Cytokinesis I is the final step of Meiosis I, where the cytoplasm divides, forming two haploid daughter cells. In animal cells, a cleavage furrow develops, which deepens and splits the cell into two. In plant cells, a cell plate forms at the center and extends outward to separate the two new cells. This process ensures that each daughter...
Definition: Minute, membrane-bound vesicles found in both plant and animal cells. Contain various enzymes necessary for cellular processes. Characteristics: Enclosed by a single membrane. Small in size, making them microscopic and distinct. Functions: Facilitate specialized metabolic reactions due to their enzyme content. Play roles in processes like: Detoxification of...
Discovery: First described by Robert Brown in 1831. The material in the nucleus stained by basic dyes was named chromatin by Flemming. Structure of Nucleus Interphase Nucleus: Components: Chromatin: Highly extended nucleoprotein fibers. Nuclear Matrix: Gel-like substance within the nucleus. Nucleoli: Spherical bodies involved in RNA synthesis. Nuclear Envelope:...
Centrosome: An organelle usually containing two cylindrical structures called centrioles. Surrounded by amorphous pericentriolar material. Plays a key role in cell division by forming the spindle apparatus in animal cells. Centrioles: Two centrioles in a centrosome are positioned perpendicular to each other. Structural organization resembles a cartwheel. Composed of:...
Definition & Structure: Hair-like outgrowths of the cell membrane. Two types: Cilia: Small structures. Function like oars to move the cell or the surrounding fluid. Flagella: Longer structures. Primarily responsible for cell movement. Prokaryotic Flagella: Present in bacteria but structurally different from eukaryotic flagella. Ultrastructure: Both cilia and flagella...
Definition: A complex network of filamentous, proteinaceous structures present in the cytoplasm. Composed of microtubules, microfilaments, and intermediate filaments. Components: Microtubules: Hollow, tube-like structures made of tubulin proteins. Microfilaments: Thin, thread-like filaments primarily composed of actin proteins. Intermediate Filaments: Intermediate-sized filaments providing tensile strength and structural support. Functions: Mechanical...
Discovery: Observed as dense particles under an electron microscope by George Palade in 1953. Granular structures composed of ribonucleic acid (RNA) and proteins. Not surrounded by any membrane. Classification: Eukaryotic Ribosomes: Size: 80S. Composed of two subunits: Larger subunit: 60S. Smaller subunit: 40S. Prokaryotic Ribosomes: Size: 70S. Composed of...
Definition & Occurrence: Plastids are present in all plant cells and euglenoids. Easily observable under a microscope due to their large size. Contain specific pigments that impart distinct colors to plants. Types of Plastids (Based on Pigments): Chloroplasts: Contain chlorophyll and carotenoid pigments. Responsible for trapping light energy essential...
Mitochondria: Definition Often called the “powerhouses” of the cell. Not easily visible under a microscope unless specifically stained. Number Varies depending on the cell’s physiological activity (more active cells have more mitochondria). Size and Shape Variable, but typically sausage-shaped or cylindrical. Diameter: 0.2 – 1.0 µm (average 0.5 µm)...
Vacuoles: Definition Membrane-bound sacs within the cytoplasm of a cell. Membrane Surrounded by a single membrane called the tonoplast. Contents Water Sap Excretory products (waste) Other materials not useful to the cell Role in Plant Cells Can occupy up to 90% of a plant cell’s volume. Tonoplast actively transports...