Cellular Biology: Nutrition, Relationship, and Reproduction

Posted on May 14, 2024 in Biology

1. The Functions of Nutrition

Nutrition is the set of processes by which organisms exchange energy and matter with their environment.

1.1 Nutrition in the Cells

It develops in three phases:

  1. The entry of materials into the cell
  2. The use of matter and energy
  3. The excretion of waste products

The Entry of Materials into the Cell

The substances needed for nutrition (nutrients) enter cells through transport mechanisms controlled by the plasma membrane. The large particles of food must be subjected to digestion to transform them into simple molecules. Digestion can be intracellular or extracellular.

The Use of Matter and Energy

Cells use the material incorporating a vast array of chemical reactions that transform substances and energy is exchanged. This is cellular metabolism. It has two objectives:

  1. The synthesis of substances in the cell.
  2. Getting energy.

The Excretion of Waste Products

Cells must remove both nutrients inside unused as waste of cellular metabolites.

1.2 The Types of Cellular Nutrition

According to their nutrition, we can distinguish two types of cells:

  • Autotrophic cells
  • Heterotrophic cells

Autotrophic Cells

Take environmental inorganic nutrients, such as water. With them, they are capable of synthesizing their own organic nutrients, using light energy. Example: algae.

Heterotrophic Cells

Take environmental organic nutrients from other living beings. Example: animals.

Nutrients

Any substance that a cell needs to perform its functions in nutrition may be inorganic or organic.

1.3 Multicellular Nutrition

Every cell in a multicellular organism carries out the processes of nutrition. Multicellularity implies certain peculiarities.

Multicellularity and the Exchange of Substances

The cells of a multicellular organism not in contact with the external environment, so do not have access to nutrients. Nor can they dump their waste products.

Strategies for the Exchange of Substances

  • Some multicellular beings are not totally isolated from the outside and have remained linked with water, allowing for dissemination to the external medium and cells. This is the case of fungi, algae, etc.
  • More complex organisms like plants and animals have specialized structures in which the input and the output is regulated and various transportation systems that drive these substances.

1.4 The Addition of Nutrients

All cells have a different internal chemistry than the environment around them. Maintaining the internal environment depends on the cell membrane, which is also responsible for selecting substances which must enter and exit the cell. The passage of substances is grouped into two types:

Small Substances

  • Transport liabilities: We performed without energy and there are two passive transport mechanisms: simple diffusion and facilitated diffusion.
  • Active transport: the molecules move against the concentration gradient, i.e., from the less concentrated area to the most concentrated.

The Transport of Large Particles

The cells have the means to introduce in their cytoplasm, or expel foreign macromolecules and large particles. The media always involve the formation of vesicles due to the deformation of the plasma membrane: they are the exocytosis and endocytosis.

  • Exocytosis is a process of removal of waste products or secretions. The role involves exocytosis of membrane vesicles generated in the cell.
  • Endocytosis: the process of incorporation of large particles inside the cell. Depending on the substances that the cell incorporates, two separate mechanisms of endocytosis: phagocytosis and pinocytosis.

Endocytosis occurs as follows:

  1. The material to be incorporated into the cell binds to the membrane.
  2. There is a vesicle that encloses the substance.
  3. The gallbladder was detached and remains in the cytoplasm.

1.5 The Metabolism

The set of chemical reactions catalyzed by enzymes, which occur inside cells. Its end is the exchange of matter and energy with the surroundings, which are processed inside the cell, with the aim of creating and maintaining cell structures and providing energy. The chemical reactions of metabolism have common characteristics:

  • They are catalyzed by specific enzymes.
  • They are chained in metabolic pathways.
  • Are oxidation-reduction (redox)

The Types of Metabolic Processes

  • The catabolism or destructive phase: reactions are exergonic (releases energy) that complex molecules are degraded to other simpler molecules.
  • The anabolism or constructive phase: They are made of complex organic molecules from simpler molecules.

The Intermediaries of Metabolism

Energy transport, electrons, and reducing power from which generate up where needed, are:

  • ATP
  • Coenzymes electron transport.

Cellular Respiration

It is the complete oxidation of one molecule of glucose, which becomes, in the presence of O2, several inorganic molecules. The process releases energy to synthesize 38 molecules of ATP.

The Stages of Cellular Respiration

  1. Glycolysis
  2. Formation of acetyl coenzyme A
  3. Krebs cycle or citric acid
  4. Respiratory chain and oxidative phosphorylation.

1.7 The Anabolism

The set of processes that lead to the synthesis of complex molecules and require the incorporation of energy. The result of these processes is the formation of proteins, nucleic acids, polysaccharides, lipids, and other complex molecules. Most anabolic pathways are common in autotrophic and heterotrophic cells, autotrophic cells have specific anabolic pathways through which they can make their simple organic molecules.

Depending on the source of energy used, we distinguish two types of autotrophic cells:

  • Photoautotrophic cells (photosynthetic): use energy from light to build its organic molecules.
  • Cells chemoautotrophic (chemosynthetic): use the energy released in exergonic chemical reactions.

Photosynthesis

It’s the anabolic process in which photoautotrophic cells synthesize organic matter using energy from light. This process occurs because these cells contain chlorophyll and other pigments that are capable of being excited by light. Photosynthesis consists of two phases:

  • Phase bright
  • Light

Chemosynthesis

With it, chemoautotrophic cells synthesize organic matter from inorganic matter, using as a source of energy that emerges from exergonic chemical reactions. It is divided into two phases:

  • Phase of obtaining energy and reducing power.
  • Phase synthesis of organic matter.

2. The Functions for Relationship

All those processes that enable organizations to recognize the changes that occur in the middle. The physical or chemical changes that occur in the external or internal to the cell and can be captured by them, are known stimuli.

2.1 Relationship in the Cells

The cells of any organism carry out the functions of relationship, always do it in two phases: one of reception of the stimuli and another of execution of the responses.

The Reception of Stimuli

To detect changes that may occur, these receptor proteins are included in the plasma membrane. These molecules are able to react to stimuli in specific ways.

The Implementation of the Responses

The cell responses to stimuli can be static and dynamic.

  • Static: It does not involve cell movement.
  • Dynamics: involve movements and, together, are called tactismos.

2.2 Types of Cell Movements

The movements are varied, and all are involved in the cytoskeleton. There are three types of motion:

  • Resonant-Stroke: This occurs by the action of threadlike structures that can be cilia when they are short and numerous and, flagella, if they are long and there are one or two.
  • Amoeboid-movement: The cell moves by the emission of pseudopods or false feet that are extensions of the cytoplasm.
  • Contractile-Movement: A shortening of the cell that produces sliding of actin and myosin filaments to the cell has in its cytoplasm.

3. International Playback Features

Reproduction is the means by which living things produce individuals with the same characteristics and, thus perpetuating the species.

3.1 Reproduction in Cells

The set of processes that suffers from a cell that forms from other preexisting until clones are called cell cycle, cell cycle generally have two periods: the interface in which the cell grows and prepares to divide, and cell division in which the cell carries out reproduction and generates two daughter cells.

The Interface

This period extends from the cell to form until he goes to start their division. Occurs during interphase DNA replication. In turn has three phases:

  • G1-phase
  • S-Phase
  • G2-phase

Cell Division

Eukaryotic cells reproduce by a process called cell division that includes mitosis and cytokinesis.

  • Mitosis or karyokinesis: consists of splitting the nucleus.
  • Cytokinesis: the separation of the cytoplasm resulting in two daughter cells.

The Phases of Mitosis

  • Prophase
  • Metaphase
  • Anaphase
  • Telophase

3.2 Reproduction in Organisms

There are two types of reproduction: sexual and asexual reproduction.

  • Asexual reproduction: a single individual produces offspring identical to itself.
  • Sexual reproduction: two individuals bring their characteristics to offspring.

In many living things, these two alternate forms of reproduction and reproduction is called alternating.

Asexual Reproduction

One or more cells from a single individual parental generated by mitosis and subsequent specialization of the daughter cells, identical offspring. The reproductive process can be done in two ways: from a single parental cell, as is the case of sporulation: or from multiple cells and poorly differentiated parent body that retain embryonic characteristics.

Types of Asexual Reproduction

  • Sporulation
  • Cleavage or fragmentation
  • Budding

Sexual Reproduction

It is produced by the union of two specialized cells, sperm cells. Sexual reproduction takes place in three phases:

  • Training of gametes: is formed in a process called gametogenesis. The formation of male gametes, spermatogenesis, sperm produced in the case of animals, and sperm in plants and algae. The female gemetogenesis called oogenesis, generates the female gametes, eggs in animals and oosphere in plants and algae.
  • Fusion of gametes: to occur, it is necessary that the gametes come into contact. The process is called fertilization, fertilization occurs after karyogamy, which is the function of the nuclei to form an egg cell, called a zygote.
  • Development of the zygote: The zygote begins to divide and is now called an embryo.

Meiosis

The reproductive cells, gametes, and spores are formed through a mechanism called meiosis cell reproduction. In meiosis, the daughter cells have half the chromosomes as the cell from which they came. Meiosis biological significance is twofold:

  • Halved the number of chromosomes in the daughter cell.
  • Increases genetic variability. Through a process called crossing over or crossing over.

Life Cycles

In sexually reproducing organisms, at some point in their life cycle meiosis must occur before the formation of gametes. One can distinguish different types of biological cycles:

  • Haplonte cycle: the cycle of organizations whose bodies are composed of haploid cells and in some fungi.
  • Cycle diplonte: is the one animal whose body is made up of diploid cells.
  • Cycle diplohaplonte:‘s own plants in alternating diploid generation.