Photosynthesis and the Calvin Cycle Quiz

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Questions and Answers

According to the chemiosmotic theory, what is the direct source of protons for the formation of ATP in chloroplasts?

Photolysis of water molecules ($H_2O$).

In non-cyclic photophosphorylation, what is the final electron acceptor?

NADP⁺.

Define the term 'reduction' in the context of chemical reactions, and identify the specific reduction step in the Calvin cycle.

Reduction is the gain of electrons or hydrogen. In the Calvin cycle, PGA is reduced to PGAL/G3P.

What are the two main products of the light-dependent reactions that are directly utilized in the Calvin cycle?

ATP and NADPH. Signup and view all the answers

Why is the Calvin cycle referred to as a 'light-independent' reaction?

It does not directly require light, but uses the ATP & NADPH generated by the light-dependent reactions. Signup and view all the answers

What is the role of the enzyme RuBisCO in photosynthesis and why is it considered important?

It catalyzes the first step of carbon fixation, combining RuBP with $CO_2$. It is very abundant and crucial for photosynthesis. Signup and view all the answers

Considering one molecule of glucose production, how many molecules of ATP and NADPH are needed in the Calvin cycle?

18 ATP and 12 NADPH. Signup and view all the answers

How is glucose formed from the products of the Calvin cycle?

Two molecules of G3P from 6 rounds of the Calvin Cycle are used to form a single molecule of glucose in the cytoplasm. Signup and view all the answers

What is the role of the promoter region in eukaryotic transcription?

The promoter region is where RNA polymerase binds to initiate transcription, marking the starting point for RNA synthesis. Signup and view all the answers

Explain the difference between the template strand and the non-template strand during transcription.

The template strand is read by RNA polymerase to create mRNA, while the non-template strand is not directly involved but has the same sequence as the mRNA (with U instead of T). Signup and view all the answers

Why is the non-template strand also referred to as the coding strand?

The non-template strand is called the coding strand because its sequence matches the mRNA sequence, except with T instead of U. Signup and view all the answers

In what direction does RNA polymerase read the template strand, and in what direction is the pre-mRNA strand assembled?

RNA polymerase reads the template strand in the 3' to 5' direction, while the pre-mRNA strand is assembled in the 5' to 3' direction. Signup and view all the answers

What are transcription factors, and what is their main role in gene expression?

Transcription factors are proteins that bind to DNA sequences near a gene's promoter. Their main role is regulating transcription by controlling when and how a gene is expressed. Signup and view all the answers

What is pre-mRNA, and what are its distinguishing features?

Pre-mRNA is the initial RNA transcript formed in eukaryotes, containing both exons (coding) and introns (non-coding) regions. Signup and view all the answers

Briefly describe the roles of exons and introns in pre-mRNA.

Exons are the coding regions of a gene that remain in the final mRNA and determine the amino acid sequence of a protein. Introns are non-coding regions removed during splicing. Signup and view all the answers

What specific sequence do transcription factors bind to near a gene's promoter?

Transcription factors bind to specific DNA sequences near a gene's promoter such as the TATA box. Signup and view all the answers

Explain why photosynthesis initially evolved before the presence of significant levels of oxygen in the atmosphere?

The early atmosphere had very little free oxygen. Photosynthesis initially evolved in anoxic conditions, using other molecules as electron donors. Signup and view all the answers

What is the primary mechanism by which the electrochemical gradient helps facilitate ATP synthesis during respiration?

The electrochemical gradient stores potential energy that drives protons through ATP synthase via chemiosmosis, converting ADP to ATP. Signup and view all the answers

In a graph representing the rate of photosynthesis relative to some factor, what does it mean when the curve plateaus?

A plateau signifies that the rate of photosynthesis has reached its maximum and is no longer increasing. This indicates some other factor is now limiting the reaction rate. Signup and view all the answers

Contrast the light requirements for photosynthesis in shade plants versus light plants.

Light plants have a higher light saturation point and a higher photosynthetic rate, whereas shade plants have a lower light saturation point and slower rate of photosynthesis. Signup and view all the answers

Explain the difference between gross and net photosynthesis rates, specifically relating to respiration.

Gross photosynthesis represents total CO₂ fixed. Net photosynthesis is the gross rate minus CO₂ used by the plant's own respiration. Signup and view all the answers

How do the cristae of the inner mitochondrial membrane contribute to the overall function of the mitochondria?

The cristae increase the surface area of the inner membrane, providing more space for the electron transport chain to function. Signup and view all the answers

Describe the role of the proton pump proteins in the electron transport chain and their relevance to ATP production?

Proton pump proteins actively transport protons across a membrane creating a charge and H⁺ gradient. The stored potential energy is used to power ATP synthesis. Signup and view all the answers

Outline the key events of the Link Reaction in aerobic respiration, specifically mentioning the molecules and location involved.

In the mitochondrial matrix, pyruvate is converted to 2C acetyl-CoA, releasing CO₂ and forming NADH. Signup and view all the answers

What is the main difference between DNA replication and transcription?

DNA replication copies the entire DNA molecule, while transcription only synthesizes specific genes into RNA. Signup and view all the answers

Describe the role of the start codon in translation.

The start codon signals the beginning of translation and specifies the amino acid methionine. Signup and view all the answers

What does it mean that the genetic code is degenerate?

It means that multiple codons can encode the same amino acid, providing redundancy in the genetic code. Signup and view all the answers

Explain the difference between the coding strand and the template strand of DNA.

The coding strand has the same sequence as the mRNA (with T replaced by U), while the template strand is the one used by RNA polymerase to synthesize RNA. Signup and view all the answers

What is the role of operons in prokaryotic gene expression?

Operons coordinate the expression of clusters of genes that function together by being transcribed into a single mRNA. Signup and view all the answers

What are stop codons, and what is their function in translation?

Stop codons, such as UAA, UAG, and UGA, signal the end of translation and help terminate protein synthesis. Signup and view all the answers

Describe how mRNA is synthesized in relation to the DNA template strand.

mRNA is synthesized in the 5' to 3' direction as RNA polymerase reads the DNA template strand in the 3' to 5' direction. Signup and view all the answers

What is the function of a promoter in transcription?

A promoter is a DNA sequence where RNA polymerase binds to initiate transcription. Signup and view all the answers

What is the primary function of RNA polymerase II in eukaryotic cells?

RNA polymerase II synthesizes pre-mRNA by using a DNA template strand. Signup and view all the answers

Describe the significance of splicing in mRNA processing.

Splicing removes introns from pre-mRNA and connects exons to create mature mRNA. Signup and view all the answers

What distinguishes transcription in eukaryotes from that in prokaryotes?

Eukaryotic transcription occurs in the nucleus and involves RNA processing, while prokaryotic transcription occurs in the cytoplasm and is coupled with translation. Signup and view all the answers

Define polycistronic mRNA and its relevance in prokaryotes.

Polycistronic mRNA codes for multiple proteins from a single transcript and is common in prokaryotes. Signup and view all the answers

What role do the 5' cap and poly(A) tail play in mRNA stability?

The 5' cap protects mRNA from degradation and aids in ribosome binding, while the poly(A) tail stabilizes mRNA and facilitates its export to the cytoplasm. Signup and view all the answers

Explain the term 'monocistronic' in relation to eukaryotic mRNA.

Monocistronic mRNA contains the coding sequence for a single protein. Signup and view all the answers

During transcription, what direction does RNA polymerase II synthesize RNA?

RNA polymerase II synthesizes RNA in the 5' to 3' direction. Signup and view all the answers

What is the role of transcription factors in eukaryotic transcription?

Transcription factors bind to the promoter region to initiate transcription by RNA polymerase II. Signup and view all the answers

Explain how the evolution of photosynthesis, a process that releases oxygen as a byproduct, impacted the early Earth's atmosphere.

Photosynthesis, which evolved before significant levels of oxygen were present, gradually released oxygen into the atmosphere, changing its composition from a reducing environment to an oxidizing one. This had a profound impact on life forms on Earth, leading to the development of oxygen-dependent organisms and the eventual emergence of complex life. Signup and view all the answers

Describe the relationship between the light intensity and the rate of photosynthesis, highlighting the concept of light saturation point.

As light intensity increases, the rate of photosynthesis also increases, but only up to a certain point. This point, known as the light saturation point, represents the maximum rate of photosynthesis that can be achieved, even with further increases in light intensity. Beyond this point, the rate of photosynthesis plateaus because other factors become limiting. Signup and view all the answers

Explain the difference in photosynthetic characteristics between light plants and shade plants, including their light saturation points and photosynthetic rates.

Light plants are adapted to high light environments and thus have a higher light saturation point and a faster maximum rate of photosynthesis. Shade plants, on the other hand, are adapted to lower light intensities and have a lower light saturation point and a slower maximum rate of photosynthesis. Signup and view all the answers

Define the compensation point for photosynthesis and explain its significance in the context of net gas exchange.

The compensation point for photosynthesis refers to the light intensity at which the rate of photosynthesis exactly balances the rate of respiration. At this point, the net gas exchange is zero, meaning there is no net uptake or release of carbon dioxide. It represents the minimum light intensity necessary for the plant to maintain a positive carbon balance. Signup and view all the answers

What is the role of the electron transport chain (ETC) in aerobic respiration, specifically highlighting its contribution to ATP synthesis?

The electron transport chain is a series of protein complexes embedded in the inner mitochondrial membrane. It functions to transfer electrons from high-energy carriers like NADH and FADH₂ down a series of redox reactions, releasing energy along the way. This energy is used to pump protons across the membrane, creating an electrochemical gradient. The flow of protons back across the membrane through ATP synthase drives the production of ATP, the cell's energy currency. Signup and view all the answers

Describe the structure of a mitochondrion and explain how its structure is related to its function in aerobic respiration.

Mitochondria are double-membraned organelles with an outer membrane and an inner membrane folded into cristae. The inner membrane encloses the mitochondrial matrix. The cristae increase the surface area for the electron transport chain and ATP synthase, key components of aerobic respiration. The matrix contains enzymes for the Krebs cycle, which produces electron carriers used in the ETC. Signup and view all the answers

Explain the process of chemiosmosis and its role in ATP synthesis during respiration.

Chemiosmosis is the process of using the electrochemical gradient created across the inner mitochondrial membrane by proton pumping to drive ATP synthesis. Protons accumulate in the intermembrane space, driven by the ETC. These protons then flow through the ATP synthase channel, releasing energy that is used to convert ADP to ATP. This process is essential for the efficient production of ATP during aerobic respiration. Signup and view all the answers

Explain the role of the proton pump in the electron transport chain, specifically highlighting its link to ATP production.

Proton pumps are proteins located in the inner mitochondrial membrane that actively transport protons (H⁺) across the membrane. These pumps are powered by the flow of electrons through the ETC. By pumping protons against their concentration gradient, they create an electrochemical gradient. The energy stored in this gradient is then used by ATP synthase to generate ATP, illustrating the critical role of proton pumps in ATP production. Signup and view all the answers

What role do nucleotides play in RNA synthesis during transcription?

Nucleotides are the building blocks of RNA, and RNA polymerase uses them to synthesize complementary RNA strands from a DNA template. Signup and view all the answers

How do prokaryotic and eukaryotic cells differ in terms of mRNA processing?

Prokaryotes do not undergo RNA processing, while eukaryotes extensively process their mRNA by adding a 5' cap, a poly-A tail, and splicing out introns. Signup and view all the answers

What is the primary function of fermentation in anaerobic conditions?

Fermentation maintains glycolysis by regenerating NAD⁺, allowing ATP production to continue in the absence of oxygen. Signup and view all the answers

Explain the significance of the carbon cycle in ecosystem functioning.

The carbon cycle involves the conversion of CO₂ into organic molecules via photosynthesis and the release of CO₂ during respiration, thereby maintaining ecological balance. Signup and view all the answers

Describe the main products of yeast fermentation used in bread-making.

Yeast fermentation produces carbon dioxide, which makes the dough rise, and ethanol, which evaporates during baking. Signup and view all the answers

What distinguishes eukaryotic translation from prokaryotic translation?

Eukaryotic translation occurs in both the nucleus and cytoplasm separately from transcription, while prokaryotic translation occurs simultaneously with transcription in the cytoplasm. Signup and view all the answers

What is the importance of ATP in the processes of transcription and translation?

ATP serves as an energy source that powers the synthesis of RNA during transcription and the assembly of amino acids into proteins during translation. Signup and view all the answers

How does respiration contribute to the carbon cycle?

Respiration breaks down organic molecules to release energy and produces CO₂, which is then available for photosynthesis by plants. Signup and view all the answers

Explain how the breakdown of proteins and fats contributes to the process of aerobic cellular respiration and the production of ATP.

Proteins are broken down into amino acids, which are deaminated to enter the Krebs cycle as intermediates. Fats are broken down into glycerol, which enters glycolysis, and fatty acids, which are converted to acetyl-CoA via β-oxidation. Both processes contribute to the production of ATP through aerobic respiration. Signup and view all the answers

Describe the role of complex IV, cytochrome c oxidase, in electron transport chain and the production of ATP.

Complex IV receives electrons from cytochrome c and transfers them to O₂, forming water. This process is essential for the electron transport chain, as it allows for the continuous flow of electrons, maintaining the proton gradient across the mitochondrial membrane, which is crucial for ATP synthesis. Signup and view all the answers

What are the key differences in terms of oxygen requirement, end products, and energy yield between aerobic and anaerobic respiration?

Aerobic respiration requires oxygen as the final electron acceptor, produces carbon dioxide and water as end products, and yields 32 ATP per glucose molecule. Anaerobic respiration does not require oxygen, produces either lactic acid or ethanol and carbon dioxide, and yields only 2 ATP per glucose molecule. Signup and view all the answers

Explain the significance of the proton gradient in ATP synthesis and how it relates to the function of ATP synthase.

The proton gradient established across the inner mitochondrial membrane during electron transport provides the energy for ATP synthesis. Protons flow down their concentration gradient through ATP synthase, a protein complex in the inner mitochondrial membrane, driving the rotation of its rotor and generating mechanical energy. This energy is used to convert ADP to ATP. Signup and view all the answers

Explain how the concentration of ATP and ADP molecules act as regulators of respiration.

High ATP levels inhibit key enzymes involved in respiration, slowing down the process. Conversely, high ADP levels stimulate respiration, leading to the production of more ATP. This feedback mechanism ensures that ATP production matches the cell's energy demands. Signup and view all the answers

What process causes protons to flow back into the stroma during ATP synthesis in chloroplasts?

Protons flow back into the stroma through ATP synthase due to the proton gradient created by the electron transport chain. Signup and view all the answers

What are the substrates and final products of glycolysis, the link reaction, the Krebs cycle, and the electron transport chain in aerobic respiration?

Glycolysis: Substrate - glucose; Final products - pyruvate, ATP, NADH. Link Reaction: Substrate - pyruvate; Final products - acetyl-CoA, CO₂, NADH. Krebs cycle: Substrate - acetyl-CoA; Final products - CO₂, NADH, FADH₂, ATP. Electron Transport Chain: Substrate - NADH, FADH₂; Final products - ATP, H₂O. Signup and view all the answers

Explain the significance of NADP⁺ in non-cyclic photophosphorylation.

NADP⁺ serves as the ultimate electron acceptor, being reduced to NADPH during the process. Signup and view all the answers

Compare and contrast the processes of lactic acid fermentation and alcoholic fermentation in terms of their substrates, products, and their respective energy yields.

Both lactic acid and alcoholic fermentation occur in the absence of oxygen. They both start with glucose and use NADH as a reducing agent. Lactic acid fermentation produces lactic acid and has a net yield of 2 ATP per glucose. Alcoholic fermentation produces ethanol and carbon dioxide, also with a net yield of 2 ATP per glucose. Signup and view all the answers

What are the three main stages of the Calvin cycle?

The three main stages are carbon fixation, reduction, and regeneration. Signup and view all the answers

Describe the role of ATP in cellular processes and explain how its structure contributes to its function.

ATP is the primary energy currency of cells. It stores energy within the bonds between its phosphate groups. When these bonds are broken by hydrolysis, energy is released, which can be used to power various cellular processes. This makes ATP ideal for transferring and storing energy within cells. Signup and view all the answers

What is the role of RuBP in the Calvin cycle?

RuBP combines with CO₂ during carbon fixation, producing 3-phosphoglycerate (PGA). Signup and view all the answers

Identify the product formed when PGA is reduced in the Calvin cycle.

PGA is reduced to glyceraldehyde-3-phosphate (G3P) using ATP and NADPH. Signup and view all the answers

How many molecules of G3P are produced from 6 CO₂ in the Calvin cycle?

2 molecules of G3P are produced from 6 CO₂. Signup and view all the answers

What is the net equation for the Calvin cycle that produces one glucose molecule?

The net equation is: $6CO₂ + 18ATP + 12NADPH \rightarrow C₆H₁₂O₆ + 18ADP + 18Pi + 12NADP^+$. Signup and view all the answers

Why is the enzyme RuBisCO important in photosynthesis?

RuBisCO catalyzes the first step of carbon fixation and is the most abundant enzyme on Earth. Signup and view all the answers

Where do the light-dependent reactions of photosynthesis occur within the chloroplast?

They occur in the thylakoid membrane. Signup and view all the answers

What is the main purpose of photolysis in the light-dependent phase?

Photolysis provides electrons for PSII and produces oxygen. Signup and view all the answers

How does cyclic photophosphorylation differ from non-cyclic photophosphorylation in terms of products?

Cyclic photophosphorylation produces only ATP, while non-cyclic produces ATP, NADPH, and O₂. Signup and view all the answers

What happens to electron energy as it moves from water to NADP⁺ during photosynthesis?

Electron energy is initially high, decreases in the electron transport chain, and then increases again in PSI. Signup and view all the answers

Why is the term 'dark phase' misleading when referring to the Calvin cycle?

The Calvin cycle does not require darkness; it operates independently of light. Signup and view all the answers

What role does chlorophyll play in the process of fluorescence in photosynthesis?

Chlorophyll absorbs light energy but cannot transfer it, resulting in energy release as light. Signup and view all the answers

What is the equation for the photolysis of water during photosynthesis?

The equation is 2H₂O + light + PSII -> 4H⁺ + 4e⁻ + O₂. Signup and view all the answers

What are the products generated during the light-dependent reactions?

The products are ATP, NADPH, and O₂. Signup and view all the answers

How do stop codons function within the process of translation?

Stop codons like UAA, UAG, and UGA signal the termination of translation and recruit release factors to release the newly synthesized protein. Signup and view all the answers

Explain the concept of degenerate codons and its significance.

Degenerate codons refer to the phenomenon where multiple codons can code for the same amino acid, providing a genetic buffer against mutations. Signup and view all the answers

What distinguishes coding strands from non-coding strands in transcription?

Coding strands have the same sequence as mRNA (with T replaced by U), while non-coding strands serve as templates for RNA synthesis. Signup and view all the answers

Describe the role of the promoter in the transcription process.

The promoter is a DNA sequence where RNA polymerase binds to initiate transcription of a gene. Signup and view all the answers

What is the direction of mRNA synthesis during transcription?

mRNA is synthesized in the 5' to 3' direction by RNA polymerase, which reads the DNA template in the 3' to 5' direction. Signup and view all the answers

How do operons function in prokaryotes?

Operons are clusters of genes that are transcribed together into a single mRNA, allowing for coordinated expression of related genes. Signup and view all the answers

Describe the process of ATP synthesis during oxidative phosphorylation, highlighting the role of the proton gradient and the F₁F₀-ATP synthase.

During oxidative phosphorylation, the electron transport chain uses the energy from electrons to pump protons across the inner mitochondrial membrane, establishing a proton gradient. This electrochemical gradient drives the rotation of the F₁F₀-ATP synthase, a molecular motor that uses the proton flow to catalyze ATP synthesis from ADP and inorganic phosphate (Pi). Signup and view all the answers

Explain the difference between fermentation and respiration, highlighting their respective energy yields and the conditions under which they occur.

Respiration is aerobic and utilizes oxygen as the final electron acceptor, yielding significantly more ATP (around 38 molecules per glucose) than fermentation. Fermentation, on the other hand, is anaerobic and uses organic molecules as the final electron acceptor, yielding only 2 ATP molecules per glucose. Fermentation occurs when oxygen is scarce or absent, allowing glycolysis to continue and a small amount of ATP to be produced. Signup and view all the answers

Explain how the carbon cycle connects photosynthesis, respiration, and fermentation.

Photosynthesis removes carbon dioxide (CO₂) from the atmosphere and incorporates it into organic molecules. Respiration breaks down these organic molecules, releasing CO₂ back into the atmosphere. Fermentation also produces CO₂ as a byproduct and can contribute to the overall carbon cycle. These interconnected processes maintain a dynamic equilibrium of carbon in the environment. Signup and view all the answers

Describe the role of nucleotides in transcription and translation.

Nucleotide monomers are the building blocks of RNA, which serves as the intermediary between DNA and protein synthesis. During transcription, RNA polymerase uses nucleotides to create a complementary RNA copy of a DNA template. In translation, mRNA carries the genetic code to ribosomes, where tRNA molecules, also composed of nucleotides, bring specific amino acids based on codon recognition, constructing the polypeptide chain. Signup and view all the answers

Compare and contrast prokaryotic and eukaryotic protein synthesis in terms of key differences in their processes and locations.

Prokaryotic protein synthesis occurs in the cytoplasm, with transcription and translation coupled, meaning both processes happen simultaneously. Eukaryotic protein synthesis, however, is divided into transcription in the nucleus and translation in the cytoplasm. Prokaryotes have polycistronic mRNA carrying multiple genes, while eukaryotes have monocistronic mRNA carrying only one gene. Additionally, eukaryotic mRNA undergoes extensive processing before translation, including 5' capping, poly-A tail addition, and splicing of introns. Ribosomes are also differently sized in prokaryotes (70S) and eukaryotes (80S), reflecting differences in the ribosomal subunits. Signup and view all the answers

Explain the significance of the Shine-Dalgarno sequence in prokaryotic translation initiation and its counterpart in eukaryotes.

In prokaryotes, the Shine-Dalgarno sequence is a short ribosomal binding site located upstream of the start codon. It serves as a recognition site for the small ribosomal subunit, initiating translation. In eukaryotes, the 5’ cap, a modified guanine nucleotide at the beginning of mRNA, performs a similar role, directing the ribosome to the mRNA for translation initiation. Signup and view all the answers

Discuss the role of fermentation in food production, providing specific examples of fermented products and the microbial processes involved.

Fermentation plays a crucial role in the production of various food items. Yeast fermentation is central to bread making, where CO₂ production causes dough to rise, and ethanol evaporates during baking. Wine and beer production rely on yeast fermentation of sugars into ethanol and CO₂. In dairy products, lactic acid bacteria ferment lactose into lactic acid, contributing to the characteristic tangy flavor of yogurt and promoting milk curdling during cheese production. Signup and view all the answers

Discuss the importance of the regulation of gene expression in maintaining cellular function.

Gene expression regulation is essential for maintaining cellular function and ensuring the proper production of proteins. This regulation ensures that genes are only expressed when needed, preventing unnecessary protein synthesis and conserving cellular resources. It also allows cells to respond to environmental cues and adapt to changing conditions. Signup and view all the answers

Flashcards

Chemiosmotic theory

Explains how ATP is produced in chloroplasts via proton gradient and ATP synthase.

Photolysis of H₂O

Process where light energy splits water to release protons for ATP production.