Lecture 10: Redox Reactions and Glycolysis Flashcards
What is end product inhibition?
When the end product of a metabolic pathway is the allosteric inhibitor, that binds to and inhibits the first enzyme of the metabolic pathway.
What is competitive inhibition?
-When a molecule that looks similar to a substrate binds to the active site and blocks the binding of the substrate that is meant to bind to the active site.
What does competitive inhibition do?
- Inhibits the catalysis of the substrate
When does competitive inhibition occur?
When you take DRUGS
What is allosteric regulation?
-When a regulatory molecule binds to an enzyme on a spot other than the active site and induces a conformational change to the enzyme preventing it from catalyzing reactions further
Why is allosteric regulation more effective than competitive inhibition?
-If you have an enzyme with allosteric inhibition you only need one inhibitor per enzyme. Also molecules can be a variety of shapes and do not need to replicate the shape of the substrate.
- With competitive inhibition you need the same number of competitive inhibitors as there are enzymes in order for it to stop catalyzing
Why is feedback inhibition good?
-Prevents the waste and over production of products
-Allows cells to control the amount of a specific compound
Why is it beneficial to regulate the first enzyme of the metabolic path?
The first enzyme is the one that is regulated to avoid a waste of resources or producing any unnecessary intermediates, also avoids waste of energy and resources
What is cooperativity with enzymes?
-Occurs with two or more identical enzyme subunits forming an enzyme complex
How does cooperativity with enzymes occur?
-When an inhibitor binds to the first enzyme and changes the first enzyme’s conformation this conformational change influences the other subunits of the enzyme to undergo a partial conformation change making the inhibitor of the other enzymes more easily able to bind .
-This helps rapidly shut down the enzyme
What type of curve does the cooperativity of enzymes produce?
A sigmoid curve
Why are the first enzymes in metabolic pathways usually made up of multiple subunits?
First enzymes are usually multiple subunits and regulated by cooperative allostery because when there are more subunits the enzyme is able to be inhibited more rapidly
What is the equation for the metabolism of glucose?
C6H12O6 + 6O2 —– 6CO2 + 6H2O + Free Energy
Why is glycolysis split into multiple steps?
-In order to harvest some of the energy in the form of ATP
-If it was done in one step the energy would all be released as heat
How much energy is harvested into ATP during glycolysis and how much is released as heat?
-About half of the energy that is released during the oxidation of glucose is converted into ATP
-The other half is still released as heat
What is the heat released from glycolysis used for?
-To help drive each step of glycolysis
What is the most important reaction in glycolysis?
Redox reaction
What is reduction?
molecules gains an electron or hydrogen molecule
What is oxidation ?
molecule loses an electron or hydrogen molecule
How to recognize oxidation reactions?
-Oxidation occurs whenever a C-H bond is lost
what molecules are often oxidized? and why?
-Fats
- Oils
-Fossil Fuels
Because they are made up of many C-H bonds and have lots of energy
What molecule is fully oxidized?
Carbon dioxide
What is NAD and its function?
- An essential electron carrier in cellular redox reactions
- Stores and Carries electrons
What is the oxidized and reduced version of NAD?
Oxidized: NAD+
Reduced: NADH
Why are energy carrier used?
Allows the process of glycolysis to be broken down into multiple steps and for energy to be released more gradually so that it is more easily harnessed.
How is NADH oxidized after glycolysis?
With O2 as an electron acceptor
What is redox potential?
The tendency of a molecule to lose/gain electrons
What do redox potential tables show?
-Where electrons will flow to
What does higher on the redox table mean?
Higher on the table means that the electron will flow to that molecule
-Oxygen is highest on the table which is why electrons flow from sugar to oxygen
What is the first step of cellular respiration?
Glycolysis
Where does glycolysis occur?
Cytoplasm
What are the two phases of glycolysis and what steps do they include?
Phase 1(Steps 1-5): Energy investment phase
Phase 2(Steps 6-10): Energy payoff phase
What is the final molecule of the energy investment phase?
G3P
How is ATP created during glycolysis?
Substrate-level phosphorylation
How many ATP molecules are invested in glycolysis and how many are made and net total?
Invested: Two ATPs
Created: Four ATPs
Net Total: Two ATPs
What is the end product of glycolysis?
Two pyruvate molecules
What are all of the products of glycolysis?
-2 Pyruvate
-2 NADH
-2 ATP
What is the key step of glycolysis?
-The reduction of NAD+ to NADH
Steps 2-3 and 4-5 have a positive delta G but no ATP is invested, how do they occur?
-For sequential reactions the delta G values are additive
-FBP to G3P step 4-5 is very unfavorable but since step 5-6 that directly follows G3P to BPG is very favorable and takes away all of the G3P molecules(lowers concentration). It reduces the concentration so much so that the step 4-5 actually becomes favorable.
-Metabolic reactions are generally pulled by one reaction that is favorable and pulls all of the other reactions along because it takes away the products of the previous reaction
How much energy total(heat and captured) is released from the complete oxidation of glucose?
-686 kcal/mol
What happens to C-H and C-O bonds during oxidation?
C-H bonds: decrease
C-O bonds: increase
What is used to generate the phosphate bond in ATP?
Hydrolysis of the “higher-energy phosphate bonds” is used to generate the phosphate bond in ATP
Why is it called substrate level phosphorylation?
Because the phosphate is
transferred from the substrate directly to ADP
What is oxidative phosphorylation?
Where free phosphate is combined with ADP by the ATP synthase enzyme
What does pyruvate become?
Acetyl CoA
Why is acetyl CoA considered an energy carrier?
It contains a C-S bond which is a “high energy bond”
Why is acetyl-coA such an important molecule?
Sugars, fats and man amino acids are all broken down into acetyl-coA
-Acetyl-coA is the building block for making fats and other metabolites
