Overview Of Photosynthesis Worksheet (Page 2 of 2) in pdf

The Light Reactions

Two ________________, two _______________________ chains, and ____________________ are the key components

of the light reactions of photosynthesis. These parts are embedded in the thylakoid membranes of a chloroplast.

The ____________________ consist of arrays of chlorophyll molecules. Chlorophyll-- the green pigment of leaves--

absorbs __________________. The absorbed energy excites electrons to a higher energy level. Energized electrons

from photosystem I are passed down an electron transport chain and added to __________ to form __________.

Meanwhile, energized electrons from photosystem II are passed through another electron transport chain. Their

energy is used to pump hydrogen ions (H

) from the _____________ into the _________________ compartment,

creating a ____________________________. Electrons leaving this electron transport chain enter photosystem I,

replenishing its lost electrons. Photosystem II replenishes its electrons by splitting __________. ______________ ions

and ____________ are released into the thylakoid compartment. This is where the oxygen gas generated by

photosynthesis comes from.

The buildup of hydrogen ions inside the thylakoid compartment stores ________________________. This energy is

harvested by an enzyme called ________________. As hydrogen ions diffuse through ATP synthase, down their

concentration gradient, the enzyme uses the energy of the moving ions to make _______. Next, ATP and NADPH are

used in the sugar-making process of the Calvin cycle.

The Calvin Cycle

So far, energy from light has been stored in the _________________ of ATP and NADPH. In the Calvin cycle, this

stored energy is used to produce ____________ molecules.

The Calvin cycle is a complex series of chemical reactions carried out in the _____________. The Calvin cycle begins

with ____________ fixation. Three molecules of carbon dioxide are added to three molecules of a five-carbon sugar

abbreviated RuBP. These molecules are then rearranged to form six molecules called 3-PGA, which have three

carbons each.

In the next two reactions, products from the light reactions are used to boost the energy of these three-carbon

molecules. First, high-energy ____________ groups are added. Six ATP molecules contribute phosphate groups, so

that each three-carbon molecule receives an additional phosphate group. Electrons are added in the next reaction.

Six molecules of ___________ are oxidized. The electrons from NADPH reduce the six three-carbon compounds,

creating six high-energy _________ molecules. G3P-- or glyceraldehyde-3- phosphate-- is a sugar, the final product

of the Calvin cycle.

One of the G3P molecules represents the three carbon dioxide molecules fixed so far. The other five G3Ps are

reshuffled to regenerate the original __________ molecules. To summarize, so far the Calvin cycle has used the

energy of the light reactions to reduce three molecules of ___________________ and produce one molecule of G3P.

Three more carbon dioxide molecules are fixed to form G3P in this same complicated way. To make each G3P, the

Calvin Cycle consumes 9 ATP molecules and 6 NADPH molecules. These are regenerated in the light reactions. G3P

is the actual final product of the Calvin cycle. The cell can combine two G3Ps to make _____________, which stores

the energy that chlorophyll originally captured from the sun.

Overview Of Photosynthesis Worksheet Page 2