Energy Generation in the Chloroplasts - Lecture 21

These flashcards cover key concepts related to chloroplast structure and function, photosynthesis processes, and the collaboration between chloroplasts and mitochondria.

What is the primary function of chloroplasts in plant cells?

Photosynthesis, which involves converting light energy into chemical energy.

What are the two main stages of photosynthesis?

Light reactions and Calvin cycle (carbon fixation reactions).

What is chlorophyll?

A green pigment that absorbs light energy for photosynthesis.

What are the thylakoid membranes?

Membrane structures within chloroplasts where light reactions occur.

What is the significance of the reaction center in a photosystem?

It transfers high-energy electrons to the electron transport chain.

Who conducted the experiment leading to the discovery of the action spectrum of photosynthesis?

Theodor Engelmann in 1882.

What is the function of photosystem II?

Generates ATP and replaces lost electrons by extracting them from water.

What molecule is produced when electrons are extracted from water in photosystem II?

Oxygen (O2).

What is the function of ferredoxin-NADP+ reductase in photosynthesis?

It transfers electrons to reduce NADP+ to NADPH.

What drives ATP synthesis in the chloroplast?

The electrochemical proton gradient created by the electron transport chain.

What is RuBisCO and its role in photosynthesis?

An enzyme that catalyzes the conversion of CO2 into organic carbon during the Calvin cycle.

How many ATP and NADPH are used to fix one molecule of CO2 in the Calvin cycle?

3 ATP and 2 NADPH.

What is the final product of the carbon fixation cycle before it is converted into glucose?

Glyceraldehyde 3-phosphate (G3P).

How do chloroplasts and mitochondria collaborate in plant cells?

They work together to produce metabolites and ATP, with chloroplasts being impermeable to ATP.

What is a characteristic feature of the thylakoid space?

It is a connected network of membranes where protons are pumped in from the stroma.

Describe the general structure of chloroplasts.

Chloroplasts have specialized membranes and compartments including the stroma and thylakoid membranes.

How do chloroplasts resemble mitochondria?

Both have double membranes and similar mechanisms for energy generation.

What is the role of light energy in photosynthesis?

It is used to create a strong electron donor from a weak one.

In what part of the chloroplast does carbon fixation occur?

In the chloroplast stroma.

What is photophosphorylation?

The process of generating ATP from ADP and inorganic phosphate using light energy.

What key process happens in the thylakoid membrane?

The light reactions of photosynthesis, including electron transport and ATP synthesis.

What is an electrochemical proton gradient?

A difference in proton concentration that drives ATP synthesis.

What happens to glyceraldehyde 3-phosphate after being produced in the Calvin cycle?

It can be converted into glucose, starch, or other organic molecules.

What is the origin of mitochondria and chloroplasts in eukaryotic cells?

They were likely acquired through symbiotic relationships.

How are most proteins in mitochondria and chloroplasts synthesized?

Most are encoded by the nucleus and imported after translation.

What is the difference between NADPH and NADH?

NADPH provides reducing power for anabolic reactions, whereas NADH is primarily involved in catabolic reactions.

How does photosystem I contribute to photosynthesis?

By transferring electrons to ferredoxin-NADP+ reductase to generate NADPH.

What is the significance of the thylakoid membrane being permeable to ATP?

It allows efficient ATP synthesis and transport within the chloroplast.

How does the absorption spectrum of chlorophyll relate to Engelmann's findings?

It matches the wavelengths where photosynthesis is most active.

What are grana in the context of chloroplast structure?

Stacks of thylakoid membranes that increase the surface area for light absorption.

What is the dark reaction also known as?

The carbon fixation cycle or Calvin cycle.

Why are chloroplasts described as having an extra compartment compared to mitochondria?

They contain the thylakoid space for light reactions.

What role do ribosomes and tRNAs play in chloroplasts?

They are involved in chloroplast gene expression.

What effect does light energy have on chlorophyll molecules during photosynthesis?

It excites electrons and converts chlorophyll to a high-energy state.

How do chloroplasts produce starch and sucrose?

By fixing carbon, producing G3P, which is then converted to glucose and stored.

What is meant by the term 'light-harvesting antenna complexes'?

Structures in photosystems that capture and transfer light energy to the reaction center.

What evidence supports the symbiotic origin of mitochondria and chloroplasts?

Both organelles have circular genomes and divide by fission, similar to bacteria.

What consequence might occur if a plant cell loses its mitochondria?

The plant might struggle to efficiently generate ATP through aerobic respiration.

What role does the water-splitting enzyme play in photosystem II?

It extracts electrons from water to replace lost ones and generate oxygen.

What is the overall purpose of the photosynthetic electron transport chain?

To convert light energy into chemical energy in the form of ATP and NADPH.