Midterm 2 study guide Flashcards
How is ATP used as a source of energy in cells
The hydrolysis of ATP to ADP and Phosphate releases energy, and this is a favorable reaction
What does “favorable” mean in terms of ΔG (aka: free energy)?
A reaction is favorable when ΔG is negative, meaning it is spontaneous
Explain the process of reaction coupling to ATP
The process where hydrolysis of ATP (A thermodynamically favorable, - ΔG, or spontaneous reaction) is coupled with a thermodynamically unfavorable reaction to lower ΔG
How does reaction coupling drive an unfavorable process or reaction?
Reaction coupling can make an overall process spontaneous by combining two reactions
As long as the products are more stable than the reactants overall
What are the 3 high energy phosphate compounds
ATP, 1,3 BPG and PEP
In general, what does it mean to have high “phosphotransfer” potential energy?
-Phosphotransfer potential energy is the standard free energy of hydrolysis
-It is a way to measure the tendency of an organic molecule to transfer a phosphoryl group to an acceptor molecule
-ATP > ADP > AMP
Name the two major electron carrier molecules in the cell
FAD and NAD+ = high reduction potential
The energy associated with electron carriers is reduction potential (ie: electron transfer potential). Explain how coupling to an electron carrier can drive an unfavorable reaction
Coupling with electron carriers like NAD⁺ and FAD enables energetically unfavorable reactions by providing a source of energy through electron transfer
How is glucose used as a fuel source in the body
Glucose is a vital fuel source for the body, providing quick and efficient energy. It can be broken down to produce ATP.
Complex carbs must be broken down to this monosaccharide to use as a fuel source
- Where does Glycolysis occur in the cell?
The cytoplasm
Where is ATP consumed in glycolysis
Step 1, Step 3
Step 1: Glucose → G6P (Hexokinase)
Step 3: F6P → F 1,6 Bisphosphate (PFK)
Where is ATP synthesized in glycolysis
Step 7: BPG → 3PG (Phosphoglycerate kinase)
Step 10: Phosphoenolpyruvate (PEP)→ Pyruvate (Pyruvate kinase)
- What are the options for pyruvate under anaerobic conditions?
If no O2 is present - glycolysis and anaerobic metabolism are the primary source of ATP
Which process provides the primary source of ATP if no oxygen is present?
Pyruvate is converted to lactate in the absence of O2
glycolysis
Where is the ATP produced in a cell if no oxygen is present?
ATP is produced in the cytosol
What metabolite (small molecule) is produced as a result of anaerobic metabolism?
Lactic acid
- If oxygen is present, what does pyruvate do?
If oxygen is present, pyruvate is converted to acetyl CoA in the mitochondria → further oxidation
- Where does pyruvate go when oxygen is present?
Mitochondria for the citric acid cycle
- What molecule is pyruvate converted to when oxygen is present?
Acetyl CoA
- Which tissues are likely to require aerobic metabolism on a regular basis?
All of them, but the brain and heart especially
Describe the Cori Cycle
Lactic acid is produced in the muscles during intense exercise/infection/disease (or under hypoxic/anaerobic conditions) and sent to the liver.
In the liver, that lactate is converted back to pyruvate and then to glucose (gluconeogenesis) which is sent back to the muscles or stored as glycogen.
Increase ATP or replenish glycogen stores in muscle
What is the purpose of the Cori Cycle?
Prevents lactic acidosis (excess accumulation of lactate) in muscle under anaerobic conditions
Reduce muscle fatigue and allow for sustained activity
Which tissues does the cori cycle involve?
Muscles
Liver tissue
- What is the major regulatory enzyme in glycolysis?
PFK
Rate limiting
Which reaction does PFK catlyze
F6P–>FBP
In muscle, what activates PFK
Activated by AMP in the allosteric site. ATP low, AMP high, turns on glycolysis (hyperbolic curve)
In muscle, what inhibits PFK
ATP in allosteric site. ATP high shuts off glycolysis, AMP is low, sigmoidal curve.
In the liver, what activates PFK
F26BP in the allosteric site
In the liver, what inhibits PFK
ATP in the allosteric site
What is the site of regulation in PFK
The allosteric site- ATP and AMP bind there. If ATP is high, AMP is low and glycolysis shuts down.
If ATP is low and AMP is high, glycolysis is on.
What is the molecule that activates PFK in the liver
F26BP
What is the enzyme that synthesizes F26BP and what does F26BP then go on to activat
PFK-2 (kinase) sinthasizes F26BP and F26BP goes on to activate PFK
Why can’t the liver use AMP the way the muscles do to activate PFK?
Liver does not have AMP and ATP does not get low because it can combine 2 ADP to make more ATP so it needs a different mechanisms compared to muscles that are more sensitive to AMP/ATP levels
How does phosphorylation impact activity of PFK2?
Phosphorylation inhibits the kinase domain and activates the phosphatase domain
converts F26BP back to F6P → shut down glycolysis
What is the purpose of the pentose phosphate pathway
How organisms generate NADPH. NADPH is needed for maintain the structure of red blood cells, stroid synthesis, etc
Where does the pentose phosphate pathway occur
the cytosol
What molecules of glycolysis are made from ribose-5-phosphate
nucleotides needed for the reproductive system and mammary glands
- Part of the pentose phosphate pathway
In gluconeogenesis, why can’t pyruvate be converted directly back to PEP
Irreversable step because of the difference in energy between PEP and pyruvate- pyruvate then goes on to the TCA cycle
What molecule is made between pyruvate and PEP
ATP
What is the relationship between glucose-6 phosphatase and glycogen levels?
Blood sugar low → glucose-6 phosphatase active & decrease glycogen levels
What happens with gluconeogenesis when blood sugar levels are low
glucose 6 phosphatase activates and decreases glycogen levels, gucagon binds to GPCR and activates PKA.
What is the role of glycogen phosphorylase? What state is it in when its on?
Glycogen phosphorylase breaks down glycogen.
When blood sugar is low, glycogen phosphorylase is active (R state)
Describe glycogen phosphorylase when blood sugar is normal/high. What state is it in?
Glycogen phosphorylase is inactive (T state), not metabolizing glycogen
What is the immediate product of glycogen metabolism
Glycogen–> G1P–> g6p
Glycogen is converted to what molecule by Glycogen phosphorylase?
G1P
While enzymes convert G1P to G6P?
Phosphoglucomutase
- How does Glycogen phosphorylase serve as a “glucose sensor” in the liver?
Low glucose levels = glucagon released = signals phosphorylase kinase to phosphorylate glycogen phosphorylase (GPb) = active state (GPa) converted glycogen to G1P
What happens in the muscles when epinephrine is released?
epinephrine → bypass eating → breakdown glycogen into G6P by GP to start glycolysis and make ATP
What happens in the liver when epinephrine is released?
glucagon release in response to low blood sugar → breakdown glycogen to G6P using GP → G6P converted to Glucose by G6P phosphatase → increase blood sugar
General path of signal transduction
Hormone binds to GPCR→ triggers conformational change in G protein → alpha subunit binds to adenyl cyclase→ ATP converted to cAMP→ cAMP phosphorylates PKA→ PKA has many effects at a cellular level (altar metabolism, etc)
- Which protein is responsible for eliciting the cellular response at the end of signal transduction pathways?
PKA
What are the 3 hormones discussed and their impacts
Epinephrine → flight or fight
Glucagon → low blood sugar
Insulin → high blood sugar (20 min after eating)
What occurs in the liver as a result of glucagon release
Glycogen break down → Glycogen phosphorylase GPa
Gluconeogenesis → pyruvate to oxaloacetate
inhibit glycolysis
What occurs in the muscle as a result of epinephrine release
epinephrine → bypass eating → breakdown glycogen into G6P by GP to start glycolysis and make ATP
What occurs in the liver as a result of insulin release
Insulin → Liver → GLUTs to the surface of the membrane
Where does the citric acid cycle occur
Mitochondiral matrix
What does pyruvate dehydrogenase do
converte pyruvate to acetyl CoA
What is the intermediate step between glycolysis and the citric acid cycl
pyruvate dehydrogenase
What activates pyruvate dehydrogenase
ADP, pyruvate, CA, MG (Muscle contraction), Insulin (When blood glucose is high)
What inhibits pyruvate dehydrogenase
ATP, ACOA, NADH, PDH kinase (Phosphorylates PDH)
What does PDH kinase do to PDH
Photophosphoylation- turns it off
What occurs when PDH kinase gets into the mitochondria?
It starts generation of ATP via interaction with oxaloacetate
What activates PDH phosphate
Muscle contraction, insulin, ADP, pyruvate
What occurs in the first step of CAC
Citrate synthase catalyzes the condensation of Acetyl CoA and oxaloacetate–>citrate
How many NADH and FADH are produced per turn of the CAC
3 NADH 1 FADH2
Where is FADH2 produced in the CAC
Step 6, succinate–> fumerate (succinate dehydrogenase)
What does glucose need for transport
GLUT transport tunnels because it’s so large
Where does the Majority of ATP synthesis occur
via oxidative phosphorylation in the mitochondria
- Trace the path of electrons from NADH through the chain to their end point in oxygen.
NADH→ complex 1→Coenzyme Q→Complex III→ Cytochrome C→Complex IV
Where oxygen is reduced to water (oxidative phosphorylation)
*Which complexes in the chain are responsible for pumping protons/generating the gradient?
Complex I, III, and IV: pump protons from mitochondrial matrix → intermembrane space and generate and maintain H+ gradient
- Why is NADH a more valuable electron carrier for ATP synthesis?
Because it donates its electrons earlier in the ETC (complex I) → allows more protons to be pumped across membrane → more ATP molecules compared to FADH2
FADH2 starts in complex II which does not pump H+
In ATP synthesis there are 3 steps (binding ADP/P, forming ATP and releasing ATP)
Which of these steps is dependent on the proton gradient?
The energy from the proton gradient drives the rotation of the enzymes rotor which facilitates the release of ATP.
Release of ATP = dependent on the proton gradient
