Cell Biology PDF

◆ Nucleus: The nucleus is a membrane-bound organelle found in most human cells that contains the cell's genetic material (DNA) and controls its growth, metabolism, and reproduction. It is often referred to as the control center of the cell, as it regulates gene expression and mediates the re...

◆ Nucleus: The nucleus is a membrane-bound organelle found in most human cells that contains the cell's genetic material (DNA) and controls its growth, metabolism, and reproduction. It is often referred to as the control center of the cell, as it regulates gene expression and mediates the replication of DNA during the cell cycle. Mature red blood cells do NOT have a nucleus. ◆ Endoplasmic reticulum: The endoplasmic reticulum (ER) is a network of membranous tubules and sacs involved in protein and lipid synthesis. It comes in two forms: rough ER, studded with ribosomes for protein synthesis, and smooth ER, which is involved in lipid synthesis and detoxification processes. ◆ Mitochondria: Mitochondria are membrane-bound organelles known as the powerhouses of the cell, as they generate ATP through cellular respiration. They also play crucial roles in energy production, regulation of the cell cycle, and apoptosis (programmed cell death). ◆ Cell membrane: The cell membrane, or plasma membrane, surrounds the cell's cytoplasm and organelles, serving as a protective barrier. It regulates the passage of substances into and out of the cell through selective permeability, crucial for maintaining cellular homeostasis and communication with the external environment. ◆ Golgi body: The Golgi apparatus, or Golgi body, is a stack of membrane-bound sacs responsible for processing, modifying, and packaging proteins and lipids synthesized in the cell. It sorts and directs these molecules to their appropriate destinations within the cell or for secretion outside the cell. ◆ Ribosomes: Ribosomes are cellular structures composed of RNA and proteins that facilitate the synthesis of proteins by translating messenger RNA (mRNA) sequences into amino acid chains. They are found either floating freely in the cytoplasm or attached to the endoplasmic reticulum, forming rough ER.