Biochemistry Chapter 5 Quiz
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Questions and Answers

What primarily determines whether a chemical reaction can occur?

  • The activation energy of the reaction.
  • The collision frequency between reactant particles.
  • The speed of the particles involved in the reaction.
  • The Gibbs energy change of the reaction. (correct)

How is the rate of a chemical reaction generally defined?

  • The total amount of products formed over the course of the reaction.
  • The Gibbs energy change divided by the duration of the reaction.
  • The change in the mass of reactants or products per unit of time. (correct)
  • The number of collisions between reactant molecules in a given time.

In the reaction $3H_2 + N_2 \rightarrow 2NH_3$, how would the rate of reaction be expressed in terms of the change in concentration of hydrogen ($H_2$)?

  • $v = -\frac{[H_2]}{time}$
  • $v = \frac{[H_2]}{time}$
  • $v = -\frac{1}{3} \frac{[H_2]}{time}$ (correct)
  • $v = -3 \frac{[H_2]}{time}$

According to collision theory, what factor directly influences the rate of a reaction?

<p>The number of active collisions between reactant molecules per unit of time. (A)</p> Signup and view all the answers

What is the correct expression for the reaction rate of a monomolecular reaction, such as $N_2O_4 \rightarrow 2NO_2$?

<p>$v = k[N_2O_4]$ (C)</p> Signup and view all the answers

What is the primary function of the active site of an enzyme?

<p>To provide a location where substrates bind and reactions occur. (B)</p> Signup and view all the answers

What characterizes isoenzymes?

<p>They are enzymes with the same function but different structure and properties. (D)</p> Signup and view all the answers

According to the Michaelis-Menten equation, what does a high KM value indicate?

<p>A low affinity of the enzyme for its substrate. (C)</p> Signup and view all the answers

Under what condition is the velocity of an enzyme-catalyzed reaction proportional to the substrate concentration?

<p>When the substrate concentration is very low compared to KM. (D)</p> Signup and view all the answers

What does the unit 'catal' (cat) measure?

<p>The amount of substrate converted by an enzyme per unit of time. (B)</p> Signup and view all the answers

What is the role of modulators in allosteric enzymes?

<p>To attach to the allosteric site and influence the enzyme's affinity for its substrate. (A)</p> Signup and view all the answers

In homotropic regulation of allosteric enzymes, what acts as a modulator?

<p>The substrate molecule itself. (A)</p> Signup and view all the answers

What is the significance of acetylcholinesterase cleaving 25,000 molecules of acetylcholine in one second?

<p>It illustrates the enzyme's ability to accelerate a reaction extremely rapidly. (C)</p> Signup and view all the answers

What is the primary function of thermogenin?

<p>To facilitate the transfer of protons, bypassing ATP synthase. (C)</p> Signup and view all the answers

Why are substances like thermogenin referred to as 'uncouplers'?

<p>Because they separate oxygen consumption from ATP production. (C)</p> Signup and view all the answers

Which type of gland does not utilize a duct system for the release of its secretions?

<p>Simple tubular glands (C)</p> Signup and view all the answers

What is a key by-product of the action of thermogenin in brown adipose tissue?

<p>Heat generation (A)</p> Signup and view all the answers

What is the function of the striated duct within a compound gland?

<p>To connect the intercalated duct to the interlobular duct. (A)</p> Signup and view all the answers

What is the consequence of using dinitrophenol as a weight loss drug?

<p>It is very difficult to prescribe safely. (B)</p> Signup and view all the answers

What is characteristic of serous secreting cells?

<p>They are typically basophilic due to peptide hormones, proteins or enzymes. (D)</p> Signup and view all the answers

When ATP production stops normally in mitochondria, what occurs?

<p>The respiratory chain’s proton pumping stops due to the built-up proton gradient. (A)</p> Signup and view all the answers

Which type of secretion is commonly associated with tubular cells?

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

What is the function of the main duct in a compound gland?

<p>To be the final duct before secretion exits the gland. (D)</p> Signup and view all the answers

If a secretion is described as basophilic, it is most likely produced by which type of cells?

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

What specific feature of mucinous secretion makes it stainable by PAS dye?

<p>Its content of polysaccharides. (A)</p> Signup and view all the answers

What is NOT a typical function of the ducts in glands?

<p>Primary secretion creation. (C)</p> Signup and view all the answers

Which enzyme catalyzes the conversion of fructose-6-phosphate to fructose-1,6-bisphosphate?

<p>Phosphofructokinase-1 (B)</p> Signup and view all the answers

During which step of glycolysis is NADH produced?

<p>The conversion of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate (D)</p> Signup and view all the answers

Which of the following enzymes is responsible for converting dihydroxyacetone phosphate (DHAP) to glyceraldehyde-3-phosphate (Gra-3-P)?

<p>Triose phosphate isomerase (D)</p> Signup and view all the answers

How many ATP molecules are consumed in the first phase of glycolysis (up to the formation of two three-carbon molecules)?

<p>2 (D)</p> Signup and view all the answers

Which enzyme catalyzes the reaction where water is removed from 2-phosphoglycerate to form phosphoenolpyruvate?

<p>Enolase (A)</p> Signup and view all the answers

Which of the following is NOT a function of mitochondria?

<p>Synthesis of proteins encoded by nuclear DNA (C)</p> Signup and view all the answers

What is the primary role of porins located within the outer mitochondrial membrane?

<p>To facilitate the movement of all molecules smaller than 10 kDa (C)</p> Signup and view all the answers

Which characteristic of the inner mitochondrial membrane is crucial for its selective permeability?

<p>It contains a high proportion of proteins (B)</p> Signup and view all the answers

Where are the enzymes of the Krebs cycle primarily located within the mitochondria?

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

How do chaperones assist in the import of proteins into the mitochondria?

<p>By keeping proteins unfolded allowing them to pass through translocator complexes (B)</p> Signup and view all the answers

What is a key difference between mitochondrial DNA (mtDNA) and nuclear DNA?

<p>mtDNA is inherited maternally, while nuclear DNA is inherited from both parents (C)</p> Signup and view all the answers

Which of these conditions represents a mitochondrial disease caused by a mutation in a gene that codes for an abnormal protein?

<p>Diabetes and deafness (DAD) (D)</p> Signup and view all the answers

Why is the CRISPR method ineffective for directly editing mitochondrial DNA?

<p>CRISPR enzymes cannot enter the mitochondrial matrix due to membrane impermeability (A)</p> Signup and view all the answers

What is the primary purpose of mitochondrial fusion?

<p>To mix contents, replenish proteins, repair mtDNA, and distribute metabolic intermediates (C)</p> Signup and view all the answers

Which of the following statements best describes the evolutionary origin of mitochondria?

<p>Mitochondria originated from a symbiosis of a bacteria (rickettsia) with an archaea cell. (D)</p> Signup and view all the answers

In the context of mitochondrial diseases, what does heteroplasmia refer to?

<p>The presence of multiple types of mitochondrial DNA in the same cell (A)</p> Signup and view all the answers

Why are mitochondria described as semi-autonomous organelles?

<p>Because they are only capable of producing some of their own proteins. (D)</p> Signup and view all the answers

What is the role of the SAM protein complex in mitochondrial protein import?

<p>It keeps proteins integrated into the outer mitochondrial membrane. (A)</p> Signup and view all the answers

Which of the following is most likely to cause cell edema due to insufficient mitochondrial activity?

<p>Disruption of the membrane's ability to selectively regulate permeability. (A)</p> Signup and view all the answers

What is the significance of cardiolipin in the inner mitochondrial membrane?

<p>It aids in membrane elasticity (D)</p> Signup and view all the answers

Flashcards

Reaction Rate

The change in the mass of reactants or products per unit of time.

Activation Energy

The minimum amount of energy required for reactants to overcome the energy barrier and start a reaction.

First-Order Reaction

A reaction whose rate depends on the concentration of one reactant raised to the power of one.

Monomolecular Reaction

A reaction that proceeds in one step, involving the breakdown of one molecule into two or more molecules.

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Second-Order Reaction

A reaction whose rate depends on the product of the concentrations of two reactants, each raised to the power of one.

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Enzyme

A protein capable of accelerating chemical reactions by lowering the activation energy required for the reaction to occur.

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Active Site

The specific region on an enzyme's surface where substrates bind and interact.

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Substrate

A molecule that binds to the active site of an enzyme and is converted into a product during the reaction.

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Isoenzymes

Enzymes with the same function but different structures.

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Michaelis Constant (Km)

The concentration of substrate at which the reaction proceeds at half its maximum speed. It reflects the enzyme's affinity for the substrate.

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Enzyme Activity

A measure of the amount of substrate converted by an enzyme per unit of time.

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Allosteric Enzymes

Enzymes with an additional site, called the allosteric site, where modulators bind, influencing the enzyme's affinity for its substrate.

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Modulators

Molecules that bind to the allosteric site of an enzyme and either increase (activators) or decrease (inhibitors) the enzyme's activity.

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Tuboalveolar Gland

Glands that have a wide lumen at the end of their tube, where secretions collect before being released. This type of gland is often associated with mammary glands during lactation and sweat glands.

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Simple Tubular Glands

Glands that do not need a duct, they open directly to the surface. Examples include crypts in the stomach.

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Compound Glands

Glands with a branching duct system that collects secretions from multiple sites into one main duct. It's like a river system with many streams feeding into a larger river.

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Intralobular Duct

The part of the duct system that is located inside the lobule of a compound gland. It connects the acinus to the interlobular duct.

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Intercalated Duct

A type of duct in the intralobular system that connects the acinus to the striated duct. It's like a small stream leading to a slightly larger stream.

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Striated Duct

A type of duct in the compound gland system that connects the intercalated duct to the interlobular duct. It's like a slightly larger stream leading to a larger river.

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Interlobular Duct

The part of the duct system located outside of the lobule, connecting multiple lobules to the main duct. It's like the large river that collects water from many streams.

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Main Duct

The final duct before the secretion exits the gland. It's like the main river that flows to the sea.

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Thermogenin

A protein found in brown adipose tissue that acts as an uncoupler, dissipating the proton gradient across the mitochondrial membrane without ATP production.

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Uncouplers

Molecules that disrupt the coupling between electron transport and ATP synthesis in mitochondria, allowing protons to leak across the membrane without generating ATP.

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Oxidative Phosphorylation

The process by which the energy stored in the proton gradient across the mitochondrial membrane is used to synthesize ATP.

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Dinitrophenol

A chemical compound that acts as an uncoupler, leading to increased heat production and weight loss.

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Brown Adipose Tissue

A type of fat tissue rich in mitochondria that allows mammals to generate heat through uncoupling.

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What is the role of 6-phosphofructo-1-kinase?

The enzyme that phosphorylates Fru-6-P to Fru-1,6-PP, using 1 ATP. This is a crucial step in glycolysis, committing glucose to the pathway.

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What happens in the cleavage step of glycolysis?

In the fourth step of glycolysis, the enzyme aldolase A cleaves Fru-1,6-PP into two three-carbon molecules: glyceraldehyde-3-phosphate (Gra-3-P) and dihydroxyacetone phosphate (DHAP). DHAP is produced in a greater quantity.

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What role does Triose phosphate isomerase play in glycolysis?

The enzyme triose phosphate isomerase converts DHAP into Gra-3-P. This is essential because only Gra-3-P can proceed through the subsequent steps of glycolysis.

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How is Gra-3-P phosphorylated in glycolysis?

In the sixth step of glycolysis, glyceraldehyde phosphate dehydrogenase phosphorylates Gra-3-P into 1,3-bisphosphoglycerate. Inorganic phosphate (Pi) enters the reaction, and NAD is reduced to NADH.

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How is ATP generated during glycolysis?

In the seventh step of glycolysis, phosphoglycerate kinase enzyme cleaves one phosphate from 1,3-PP-Gly to form 3-phosphoglycerate and one ATP. This is the first step where ATP is produced in the glycolytic pathway.

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What are mitochondria and what is their main function?

Mitochondria are double-membraned organelles responsible for producing energy in the form of ATP through oxidative phosphorylation.

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What makes the outer mitochondrial membrane permeable?

The outer membrane of mitochondria is permeable to small molecules due to the presence of porins.

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What is found in the intermembrane space of mitochondria?

The intermembrane space of mitochondria contains proapoptotic proteins like cytochrome C and a high concentration of protons.

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What makes the inner mitochondrial membrane selectively permeable?

The inner mitochondrial membrane is selectively permeable, requiring carrier proteins for most molecules to pass through.

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What important metabolic processes occur in the mitochondrial matrix?

The mitochondrial matrix contains enzymes for the Krebs cycle, β-oxidation, and the ornithine cycle.

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Where do mitochondrial proteins come from and how are they transported?

Mitochondria import most of their proteins from the cytoplasm, utilizing chaperones to keep them unfolded for transport.

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What is mitochondrial DNA (mtDNA) and what does it encode?

Mitochondrial DNA (mtDNA) is a small, circular molecule encoding essential proteins and RNAs.

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How is mtDNA inherited and what are some disorders associated with mutations in mtDNA?

Mutations in mtDNA are inherited maternally and can cause various disorders, such as Leber's hereditary optic neuropathy (LHON).

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How are mitochondria involved in apoptosis?

Mitochondria play a crucial role in apoptosis by releasing proapoptotic factors from the intermembrane space.

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Explain the mitochondrial theory of aging.

Mitochondrial theory of aging suggests that accumulation of mutations in mtDNA leads to decreased mitochondrial function and contributes to aging processes.

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What are mitochondrial diseases and what causes them?

Mitochondrial diseases are often caused by mutations in either mtDNA or nuclear DNA, leading to a range of symptoms.

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How do mitochondria divide and fuse?

Mitochondria undergo both fission, which increases their number, and fusion, which allows for content mixing and DNA repair.

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How is mtDNA inherited?

Mitochondrial inheritance is entirely maternal, meaning all mtDNA is passed down from the mother.

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What is the evolutionary origin of mitochondria?

Mitochondria are believed to have evolved from independent bacteria that entered ancient eukaryotic cells.

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What is the electron transport chain and where is it located?

The electron transport chain, located in the inner mitochondrial membrane, is responsible for generating a proton gradient that drives ATP synthesis.

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Study Notes

Course 2: Metabolism

  • This document is a table of contents for Course 2: Metabolism.
  • The course is taught by Stanislav Skamene, Svatava Vyhnánková, Filip Otepka, and Dominika Kubátová.
  • Course materials were translated by Kamila Kočí.
  • The document covers a variety of topics in metabolism, including metabolic reactions, enzymes, coenzymes, vitamins, trace elements, and the role of molecules in various organs and systems.

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Course 2 Metabolism PDF

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Test your knowledge on key concepts in biochemistry, including chemical reaction rates, enzyme activity, and modulation. This quiz covers essential topics such as collision theory, the Michaelis-Menten equation, and the role of active sites in enzyme function. Prepare to dive deep into the fascinating world of biochemical processes!

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