Compare and Contrast the Functions and Processes of Respiration and Photosynthesis

Hydrogen atoms get picked up by special acceptor molecules. These molecules bring the electrons into a series of chemical reactions called the electron transport chain. Enzymes on the inner membranes of the mitochondria pass the electrons through a chain of chemical reactions. The electrons get passed down the chain. On each step they lose a little of their energy. But energy is not lost it only changes form. At the end of this process it is essential to have oxygen molecules in the mitochondria to "soak up" the extra protons and electrons (hydrogen atoms) and use them to make water so they don't harm the cell.

By the time the all of cell respiration is complete, enough energy is released from one molecule of glucose to make 38 ATP molecules. The cell can now use the energy for movement, growth, digestion and to power all of the other chemical reactions. The atoms that were in the glucose sugar and oxygen molecules are now in the carbon dioxide and water molecules formed during cellular respiration.

Photosynthesis

The process of photosynthesis takes energy in the form of light and changes it to chemical energy. Photosynthesis can be divided into two main parts. The first stage is called the light reaction. This reaction needs light.

) The light reaction.

Light energy hits the chlorophyll molecules in the thylakoid membranes. In the reaction centers the collected energy energizes electrons until they move completely off the chlorophyll molecules. To get the missing electrons back, the chlorophyll will steal electrons from water molecules. This makes the water molecule fall apart. OH molecules that join to make water and the oxygen gas that is released into the air. High-energy electrons and Protons that are used to help make the ATP energy. After the light reactions are completed, the sun's energy will end up stored in the ATP molecules and in high-energy hydrogen atoms, both of which will be used to make glucose sugar.

The protons and high-energy electrons which moved off chlorophyll are picked up by an acceptor molecule. Some of the energy stored in the electrons is released, step-by-step, in a series of chemical reactions called the electron transport chain. On each step it has less energy than before. The energy lost is used to push the protons into membrane chambers inside the thylakoids. When a lot of protons build up inside the thylakoid, they start diffusing back out through channels in the membrane. In these channels the energy that was collected as the protons were moved, is released and used to make ATP in a process called oxidative phosphorylation. ATP is a very important energy-storing molecule.

2) The Dark Reaction.

The ATP energy and the high-energy hydrogen from the light reaction now begin one of the most important parts of photosynthesis. Glucose has to be made. Glucose is a complex molecule with energy stored in its bonds. To make food you have to build these complex carbon compounds. This is called carbon fixation. The carbon comes from carbon dioxide that enters the plant through holes in the leaves (stomata). In a continuous cycle of chemical reactions, carbon dioxide, high-energy hydrogen atoms and ATP energy are combined with a starter molecule already in the plant. Each turn of the cycle creates the beginning of glucose sugar molecules and also recreates more of the starter molecule. This cycle, controlled by enzymes in the chloroplast, is called the Calvin cycle. The Calvin cycle has to turn twice for each glucose molecule that enters it.

The comparisons of the two are that in respiration energy is released and in photosynthesis, energy is stored. The reason that energy is released in respiration is that the cell needs to respire to stay alive. In photosynthesis energy is stored to keep the cells of the plant alive in the hours of darkness.

In the process of respiration glucose is the reactant that starts the chain of reactions, which in the end lets the cell respire. In photosynthesis co2 and h2o are the reactants that aid the plant in storing energy.

The products of the two reactions are the exact opposite. In respiration the end product is co2 and h2o. These are the reactants of the photosynthesis reaction. In photosynthesis the end product is glucose that is stored. Glucose is the reactant in the process of respiration.

In both of the processes, electrons are passes across an inner membrane i.e. in photosynthesis electrons are passed across the inner membrane of the chloroplast. Also in both processes ATP synthesis occurs on the inner membrane of either the chloroplast or the mitochondria.