Cellular Processes and Biological Kingdoms: An In-Depth Look
Photosynthesis: How Plants Make Food
Photosynthesis is the process by which plants make their own food. It is based on the ability of plants to transform the sun’s energy into chemical energy stored in the bonds of certain molecules. Through this process, different lifestyles we see on Earth are possible. This process takes place in beings that have the pigment chlorophyll, located in specific cell organelles. The keepers of chlorophyll are green vegetables and some bacteria. In green plants, the chlorophyll-containing organelles are the chloroplasts, lamellar structures that exist in many plant cells. In bacteria that possess chlorophyll, it is located in very small granules called chromatophores.
Chemical Events in Photosynthesis
The light energy is captured by a molecule of chlorophyll, which becomes rich in energy. This “excited” molecule is in an unstable state, and to return to the lower energy state it had before, a stable state, it needs to get rid of the energy that the light gave it. This energy is now chemical energy, no longer light energy. The chemical reaction that occurs in the plant is the formation of a substance rich in energy that is very important in living beings, a substance that contains phosphoric acid in its molecules. The main consequences of this process for the plant and the environment are:
- Utilization of light energy by plants
- Manufacture of glucose
- Depletion of atmospheric CO2
- Enrichment of the atmosphere with O2
Meiosis: Cell Division for Sexual Reproduction
Meiosis is a process of splitting the nucleus of the cell that is designed to form daughter nuclei with half the chromosomes of the mother cell. The number of chromosomes that the stem cell possesses before meiosis is called the diploid number, while the number of chromosomes in daughter cells is called haploid.
Phases of Meiosis
Prophase I
Chromosomes condense and become visible. The nuclear membrane disappears, and the spindle begins to form.
Metaphase I
Chromosomes are placed on the spindle equator. They have previously been paired, meaning the two homologous chromosomes of each pair are attached closely together.
Anaphase I
The paired chromosomes separate, and each component of the pair migrates to a separate pole of the cell. The two sets of chromosomes come together, and each pole has a haploid number. Each of these chromosomes is composed of two chromatids.
Telophase I
A nuclear membrane is formed around each of the sets of chromosomes, forming two daughter nuclei.
Prophase II
This phase is usually very short since the second division immediately follows the first, and the chromosomes are often already condensed. Two new spindles are organized perpendicular to the one that presided over the first division. The nuclear membrane disappears, sometimes not even forming.
Metaphase II
The chromosomes of both nuclei are arranged in the equatorial zones of their respective spindles.
Anaphase II
The two chromatids of each chromosome separate and are directed to opposite poles of the spindles. The result is the formation of four groups of chromatids, each with a haploid number.
Telophase II
A membrane forms around each set of chromatids, resulting in four daughter nuclei. The final balance of meiosis is that, at the expense of a diploid stem cell, four haploid cells have been formed.
Biological Kingdoms
Monera
The Monera kingdom includes all living organisms with prokaryotic organization, meaning a very simple cytoplasmic structure, lacking all organelles except ribosomes. Most characteristically, they lack a cell membrane to wrap the hereditary material. Their division, therefore, is not mitotic. They are very primitive, microscopic, and very abundant. This kingdom includes bacteria and cyanobacteria (blue-green algae).
Protista (or Plantae)
The Protista kingdom includes a wide variety of organisms, both plant and animal in appearance, unicellular or multicellular, but they do not have cell or tissue differentiation. Protoctists are eukaryotes and aerobic. This kingdom includes algae and protozoa.
Fungi
The Fungi kingdom includes unicellular and multicellular eukaryotic organisms that look like plants but have heterotrophic nutrition by absorption of previously digested food outside the cells, through the secretion of potent enzymes.
Plants (Metafita)
Plants are eukaryotes, multicellular, and primarily terrestrial photosynthetic organisms. They have different degrees of cell differentiation, ranging from the existence of an outer cell layer similar to the epidermis to the diversification of tissues that appear in higher plants.
Animal Kingdom (Metazoa)
The Animal Kingdom comprises all multicellular organisms with typical animal features. They are eukaryotes that do not conduct photosynthesis, being, therefore, heterotrophic. Their cells are specialized in tissues that form groups which, in turn, are organs whose group leads to the apparatus and systems present in the most developed animals.
Mitosis: Cell Division for Growth and Repair
Mitosis is the cell reproduction process leading to the reproduction of organisms, a process that allows two or more daughter cells, identical to the progenitor, to form from a stem cell.
Interphase
This is the phase before and after prophase to telophase, as the process is continuous.
Prophase
This is the most important and longest phase of mitosis. The two centrioles separate, forming the mitotic spindle. The nucleolus and the nuclear membrane begin to disintegrate and disappear at the end of this phase. The chromatin in the interphase nucleus, which has a lumpy appearance, changes and becomes double filaments that are increasingly apparent as they shorten and thicken.
Metaphase
The spiral filaments are very short and thick, forming the chromosomes. These are divided into two identical parts called chromatids, identical in form and information. The chromosomes are placed in the equator of the cell, forming a plane called the equatorial plate.
Anaphase
In this stage, the chromatids separate, one to each pole of the cell, finally getting one chromatid of each chromosome to each pole.
Telophase
The chromatids reach the poles of the cell, and a nuclear membrane forms around each group of chromatids. Nucleoli appear. The mitotic spindle begins to disappear, and each centriole duplicates.