beyond glucose & control of respiration
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Beyond Glucose & Control of Respiration. Phosphofructokinase (active v. inactive form). Big Questions. 1. How are the processes of cellular respiration controlled in the cell? 2. How do control mechanisms operate in the cell to respond to energy constraints of the environment?. - PowerPoint PPT PresentationTRANSCRIPT
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Beyond Glucose & Control of Respiration
Phosphofructokinase(active v. inactive form)
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Big Questions
1. How are the processes of cellular respiration controlled in the cell?
2. How do control mechanisms operate in the cell to respond to energy constraints of the environment?
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Cellular respiration
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Beyond glucose: Other carbohydrates
• Glycolysis accepts a wide range of carbohydrates fuels
polysaccharides glucosehydrolysis
other 6C sugars glucosemodified
ex. starch, glycogen
ex. galactose, fructose
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NH
HC—OH||OH
|—C—
|R
Beyond glucose: Proteins
amino group = waste product
excreted as ammonia, urea,
or uric acid
NH
HC—OH||OH
|—C—
|R
waste glycolysisKrebs cycle
proteins amino acidshydrolysis
2C sugar = carbon skeleton = enters glycolysis or Krebs cycle at different stages
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fatty acids 2C acetyl acetyl Krebs groups coA cycle
Beyond glucose: Fats
3C glycerol
entersglycolysis
as G3P
enterKrebs cycle
as acetyl CoA
2C fatty acids
fats glycerol + fatty acidshydrolysis
glycerol (3C) G3P glycolysis
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Carbohydrates vs. Fats
fat
carbohydrate
• Fat generates 2x ATP vs. carbohydrate– more C in gram of fat
• more energy releasing bonds– more O in gram of carbohydrate
• so it’s already partly oxidized• less energy to release
That’s whyit takes so much
to lose a pound a fat!
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• Coordination of chemical processes across whole organism– digestion
• catabolism when organism needs energy or needs raw materials
– synthesis• anabolism when organism
has enough energy & a supply of raw materials
– by regulating enzymes• feedback mechanisms• raw materials stimulate
production• products inhibit further
production
Metabolism
CO2
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• Digestion– digestion of carbohydrates,
fats & proteins• all catabolized through
same pathways• enter at different points
– cell extracts energy from every source
Metabolism
CO2
Cells areversatile &
selfish!
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Metabolism
Krebs cycleintermediaries amino
acids
pyruvate glucose
acetyl CoA fatty acids
• Synthesis– enough energy?
build stuff!– cell uses points in glycolysis &
Krebs cycle as links to pathways for synthesis
• run pathways “backwards”– have extra fuel, build
fat!
Cells areversatile &
thrifty!
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coenzyme Aacetyl group
Acetyl coA
ATPFat
CO2
Protein
Lipid
NADHNAD+
Pyruvate
Glycolysis Glucose
Krebscycle
ETC
Glycolysis
Pyruvateoxidation
Central Role of Acetyl CoA• Acetyl CoA is central
to both energy production & biomolecule synthesis
• Depending on organism’s need– build ATP
• immediate use– build fat
• stored energy
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2006-2007
Control of Respiration
Feedback Control
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Feedback Inhibition
• Regulation & coordination of production– final product is inhibitor of earlier step
• allosteric inhibitor of earlier enzyme– no unnecessary accumulation of product – production is self-limiting
A B C D E F G
allosteric inhibitor of enzyme 1
enzyme1
enzyme2
enzyme3
enzyme4
enzyme
5
enzyme6
X
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Respond to cell’s needs
Why is this regulation important?Balancing act: availability of raw materials vs. energy demands vs. synthesis
• Key point of control– phosphofructokinase
• allosteric regulation of enzyme
– why here?“can’t turn back” step before splitting glucose
• AMP & ADP stimulate• ATP & citrate
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A Metabolic economy• Basic principles of supply & demand regulate metabolic
economy– balance the supply of raw materials with the products
produced – these molecules become feedback regulators
• they control enzymes at strategic points in glycolysis & Krebs cycle
– levels of AMP, ADP, ATP» regulation by final products & raw materials
– levels of intermediates compounds in pathways » regulation of earlier steps in pathways
– levels of other biomolecules in body» regulates rate of siphoning off to synthesis
pathways
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ATPFat
Protein
Lipid
Glucose
Krebscycle
ETC
Glycolysis
Pyruvateoxidation
Pyruvate
GlycolysisIt’s a Balancing Act
• Balancing synthesiswith availability of both energy & raw materials is essential for survival!– do it well & you
survive longer– you survive longer &
you have more offspring– you have more offspring &
you get to “take over the world”
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Got the energy…Ask Questions!!
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Review Questions
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1. Glycolysis does not continue if:A. There is no oxygen presentB. NADH is not oxidizedC. FADH is not reducedD. There is excess glucoseE. There is excess CO2
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2. All of the following can serve as the starting material for respiration EXCEPT:
A. GlucoseB. Amino AcidsC. Tri-glyceridesD. StarchE. ATP
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3. You are researching starvation. Which of the following do you hypothesize to be the most likely order of digestion of classes of macromolecules in starving animals?
A. Carbohydrates ->proteins ->lipidsB. Lipids ->carbohydrates ->proteinsC. Carbohydrates ->lipids ->proteinsD. Proteins ->lipids ->carbohydrates
Explain your reasoning.