Chapter 1: Cell and Cytoplasm
Resolution of the Human Eye
Distance Resolution: The human eye has a limit to its resolving power, capable of distinguishing two distinct points or pores separated by a minimum distance of () under adequate light conditions. Below this distance, two separate points appear as a single merged object.
Cell Structure and Cytoplasm
Cytoplasm Structure: A semi-fluid, jelly-like cytosol that fills the interior of the cell between the plasma membrane and the nucleus.
Cytoplasm Functions:
Holds and maintains all cellular organelles in their designated positions via the cytoskeleton.
Serves as the primary medium for vital metabolic and chemical reactions within the cell, including enzymatic reactions and glycolysis.
Facilitates internal transport and movement of materials through cytoplasmic streaming.
Cellular Organelles and Structures
Plasma Membrane: A selectively permeable phospholipid bilayer that bounds the cell, regulating the transport of substances into and out of the cellular environment.
Cell Wall: A rigid outer structural layer present outside the plasma membrane in plant cells, fungi, and bacteria, composed primarily of cellulose in plants to provide mechanical protection and shape.
Nucleus: The primary control center of eukaryotic cells enclosed by a double nuclear membrane, housing the cell's genetic material (DNA) and directing activities such as cellular growth, metabolism, and division.
Nucleolus: A specialized dense region located within the nucleus responsible for synthesizing ribosomal RNA (rRNA) and assembling ribosome subunits.
Endoplasmic Reticulum (ER):
Composed of an extensive network of interconnected tubules and sacs (cisternae) extending throughout the cell cytoplasm.
Serves as a intracellular transport pathway for conducting molecules across the cell interior.
Exists as Rough ER (studded with ribosomes for protein synthesis) and Smooth ER (involved in lipid synthesis, carbohydrate metabolism, and toxin removal).
Golgi Body (Golgi Apparatus): A series of flattened membranous sacs involved in modifying, sorting, packaging, and transporting synthesized proteins and lipids for secretion or intracellular delivery.
Mitochondria: Double-membrane organelles known as the powerhouses of the cell, responsible for cellular respiration and energy generation in the form of ATP ().
Chloroplast: Specialized organelles found in plant cells and algae containing chlorophyll, responsible for absorbing light energy to synthesize organic nutrients through photosynthesis.
Cellular Storage and Functions
Storage of Materials: Cells synthesize, store, and process essential biochemical nutrients and energy reserves in various chemical forms, including:
Proteins (structural and functional amino acid polymers)
Starch (complex storage carbohydrates in plant cells)
Oils and Lipids (energy-dense storage molecules and cell membrane components)
Excretory and Stored Substances: Includes the accumulation, processing, and handling of metabolic waste substances, urine components in specialized organ systems, and stored energy compounds inside cellular vacuoles or storage granules.
Muscle Cells
Contraction and Relaxation: Muscle tissues are composed of specialized elongated cells (myocytes) containing contractile protein filaments (actin and myosin) that undergo controlled contraction and relaxation to produce mechanical movement and physical force.
Stem Cells
Master Cells: Stem cells are designated as the body's master precursor cells because of their distinct self-renewal capacity, dividing indefinitely to create new stem cells.
Differentiation Capability: Stem cells possess cellular potency, allowing them to differentiate and specialize into diverse somatic cell types across the organism, such as:
Muscle cells (myocytes)
Blood cells (erythrocytes, leukocytes, and platelets)
Other specialized somatic cell lineages (neurons, osteocytes, skin cells)