Plants are autotrophs capable of producing complex molecules from the suns energy and other simple substances such as water, carbon dioxide, and minerals. Heterotrophs cannot fix their own carbon and must use organic molecules as their carbon sources. Auxotrophs are organisms that are unable to synthesize a particular compound required for its growth/survival. Lithotrophs use inorganic substrates to obtain their energy (often from dissolved minerals in rocks). Detritivores are a type of heterotroph that feed on dead animal and plant matter, and the waste products of each.

Plants undergo both photosynthesis and cellular respiration. Glucose is made during photosynthesis and then this glucose is used to generate ATP in cellular respiration. This ATP can then be used to drive the complex anabolic processes of plants. Lactic acid metabolism commonly occurs in muscle tissue under anaerobic conditions but is not found to occur in plants.

Carbon dioxide, water, and light are the photosynthetic inputs. Oxygen gas is an output product of photosynthesis, not an input.

In the light reactions of photosynthesis the energetic intermediates NADPH and ATP are generated through chlorophyll pigments excited by sunlight. These then provide the energy and reducing power necessary for the generation of glucose in the Calvin cycle.

 is the molecular formula for a monosaccharide (sugar). This sugar can then be used in cellular respiration to create chemical energy to drive the various anabolic processes of the plant. The oxygen that is produced through photosynthesis provides the oxygen that we breathe in order to undergo our own cellular respiration. Water is an input of photosynthesis.

Chlorophyll is green because it absorbs all wavelengths of visible light except it reflects, not absorbs green. This green light reflected and is therefore the color that we perceive. The wavelengths of red and blue light work well to excited the two different photosystems involved in photophosphorylation. While ultraviolet light is found on the electromagnetic spectrum, it is not considered to be visible light. Ultraviolet light is more energetic and has a shorter wavelength than that of visible light.

The pH is lowest in the thylakoid lumen. During photophosphorylation, protons are pumped into the thylakoid lumen from the stroma. The more protons found in the thylakoid space results in its lower pH. This lumen can have a pH of as low as 4. Protons then move down there concentration gradient out into the stroma in a process that produces ATP.

The stroma of the chloroplast has a pH of approximately 8, while the pH of the cytosol is closer to 7.

The carbon fixed in the Calvin cycle comes from the air in the form of . This carbon is reduced through the usage of NADPH and ATP, produced in the light reactions of photosynthesis, in order to make glucose.

The soil provides valuable water and mineral nutrients for the plant. The sun provides the energy necessary to drive photosynthesis. And pure water contains only hydrogen and oxygen. Lithotrophs utilize inorganic carbon, usually from rocks.

Plants that undergo C4 respiration must also utilize the enzyme PEP carboxylase. This enzyme allows for carbon dioxide to be fixed to PEP to produce oxaloacetate. C4 respiration allows for lower levels of photorespiration, which can cause a decrease in photosynthetic efficiency.

Rubisco is the enzyme that adds carbon dioxide to ribulose bisphosphate to produce two molecules of 3-phosphoglycerate. Alkaline phosphatase is an enzyme that hydrolyzes phosphates from a variety of substrates under alkaline conditions. Kinases are enzyme which add phosphate groups to specific targets, such as fructose-1-phosphate.

CAM plants utilize C4 photosynthesis and keep their stomata closed during the day. By using the enzyme PEP carboxylase, CAM plants are able to store up enough fixed carbon during the night in order to keep their stomata closed during the day. The closure of the stomata prevents the loss of water from the plant. This is especially important in hot, dry climates.

When oxygen is not readily available in the blood, cells use fermentation as a means of anaerobic respiration. The process is used to generate NAD⁺, which can be used as a reactant in glycolysis to produce small amounts of ATP. Glycolysis still occurs in this environment, breaking glucose into pyruvate and producing two ATP per cycle.

Fermentation in humans converts pyruvate to lactate (lactic acid) and NADH to NAD⁺.