Metabolic Pathways and ATP Regulation

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Questions and Answers

Which of the following cofactors are found within Complex I?

  • Cytochrome C and CoQH2
  • Cytochrome B and FAD
  • CoQ and Cytochrome C
  • FMN and Iron-Sulfur Clusters (correct)

Which cofactor directly receives electrons from NADH in Complex I?

  • FMN (correct)
  • FAD
  • CoQ
  • Iron-Sulfur Cluster

What is the role of CoQ in electron transport?

  • To receive electrons from Complex II and pass them to Complex IV
  • To receive electrons from Complex I and pass them to Complex III (correct)
  • To receive electrons from FADH2 and pass them to Complex III
  • To receive electrons from NADH and pass them to Complex II

Which of the following complexes has a domain that sticks out into the mitochondrial matrix?

<p>All of the above (D)</p> Signup and view all the answers

What is the role of Cytochrome c in electron transport?

<p>To receive electrons from CoQH2 and pass them to Complex IV (C)</p> Signup and view all the answers

Which of the following complexes is involved in the oxidation of succinate to fumarate?

<p>Complex II (D)</p> Signup and view all the answers

Which of the following statements is TRUE regarding the transfer of electrons in the Electron Transport Chain?

<p>CoQH2 is a two-electron donor, transferring electrons to one-electron acceptors. (B)</p> Signup and view all the answers

Which of the following statements accurately describes the role of FAD in Complex II?

<p>FAD receives electrons from succinate and transfers them to CoQ. (B)</p> Signup and view all the answers

Which of the following statements is TRUE about the electron transport chain?

<p>It involves a series of proteins that receive high energy electrons from NAD+ and FADH2. (B)</p> Signup and view all the answers

Where are the protein complexes involved in the electron transport chain located?

<p>Inner mitochondrial membrane (A)</p> Signup and view all the answers

Which of the following is NOT a component of the electron transport chain?

<p>ATP synthase (B)</p> Signup and view all the answers

What is the role of CoQ in the electron transport chain?

<p>It acts as a mobile carrier for electrons between Complex I and Complex III. (D)</p> Signup and view all the answers

What specifically is reduced in the electron transport chain?

<p>Oxygen (B)</p> Signup and view all the answers

Which of these is NOT a product of cellular respiration?

<p>Glucose (D)</p> Signup and view all the answers

What is the primary function of the proton gradient established by the electron transport chain?

<p>To provide the energy for ATP synthase to produce ATP. (B)</p> Signup and view all the answers

What is the direct source of high-energy electrons for the electron transport chain?

<p>NADH and FADH2 (B)</p> Signup and view all the answers

Which complex in the electron transport chain is directly involved in the synthesis of ATP?

<p>Complex V (D)</p> Signup and view all the answers

What is the role of the inner mitochondrial membrane in cellular respiration?

<p>It provides a compartmentalized space for the electron transport chain. (A)</p> Signup and view all the answers

What is the primary reason for the highly energetic nature of ATP?

<p>The presence of a high-energy phosphate bond, readily hydrolyzed. (B)</p> Signup and view all the answers

Which of the following statements accurately describes the high-energy character of ATP?

<p>The phosphoanhydride bonds in ATP are responsible for its high-energy character. (A)</p> Signup and view all the answers

Why is the kinetic stability of ATP to hydrolysis important for its bioenergetic function?

<p>It ensures that ATP's energy is released only when needed, preventing spontaneous hydrolysis. (B)</p> Signup and view all the answers

Which statement is TRUE about the variability of ion, coenzyme, and metabolite concentrations across cellular compartments?

<p>These variations are critical for maintaining the appropriate function of different organelles. (A)</p> Signup and view all the answers

Which option accurately describes the role of high-energy phosphate bonds in ATP hydrolysis?

<p>They are responsible for the release of free energy, powering cellular processes. (B)</p> Signup and view all the answers

What complex is responsible for facilitating the re-entry of protons into the mitochondrial matrix?

<p>F0/F1 or Complex V (ATP Synthase) (C)</p> Signup and view all the answers

How many moles of ATP are yielded from one mole of NADH?

<p>2.5 moles (D)</p> Signup and view all the answers

What is the primary role of the Iron-Copper Centers in the electron transport process?

<p>They transfer electrons from cytochrome c to oxygen. (B)</p> Signup and view all the answers

What happens to osmotic energy in the process described?

<p>It remains latent until a complex facilitates proton re-entry. (B)</p> Signup and view all the answers

Where are the electron transport complexes embedded?

<p>Inner mitochondrial matrix (B)</p> Signup and view all the answers

Which element is involved in the initial oxidation of cytochrome c?

<p>Iron (C), Copper (A)</p> Signup and view all the answers

What is the function of ATP Synthase in cellular respiration?

<p>To form ATP from ADP and inorganic phosphate using the proton gradient. (C)</p> Signup and view all the answers

The electron transport chain involves transferring electrons from which type of molecule to oxygen?

<p>Both A and C (B)</p> Signup and view all the answers

What is the name of the technique used by scientists to study the details of proteolytic cleavage in the crystal forms of proteins?

<p>X-ray diffraction (A)</p> Signup and view all the answers

Which of the following enzymes is NOT activated by trypsin?

<p>Pepsin (C)</p> Signup and view all the answers

What is the specific bond that trypsin cleaves in chymotrypsinogen during its activation?

<p>The bond between Arginine (15) and Isoleucine (16) (B)</p> Signup and view all the answers

Which of the following statements accurately describes the role of chymotrypsin in digestion?

<p>Chymotrypsin hydrolyzes peptide bonds adjacent to aromatic amino acids. (A)</p> Signup and view all the answers

Which of the following processes is NOT a characteristic of zymogen activation?

<p>Reversible phosphorylation of the zymogen. (C)</p> Signup and view all the answers

What is the primary reason why digestive enzymes are synthesized as inactive zymogens?

<p>To prevent self-digestion of the pancreas. (A)</p> Signup and view all the answers

What is the role of the intestinal epithelium in protein digestion?

<p>Absorbing the smaller peptides and amino acids produced by protein digestion. (A)</p> Signup and view all the answers

Which of the following statements correctly describes the process of trypsin activation?

<p>Trypsinogen is activated by a specific protease called enteropeptidase. (D)</p> Signup and view all the answers

Which of the following is NOT a characteristic of heteroallosteric inhibitors in terms of their impact on hemoglobin?

<p>They promote the cooperative binding of oxygen to hemoglobin. (C)</p> Signup and view all the answers

Which of the following amino acids are most likely involved in phosphorylation?

<p>Serine (Ser), Threonine (Thr), Tyrosine (Tyr) (D)</p> Signup and view all the answers

What is the primary function of phosphatases in the context of enzyme regulation?

<p>To remove a phosphate group from an enzyme, deactivating it. (D)</p> Signup and view all the answers

Which of the following is NOT a characteristic of cooperative binding in proteins like hemoglobin?

<p>The binding affinity of the protein for the substrate remains constant across all substrate concentrations. (A)</p> Signup and view all the answers

What happens to the oxygen-binding curve of hemoglobin in the presence of heteroallosteric inhibitors?

<p>The curve shifts to the right, indicating a decrease in oxygen affinity. (A)</p> Signup and view all the answers

Which of the following is an example of a covalent modification that can influence gene expression?

<p>All of the above (D)</p> Signup and view all the answers

What is the role of ATP in phosphorylation?

<p>ATP provides energy for the kinase to catalyze the phosphorylation reaction. (C)</p> Signup and view all the answers

Which of the following best describes how phosphorylation can influence the activity of an enzyme?

<p>Phosphorylation can either activate or inactivate the enzyme, depending on the specific enzyme. (C)</p> Signup and view all the answers

What is the primary role of kinases in the context of phosphorylation?

<p>To catalyze the addition of a phosphate group to a protein. (A)</p> Signup and view all the answers

Which of the following statements correctly describes the role of ATP in phosphorylation?

<p>ATP provides a phosphate group for the phosphorylation reaction. (D)</p> Signup and view all the answers

Which of the following is an example of how a mutation that affects a phosphorylation site could impact enzyme activity?

<p>The enzyme might be constitutively inactive, even in the presence of an activating signal. (B)</p> Signup and view all the answers

In the context of hemoglobin, what is the functional difference between the Tense (T) state and the Relax (R) state?

<p>The T state has a lower affinity for oxygen, while the R state has a higher affinity for oxygen. (D)</p> Signup and view all the answers

How does the presence of multiple subunits in a protein like hemoglobin contribute to cooperative binding?

<p>The subunits interact with each other, influencing the binding affinity of other subunits for the substrate. (A)</p> Signup and view all the answers

What is the main difference between homoallostery and heteroallostery, as described in the context of hemoglobin?

<p>Homoallostery involves interactions between identical subunits, while heteroallostery involves interactions between different subunits. (C)</p> Signup and view all the answers

Which of the following is a consequence of cooperative binding in proteins?

<p>The protein exhibits a sigmoidal binding curve, showing a gradual increase followed by a sharp increase in binding. (C)</p> Signup and view all the answers

Which of the following best describes how ribosylation can modify proteins?

<p>Ribose moieties are added to the ADP residue of a protein. (C)</p> Signup and view all the answers

What is the primary function of phosphatases in terms of enzymatic regulation?

<p>To remove phosphate groups from proteins. (A)</p> Signup and view all the answers

Flashcards

Osmotic Energy

Energy that remains latent until utilized by a process.

Cytochrome C

A protein that transfers electrons to oxygen in cellular respiration.

Iron-Copper Centers

Complexes that facilitate electron transfer from cytochrome C to oxygen.

Complex V (ATP Synthase)

An enzyme that re-enters protons into the mitochondrial matrix, generating ATP.

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ATP Yield from NADH

NADH produces approximately 2.5 moles of ATP during respiration.

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Proton Gradient

A difference in proton concentration across a membrane, driving ATP synthesis.

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Mitochondrial Matrix

The space within the inner membrane of mitochondria, where key processes occur.

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Reducing Equivalent

A measure of how many moles of ATP can be generated from electron carriers like NADH.

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Ion Concentration Variation

The differences in ion concentrations across organelle membranes, often by several orders of magnitude.

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Coenzymes

Molecules that assist enzymes in catalyzing reactions, often by donating or accepting chemical groups.

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High Energy Bonds

Chemical bonds in compounds like ATP that release significant energy when broken, e.g., -25 kJ/mol.

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ATP's High Energy Character

ATP has high-energy character due to its stable bonds that release large amounts of free energy upon hydrolysis.

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Phosphoryl Transfer Reactions

Reactions where a phosphate group is transferred, crucial for energy transfer in biological systems.

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Zymogens

Inactive enzyme precursors synthesized by the pancreas.

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Proteolytic activation

The irreversible process of converting zymogens to active enzymes.

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Chymotrypsin

An active proteolytic enzyme activated from chymotrypsinogen.

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Auto-catalysis

Activation process where an enzyme activates itself and others.

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Trypsinogen

The inactive form of trypsin, an essential digestive enzyme.

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X-ray crystallography

Technique to analyze protein structures through X-ray diffraction.

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Specific cleavage

The precise cutting of a protein at specific amino acid sites.

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Pepsin

An enzyme secreted by the stomach that starts protein digestion.

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Flavin Mononucleotide (FMN)

A cofactor that receives electrons from NADH and transfers them to Fe-S clusters.

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Iron-Sulfur clusters (Fe-S)

Cofactors within Complex I that accept electrons from FMN, transferring them onward.

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Coenzyme Q (CoQ)

A mobile electron transporter that takes electrons from Fe-S clusters and transfers them.

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Respiratory Complex III

Complex that catalyzes the transfer of electrons from CoQH2 to cytochrome c.

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Complex II (Succinate-Coenzyme Q reductase)

Enzyme that extracts electrons from succinate using FAD as a coenzyme.

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FADH2

A coenzyme that donates electrons during the oxidation of succinate in Complex II.

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NADH oxidation

A process where NADH is converted to NAD+, allowing electron flow into the transport chain.

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Mitochondria structure

Double membranous organelle consisting of an outer and inner membrane.

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Outer membrane

The outer layer of mitochondria that separates it from the cytoplasm.

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Inner membrane

The inner layer tightly folded into cristae, housing protein complexes.

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Cristae

Folded invaginations of the inner membrane that increase surface area for reactions.

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Electron transport chain

A series of protein complexes that transfer electrons from NADH and FADH2.

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ATP synthesis

The process of producing ATP, fueled by electrons from the chain.

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Complex I

First protein complex in the chain, acts as a proton pump.

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Oxidative phosphorylation

Process of ATP formation linked to the transfer of electrons to O2.

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Tense State (T)

The state of hemoglobin with lower affinity for oxygen.

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Relaxed State (R)

The state of hemoglobin with higher affinity for oxygen.

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Heteroallosteric Inhibitors

Substances that drive proteins toward the T state, reducing their function.

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Cooperative Binding

The enhanced affinity of subunits for a substrate due to the binding of another subunit.

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Homoallosteric Regulation

Regulation where the binding of a ligand to one subunit influences others in identical subunits.

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Phosphorylation

The addition of a phosphate group to proteins that alters their function.

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Kinase

An enzyme that adds phosphate groups to other molecules.

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Phosphatase

An enzyme that removes phosphate groups from molecules.

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Covalent Modification

A chemical change in proteins affecting their function through various additions.

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Ribosylation

Addition of ribose moieties to a protein affecting its function.

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Acetylation

Addition of acetyl groups that can alter gene expression.

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Sigmoidal Curve

Graph shape indicating cooperative binding behavior in enzymes.

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Hyperbolic Curve

Graph shape indicating non-cooperative binding behavior.

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Conformational Change

A structural change in a protein due to post-translational modification.

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Electrostatic Interactions

Forces between charged amino acids that can influence protein structure.

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Study Notes

Metabolic Pathways

  • Metabolic pathways are a series of linked enzymatic reactions
  • Pathways are irreversible to ensure proper directionality
  • Catabolic and anabolic pathways must differ to allow independent control

Committed Steps

  • Every pathway has a committed step (often a rate-limiting step)
  • This step is a key regulation point for the entire pathway

Regulation

  • Regulation ensures metabolic pathways don't run uselessly or wastefully
  • Pathways are tightly controlled, dictated by physiological status of a cell

ATP

  • ATP is the energy currency for the cell
  • ATP is a nucleotide with 3 phosphate groups
  • Phosphate groups are connected via phosphoanhydride bonds
  • ATP hydrolysis releases large amounts of energy for endergonic reactions

In Vitro vs. In Vivo Free Energy

  • Free energy in experiments (in vitro) often differs than free energy in living systems (in vivo)
  • In vivo free energy is affected by concentration of substances, pH and ionic strength

Phosphorylation

  • A type of covalent modification of proteins
  • Phosphorylation involves adding a phosphate group to a protein
  • This modification affects the proteins ability.

Homoallostery

  • Subunit interactions affect each other, this determines a cooperative binding of a substrate to subunits
  • This affects proteins with multiple subunits, such as hemoglobin

Heteroallostery

  • The subunits do not affect one another
  • Cooperative, sigmoidal curve
  • Non-cooperative, hyperbolic curve

###Zymogens

  • Inactive form of enzymes
  • Synthesized in inactive form in the pancreas
  • Activation is irreversible to avoid uncontrolled enzyme action.

###Oxidative Phosphorylation

  • The third stage of metabolic oxidation of substrates
  • NADH and FADH2 are reoxidized by electron transport proteins in inner mitochondrial membrane
  • ATP is synthesized (energy is produced for the cell)

Protein Complexes

  • Complexes I-IV shuttle electrons
  • Complex V is responsible for ATP synthesis
  • Protein complexes are crucial in the cellular respiration process, shuttling electrons and generating electrochemical gradient
  • Complexes are bound by the inner mitochondrial membrane to maintain the electrochemical gradient.

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