BIOC 3560 - FINAL
What is metabolism?
The sum of chemical transformations
What do metabolic pathways involve?
Enzymes
What is catabolism?
Degradation of biomolecules
What is anabolism?
Synthesis of biomolecules
In the process of catabolism, what do precursor molecules become?
Precursor molecules become cell macromolecules
In the process of anabolism, what do energy containing nutrients become?
Energy containing nutrients become energy depleted end products
What are 3 types of pathways in carbohydrate metabolism?
1. Converging catabolism
2. Cyclic pathway
3. Diverging anabolism
What do the coloured shaped in the rate-limiting steps represent?
Substrates and products
What do the number of shapes correspond to in the rate limiting steps?
Number of shapes corresponds to the relative concentration of the
substrate/product
What do the rates of biochemical pathways depend on?
Rates of biochemical pathways depend on the activities of enzymes that catalyze
each step
,How are the rates of most steps limited?
Most steps limited by substrate availability (enzyme is in excess)
What is the reason for having the rate limiting step?
The rate limiting step will set the overall speed of the pathway
What are rate limiting steps? (2)
1. Exergonic
2. Irreversible
What does it mean to be strongly exergonic?
Makes reactions essentially irreversible
Are enzymes that catalyze exergonic rate-limiting steps a target of metabolic
regulation? What does this allow the cell to regulate?
Yes
This allows the cell to regulate the overall rate of metabolic pathway without
regulating every single enzyme involved
How are enzymes regulated?
1. Extracellular signals
2. Transcription of specific genes
3. mRNA degradation
4. mRNA translation on ribosome
5. Protein degradation (ubiquitin; proteasome)
6. Enzyme sequestered in sub cellular organelle
7. Enzyme binds substrate
8. Enzyme binds ligand (allosteric effector)
9. Enzyme undergoes phosphorylation/dephosphorylation
10. Enzyme combines with regulatory protein
In glycolysis, what enzymes are highly exergonic and regulated?(3)
1. Hexokinase
2. Phosphofructokinase-1
3. Pyruvate kinase
How is hexokinase inhibited by its product?
, Allosterically
How does hexokinase catalyze the reaction in step 1 of glycolysis?
Hexokinase catalyzes the reaction that allows entry of glucose into glycolysis
In the muscle, what type of hexokinase is expressed? What are its
characteristics? (2)
Hexokinase 1
1. Maximal acitivty
2. If [Glucose 6-P] increases, enzyme is inhibited (-ve feedback)
In the liver, what type of hexokinase is expressed? What are its
characteristics? (4)
Hexokinase IV (glucokinase)
1. Isozyme
2. Lower affinity for glucose
3. Inhibited by fructose 6-P not glucose 6-P
4. Inhibition by fructose 6-P effected through glucokinase regulatory protein
How does [fructose-6-P] act to regulate hexokinase IV?
When [fructose-6-P] is high, glucokinase regulatory protein sequesters hexokinase
IV in the nucleus
What does high glucose do to the enzyme/regulator interaction?
High glucose weakens the enzyme/regulator interaction, encouraging cytosolic
localization
Does Glucose-6-P have several possible fates in the cell?
Yes
What does phosphorylation of Phosphofructokinase-1 (PFK-1) do?
Commits fructose 6-phophate to glycolysis
How is allosteric regulation of PFK-1 complex? (4)
1. ATP binds to an allosteric site on PFK-1 and lowers affinity for fructose 6-P
2. ADP and AMP receive inhibition of ATP
3. Citrate increases the inhibition by ATP
4. Fructose 2,6-bisphosphate is a strong activator
What is metabolism?
The sum of chemical transformations
What do metabolic pathways involve?
Enzymes
What is catabolism?
Degradation of biomolecules
What is anabolism?
Synthesis of biomolecules
In the process of catabolism, what do precursor molecules become?
Precursor molecules become cell macromolecules
In the process of anabolism, what do energy containing nutrients become?
Energy containing nutrients become energy depleted end products
What are 3 types of pathways in carbohydrate metabolism?
1. Converging catabolism
2. Cyclic pathway
3. Diverging anabolism
What do the coloured shaped in the rate-limiting steps represent?
Substrates and products
What do the number of shapes correspond to in the rate limiting steps?
Number of shapes corresponds to the relative concentration of the
substrate/product
What do the rates of biochemical pathways depend on?
Rates of biochemical pathways depend on the activities of enzymes that catalyze
each step
,How are the rates of most steps limited?
Most steps limited by substrate availability (enzyme is in excess)
What is the reason for having the rate limiting step?
The rate limiting step will set the overall speed of the pathway
What are rate limiting steps? (2)
1. Exergonic
2. Irreversible
What does it mean to be strongly exergonic?
Makes reactions essentially irreversible
Are enzymes that catalyze exergonic rate-limiting steps a target of metabolic
regulation? What does this allow the cell to regulate?
Yes
This allows the cell to regulate the overall rate of metabolic pathway without
regulating every single enzyme involved
How are enzymes regulated?
1. Extracellular signals
2. Transcription of specific genes
3. mRNA degradation
4. mRNA translation on ribosome
5. Protein degradation (ubiquitin; proteasome)
6. Enzyme sequestered in sub cellular organelle
7. Enzyme binds substrate
8. Enzyme binds ligand (allosteric effector)
9. Enzyme undergoes phosphorylation/dephosphorylation
10. Enzyme combines with regulatory protein
In glycolysis, what enzymes are highly exergonic and regulated?(3)
1. Hexokinase
2. Phosphofructokinase-1
3. Pyruvate kinase
How is hexokinase inhibited by its product?
, Allosterically
How does hexokinase catalyze the reaction in step 1 of glycolysis?
Hexokinase catalyzes the reaction that allows entry of glucose into glycolysis
In the muscle, what type of hexokinase is expressed? What are its
characteristics? (2)
Hexokinase 1
1. Maximal acitivty
2. If [Glucose 6-P] increases, enzyme is inhibited (-ve feedback)
In the liver, what type of hexokinase is expressed? What are its
characteristics? (4)
Hexokinase IV (glucokinase)
1. Isozyme
2. Lower affinity for glucose
3. Inhibited by fructose 6-P not glucose 6-P
4. Inhibition by fructose 6-P effected through glucokinase regulatory protein
How does [fructose-6-P] act to regulate hexokinase IV?
When [fructose-6-P] is high, glucokinase regulatory protein sequesters hexokinase
IV in the nucleus
What does high glucose do to the enzyme/regulator interaction?
High glucose weakens the enzyme/regulator interaction, encouraging cytosolic
localization
Does Glucose-6-P have several possible fates in the cell?
Yes
What does phosphorylation of Phosphofructokinase-1 (PFK-1) do?
Commits fructose 6-phophate to glycolysis
How is allosteric regulation of PFK-1 complex? (4)
1. ATP binds to an allosteric site on PFK-1 and lowers affinity for fructose 6-P
2. ADP and AMP receive inhibition of ATP
3. Citrate increases the inhibition by ATP
4. Fructose 2,6-bisphosphate is a strong activator
