.

2. Glucokinase (aka Hexokinase D) is the predominant isozyme of hexokinase in the liver. It is specific for glucose. Its Km is 10mM.
Why are metal ions good?
-act like H+ to neutralize - charge
-act as Lewis acids
-more effective catalysts than H+ b/c can be present at high []s at neutral pH and can have more than one + charge
alcohol dehydrogenase contains ___.
contains Zn+2 which functions to polarize the carbonyl group of acetylaldehyde
TPP stands for__________. It is a derivative of __________. It is required for the enzyme __________ because _____________.
-thiamine pyrophosphate
-a derivative of vitamin B1
-required because decarboxylation of an alpha-keto acid such as pyruvate requires buid-up of - charge on teh carbonyl carbon in TS.
pyruvate decarboxylase info
-contains tightly, non-covalently associated coenzyme TPP
Which organisms is pyruvate decarboxylase present in?
not in animals
What is the fate of lactate made in muscle cells?
-exported from muscles
-carries by blood to liver
-converted to pyruvate and oxidized by TCA cycle
-or, reconverted to glucose via gluconeogenesis
Is lactate dehydrogenase stereo-specific? What does it make?
yes--> creates L-Lactate
alcoholic fermentation occurs in _______________. It uses the enzyme _______________.
yeast
pyruvate decarboxylase
lactic acid fermentation occurs in ____________. It uses the enzyme _______________.
muscle
lactic dehydrogenase
2 processes of anaerobic replenishment
1. lactic acid fermentation
2. alcoholic fermentation
overall rxn of anaerobic glycolysis
glucose + 2 ADP + 2 Pi --> 2 lactate + 2 ATP + 2 H2O
*Chemical Strategy of Glycolysis
1. Add phosphoryl group to glucose
2. Convert phosphorylated intermediates into compounds with high phosphate group-transfer potentials ("super high energy compounds"
3. Couple hydrolysis of super-high-energy compounds to ATP synthesis (substrate-level phosphorylation)
2,3- biphosphoglycerate
-present in RBCs
-binds with greater affinity to deoxygenated hemoglobin
-2,3-BPG stabilizes the T state of deoxy Hb, making it harder for oxygen to bind to Hb
-helps O2 release to tissues
mutase
enzyme transfers a functional group from one position to another on the same molecule
1,3-biphosphoglycerate is a mixed ___________ between ______________ and ______________.
-anhydride
-carboxylic acid
-phosphoric acid
How many -'s are on ATP?
4
What steps produce ATP?
7. Phosphoglycerate kinase (makes 2)
10. pyruvate kinase (makes 2)
How many high energy compounds are in glycolysis?

What are they?
6. 1,3 bisphosphoglycerate
9. Phosphoenolpyruvate (PEP)
Which rxn is one of catalytic perfection? What is it limited by?
5. triose phosphate isomerase

[dihydroxyacetone phosphate]
catalytic perfection
enzyme produces products as fast as they collide
rate limiting rxn in glycolysis
3. phosphofructokinase
Mg+2
-required for kinase activity
-shields - charges of ATP to facilitate nucleophilic attack of glucose on gamma-phosphate of ATP
hexokinase can operate on...
...glucose, D-mannose, D-fructose
Km of hexokinase vs. glucokinase
Hexo- 10-20 microM
Gluco- 10 mM
glucokinase
-aka hexokinase D
-predominant isozyme of hexokinase in the liver
-Km= 10mM
Glycolysis Step 1 enzyme and mechanism
-Hexokinase
-nucleophilic substitution
Phase 1 begins with the molecule ______________. Phase 2 begins with x_____________.
-glucose
-2 glyceraldehyde-3-phosphates
NADH is a __________ power.
-reducing
Net Profit of Glycolysis
-2 ATP
-2 NADH
-2 pyruvate
Phase 2 of Glycolysis is called the ________________. It creates x_____________.
-Energy Generation or Payoff phase
-4 ATPs
Phase 1 of Glycolysis is called the ________________. It uses x__________.
-Preparatory or Investment phase
-2 ATPs
substrate-level phosphorylation
Couple hydrolysis of super-high-energy compounds to ATP synthesis
anaerobic alcoholic fermentation occurs in ___________ and uses x ________ to create x ___________ molecule(s).
-yeast
-2 NADH
-2 CO2 and 2 ethanol
Aerobic oxidation goes through ____________, uses x__________, goes through _______________, and creates x_____________.
-the citric acid cycle
-2 NADH
-oxidative phosphorylation
-6 CO2 and 6 H2O
anaerobic homolactic fermentation occurs in ___________ and uses x ________ to create x ___________ molecule(s).
-muscle
-2 NADH
-2 lactate
Fermentation
-energy metabolism with no net oxidation of the fuel compounds
Why glycolysis?
-central role
-used by most organisms
-very ancient (developed before lots of O2 in air)
-1st metabolic pathway to be understood
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