CELLS🧬🔬

• Ribosomes are small granules of protein and RNA, produced in the nucleus and then exported into the cytoplasm
• Ribosomes function by reading coded genetic messages from the nucleus and assembling amino acids into proteins specified by the code, which can become lysosomes and make enzymes
• The Golgi Complex is a small cluster of cisternae that synthesize carbohydrates and add finishing touches on glycoprotein synthesis
• Edges of the Golgi pinch off membranous sacs called Golgi vesicles, filled with synthesized proteins; some become secretory vesicles or lysosomes, which are packages of enzymes enclosed in a membrane
• Lysosomes function by breaking down proteins, nucleic acid, carbohydrates, phospholipids, and more
• Peroxisomes contain different enzymes than ribosomes and function to break down fatty acids, aid in ATP synthesis, and kill bacteria
• Organelles are little organs that play individual roles in the survival of the body
• The nucleus is the largest organelle in most cells, containing chromosomes
• The Endoplasmic Reticulum is a network within the cytoplasm, consisting of interconnected channels called cisternae; Rough ER has ribosomes while Smooth ER does not
• The cytoskeleton is a system of protein microfilaments, intermediate filaments, and microtubules serving in physical support, cellular movement, and the routing of molecules and organelles within the cell
• Microfilaments are thin protein filaments made of actin, forming a tight mesh called the terminal web
• Intermediate filaments are thicker and stiffer than microfilaments, contributing to the strength of desmosomes and including the tough protein keratin found in the cells of the epidermis
• Microtubules are intracellular cylinders of protein, forming centrioles, the axonemes of cilia and flagella, and are part of the cytoskeleton
• Cell membranes are selectively permeable, allowing chemicals to pass through via processes like filtration, simple diffusion, vesicular transport, phagocytosis, pinocytosis, receptor-mediated endocytosis, and exocytosis
• Cell junctions like tight junctions, desmosomes, and gap junctions connect cells in complex multicellular organisms, allowing cells to grow, divide normally, and communicate
• The glycocalyx consists of short chains of sugars belonging to glycolipids and glycoproteins, aiding in cell adhesion and distinguishing healthy cells from diseased cells
• Cell surface extensions like microvilli, cilia, and pseudopods play roles in absorption, sensory functions, and cell movement
• The plasma membrane defines the boundary of the cell, controlling interactions with other cells and regulating what comes in and out
• The plasma membrane is an oily, two-layered lipid film with embedded proteins; membrane proteins vary and can be integral (penetrating through the membrane) or peripheral (on the surface of the membrane)
• All cells are covered with a fuzzy carbohydrate coat called the glycocalyx, which aids in cell adhesion and helps distinguish healthy cells from diseased cells
• The general structure of cells includes major components like the plasma membrane, cytoplasm, cytoskeleton, organelles, inclusions, and cytosol
• Cell sizes are measured in micrometers (μm), with most cells being 10-15 μm in size
• The cell cycle:

  • All cells come from other cells
  • Most cells have a finite life-span
  • Divided into 4 phases: G₁, S, G₂, M
  • G₁: Normal metabolic activities
  • S: DNA replication
  • G₂: Growth & preparation for Mitosis
• Mitosis process:

  • Prophase: chromosomes coil into short dense rods (chromatids)
  • Metaphase: chromosomes align on the cell equator
  • Anaphase: splits each centromere in two
  • Telophase: chromatids cluster on each side of the cell, new nuclear envelope forms around each cluster
• Protein Synthesis:

  • Transcription: enzyme unzips DNA, creates mRNA, edited to remove non-coding segments
  • Translation: ribosomes translate mRNA codons into amino acids, protein processing & secretion involve organelles
• Organelles:

  • Mitochondria: specialized in ATP synthesis, surrounded by a double membrane with cristae folds, contains enzymes, ribosomes & MtDNA
  • Centrioles: short assembly of microtubules near the nucleus, help with cell division