Concept 10.2: Photosynthesis converts light energy to the chemical energy of food

Flashcards from Concept 10.2 of Pearson's Campbell Biology, Twelfth Edition.

Chloroplasts

Organelles within plants and other photosynthetic organisms that are structurally similar to and likely evolved from photosynthetic bacteria

• Structure allows for chemical reactions of photosynthesis

Leaves

The area of most photosynthesis in plants

Mesophyll

The interior tissue of the leaf where chloroplasts are mainly found

Stomata

Pores in a plant’s leaf where CO₂ enters and O₂ exits for gas exchange

Veins

Structures within a plant that transport water from the roots and export sugar to nonphotosynthetic parts of the plant

Stroma

Dense fluid within the chloroplast envleloped by two membranes

Thylakoids

Connected sacs in the chloroplast that compose a third membrane system, stacked in columns called grana

Chlorophyll

The pigment that gives leaves their green color that resides in thylakoid membranes

Photosynthesis

A complex series of reactions represented by the equation 6CO₂ + 12H₂O + Light energy → C₆H₁₂O₆ + 6O₂ + 6H₂O

• Represents the effective reverse of cellular respiration in electron flow to make sugar in two stages

• Oxidizes H₂O and reduces CO₂ in an endergonic process powered by light

Water

Substance used in photosynthesis as it is split into hydrogen and oxygen

• Electrons from hydrogen are used to create sugar molecules while releasing O₂ as a by-product

• Hydrogen may also be obtained via other sources, such as from H₂S that creates S₂ as a waste product

Light reactions

The first part of photosynthesis that occurs in the thylakoids

• Splits H₂O, recieving electrons and protons as H⁺

• Releases O₂ as a by-product

• Reduces the electron acceptor NADP⁺ to NADPH

• Generates ATP from ADP by photophosphorylation

NADP⁺

An electron acceptor reduced in the light reactions in the thylakoids to NADPH for transfer to oxygen

Photophosphorylation

The generation of ATP from ADP in the light reactions in the thylakoids

Calvin cycle

Second part of photosynthesis within the stroma that makes sugar from CO₂, using ATP and NADPH generated from light reactions

• Begins with carbon fixation, incorporating CO₂ into organic molecules

• Reduces fixed carbon to carbohydrate by transferring electrons from NADPH

Carbon fixation

The incorporation of carbon from CO₂ into organic molecules via the Calvin cycle in the stroma