Anatomy of Cells.pdf

Anatomy of Cells Allen, C. & Harper, V., (2020). Laboratory manual for anatomy & physiology (LL) (7th ed.). John Wiley & Sons, Canada. ISBN: 9781119662556. Tortora, G. & Derrickson, B. (2020). Principles of anatomy and physiology (1...

Anatomy of Cells Allen, C. & Harper, V., (2020). Laboratory manual for anatomy & physiology (LL) (7th ed.). John Wiley & Sons, Canada. ISBN: 9781119662556. Tortora, G. & Derrickson, B. (2020). Principles of anatomy and physiology (16th ed.). John Wiley & Sons, Canada. ISBN: 9781119662686. Tortora, G. & Derrickson, B. (2020). Principles of anatomy and physiology (LL) (16th ed. Incorporated). John Wiley & Sons, Canada. ISBN: 9781119662792. Learning Outcomes: 1.5, 2.3 , 2.5,4.1 SN100 Confederation College The Cell: 2 Cell structures Ø Plasma membrane—separates the cell from its surrounding environment Ø Cytoplasm—thick gel-like substance inside the cell composed of numerous organelles suspended in watery cytosol; each type of organelle is suited to perform particular functions Ø Nucleus—large membranous structure near the center of the cell 3 4 Cell Membranes Each cell contains a variety of membranes Ø Plasma membrane —outer boundary of cell Ø Membranous organelles—sacs and canals made of the same material as the plasma membrane 5 6 Cell Membranes Fluid mosaic model—theory explaining how cell membranes are constructed Ø Molecules of the cell membrane are arranged in a sheet Ø The mosaic of molecules is fluid; that is, the molecules are able to float around slowly Ø This model illustrates that the molecules of the cell membrane form a continuous sheet 7 Cell Membranes l Chemical attractions are the forces that hold membranes together l Groupings of membrane molecules form rafts that float as a unit in the membrane ( Ø Rafts may pinch inward to bring material into the cell or organelle Ø Primary structure of a cell membrane is a double layer of phospholipid molecules Ø Heads are hydrophilic (water loving) 8 9 Cell Membranes l Groupings of membrane molecules form rafts that float as a unit in the membrane (cont) Ø Tails are hydrophobic (water fearing) Ø They arrange themselves in bilayers in water Ø Cholesterol molecules are scattered among the phospholipids to allow the membrane to function properly at body temperature Ø Most of the bilayer is hydrophobic; therefore water or water-soluble molecules do not pass through easily 10 Cell Membranes l Integral membrane proteins (IMPs) Ø A cell controls what moves through the membrane by means of IMPs embedded in the phospholipid bilayer Ø Some IMPs have carbohydrates attached to them and as a result form glycoproteins that act as identification markers Ø Some IMPs are receptors that react to specific chemicals, sometimes permitting a process called signal transduction 11 Cytoplasm and Organelles l Cytoplasm—gel-like internal substance of cells that includes many organelles suspended in watery intracellular fluid called cytosol l Two major groups of organelles Ø Membranous organelles are sacs or canals made of cell membranes Ø Nonmembranous organelles are made of microscopic filaments or other nonmembranous materials 12 Cytoplasm and Organelles l Endoplasmic reticulum Ø Made of membranous-walled canals and flat, curving sacs arranged in parallel rows throughout the cytoplasm; extend from the plasma membrane to the nucleus Ø Proteins move through the canals 13 14 Cytoplasm and Organelles l Endoplasmic reticulum (cont) Ø Two types of endoplasmic reticulum l Rough endoplasmic reticulum Ø Ribosomes dot the outer surface of the membranous walls Ø Ribosomes synthesize proteins, which move toward the Golgi apparatus and then eventually leave the cell Ø Function in protein synthesis and intracellular transportation 15 Cytoplasm and Organelles Ø Two types of endoplasmic reticulum (cont) l Smooth endoplasmic reticulum Ø No ribosomes border the membranous wall Ø Functions are less well established and probably more varied than for the rough endoplasmic reticulum Ø Synthesizes certain lipids and carbohydrates and creates membranes for use throughout the cell Ø Removes and stores Ca+ from the cell’s interior 16 Cytoplasm and Organelles l Ribosomes Ø Many are attached to the rough endoplasmic reticulum and many lie free, scattered throughout the cytoplasm Ø Each ribosome is a nonmembranous structure made of two pieces, a large subunit and a small subunit; each subunit is composed of rRNA and protein Ø Ribosomes in the endoplasmic reticulum make proteins for “export” or to be embedded in the plasma membrane; free ribosomes make proteins for the cell’s domestic use 17 18 Cytoplasm and Organelles l Golgi apparatus Ø Membranous organelle consisting of cisternae stacked on one another and located near the nucleus Ø Processes protein molecules from the endoplasmic reticulum Ø Processed proteins leave the final cisterna in a vesicle; contents may then be secreted to outside the cell 19 20 21 Cytoplasm and Organelles l Lysosomes Ø Made of microscopic membranous sacs that have “pinched off” from Golgi apparatus Ø The cell’s own digestive system; enzymes in lysosomes digest the protein structures of defective cell parts, including integral membrane proteins and particles that have become trapped in the cell 22 Cytoplasm and Organelles l Proteasomes Ø Hollow, protein cylinders found throughout the cytoplasm Ø Break down abnormal/misfolded proteins and normal proteins no longer needed by the cell (and which may cause disease) 23 24 Cytoplasm and Organelles l Peroxisomes Ø Small membranous sacs containing enzymes that detoxify harmful substances that enter the cells Ø Often seen in kidney and liver cells 25  Cytoplasm and Organelles l Mitochondria Ø Made up of microscopic sacs; wall composed of inner and outer membranes separated by fluid; thousands of particles make up enzyme molecules attached to both membranes Ø The “power plants” of cells; mitochondrial enzymes catalyze series of oxidation reactions that provide almost all of a cell’s energy supply Ø Each mitochondrion has a DNA molecule, which allows it to produce its own enzymes and replicate copies of itself 26 27 Nucleus l Definition—spherical body in center of a cell; enclosed by an envelope with many pores l Structure Ø Consists of a nuclear envelope (composed of two membranes, each with essentially the same molecular structure as the plasma membrane) surrounding nucleoplasm l Nuclear envelope has holes called nuclear pores l Nuclear pore complexes (NPCs) are elaborate gateways into and out of the nucleus 28 29 30 Nucleus l Structure (cont) Ø Contains DNA (heredity molecules), which appear as: l Chromatin threads or granules in nondividing cells l Chromosomes in early stages of cell division l Functions of the nucleus are functions of DNA molecules; DNA determines both the structure and function of cells and heredity 31 Cytoskeleton l The cell's internal supporting framework Ø Made up of tiny, flexible fibers and rigid, rodlike pieces Ø Provides support for cell shape Ø Can move the cell or its parts Ø Detects changes inside and outside the cell 32 33 Cytoskeleton l Cell fibers Ø Intricately arranged fibers of varying length that form a three-dimensional, irregularly shaped lattice Ø Fibers appear to support the endoplasmic reticulum, mitochondria, and “free” ribosomes 34 Cytoskeleton l Cell fibers (cont) Ø Microfilaments (Figure 3-15)--smallest cell fibers l Serve as “cellular muscles” l Made of thin, twisted strands of protein molecules that lie parallel to the long axis of the cell l Can slide past each other and cause shortening of the cell 35 36 Cytoskeleton l Cell fibers (cont) Ø Intermediate filaments—twisted protein strands slightly thicker than microfilaments; form much of the supporting framework in many types of cells Ø Microtubules—tiny, hollow tubes that are the thickest of the cell fibers l Made of protein subunits arranged in a spiral fashion l Their function is to move things around inside the cell 37 Cytoskeleton l Centrosome Ø An area of the cytoplasm near the nucleus that coordinates the building and breaking apart of microtubules in the cell Ø Nonmembranous structure also called the microtubule organizing center (MTOC) Ø Plays an important role during cell division Ø The general location of the centrosome is identified by the centrioles 38 39 Cytoskeleton l Cell extensions Ø Cytoskeleton forms projections that extend the plasma membrane outward to form tiny, fingerlike processes Ø There are three types of these processes; each has specific functions l Microvilli—found in epithelial cells that line the intestines and other areas where absorption is important; they help increase the surface area 40 41 Cytoskeleton Ø There are three types of these processes; each has specific functions (cont) l Cilia and flagella—cell processes that have cylinders made of microtubules and molecular motors at their core Ø Cilia are shorter and more numerous than flagella; some cilia found in groups have coordinated oarlike movements that brush material past the cell’s surface; all cilia have sensory functions Ø Flagella are found only on human sperm cells; flagella move with a tail-like movement that propels the sperm cell forward 42 43 Cell Connections l Three types of direct cell connections Ø Desmosome l Fibers on the outer surface of each desmosome interlock with each other; anchored internally by intermediate filaments of the cytoskeleton l Spot desmosomes are like “spot welds” at various points connecting adjacent membranes l Belt desmosomes encircle the entire cell 44 45 Cell Connections l Three types of direct cell connections (cont) Ø Gap junctions—membrane channels of adjacent plasma membranes adhere to each other; have two effects: l Form gaps or “tunnels” that join the cytoplasm of two cells l Fuse two plasma membranes into a single structure 46 Cell Connections l Three types of direct cell connections (cont) Ø Tight junctions l Occur in cells that are joined by “collars” of tightly fused material l Molecules cannot permeate the cracks of tight junctions l Occur in the lining of the intestines and other parts of the body where it is important to control what gets through a sheet of cells 47 SN 200 BScN (2023-2024) Anatomy of Cell: Questions?