Photosynthesis
The shared evolutionary history of all photosynthetic organisms is conspicuous, as the basic process has changed little over eras of time. Even between the giant tropical leaves in the rainforest…
The Calvin Cycle
After the energy from the sun is converted and packaged into ATP and NADPH, the cell has the fuel needed to build food in the form of carbohydrate molecules. The…
The Light-Dependent Reactions of Photosynthesis
How can light be used to make food? It is easy to think of light as something that exists and allows living organisms, such as humans, to see, but light…
Introduction to Photosynthesis
Figure 5.1 This sage thrasher’s diet, like that of almost all organisms, depends on photosynthesis. (credit: modification of work by Dave Menke, U.S. Fish and Wildlife Service) No matter how…
Anaerobic Cellular Respiration
Certain prokaryotes, including some species of bacteria and Archaea, use anaerobic respiration. For example, the group of Archaea called methanogens reduces carbon dioxide to methane to oxidize NADH. These microorganisms…
Fermentation
In aerobic respiration, the final electron acceptor is an oxygen molecule, O2. If aerobic respiration occurs, then ATP will be produced using the energy of the high-energy electrons carried by…
Citric Acid Cycle and Oxidative Phosphorylation
The Citric Acid Cycle In eukaryotic cells, the pyruvate molecules produced at the end of glycolysis are transported intomitochondria, which are sites of cellular respiration. If oxygen is available, aerobic…
Glycolysis
You have read that nearly all of the energy used by living things comes to them in the bonds of the sugar, glucose. Glycolysis is the first step in the breakdown…
ATP in Living Systems
A living cell cannot store significant amounts of free energy. Excess free energy would result in an increase of heat in the cell, which would result in excessive thermal motion…
Electrons and Energy
The removal of an electron from a molecule, oxidizing it, results in a decrease in potential energy in the oxidized compound. The electron (sometimes as part of a hydrogen atom)…
