Photosynthesis and cellular respiration are the life processes ..

Now we need to understand how cells can use the products ofphotosynthesis to obtain energy.
Photo provided by Flickr

The processes of photosynthesis and cellular respiration are ..

Photoaututrophs utilize sunlight for energy and CO2 for theircarbon source by this process of PHOTOSYNTHESIS whereby sunlightis absorbed by a complex compound known as chlorophyll andconverted to energy which drives a series of chemical reactionsthat ultimately removes hydrogen from water or other compoundsand then combines the hydrogen with carbon dioxide in a way thatproduces sugars.

Photosynthesis must constantly make more ATP by restoring ADP molecules.
Photo provided by Flickr

In this stage of photosynthesis, ..

Chloroplasts have many shapes in different species but aregenerally fusiform shaped (and much larger than mitochondria) andhave many flattened membrane-surrounded vesicles called thylakoidswhich are arranged in stacks called grana. Thesethylakoid membranes contain all of the photosynthetic pigments ofthe chloroplast and all of the enzymes required for Light Phasereactions. The fluid in the stroma surrounding the thylakoidvesicles contains most of the enzymes for Dark phase reactions.

These molecules are used as the energy source to carry out the chemical changes in the next stage of photosynthesis.
Photo provided by Flickr

The oxidative chemical reactions of respiration releaseenergy, some of which is heat and some of it is captured in theform of high energy compunds such as Adenosine triphosphate (ATP)and Nicotinamide adenide dinucleotide phosphate (NADPH). Thesecompounds have a high energy (unstable) terminal phosphate bondand that terminal phosphate is easily detached with the transferof the energy to drive chemical reactions in the synthesis ofother biomolecules. In this case, the ATP loses one phosphate tobecome the energy-depleted ADP (Adenosine diphosphate)and the NADPH loses one electron to become energy-depleted NADP+.

Cellular respiration uses glucose molecules and oxygen to produce ATP molecules and carbon dioxide as the by-product.
Photo provided by Flickr

the first stage of photosynthesis, ..

Now what are the "Dark Phase Reactions" (aka CalvinCycle)? This is the cycle that converts CO2 into glucose. Sinceit utilizes the chemical energy in the ATP and NADPH, it does notrequire sunlight (hence the name). It is a complex cycle ofmostly phosphorylation (adding or removing phosphate) andoxidative (electron removal) chemical reactions whereby 6molecules of CO2 are converted into one molecule of glucose. Itrequires the energy-releasing cleavage of high energy bonds of 18ATPs and 12 NADPHs . The resulting 18 ADPs and 12 NADP+s are thenrestored by the Light Phase process to their high energy forms(ATP and NADPH).

What are the roles of NADPH and ATP during the chemical stage of ..

These intermediates are characterized by their resistance to so that they can operate in higher temperatures and dryer environments than . At right, the ranges of CO2 compensation points for the three types of plants are shown. These compensation points are the values at which the plants cease to provide net photosynthesis.

The second stage of photosynthesis takes place ..

For each electron flowing from water to NADP+ (a net change in1.14 volts), two quanta of light are absorbed, one by eachPhotosystem. Each molecule of oxygen released involves the flowof four electrons from two water molecules to two NADP+s andrequires four quanta of sunlight absorbed by each Photosystem toprovide the energy to do this. These are the "Light PhaseReactions" of photosynthesis, which produce two high energychemical products, namely NADPH and ATP.

During the first stage of photosynthesis

The Z Scheme diagram shows the pathway of an electron fromwater (lower right) to NADP+ (upper left). It also shows theenergy relationships which are measured as voltage potentialshown on the scaleon the right. To raise the energy of theelectrons derived from water (+0.82 volts) to the level necessaryto reduce NADP+ to NADPH (-0.32 volts), each electron must beboosted twice (vertical red arrows) by light energy absorbed inPhotosystems I and II. After each boosting , the energizedelectrons flow "downhill" (diagonal black lines) and inthe process transfer some of their energy to a series ofreactions which ultimately adds a phosporus to ADP to producehigh energy ATP and reduces NADP+ to NADPH. There is analternative shunt whereby the electron flow turns back tocytochrome b563 (green line)and this is called and it occurs when there is no need for NADPH, so onlyATP is produced.