Plant Processes: Photosynthesis and Respiration

Photosynthesis

It is a unique process of plants containing chlorophyll, transforming simple substances such as water and carbon dioxide into more complex substances like carbohydrates.

Chlorophyll

It is a green pigment that absorbs radiation reflected in colors like blue, purple, and red. There are four types of chlorophyll (a, b, c, and d), with slight chemical variations in their formulas.

Chloroplasts

These are cytoplasmic organelles formed by polymembranous structures containing areas called grana, where light-phase reactions occur. There are other areas called stroma, where enzymatic reactions take place.

Factors Affecting Photosynthesis

1. Light: A decisive factor in this process because it can accelerate or retard the reaction. This energy is formed by a set of radiation with different wavelengths and energy. It comes in different colors in the light spectrum: red, orange, yellow, purple, blue, and violet. Different colors manifest different characteristics. Yellow and green radiation are not efficiently absorbed by plants.
2. Temperature Effect: It influences the speed of the reaction; warmer temperatures generally lead to faster reactions, with an optimum range between 10°C and 35°C, and an optimum around 25°C.
3. Carbon Dioxide Concentration: Plants that live outdoors, where the normal CO2 content is about 0.04% of the volume, perform photosynthesis faster with temperature changes. Photosynthesis is faster with a higher concentration of CO2 (e.g., 1.25%).

Respiration

It is a process whereby glucose is burned in the presence of oxygen, resulting in water, carbon dioxide, and the release of large amounts of energy. This process occurs at the cellular level in organelles called mitochondria.

It is also defined as the oxidation of food to produce energy in living things, which can be stored in ATP.

Formula for Respiration

Glucose + O2 -> H2O + CO2 + ATP (Glucose = C6H12O6)

Phases of Respiration

1. Anaerobic Phase: It is done without the intervention of molecular oxygen and occurs outside the mitochondria. A series of reactions involving 12 types of enzymes split the glucose molecule into two molecules of pyruvic acid, using the energy provided by ATP.
2. Aerobic Phase: This occurs in the presence of molecular oxygen. In this phase, pyruvic acid is broken down to form carbon dioxide and water, releasing large amounts of energy.

Pathway of CO2 in Respiration

The glucose molecule, through a process called glycolysis, is divided into two molecules formed by three carbon atoms, called pyruvic acid. Each molecule of this acid loses a molecule of CO2 and becomes a 2-carbon molecule called acetic acid.

Krebs Cycle (Citric Acid Cycle)

A carbon atom is separated from the citric acid, forming a 5-carbon acid and a molecule of carbon dioxide. A second separation occurs, forming a 4-carbon acid. The combination of this 4-carbon acid with acetic acid reforms citric acid.