Biology Chapter on Cellular Respiration and C4 Plants

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Questions and Answers

What is the primary function of glycolysis in cellular respiration?

To split glucose into two pyruvate molecules (correct)

To convert pyruvate into carbon dioxide

To oxidize NADH and FADH2

To produce ATP from the electron transport chain

Which of the following occurs during the citric acid cycle?

Glucose is broken down into ATP

Pyruvate is broken down into carbon dioxide (correct)

Oxygen is consumed directly

NADH is converted back to NAD+

What is the end product of aerobic respiration in the mitochondria?

Lactic acid

Glucose

ATP, carbon dioxide, and water (correct)

Alcohol

Which statement is true regarding fermentation?

It occurs without mitochondria and is less efficient Signup and view all the answers

Which of the following statements accurately characterizes C4 plants?

They efficiently fix CO2 at low concentrations Signup and view all the answers

What is the primary function of bundle sheath cells in C4 plants?

They fixate CO2 through the Calvin cycle. Signup and view all the answers

Which enzyme plays a crucial role in the initial step of C4 metabolism?

Phosphoenolpyruvate carboxylase Signup and view all the answers

What is a significant advantage of C4 metabolism in plants?

It facilitates CO2 capture even at low concentration. Signup and view all the answers

How do C4 plants differ from CAM plants in terms of CO2 fixation timing?

C4 plants fix CO2 during the day while CAM plants do it at night. Signup and view all the answers

Why are most C4 plants especially suited for hot, dry environments?

They have a high affinity for CO2 and a large catchment area. Signup and view all the answers

What is the primary product of the light reactions that is used in the Calvin cycle?

NADPH Signup and view all the answers

Which enzyme is responsible for carbon fixation in the Calvin cycle?

Ribulose bisphosphate carboxylase Signup and view all the answers

During which phase of the Calvin cycle does phosphorylation occur?

Phosphorylation and reduction Signup and view all the answers

What is the overall purpose of the Calvin cycle?

To incorporate CO2 into sugars Signup and view all the answers

What drives the ATP synthesis during the light reactions?

H+ gradient Signup and view all the answers

What behavior does Elysia chlorotica exhibit to utilize chloroplasts for photosynthesis?

Kleptoplasty Signup and view all the answers

What is produced from the reduction of C3 during the Calvin cycle?

Glucose Signup and view all the answers

In which of the following organisms does chemosynthesis typically occur?

Archaea Signup and view all the answers

Which statement correctly describes the relationship between the light reactions and the Calvin cycle?

Energy produced in light reactions fuels the Calvin cycle. Signup and view all the answers

What process describes the movement of protons across a selectively permeable membrane to drive ATP synthesis?

Chemiosmosis Signup and view all the answers

What key conclusion did Jan Baptist Van Helmont reach from his experiments regarding plant biomass?

Plants obtain their biomass primarily from water. Signup and view all the answers

Which structure within the chloroplast is responsible for the photosynthetic process?

Thylakoid membranes Signup and view all the answers

In the process of photosynthesis, what is primarily converted into chemical energy?

Light energy Signup and view all the answers

What characteristic is NOT true about the chloroplast according to the provided information?

Has a single membrane Signup and view all the answers

What is the primary role of chlorophyll in plants?

To capture light energy Signup and view all the answers

What process can be considered as partial endosymbiosis in Elysia chlorotica?

Incorporation of algal chloroplasts Signup and view all the answers

What role do autotrophs play in the ecosystem?

They convert CO2 into organic carbon. Signup and view all the answers

Which of the following statements is true about heterotrophs?

They rely on organic carbon as their source of energy. Signup and view all the answers

What is the primary energy transformation that occurs during photosynthesis?

Light energy is converted into chemical energy. Signup and view all the answers

Which group of organisms is considered primary producers?

Plants and unicellular eukaryotes. Signup and view all the answers

What do both autotrophs and heterotrophs produce during respiration?

Carbon dioxide through oxidation of organic carbon. Signup and view all the answers

Which of the following is a characteristic of parasitic plants?

They obtain nutrients by living on other plants. Signup and view all the answers

Which statement correctly describes the relationship between the carbon cycle and photosynthesis?

Photosynthesis is a process that sequesters carbon from CO2. Signup and view all the answers

What do organisms classified as consumers primarily obtain from their diet?

Organic carbon. Signup and view all the answers

What is the role of chlorophyll in photosynthesis?

To absorb light energy Signup and view all the answers

What does the Calvin cycle primarily achieve?

Production of glucose from carbon dioxide Signup and view all the answers

Which of the following best describes the process of non-cyclic electron flow?

Electrons flow from water to NADP+ through both PSII and PSI Signup and view all the answers

What did Joseph Priestley contribute to the understanding of air?

He described oxygen as 'dephlogisticated air' Signup and view all the answers

Which of the following statements about light reactions is true?

They convert light energy into chemical energy Signup and view all the answers

What is the overall equation for photosynthesis?

6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2 Signup and view all the answers

What are the two main components of a photosystem?

Chlorophyll and a reaction center Signup and view all the answers

What is one product of the light reactions in photosynthesis?

Oxygen Signup and view all the answers

What drives the energy requirements of the electron transfer in the light reactions?

Absorbed photons of light Signup and view all the answers

What occurs after chlorophyll absorbs a photon?

It enters a ground state and releases energy as heat or fluorescence Signup and view all the answers

Study Notes

Photosynthesis

Photosynthesis is a process that impacts the entire planet.
It involves the conversion of light energy into chemical energy (sugars).
The process requires carbon dioxide, water, and light.
Carbohydrates and oxygen are the products of photosynthesis.

Photosynthesis (Campbell and Reece)

Edition 7, 8, 9.
Chapter 10 overview.
Chapter 10 concepts 10.1, 10.2 (excluding cyclic electron flow), 10.3, and 10.4 (excluding photorespiration).
Chapter 9 concept 9.1 (only stages of cellular respiration).

Photosynthesis impacts the biosphere

Photosynthesis impacts the atmosphere, hydrosphere, lithosphere, and ecosphere.

The pyramid of life

Shows the flow of energy through organisms.
Photosynthesizing organisms are at the base of the pyramid.
Herbivores feed on these organisms.
Carnivores feed on herbivores.
Photons from the sun are the primary source of energy.

Autotrophs and Heterotrophs

Autotrophs use inorganic forms of carbon (like CO2) and require external energy sources to create organic compounds (like sugars.)
Heterotrophs need organic carbon (like sugar) and depend on dead or living biological matter for the energy to oxidize and make CO2.

The Carbon Cycle

Shows the flow of carbon between different parts of the ecosystem.
Includes processes like combustion, photosynthesis, respiration, and sedimentation.
Carbon is measured in billion tonnes (a unit of measurement)

Photosynthesis (Self-feeders)

Autotrophs are "self-feeders"
They use inorganic carbon and other nutrients as primary producers.
Types of autotrophs include plants and single/multi-celled eukaryotic algae (protists) and prokaryotes.

Heterotrophs

Heterotrophs rely on organic forms of carbon and other nutrients produced by other organisms.
They include consumers, like herbivores, carnivores, and decomposers.

Anatomy of a Leaf

Leaves contain a cuticle, collenchyma, veins, stomata, upper epidermis, palisade parenchyma, spongy parenchyma, and lower epidermis.
Guard cells are part of the leaf structure.
Xylem and phloem are components within the veins of a leaf.

Chloroplasts

Chloroplasts contain chlorophyll.
They generally have 40 chloroplasts per cell.
The green color comes from chlorophyll.
Multiple membranes.
Contains chloroplast DNA (ctDNA).

Endosymbiosis & the Origin of Chloroplasts

The chloroplast's origin stems from a unicellular, photosynthesizing algal cell being incorporated into a heterotrophic host cell.

Energy for Autotrophs

Photoautotrophs use light energy (plants, algae, and prokaryotes.)
Chemoautotrophs use chemical energy (archaea, a group of early prokaryotes.)

Properties of Chlorophyll and Light

Chlorophyll absorbs photons and becomes excited.
Energy is released as heat or fluorescence, when the chlorophyll goes back to the ground state.

Photosynthesis: A Two-Step Process

Photosynthesis consists of two phases: Light reactions, and Calvin cycle.
Light reactions convert light energy to chemical energy (ATP and NADPH.)
Calvin cycle uses CO2, ATP, and NADPH to make sugars.

Light Reactions-1

Light reactions are a redox process (reduction-oxidation)
Electrons move from a donor (like water) to an acceptor molecule with a lower redox potential.
Energy is required.
These reactions are driven by absorbed light energy.

Two-pumps drive Photosynthesis

Two photosystems (Photosystem II and Photosystem I) are crucial in photosynthesis.
The two photosystems work sequentially.
The pumps use redox potentials to build up energy.

A Photosystem

A photosystem includes antenna pigments and a reaction center chlorophyll.
Light causes the antenna pigments to excite and pass the energy to the reaction center.
The reaction center chlorophyll then transfers energy to a primary electron acceptor.

Photosystems - 3 Components

Chlorophyll is organized as light-harvesting complexes (antennae).
These complexes capture photons.
A reaction center includes a special pair of chlorophylls to catalyze charge separation.
A primary electron acceptor is also present.

Non-cyclic electron flow

Non-cyclic electron flow begins in photosystem II.
It involves transferring electrons from water to the primary electron acceptor and onward to photosystem I.
Re-reduction of photosystem II happens through electrons from water.
Photosystem I also involves charge separation and moving electrons to the primary electron acceptor.
These electrons are then transferred to NADP+ to generate NADPH.

Water splitting

Water splitting produces electrons, H+, and oxygen. 2 H₂O → 4H+ + O2 + 4 e-

Acidification of the lumen

The light reactions produce a high concentration of H+ inside the thylakoid space.
This process acidifies the thylakoid lumen.

ATP-synthesis

Energy is stored as a H+ gradient across the thylakoid membrane.
The gradient drives ATP synthesis by ATP synthase.
Chemiosmosis involves the movement of protons across a membrane against an electrochemical gradient, driving photophosphorylation.

End-products non-cyclic Electron Flow

NADPH and ATP are the end-products of non-cyclic electron flow.
They are forms of energy that are essential for the Calvin cycle.

Speed Calvin cycle depends on light reactions

The rate of the Calvin cycle relies on the products of the light reactions (ATP and NADPH.)

Calvin Cycle

Also known as the dark reactions.
The main job of the Calvin cycle is to incorporate carbon dioxide (CO2) into sugars using the chemical energy from light reactions (ATP & NADPH.)

Calvin cycle phase 1

Carbon fixation.
CO2 combines with RuBP (ribulose bisphosphate) using the enzyme RuBisCo.
Produces an unstable 6-carbon compound, which splits into two molecules of 3-phosphoglycerate (3-PGA.)

Calvin cycle phase 2

Phosphorylation and reduction
3-PGA is phosphorylated by ATP.
Then, 3-PGA is reduced using NADPH.
This creates glyceraldehyde 3-phosphate (G3P).
G3P can be converted to glucose and other sugars

Calvin cycle phase 3

Regeneration of the CO2 acceptor (RuBP).
Five out of six molecules of G3P are used to regenerate RuBP, using ATP.
The regenerated RuBP is available to start the cycle again.

The Calvin Cycle

Overall, the Calvin cycle incorporates CO2 into organic molecules.
These reactions are powered by light-reaction products (ATP & NADPH.)

C4 Metabolism

C4 adaptations increase CO2 concentration in leaves and minimize transpiration.
It's a process where all CO2 is gathered in a small group of cells, before going to the Calvin cycle.
C4 cycle is prefaced with the Calvin cycle.

C4-photosynthesis

CO2 is bound to phosphoenolpyruvate by PEP carboxylase.
This forms a four-carbon compound, which is transported to bundle sheath cells.
The four-carbon compound releases CO2 in the bundle sheath.
CO2 is then used by the Calvin cycle.
C3 is returned to the mesophyll.

Function linked to structure (C4 leaf anatomy)

In C4 plants, bundle sheath cells fix CO2 and use Calvin cycle.
Mesophyll cells collect CO2 as a C4 compound and transport it to bundle sheath.

C4 metabolism comes at a cost

C4 plants are more common in hot, dry regions.
Examples of C4 plants include maize, sugarcane, millet, and sorghum.

CAM-metabolism

CAM plants (Crassulacean Acid Metabolism) are adapted to arid conditions.
CO2 is taken up at night, when temperatures are cooler and transpiration rates are lower.
In CAM plants, 4C acids accumulate in vacuoles during the night.
CO2 is released during the day, for use in the Calvin cycle, reducing water loss.
CAM plants separate C3 and C4 cycles temporally instead of spatially.

C4 plants, climate change and the rise in CO2

C4 plants are adapted to low CO2 levels.
C4 plants are adapted to heat and drought.

Photosynthesis in reverse = mitochondrial respiration

Cellular respiration converts the energy in complex molecules (like sugars) into ATP. Mitochondrial reaction is opposite of photosynthesis.

Mitochondrial respiration

Unlike photosynthesis, respiration is shared among plants and animals.
Aerobic respiration requires oxygen.