Essential Functions and Structures of Cells and Tissues
Essential Functions of Cells
Nutrition Function
Type:
- Autotroph bodies: Taken from the exterior with simple inorganic molecules that build organic molecules they need.
- Heterotrophic organisms: Are unable to synthesize organic molecules and have to obtain them from other agencies. They depend on the material synthesized by autotroph-based organizations.
Cellular metabolism: The nutrients undergo a series of complex chemical reactions. These chain reactions are called metabolic pathways, and all the metabolic reactions are catalyzed. Most metabolic reactions are redox reactions.
Type:
- Anabolism: ATP → ADP + phosphate.
Relationship Function
- Receiving information: Receiving information changes are called biological stimuli, and cells have specialized capabilities to capture them.
- Integration of information: Once the information is processed, it produces an adequate response to the stimulus.
- Production of the answer: There are many varied responses, or the stimulus can be in the opposite direction.
Reproduction Function
Cell Reproduction
Cell organisms reproduce to replace the old ones.
Mitosis: The process by which duplicated chromosomes are distributed equally between daughter cells.
- Prophase: Chromosomes begin to be visible in the form of filaments. The condensation of the chromosomes continues throughout prophase. Each chromosome consists of two chromatids. The cytoplasm is formed between the mitotic spindle that the two centrosomes are separated.
- Prometaphase: The nuclear envelope breaks. Chromosomes interact with microtubules of the mitotic spindle and unite through its kinetochores.
- Metaphase: The chromosomes are arranged in the equatorial plane of the spindle. The microtubules in each chromosome are linked to the spindle poles.
- Anaphase: Begins when the sister chromatids of each chromosome are separated and are directed towards the spindle poles. Each chromosome is now a chromatid.
- Telophase: The nuclei are reconstructed from the daughter cells. The nuclear envelopes are formed from fragments of the nuclear envelope of the progenitor cell.
Cytokinesis: The division ends when the cell cytoplasm is divided by the process of cytokinesis.
- Animal Cell: The cytoplasm is divided into two by the formation of a contractile ring of actin and myosin filaments that just strangles the cell.
- Plant cells: A new wall is formed in the equatorial plane of the cell from vesicles that precede the Golgi apparatus.
The Reproduction of Organisms
- Asexual: From a group of cells, a new individual is generated. The process is carried out by successive cell divisions.
- Sexual: Intervention of special cells, called gametes or sex cells, is needed.
Meiosis: The process of cell division in a diploid cell gives rise to 4 haploid daughter cells (sexual reproduction).
- 1st division: Prophase I: Chromosomes began to condense and become visible as filaments to the interior of the nucleus.
- Leptotene: Homologous chromosomes began to pair.
- Zygotene: Homologous chromosomes pair gene to gene, a process called synapsis. Each chromosome pair is called bivalent.
- Pachytene: Chromosome crossing occurs, a process by which fragments of DNA are exchanged between homologous chromosomes.
- Diplotene: Homologous chromosomes are separated a little, and points where crossing over has occurred are observed, called chiasmata.
- Diakinesis: Chromosomes are still condensed. The other phenomena that occur are the same that occur in the prophase of mitosis.
- Metaphase I, Anaphase I, Telophase I, and Cytokinesis.
- 2nd division: Prophase II, Metaphase II, Anaphase II, Telophase II – daughter cells.
Biological Cycles
According to the time when meiosis is performed, the following are distinguished:
- Haplont organisms: (Algae and fungi) Meiosis occurs in the first division of the zygote. The organism formed from this zygote is haploid (the only diploid cell is the zygote).
- Diplont Organizations: (Animals) Meiosis occurs during the formation of gametes, which are the only haploid cells. When gametes of two individuals unite, they form a diploid zygote.
- Diplohaplont Organisms: (Higher plants and algae) The diploid zygote gives rise to a diploid organism, also called a sporophyte because it is reproduced by spores. Meiosis occurs in the formation of these spores, which are haploid and give rise to haploid organisms called gametophytes.
Plant Tissues
Trainers or Meristem Tissues
They are responsible for plant growth in length and thickness. Their cells are increasing continuously. There are two types:
- Primary Meristem: Come directly from embryonic cells and are at the exterior of the roots and stems.
- Secondary meristem: The cells are derived from other adult cells that regained an ability to multiply. There are two more: on the inner cambium, it produces increased thickness of the stem and phellogen; the outer cells divide and generate a protective outer layer.
Adult Tissues
They originate from meristem cells and have lost the ability to multiply.
Parenchyma Tissue or Fundamental
They are responsible for the nutrition of the plant. Photosynthesis, respiration, and the storage of reserves occur here.
- Chlorophyll Parenchyma: Its cells contain many chloroplasts. The fabric is responsible for carrying out photosynthesis.
- Reserve Parenchyma: Its cells are specialized to accumulate reserve substances such as starch, fats, and proteins. They do not contain chloroplasts and are found in the stems, roots, and seeds.
- Aquifer Parenchyma: It is a specialization of xerophile plants, such as cacti, that store large amounts of water.
- Aeriferous Parenchyma: The cells are widely separated to store and improve air circulation (aquatic plants).