Histo lec

• Histology is the study of the tissues of the body and how they are arranged to constitute organs
• Cells are the basic structural and functional units of all multicellular organisms
• Prokaryotic cells have a cell wall, lack nuclei, and membranous cytoplasmic structures
• Eukaryotic cells have cell membranes, nucleus, and cytoplasm
• Cell differentiation is a specialization process where cells express sets of genes that mediate specific activities and become efficiently organized in tissues with specialized functions
• Cellular components include the cell membrane, cytoplasm, and nucleus
• The plasma membrane is a lipid bilayer that functions as a selective barrier regulating the passage of materials into and out of the cell
• Biochemical components of the plasma membrane include lipids, proteins, and carbohydrates
• Integral Proteins are incorporated directly within the lipid bilayer, while Peripheral Proteins are bound to one of the two membrane surfaces, particularly on the cytoplasmic side
• Passive processes involve the movement of substances down a concentration gradient without the expenditure of cellular energy
• Active processes involve the movement of substances that require the expenditure of cellular energy
• Passive processes include simple diffusion and facilitated diffusion
• Osmosis is the diffusion of water across a selectively permeable membrane
• Facilitated diffusion can be channel-mediated or carrier-mediated
• Active transport involves the transport of ions or small molecules across the membrane against a concentration gradient by transmembrane protein pumps
• Vesicular transport includes endocytosis and exocytosis
• Endocytosis involves the movement of substances by vesicles forming at the plasma membrane
• Major types of endocytosis are Phagocytosis, Pinocytosis, and Receptor-mediated endocytosis
• Phagocytosis is the ingestion of particles such as bacteria or dead cell remnants
• Pinocytosis involves smaller invaginations of the cell membrane that entrap extracellular fluid and its dissolved contents
• Receptor-mediated endocytosis occurs when plasma membrane receptors first bind specific substances and are taken up by the cell
• Exocytosis is the bulk movement of substances out of the cell by fusion of secretory vesicles with the plasma membrane
• Ribosomes are found free or attached to rough ER
• Nucleolus - site of ribosome synthesis
• The nucleus is the largest organelle, containing DNA
• Free ribosomes synthesize proteins destined for use within the cytoplasm
• Bound ribosomes synthesize proteins destined for export from the cell (secreted) or incorporated into organelles
• Golgi apparatus - modifies, sorts, packages, and transports proteins and lipids within the cell
• The Golgi apparatus modifies, sorts, packages, and transports newly made proteins and lipids
• Lysosomes contain hydrolytic enzymes used in digesting food materials and worn-out organelles
• Lysosomes contain hydrolytic enzymes used for digestion
• Peroxisomes contain oxidative enzymes involved in detoxification reactions
• Mitochondria produce ATP through oxidative phosphorylation
• Golgi apparatus modifies proteins and lipids produced by RER
• Bound ribosomes (rough ER) synthesize proteins that will be transported into the lumen of the ER
• Golgi apparatus modifies and packages newly made proteins
• Glycolysis occurs in the cytosol
• Mitochondria are the powerhouse of the cell