Cell Structure, DNA, and Cell Division: An Explanation
Cell Structure, DNA, and Cell Division
Interface: The stage of cellular development without division, where genetic material exists as chromatin. During division, the cell prepares by doubling its DNA and condensing its components into chromosomes.
DNA
DNA is formed by the union of nucleotides, which are composed of deoxyribose, an organic nitrogenous base, and a phosphate group.
DNA Structure
DNA consists of two polynucleotide chains linked together, complementary to each other through their bases.
DNA Properties
- Duplication: The double helix of DNA opens, and each strand serves as a template for creating a complementary strand, resulting in two identical DNA molecules.
- Information Storage: The four nucleotides act as instructions to control the characteristics of descendant cells.
The cell cycle period between cell birth and division is called the interface, where the cell thrives, develops, and carries out vital activities with its DNA in the form of chromatin.
Mitosis Stages
- Prophase: DNA or chromosomes condense, centriole pairs duplicate and move to opposite poles of the cell, and the nuclear membrane disappears.
- Metaphase: Chromosomes align along the central spindle apparatus.
- Anaphase: Chromosomes double, and the centromere of each separates, causing the two chromatids to be pulled towards opposite poles of the cell (chromosomes move).
- Telophase: Chromatids arrive at the poles and decondense into chromatin. The mitotic spindle disappears, and the nuclear membrane reforms.
Cell Theory
- The cell is the basic structural unit of all living beings. Organisms are composed of one or more cells.
- The cell is the basic physiological unit of all living beings, carrying out functions necessary for life and development.
- Cells arise from pre-existing cells through cell division.
- The cell is the basic genetic unit of all living beings, containing instructions that regulate its functioning and are passed down to its descendants.
Microorganisms
Microorganisms are living beings of small size, visible only with a microscope. Examples include prokaryotic bacteria and eukaryotic organisms like algae, molds, and yeasts, as well as viruses.
Cell Components
Cells are composed of the following:
- Plasma Membrane: A thin envelope that defines the cell and controls the exchange of substances with the external environment.
- Cytoplasm: The internal region of the cell, occupied by the cytosol and various organelles.
- Genetic Material: Molecules containing the information necessary to direct cellular activity.
Differences Between Plant and Animal Cells
- Plant cells are often polyhedral, while animal cells are more rounded.
- Plant cells have cell walls, while animal cells do not.
- Plant cells contain vacuoles and chloroplasts, while animal cells do not.
- Animal cells have centrioles, while plant cells typically do not.
Nucleus
The nucleus directs and controls cellular activity through the genetic information contained within its DNA.
Nuclear Components
- Nuclear Membrane: Two membranes that separate the nuclear contents from the rest of the cell.
- Nucleoplasm: The fluid within the nucleus, containing molecules involved in nuclear activity.
- Nucleolus: The region where genetic material responsible for ribosome production is concentrated.
- Chromatin: The substance within the nucleoplasm, composed of DNA and histones.
Interface: The stage of cellular development without division, where genetic material exists as chromatin. During division, the cell prepares by doubling its DNA and condensing its components into chromosomes.
DNA
DNA is formed by the union of nucleotides, which are composed of deoxyribose, an organic nitrogenous base, and a phosphate group.
DNA Structure
DNA consists of two polynucleotide chains linked together, complementary to each other through their bases.
DNA Properties
- Duplication: The double helix of DNA opens, and each strand serves as a template for creating a complementary strand, resulting in two identical DNA molecules.
- Information Storage: The four nucleotides act as instructions to control the characteristics of descendant cells.
The cell cycle period between cell birth and division is called the interface, where the cell thrives, develops, and carries out vital activities with its DNA in the form of chromatin.