CH. 10 Photosynthesis

plants, algae, and certain prokaryotes

convert light energy to chemical energy, store the chemical energy in sugar made from carbon dioxide and water

C3, C4, CAM

categories to divide plants based upon the mechanisms plants employ in their use of photosynthesis

chloroplasts

the major site of photosynthesis in green plants

photosynthesis

this process in plants converts carbon dioxide and water into organic molecules and releases oxygen

chlorophyll

is an important light-absorbing pigment in chloroplasts, responsible for the green color of plants, plays central role in converting solar energy to chemical energy

mesophyll

chloroplasts are concentrated in the cells of this, are the green tissue in the interior of the leaf

stomata

are tiny pores in the leaf that allow carbon dioxide to enter and oxygen to exit

veins

these in the leaf deliver water absorbed by roots

thylakoids

are often concentrated in stacks called grana, house much of the machinery that converts light energy to chemical energy

thylakoid space

has functions analogous to the intermembrane space of a mitochondrion, internal compartment of thylakoid

chlorophyll molecules

are built into the thylakoid membrane and capture light energy

redox (oxidation-reduction) process

photosynthesis, like respiration is a ___

CO2, sugar

___becomes reduced to ___ as electrons along with hydrogen ions from water are added to it

water molecules

___are oxidized when they lose electrons along with hydrogen ions

light energy

what type of energy, captured by chlorophyll molecules to boost energy of electrons, is converted to chemical energy that is then stored in the chemical bonds of sugars?

light reactions

occur in the thylakoid membranes

water is split, ATP is generated, light energy is absorbed, NADPH is produced

what happens in the light reactions of photosynthesis?

Calvin-Benson cycle (dark reactions)

occurs in the stroma of the chloroplast, is a cyclic series of reactions that assembles sugar molecules using CO2 and energy-rich products of the light reactions

carbon fixation

process during the Calvin cycle where CO2 is incorporated into organic compounds

require light directly

Calvin cycle is called dark reactions or light-independent reactions because none of the steps ___

pigments

absorb light and are built into the thylakoid membrane

plant pigments

absorb some wavelengths of light and reflect or transmit other wavelengths

chlorophyll a

absorbs blue-violet and red light and reflects green

green wavelengths

chlorophyll transmits these kind of wavelengths

chlorophyll b

absorbs blue and orange and reflects yellow-green

carotenoids

broaden the spectrum of colors that can drive photosynthesis and provide photoprotection

photoprotection

absorbing and dissipating excessive light energy that would otherwise damage chlorophyll or interact with oxygen to form reactive oxidative molecules

photosystems

in the thylakoid membrane, chlorophyll molecules are organized along with other pigments and proteins into ___

photosystem

capture solar energy, consists of a number of light-harvesting complexes surrounding a reaction-center complex

light-harvesting complexes

contain various pigment molecules bound to proteins, function as a light-gathering antenna

photosystem II

functions first, called P680 because its pigment absorbs light with a wavelength of 680 nm

photosystem I

functions second, is called P700 because it absorbs light with a wavelength of 700 nm

electron transport chain

the two photosystems are connected by an ___

ATP and NADPH

in the light reactions, light energy transformed into the chemical energy of ___

removed from water, passed from photosystem II to I, accepted by NADP+

to transform light energy into chemical energy of ATP and NADPH, electrons are ___

move down electron transport chain, provide energy for ATP synthesis

between the two photosystems, electrons ___

NADPH, ATP, oxygen

the products of the light reactions are ___

chemiosmosis

the mechanism that generates ATP in chloroplasts

concentration gradient of hydrogen ions across a membrane

ATP is generated because the electron transport chain produces a ___

photophosphorylation

chloroplasts use ___ to transfer light energy into the chemical energy of ATP

plastocyanin

a copper containing metalloprotein that serves as an electron transfer agents between the Z-scheme cytochrome b6f complex from photosystem II and I

plastiquinone

is reduced when it accepts two electrons from photosystem II and two hydrogen cations from the stroma of the chloroplast, thereby forming plastoquinol (PGH2), then transfers the electrons further down the electron transport chain to plastocyanin, a mobile water soluble electron carrier through the cytochrome b6f complex

rubisco

the single most abundant protein structure in the world, catalyzes the first step of carbon fixation in the C3 pathway or Calvin cycle (carboxylation of RuBP, results in the formation of 2 molecules of 3-PGA

atmospheric CO2; ATP and NADPH generated by light reactions

the necessary ingredients to produce sugar

glyceraldehyde-3-phosphate (G3P)

the Calvin cycle uses these three ingredients to produce an energy rich three carbon sugar called ___

carbon fixation, reduction, release of G3P, regeneration of starting molecule (RuBP)

the steps of the Calvin cycle include ___

C3 plants

use CO2 directly from the air and carbon fixation occurs when the enzyme rubisco adds CO2 to RuBP, first product of carbon fixation is thee-carbon compound (3-PGA)

stomata, CO2, O2

in hot and dry weather, C3 plants:

close their ___ to reduce water loss

prevent ___ from entering the leaf and ___ from leaving

photorespiration

O2 builds up in a leaf, rubisco adds O2 instead of CO2 to RuBP, and a two-carbon product of this reaction is then broken down in the cell, process called ___ because it occurs in the light, consumes O2, and releases CO2

C4 plants

have evolved means of carbon fixation that saves water during photosynthesis while optimizing the Calvin cycle, first fix CO2 into a four-carbon compound

mostly closed

when the weather is hot and dry, C4 plants keep their stomata ___ thus conserving water

CAM

such as pineapples and cacti, conserve water by opening their stomata and admitting CO2 only at night

chloroplast

integrates the two stages of photosynthesis and makes sugar from CO2

greenhouse effect

operates on a global scale, heat radiating from the warmed planet is absorbed by gases in the atmosphere, which then reflects some of the heat back to Earth

roots, tubers, seeds, fruits

excess food made by plants is stockpiled as starch in ___

proteins, lipids, cellulose

sugars also serve as the starting material for making other organic molecules, such as ___

half of the carbohydrates

about ___ made by photosynthesis are consumesd as fuel for cellular respiration in the mitochondria of plant cells