Biology Pyruvate and Krebs Cycle Overview
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Questions and Answers

What is the primary role of protons in oxidative phosphorylation?

  • To create a charge difference across the membrane (correct)
  • To convert NADH to NAD+
  • To generate heat for the cell
  • To directly synthesize glucose

Which process involves the utilization of ATP and NADPH to produce sugars?

  • Oxidative Phosphorylation
  • Calvin Cycle (correct)
  • Light-dependent reactions
  • Citric Acid Cycle

During the process of chemiosmosis, protons flow through which essential structure?

  • Chlorophyll
  • Cytoplasmic membrane
  • Nuclear envelope
  • ATP synthase (correct)

What is a byproduct of photosynthesis that is released into the atmosphere?

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

What is the role of chlorophyll during photosynthesis?

<p>To capture light energy (C)</p> Signup and view all the answers

What happens to the mitochondrial matrix during oxidative phosphorylation?

<p>It becomes negatively charged (B)</p> Signup and view all the answers

Which component acts as an electron carrier in the second phase of photosynthesis?

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

In which cellular structures does the majority of photosynthesis occur?

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

What is the primary function of the Calvin Cycle in photosynthesis?

<p>To fix carbon dioxide and produce organic molecules (B)</p> Signup and view all the answers

Which enzyme is crucial for the carbon fixation stage of the Calvin Cycle?

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

During which stage of the Calvin Cycle is ATP utilized to convert 3PGA into glyceraldehyde?

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

How does the C4 photosynthesis pathway differ from the C3 pathway?

<p>It has a higher concentration of PEP carboxylase (D)</p> Signup and view all the answers

Which of the following compounds is the first stable product formed during the Calvin Cycle?

<p>3-phosphoglycerate (3PGA) (B)</p> Signup and view all the answers

What structural adaptation allows C4 photosynthesis to efficiently fix carbon in higher temperatures?

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

In C4 photosynthesis, where does the initial fixation of carbon dioxide occur?

<p>In the mesophyll cells (D)</p> Signup and view all the answers

Which of the following is NOT a product of the Calvin Cycle?

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

What is the primary function of the enzyme PEPC in crassulacean acid metabolism?

<p>Converts CO2 to organic acids at night (B)</p> Signup and view all the answers

During which time do desert plants primarily take in CO2, and how is it stored?

<p>Nighttime; as malic acid in vacuoles (D)</p> Signup and view all the answers

What happens to malic acid during the daytime in desert plants?

<p>It releases CO2 for the Calvin cycle (B)</p> Signup and view all the answers

Which of the following individuals contributed to our understanding of photosynthesis?

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

Which type of tissue is defined by being composed of only one type of cell?

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

What is a correct function of oxaloacetate in the crassulacean acid metabolism process?

<p>It acts as a precursor for malic acid (B)</p> Signup and view all the answers

What did Jan Ingen-Housz demonstrate about the process of plant photosynthesis?

<p>Only green parts of plants restore air when exposed to sunlight (B)</p> Signup and view all the answers

What role does the intercellular matrix play in plant tissue functionality?

<p>It separates cells and supports tissue structure (B)</p> Signup and view all the answers

Flashcards

Calvin Cycle

The light-independent reactions in photosynthesis where carbon dioxide is fixed and converted to organic molecules, producing carbohydrates.

C3 Pathway

A photosynthetic pathway where carbon dioxide is fixed to a 5-carbon molecule, producing a 3-carbon molecule as the first stable product.

Carbon Fixation

The crucial process in the Calvin Cycle where carbon dioxide is combined with a 5-carbon sugar to begin the conversion into organic molecules.

RuBP

A 5-carbon sugar molecule that combines with carbon dioxide in the first step of the Calvin Cycle.

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3-PGA

A 3-carbon molecule, the first stable product of carbon fixation in the Calvin Cycle.

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C4 Photosynthesis

A photosynthetic pathway that reduces photorespiration by concentrating carbon dioxide around the enzyme RuBisCo, allowing photosynthesis in high temperatures or low CO2 levels.

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Photorespiration

A metabolic process that reduces the efficiency of photosynthesis by wasting energy when Rubisco binds to oxygen instead of carbon dioxide.

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Light-independent reactions

The reactions in photosynthesis that do not directly require light energy but use ATP and NADPH produced by the light-dependent reactions.

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Anabolism

The process of building up complex molecules from simpler ones.

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Catabolism

The process of breaking down complex molecules into simpler ones.

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Photosynthesis

The process by which plants use sunlight to convert carbon dioxide and water into sugars and oxygen.

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Chemiosmosis

Using the flow of protons to create ATP.

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Chlorophyll

A green pigment in plants that absorbs light energy for photosynthesis.

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ATP

The energy currency of the cell.

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Intermembrane space

The space between the inner and outer mitochondrial membranes.

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Carbon Dioxide

A gas required for photosynthesis.

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CAM Photosynthesis

A type of photosynthesis in desert plants where carbon dioxide is taken up at night and stored as an acid, then used for photosynthesis during the day. This allows the plant to conserve water.

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Stomata

Small pores on the surface of leaves that allow gas exchange. These open and close to regulate water loss and gas intake.

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Oxaloacetate

A four-carbon molecule that is the first product of carbon fixation in CAM photosynthesis.

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Malic Acid

A four-carbon organic acid to which oxaloacetate is converted in CAM plants, acting as a storage form of CO2.

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PEPC Enzyme

An enzyme crucial for converting carbon dioxide to usable forms in CAM plants, especially at night.

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Intercellular Matrix

The substance within plant cells that separates cells and acts as a barrier between them and their environment.

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Simple Tissues

Plant tissues consisting of only one type of cell, performing a specific function.

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Joseph Priestley

A scientist who demonstrated that plants release oxygen, part of the study of photosynthesis.

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Study Notes

Pyruvate 3 Fates

  • Anaerobic (lactic acid fermentation): Uses NADH to regenerate NAD+ for glycolysis.
  • Anaerobic (alcoholic fermentation)
  • Aerobic oxidation

Aerobic Respiration: Pyruvate Breakdown

  • Oxidative decarboxylation of pyruvate: Removal of carbon via carbon dioxide.
  • Pyruvate dehydrogenase complex: Simplifies pyruvate into acetyl-CoA.
  • Bridge between glycolysis and citric acid cycle.

Entry of Pyruvate into the Mitochondrion

  • Pyruvate diffuses through the outer mitochondrial membrane.
  • Pyruvate translocase: Transports pyruvate from the intermembrane space to the matrix, exchanging with H+.

Conversion of Pyruvate to Acetyl-CoA

  • Pyruvate dehydrogenase complex (PDH complex): Multienzyme complex converting pyruvate to acetyl-CoA.

Krebs Cycle Overview

  • Discovered by Hans Adolf Krebs.
  • Also known as the citric acid cycle or tricarboxylic acid cycle.
  • Citrate is the first product, formed from acetyl-CoA and oxaloacetate.

Krebs Cycle Steps

  • Citrate Synthase: Irreversible reaction producing citrate from acetyl-CoA and oxaloacetate. Forms C-C bond.
  • Aconitase: Reversible reaction isomerizing citrate to isocitrate. Eliminates H2O to form C=C bond.
  • Isocitrate Dehydrogenase: Irreversible oxidative decarboxylation of isocitrate to α-ketoglutarate. Eliminates CO2. One of four redox reactions in the cycle. Reduces NAD+ to NADH.
  • α-ketoglutarate Dehydrogenase complex: Similar to PDH complex, oxidizes α-ketoglutarate to succinyl-CoA while producing CO2, NADH and GTP (ATP in plants and some bacteria).
  • Succinyl-CoA Synthetase: Forms succinate and produces GTP (ATP in plants and some bacteria). The process of substrate level phosphorylation.
  • Succinate Dehydrogenase: Reversible oxidation of succinate to fumarate and reducing FAD to FADH2 to contribute to the electron transport chain.
  • Fumarase: Reversible addition of water to fumarate, forming L-malate.
  • Malate Dehydrogenase: Reversible oxidation of malate to oxaloacetate, producing NADH.

Electron Transport Chain

  • Located in the inner mitochondrial membrane.
  • Groups of redox proteins.
  • NADH and FADH2 are oxidized and hydride ions are passed to the ETC.
  • Electrons are transferred from one complex to another, with an increase in electron negativity.
  • ATP is generated by oxidative phosphorylation. 1 NADH ~ 2.5 or 3 ATP 1 FADH2~ 1.5 or 2 ATP

Oxidative Phosphorylation

  • Combines electron transport chain and chemiosmosis.
  • Phosphorylation of ADP to ATP coupling the electron transfers of the respiratory chain
  • Creates proton gradient that drives ATP synthesis.

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Description

Explore the fates of pyruvate in cellular respiration, including anaerobic fermentation and aerobic oxidation. This quiz covers the conversion of pyruvate to acetyl-CoA and the intricacies of the Krebs cycle. Test your knowledge on key processes such as oxidative decarboxylation and the role of the pyruvate dehydrogenase complex.

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