Chapter 9: Photosynthesis: Capturing Light Energy

Photoautotrophs

________ use light as an energy source and are able to incorporate atmospheric CO2 into pre- existing carbon skeletons.

Photosynthesis

________ is the ultimate source of all chemical energy and organic molecules available to photoautotrophs, such as plants, and to virtually all other organisms as well.

Photons

________ excite biological molecules such as chlorophyll and other photosynthetic pigments, causing one or more electrons to become energized.

Thylakoid membrane

Some of the energy of the electrons is used to pump protons across the ________, providing the energy to generate ATP by chemiosmosis.

Series of redox reactions

A(n) ________ takes place as energized electrons are passed along the electron transport chain from photo- system II to photosystem I.

Mesophyll

In plants photosynthesis occurs in chloroplasts, which are located mainly within ________ cells inside the leaf.

CO2

The ________ is fixed in oxaloacetate, which is then converted to malate.

Chemoheterotrophs

________ obtain energy by oxidizing chemicals and obtain carbon as organic molecules from other organisms.

Chloroplasts

________ are organelles enclosed by a double membrane; the inner membrane encloses the stroma in which membranous, saclike thylakoids are suspended.

Photosystems

________ I and II are the two types of photosynthetic units involved in photosynthesis.

P700

Electrons given up by ________ in photo- system I are replaced by electrons from P680 in photosystem II.

Photophosphorylation

________ is the synthesis of ATP coupled to the transport of electrons energized by photons of light.

crassulacean acid metabolism

The ________ (CAM) pathway is similar to the C4 pathway.

PEP carboxylase

________ fixes carbon at night in the mesophyll cells, and the Calvin cycle occurs during the day in the same cells.

Malate

The ________ moves into a bundle sheath cell, and CO2 is removed from it.

ATP

________ is produced by chemiosmosis, but no NADPH or oxygen is generated.

Photorespiration

________ is significant on bright, hot, dry days when plants close their stomata, conserving water but preventing the passage of CO2 into the leaf.

cyclic electron transport

During ________, electrons from photosystem I are eventually returned to photosystem I.

Chlorophyll

________ a, ________ b, carotenoids, and other photosynthetic pigments are components of the thylakoid membranes of chloroplasts.

C4 reactions

________ take place within mesophyll cells.

regeneration phase

In the ruBP ________ of the Calvin cycle, the remaining G3P molecules are modified to regenerate ruBP.

reduction phase

In the carbon ________ of the Calvin cycle, the energy and reducing power of ATP and NADPH are used to convert PGA molecules to glyceraldehyde- 3- phosphate (G3P)

C4 pathway

In the ________, the enzyme PEP carboxylase binds CO2 effectively, even when CO2 is at a low concentration.

ATP synthase

As protons diffuse through ________, an enzyme complex in the thylakoid membrane, ADP is phosphorylated to form ATP.

Carbon fixation reactions

The ________ proceed by way of the Calvin cycle, also known as the C3 pathway.

Light consists of particles

________ called photons that move as waves.

electron transport

Electrons in photosystem I are energized by the absorption of light and passed through a(n) ________ chain to NADP** +**, forming NADPH.

P700

________ is in the reaction center for pho- tosystem I; P680 is in the reaction center for photosystem II.

photosystem

Each ________ includes chlorophyll molecules and accessory pigments organized with pigment- binding proteins into antenna complexes.

CO2

In the ________ uptake phase of the Calvin cycle, ________ is combined with ribulose bisphosphate (RuBP), a five- carbon sugar, by the enzyme ribulose bisphosphate carboxylase /oxygenase, commonly known as rubisco, forming the three- carbon molecule phosphoglycerate (PGA)

Photons

________ with shorter wavelengths have more energy than those with longer wavelengths.

P700 is in the reaction center for pho

tosystem I; P680 is in the reaction center for photosystem II

Electrons given up by P700 in photo

system I are replaced by electrons from P680 in photosystem II

A series of redox reactions takes place as energized electrons are passed along the electron transport chain from photo

system II to photosystem I