Photoautotrophs are autotrophs that use light energy to power this activity.

• This chapter will go over photosynthesis, the method through which photoautotrophs synthesize organic molecules.

• Before delving into all of the processes related with photosynthesis, it is critical to first grasp the fundamentals of this process.

• It is worth noting that during photosynthesis, carbon atoms from carbon dioxide receive hydrogen atoms (carbon is reduced) whereas oxygen atoms in water lose hydrogen atoms (oxygen is oxidized).

Heterotrophs are creatures that devour other species to obtain organic compounds.

Photosynthesis is separated into two major components:

• light-dependent processes and light-independent reactions (also known as the Calvin cycle).

The light-dependent processes divide water using sunlight's energy, creating oxygen gas, protons, and high-energy electrons.

• Oxygen gas is emitted.

• The atmosphere is filled with oxygen gas.

• Protons and high-energy electrons are employed to power ATP and NADPH synthesis (which are sent to the light-independent reactions).

• These ATP and NADPH, together with carbon dioxide, are used by light-independent processes to generate sugars.

• The light-independent processes subsequently return ADP, Pi, and NADP+ to the light-dependent reactions, allowing photosynthesis to resume.

• As a result, the two components of photosynthesis are interconnected.

Photosynthesis happens in chloroplasts of plants.

• Chloroplasts have an exterior membrane that is filled with stroma, a liquid.

• Stacks of membrane sacs called grana float in the stroma, and each individual sac is termed a thylakoid.

• The light-independent reactions take place in the stroma, while the light-dependent reactions take place in the thylakoid.

Some prokaryotes, like as cyanobacteria, can also photosynthesis.

• Prokaryotes, on the other hand, lack membrane-bound organelles.

• The light-dependent processes of photosynthesis occur on infoldings of the plasma membrane in photosynthetic prokaryotes, whereas the light-independent reactions occur in the cytosol.

Light energy is utilized to stimulate the creation of ATP in light-dependent processes.

• This is referred to as photophosphorylation.

• Light energy causes electrons in chloroplasts to become more energetic.

Energy is released when these excited electrons pass through the chloroplast.

• NADP+ takes these electrons at the conclusion of the light-dependent processes, creating NADPH, which is a source of reducing power for the light-independent reactions.

• Chlorophyll is a light-absorbing pigment that absorbs photons from the sun.

The principal light-absorbing pigments in photosynthesis are chlorophyll.

• Photosystems I and II include chlorophylls (PSI and PSII).

• Proteins, chlorophyll, and other light-absorbing pigments known as accessory pigments make up a photosystem.

PSI and PSII include distinct forms of chlorophyll that absorb the greatest amount of light energy at slightly different wavelengths (700 nm and 680 nm, respectively).

• Photosystems are found in the chloroplast's thylakoid membrane and are linked by an electron transport chain (ETC).

Another photon of light energy from the sun boosts the electron from the ETC (which is now on PSI).

The electron is converted to NADP+ coupled with a proton by the enzyme NADP+ reductase after passing through a sequence of carriers similar to that of the ETC.

• This results in the formation of a molecule of NADPH, which provides reducing power for the light-independent processes.

Because photosynthesis requires light energy, limiting the intensity of the light would reduce the quantity of photosynthesis performed by the chloroplasts as well as the amount of food accessible to Elysia crispata from those chloroplasts.

• The sea slug may grow more reliant on alternative food sources.

• Glycolysis and fermentation can be performed by anaerobic organisms that do not have access to or require oxygen.

• Aerobic organisms that lack oxygen can also engage in glycolysis and fermentation.

• Furthermore, in the presence of oxygen, aerobic organisms may execute pyruvate oxidation, the Krebs cycle, and oxidative phosphorylation.

• The differences between anaerobic and aerobic species in the presence and absence of oxygen.

• The six-carbon molecule glucose, coupled with two molecules of the electron transporter NAD+, enters glycolysis.