Chapter 4 - Photosynthesis

Flashcards for reviewing Chapter 4 - Photosynthesis lecture notes.

Photosynthesis

A metabolic pathway that converts carbon dioxide and water, with the addition of energy from the Sun, into glucose and oxygen. This process is vital for plant life and, by extension, nearly all life on Earth. It occurs in two main stages: light-dependent and light-independent reactions.

Light-dependent reaction

The reaction that traps solar energy and uses it to generate ATP and NADPH. During these reactions, water molecules are split, releasing oxygen as a byproduct. They occur in the thylakoid membranes of the chloroplasts.

Light-independent reaction

The reaction that assimilates carbon dioxide to produce an organic molecule that can be used to produce biologically important molecules such as carbohydrates. This stage doesn't directly require light and occurs in the stroma of the chloroplasts, utilizing ATP and NADPH from the light-dependent reactions.

Thylakoid

One of many interconnected sac-like membranous disks within the chloroplast, containing the molecules that absorb energy from the Sun. These are the sites of the light-dependent reactions, where chlorophyll and other pigments capture solar energy.

Pigment

A compound that absorbs certain wavelengths of visible light while reflecting others. Different pigments absorb different wavelengths, allowing plants to capture a wide range of light energy. Chlorophyll is the primary pigment in photosynthesis.

Photosystem

One of two protein-based complexes composed of clusters of pigments that absorb light energy. These systems, Photosystem I and Photosystem II, work together to capture photons and transfer the energy to electrons, initiating the electron transport chain.

Photophosphorylation

The use of photons of light to drive the phosphorylation of ADP to produce ATP via chemiosmosis. This process occurs during the light-dependent reactions, converting light energy into chemical energy in the form of ATP.

Calvin cycle

In photosynthesis, the reactions that convert carbon dioxide to the three-carbon organic molecule glyceraldehyde-3-phosphate (G3P); can occur in the absence or presence of light; also called the dark reactions and the Calvin-Benson cycle. This cycle occurs in the stroma of the chloroplasts.

Carbon dioxide fixation

In the Calvin cycle of photosynthesis, the reaction of carbon dioxide with ribulose bisphosphate to produce two identical three-carbon molecules, 3-phosphoglycerate. This initial step is crucial for incorporating inorganic carbon into organic molecules.

C3 photosynthesis

A process of converting carbon dioxide to glyceraldehyde-3-phosphate using only the Calvin cycle; involves production of a three-carbon intermediate (PGA). This is the most common photosynthetic pathway, especially in moderate environments.

Photorespiration

The reaction of oxygen with ribulose-1,5-bisphosphate in a process that reverses carbon fixation and reduces the efficiency of photosynthesis. This usually happens when carbon dioxide levels are low and oxygen levels are high, particularly in hot and dry conditions.