AP bio photosynthesis

What are autotrophs?

Organisms that sustain themselves without eating anything made from other organisms; they are producers in ecosystems.

What are the two types of autotrophs?

Chemoautotrophs and photoautotrophs.

How do chemoautotrophs obtain energy?

They build organic compounds from carbon dioxide using energy from inorganic compounds.

What is photosynthesis?

The process that converts solar energy into chemical energy (food) in plants.

What is the overall equation for photosynthesis?

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

What is the role of chloroplasts in photosynthesis?

Chloroplasts contain chlorophyll and are specialized cells where photosynthesis occurs.

What is the significance of stomata in leaves?

Stomata are microscopic pores that allow CO2 to enter and O2 to exit the leaf.

What are the two phases of photosynthesis?

The light reactions and the Calvin cycle.

What occurs during the light reactions of photosynthesis?

Water is split, oxygen is released, ATP is produced, and NADPH is formed.

What is the function of pigments in photosynthesis?

Pigments absorb certain wavelengths of light; chlorophyll is the main pigment.

What is the absorption spectrum?

A graph showing which wavelengths of light are absorbed by pigment molecules.

What is the role of chlorophyll a in photosynthesis?

Chlorophyll a is the main photosynthetic pigment that captures light energy.

What is a photosystem?

A protein complex in the thylakoid membrane that converts light energy into chemical energy.

What happens when chlorophyll absorbs light?

It goes from a ground state to an excited state, leading to the emission of photons when returning to ground state.

What is linear electron flow in the light reactions?

The primary pathway that involves both photosystems and produces ATP and NADPH using light energy.

What is the role of NADP+ in photosynthesis?

NADP+ serves as an electron acceptor and becomes NADPH when reduced.

Where do the light reactions occur?

In the thylakoid membranes of chloroplasts.

What is the Calvin cycle?

The phase of photosynthesis that forms sugar from CO2 using ATP and NADPH.

What is the significance of the hydrocarbon tail in chlorophyll?

It interacts with hydrophobic regions of proteins inside thylakoid membranes.

What are accessory pigments?

Pigments like chlorophyll b and carotenoids that broaden the spectrum of wavelengths used for photosynthesis.

What is the role of ATP synthase in photosynthesis?

ATP synthase synthesizes ATP during the light reactions.

What is fluorescence in relation to chlorophyll?

Fluorescence is the light emitted when excited electrons fall back to the ground state.

What is the primary electron acceptor in photosystems?

A molecule that captures high-energy electrons and transfers them out of the photosystem.

What is the structure of chloroplasts?

Chloroplasts contain thylakoids, grana, and stroma, where photosynthesis occurs.

What are the main components of the light reactions in photosynthesis?

Photosystems II, an electron transport chain, Photosystem I, NADP+ Reductase, and ATP Synthase.

What is the primary pathway for electron flow during the light reactions?

Linear electron flow, which produces ATP and NADPH using light energy.

What role does Photosystem II play in the light reactions?

It excites electrons from chlorophyll a molecules (P680), splits water into oxygen, H+ ions, and electrons, and captures high-energy electrons.

How does the electron transport chain function in the light reactions?

Electrons from Photosystem II are transported, losing energy, which is used to pump H+ ions into the thylakoid space, creating a gradient.

What is the role of NADP+ Reductase in photosynthesis?

It receives high-energy electrons from Photosystem I and reduces NADP+ to form NADPH, the final electron acceptor in the light reactions.

What is cyclic electron flow and its significance?

Cyclic electron flow uses only Photosystem I to produce ATP without NADPH, generating surplus ATP for the Calvin cycle.

What is chemiosmosis in the context of photosynthesis?

It refers to the process where the H+ gradient created by the electron transport chain drives ATP synthesis via ATP synthase.

What is the starting material for the Calvin cycle?

Ribulose bisphosphate (RuBP), a 5-carbon molecule.

What are the three phases of the Calvin cycle?

Carbon Fixation, Reduction, and Regeneration of RuBP.

What happens during the carbon fixation phase of the Calvin cycle?

Three CO2 molecules are fixed to three RuBP, forming six 3-carbon compounds (3-PGA).

How does the reduction phase of the Calvin cycle work?

NADPH reduces six 3-PGA molecules into G3P, requiring ATP, resulting in six G3P molecules, one of which leaves the cycle.

What occurs during the regeneration of RuBP phase?

Five G3P molecules are converted back into three RuBP molecules, requiring ATP, allowing the cycle to continue.

What can G3P be used for in the plant cell?

It can be used to build glucose, fatty acids, glycerol, fructose, starch, cellulose, and amino acids.

What is photorespiration and why is it a problem for plants?

Photorespiration occurs when rubisco adds O2 instead of CO2, consuming O2 and releasing CO2 without producing ATP or sugar, which can drain carbon fixed by the Calvin cycle.

How do C4 plants minimize photorespiration?

They incorporate CO2 into four-carbon compounds in mesophyll cells using PEP carboxylase, which has a higher affinity for CO2.

What is the function of CAM plants in photosynthesis?

CAM plants fix carbon by opening stomata at night to incorporate CO2 into organic acids, which are then used during the day when stomata are closed.

What is the significance of the proton gradient created during the light reactions?

It drives ATP synthesis through ATP synthase, which is crucial for the energy needs of the Calvin cycle.

What is the difference between cyclic and linear electron flow?

Cyclic electron flow produces only ATP and uses only Photosystem I, while linear electron flow produces both ATP and NADPH using both Photosystems.

What enzyme is responsible for fixing carbon dioxide in the Calvin cycle?

Rubisco.

How many times must the Calvin cycle turn to produce one G3P molecule?

The cycle must turn three times to fix three CO2 molecules.

What is the end product of the Calvin cycle after three turns?

One G3P molecule, which can be converted into glucose or other organic compounds.

What happens to the electrons lost by P700 in Photosystem I?

They are replaced by the electron pair from Photosystem II that traveled through the electron transport chain.

What is the role of ATP in the Calvin cycle?

ATP provides the energy required for the reduction phase and the regeneration of RuBP phase.

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

NADPH and ATP.

What is the relationship between the light reactions and the Calvin cycle?

The light reactions produce ATP and NADPH, which are then used in the Calvin cycle to synthesize sugars.