Core Cell Processes: Photosynthesis, Respiration, Division

Photosynthesis: Energy from Sunlight

Photosynthesis is the process by which organisms, typically plants, create energy-rich organic substances from inorganic substances, using sunlight as an energy source.

Photosynthesis Reaction and Phases

It is an anabolic process that takes place in chloroplasts. In this process, water, carbon dioxide, and minerals are transformed into organic compounds (glucose).

For photosynthesis to occur, it requires an energy source from sunlight. This light energy is captured by a pigment present in chloroplasts, called chlorophyll. The general equation is:

CO₂ + H₂O + Light Energy + Minerals → Glucose + O₂

Photosynthesis has two main phases:

• Light-dependent phase: Energy captured from the sun is converted into chemical energy (ATP and NADPH).
• Light-independent phase (Calvin Cycle or dark phase): This chemical energy is used to synthesize organic matter (glucose) from inorganic material (CO₂).

Importance of Photosynthesis

A crucial outcome of photosynthesis is the release of oxygen, which is essential for the life of most organisms, including humans.

Cellular Respiration: Energy Release

Cellular respiration is the process of total degradation (by oxidation) of certain organic substances (like glucose) into inorganic materials (carbon dioxide and water) to release energy. Oxygen is typically required for this process. The general equation is:

Glucose + O₂ → H₂O + CO₂ + Chemical Energy (ATP)

The energy released in this process is stored in a molecule called ATP (adenosine triphosphate). This ATP transports energy to any part of the cell where it is needed. Cellular respiration primarily takes place in the mitochondria.

Cell Reproduction: Creating New Cells

Cell reproduction, or cell division, is the process by which a parent cell divides, giving rise to new cells, called daughter cells.

Purpose of Cell Division

• In unicellular organisms, cell division results in the creation of new individuals identical to the parent.
• In multicellular organisms, cell division leads to an increase in the number of body cells, contributing to growth, repair, and development.

Types of Cell Division

There are several types of asexual cell division:

Bipartition (Binary Fission)

The nucleus of the parent cell divides into two identical nuclei. Subsequently, the parent cell divides into two daughter cells of approximately the same size. This is common in bacteria and protozoa.

Multiple Fission (Pluripartition)

The parent cell's nucleus divides multiple times. Each new nucleus becomes surrounded by cytoplasm and a cell membrane, forming multiple daughter cells. This occurs in some protozoa.

Budding

The parent cell's nucleus divides into two. Simultaneously, the cytoplasm produces a small outgrowth, or bud, on its surface. One nucleus moves into the bud, which then detaches to form a new, smaller individual. This is seen in yeasts.

Sporulation

The nucleus of the parent cell divides successively multiple times. Each resulting nucleus is surrounded by a small amount of cytoplasm and a protective wall, giving rise to daughter cells called spores. This method is used by algae, mosses, and ferns.

Genetic Material and Chromosomes

In the nucleus of eukaryotic cells, DNA (deoxyribonucleic acid) is associated with proteins, forming a complex tangle of fibers known as chromatin. During cell division, these chromatin fibers condense to form distinct, visible structures called chromosomes, which carry the genetic information.

Mitosis: Nuclear Division Process

Mitosis is the process of nuclear division in eukaryotic cells where the duplicated genetic material (chromosomes) is meticulously segregated into two equal halves. This results in two daughter nuclei, each containing an identical set of chromosomes to the parent nucleus. Mitosis is typically followed by cytokinesis (cell division), producing two genetically identical daughter cells.