Understanding Biomolecules, Cell Structures, and Cellular Processes

Posted on Aug 25, 2024 in Biology

Biomolecules: The Building Blocks of Life

Biomolecules are essential for all living organisms, playing crucial roles in various biological processes. They are primarily composed of carbon, hydrogen, oxygen, nitrogen, sulfur, and phosphorus.

Organic Biomolecules

Organic biomolecules are unique to living organisms. There are four main types:

  1. Carbohydrates: These are the most abundant organic compounds, also known as saccharides. Carbohydrates consist of molecules called monosaccharides, which are colorless, crystalline substances with a sweet taste and dissolve in water. Examples include glucose and fructose. Most carbohydrates are responsible for storing and transporting energy.
  2. Lipids: This diverse group of organic compounds occurs naturally and is insoluble in water. Lipids serve many functions, including energy storage (fats and oils), cell membrane structure (phospholipids), hormone production (steroids like sexual hormones and vitamin D), and protection (waxes produced by animals and plants).
  3. Proteins: These macromolecules have complex structures made up of chains of smaller molecules called amino acids. Proteins have several vital functions:
    • Providing structure to cells (e.g., collagen in the skin)
    • Transporting substances throughout the body (e.g., hemoglobin)
    • Regulating chemical reactions (e.g., enzymes)
    • Protecting the body from bacteria and microorganisms (e.g., antibodies)
  4. Nucleic Acids: These macromolecules are formed by the union of smaller molecules known as nucleotides. Nucleic acids are found in the genetic material of cells. There are two types:
    • Deoxyribonucleic acid (DNA) stores all the information necessary for the functioning and development of living things. DNA is found in the cell nucleus and makes up the genetic code of the chromosomes.
    • Ribonucleic acid (RNA) participates in the synthesis of proteins. RNA is found in the cytoplasm.

Inorganic Biomolecules

Inorganic biomolecules, while not exclusive to living beings, are crucial for life.

  • Water: The most abundant substance in living beings, making up about 65% of the human body. It is present in tissues, blood, and teeth, and is essential for chemical reactions, substance transport, and temperature regulation.
  • Mineral Salts: These form the solid structure of living beings, such as skeletons. Mineral salts are also involved in chemical reactions and are necessary for transmitting nervous impulses.

Cells: The Fundamental Units of Life

Cells are the structural and functional units of all living beings. They have three basic structures:

  • Cell Membrane: The thin layer that separates the inside of the cell from its surrounding environment.
  • Cytoplasm: The gelatinous, semi-transparent fluid that fills most cells. It contains structures called organelles, which are responsible for cell functions.
  • Nucleus: Carries the genetic information of living things, passed from one generation to the next. Genetic material can refer to anything from a small fragment of DNA to the entire genome. A genome is the chemical units of hereditary information carried by a cell.

Types of Cells

  • Eukaryotic Cells: The genetic material is enclosed in a structure called the nucleus. Examples include animals and plants.
  • Prokaryotic Cells: The genetic material is loose in the cytoplasm. Examples include bacteria.

Animal Cell

  • Cell Membrane: Encloses the cell and regulates the substances exchanged between the inside and outside of the cell.
  • Nucleus: Contains the genetic material of the cell.
  • Rough ER: Where proteins formed in the ribosomes are stored and processed.
  • Cytoplasm: The inside of the cell, which contains the nucleus and the organelles.
  • Vacuoles: Sacs that contain storage or waste substances. They are much larger in plant cells.
  • Vesicles: Transport substances.
  • Mitochondrion: Responsible for cell respiration.
  • Golgi Body: Where substances produced in the ER are processed.

Plant Cell

Plant cells share many structures with animal cells, including the cell membrane, nucleus, rough ER, cytoplasm, vacuoles, vesicles, mitochondrion, and Golgi body. In addition, plant cells have:

  • Cell Wall: A thick, rigid layer that provides support and protection.
  • Chloroplast: Where photosynthesis takes place.

Cellular Nutrition and Metabolism

Cellular nutrition encompasses all the processes by which cells obtain matter and energy to perform vital functions. Cells take in substances from the outside, obtaining nutrients from food. Once inside the cell, nutrients undergo chemical processes called cellular metabolism.

Types of Metabolic Reactions

  • Catabolism: The degradation of complex organic substances into simple substances, producing energy.
  • Anabolism: The production of more complex organic substances from simple substances, requiring energy from catabolism or photosynthesis.

Types of Nutrition

  • Autotrophic Nutrition: Characteristic of cells that use an energy source to make their own organic matter from inorganic matter. There are two processes:
    • Photosynthesis: Energy comes from the Sun. This takes place in plant and algae cells and cyanobacteria.
    • Chemosynthesis: Energy comes from chemical reactions. This takes place in some bacteria.
  • Heterotrophic Nutrition: Characteristic of cells that feed on organic matter produced by other living beings. They transform this organic matter to obtain nutrients and energy. It takes place in the cells of animals, fungi, protozoa, and many bacteria.

Cellular Respiration and Fermentation

Respiration is the release of energy from organic substances into living cells. All cells need energy to carry out vital functions.

  • Cellular Respiration: Describes the metabolic reactions and processes that take place in a cell to obtain chemical energy from specific organic molecules. The cell takes in organic substances and oxygen, breaking them down into simpler substances and releasing energy. The basic equation for respiration is: Glucose + O2 –> H2O + CO2 + chemical energy.
  • Fermentation: The process by which cells release energy in the absence of oxygen. It takes place in all living things, but especially in some bacteria and yeasts.

Cellular Division

Cellular division is a process by which a cell, known as the parent cell, divides into two or more cells, called daughter cells.

  • Unicellular Organisms: Cellular division replicates an entire organism, forming new individuals and increasing the population. There are two types:
    • Binary Fission: The nucleus of the parent cell divides into two identical nuclei, and then the parent cell divides into two identical daughter cells of the same size, which grow into adult cells.
    • Multiple Fission: The nucleus of the parent cell divides into several nuclei. After the nuclear divisions, the cytoplasm separates, and each nucleus becomes encased in its own membrane to form an individual cell.
  • Multicellular Organisms: Cellular division increases the number of cells in an organism, contributing to growth or the repair of damaged parts.