Unit 7 (copy)

What is photosynthesis?

The process of converting light energy into chemical energy.

What are the two main stages of photosynthesis?

Light reactions and the Calvin Cycle.

What occurs during the light reactions of photosynthesis?

Light energy is absorbed by pigments and converted into two forms of chemical energy: ATP and NADPH.

What is the general equation of photosynthesis?

6CO₂ + 2H₂O + Light Energy → C₆H₁₂O₆ + 6O₂.

What drives photosynthesis?

Energy from the sun.

What are the two categories of organisms based on their food acquisition?

Autotrophs (organisms that make their own food) and heterotrophs (organisms that consume food to live).

What is a photoautotroph?

An organism that uses light energy to produce food.

Where does photosynthesis occur within plant cells?

In chloroplasts.

What pigment is primarily involved in photosynthesis, and where is it located?

Chlorophyll, found in the thylakoid membrane of chloroplasts.

What are mesophyll tissues?

Tissues in plants that contain cells with chloroplasts, facilitating photosynthesis.

How do CO₂ and O₂ enter and exit the chloroplast?

Through small openings called stomata.

Describe the membrane structure of chloroplasts.

Chloroplasts have three membranes: inner and outer membranes, and the thylakoid membrane which contains pigment molecules and forms thylakoids.

What is the stroma in a chloroplast?

The fluid-filled region between the thylakoid membrane and the inner membrane.

Where do the light-dependent reactions occur?

In the thylakoid membrane.

Where do the light-independent reactions (Calvin Cycle) take place?

In the stroma of chloroplasts.

What are ATP and NADPH's roles in photosynthesis?

They serve as energy intermediates that provide the energy and electrons needed to synthesize carbohydrates during the Calvin Cycle.

What is light energy, and how does it travel?

Light energy is a form of electromagnetic radiation that travels as waves.

Define wavelength.

The distance between peaks in a wave pattern.

What is the electromagnetic spectrum?

It encompasses all possible wavelengths of electromagnetic radiation.

What are photons?

Particles that light possesses, exhibiting both wave-like and particle-like properties.

What happens when light energy contacts a pigment?

The light may pass through the object, change the path, or be absorbed.

What is a pigment?

A molecule that absorbs light energy, boosting an electron to a higher energy level, known as the excited state.

What occurs when an electron is in an excited state?

This condition is unstable and can release energy in several ways: as heat, light, or by transferring energy to a nearby electron (resonance energy transfer).

Name the two types of chlorophyll and their function.

Chlorophyll a and Chlorophyll b; they reflect green light and are bound to the thylakoid membrane.

What are carotenoids?

A type of pigment that reflects red, yellow, and orange light.

What is an absorption spectrum?

A graph that plots a pigment’s light absorption as a function of the light’s wavelength.

What are Photosystem II (PSII) and Photosystem I (PSI)?

Two distinct complexes of protein and pigment molecules in thylakoid membranes vital for photosynthesis.

Describe the function of PSII.

PSII is the initial step in photosynthesis where light excites electrons, and water is oxidized to create O₂.

How do electrons move through the electron transport chain?

Electrons pass through two protein complexes, maintaining an H+ gradient across the thylakoid membrane.

What is the main role of PSI?

To synthesize NADPH by transferring electrons to NADP+ Reductase.

Define phosphorylation in the context of chloroplasts.

The process of ATP synthesis where H+ ions move through ATP synthase due to the electrochemical gradient established by the movement of electrons.

How is the H+ electrochemical gradient created in chloroplasts?

Through the oxidation of water, movement of electrons through the electron transport chain, and the formation of NADPH, which uses H+ from the stroma.

What is linear electron flow?

A mechanism that harvests light energy, resulting in the production of ATP and NADPH in roughly equal amounts.

Explain cyclic photophosphorylation.

A pattern of electron flow that results in the production of only ATP and does not involve the reduction of NADP+.

Describe the Z scheme of photosynthesis.

This model represents how electrons change energy levels; beginning at low energy in non-excited pigments, gaining energy in PSII, losing energy in the electron transport chain, and gaining energy again in PSI before reducing NADP+.

What are the three steps of the Calvin Cycle?

1. Carbon Fixation

2. Reduction and Carbohydrate Production

3. Regeneration of RuBP

What factors can alter the operation of the Calvin Cycle?

Temperature, water availability, and light intensity.

What is photorespiration, and why is it harmful for plants?

When CO₂ is low and O₂ is high, Rubisco adds O₂ to RuBP, reducing the efficiency of photosynthesis.

What are CAM plants?

Plants that have unique leaf anatomy to minimize photorespiration, thriving in warm, arid climates by closing their stomata to conserve water.

Carbon Fixation

CO₂ is incorporated into RuBP, catalyzed by Rubisco.

Reduction and Carbohydrate Production

ATP and NADPH convert the fixed carbon into G3P, forming glucose.

Regeneration of RuBP

RuBP is regenerated for the cycle to continue.

Resonance energy transfer

Transferring energy to a nearby electron.