mosby items and derived items © 2007, 2003 by mosby, inc. slide 1 chapter 3 anatomy of cells

Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 1

Chapter 3Chapter 3 Anatomy of Cells Anatomy of Cells


Functional Anatomy of CellsFunctional Anatomy of Cells

The typical cell (Figure 3-1)The typical cell (Figure 3-1)

Also called composite cellAlso called composite cell

Varies in size; all are microscopic (Table 3-1)Varies in size; all are microscopic (Table 3-1)

Varies in structure and function (Table 3-2)Varies in structure and function (Table 3-2)


Functional Anatomy of CellsFunctional Anatomy of Cells

Cell structuresCell structures

Plasma membrane—separates the cell from its Plasma membrane—separates the cell from its surrounding environmentsurrounding environment

Cytoplasm—thick gel-like substance inside of the Cytoplasm—thick gel-like substance inside of the cell composed of numerous organelles suspended cell composed of numerous organelles suspended in watery cytosol; each type of organelle is suited in watery cytosol; each type of organelle is suited to perform particular functions (Figure 3-2)to perform particular functions (Figure 3-2)

Nucleus—large membranous structure near the Nucleus—large membranous structure near the center of the cellcenter of the cell


Cell MembranesCell Membranes

Each cell contains a variety of membranes:Each cell contains a variety of membranes:

Plasma membrane (Figure 3-3)Plasma membrane (Figure 3-3)

Membranous organelles—sacs and canals made Membranous organelles—sacs and canals made of the same material as the plasma membraneof the same material as the plasma membrane



Fluid mosaic model—theory explaining how Fluid mosaic model—theory explaining how cell membranes are constructedcell membranes are constructed

Molecules of the cell membrane are arranged in a Molecules of the cell membrane are arranged in a sheetsheet

The mosaic of molecules is fluid; that is, the The mosaic of molecules is fluid; that is, the molecules are able to float around slowlymolecules are able to float around slowly

This model illustrates that the molecules of the cell This model illustrates that the molecules of the cell membrane form a continuous sheetmembrane form a continuous sheet



Chemical attractions are the forces that hold Chemical attractions are the forces that hold membranes togethermembranes together

Groupings of membrane molecules form rafts, Groupings of membrane molecules form rafts, each of which float as a unit in the membrane each of which float as a unit in the membrane (Figure 3-4)(Figure 3-4)

Rafts may pinch inward, bringing material into the Rafts may pinch inward, bringing material into the cell or organellecell or organelle



Primary structure of a cell membrane is a double Primary structure of a cell membrane is a double layer of phospholipid moleculeslayer of phospholipid molecules Heads are hydrophilic (water-loving)Heads are hydrophilic (water-loving)

Tails are hydrophobic (water-fearing)Tails are hydrophobic (water-fearing)

Molecules arrange themselves in bilayers in waterMolecules arrange themselves in bilayers in water

Cholesterol molecules are scattered among the Cholesterol molecules are scattered among the phospholipids to allow the membrane to function phospholipids to allow the membrane to function properly at body temperatureproperly at body temperature

Most of the bilayer is hydrophobic; therefore water or Most of the bilayer is hydrophobic; therefore water or water-soluble molecules do not pass through easilywater-soluble molecules do not pass through easily



Membrane proteins (Table 3-4)Membrane proteins (Table 3-4)

A cell controls what moves through the membrane A cell controls what moves through the membrane by means of membrane proteins embedded in the by means of membrane proteins embedded in the phospholipid bilayerphospholipid bilayer

Some membrane proteins have carbohydrates Some membrane proteins have carbohydrates attached to them, forming glycoproteins that act as attached to them, forming glycoproteins that act as identification markersidentification markers

Some membrane proteins are receptors that react Some membrane proteins are receptors that react to specific chemicals, sometimes permitting a to specific chemicals, sometimes permitting a process called signal transductionprocess called signal transduction


Cytoplasm and OrganellesCytoplasm and Organelles

Cytoplasm—gel-like internal substance of Cytoplasm—gel-like internal substance of cells that includes many organelles cells that includes many organelles suspended in watery intracellular fluid called suspended in watery intracellular fluid called cytosolcytosol



Two major groups of organelles (Table 3-3):Two major groups of organelles (Table 3-3):

Membranous organelles are specialized sacs or Membranous organelles are specialized sacs or canals made of cell membranescanals made of cell membranes

Nonmembranous organelles are made of Nonmembranous organelles are made of microscopic filaments or other nonmembranous microscopic filaments or other nonmembranous materialsmaterials



Endoplasmic reticulum (Figure 3-5)Endoplasmic reticulum (Figure 3-5)

Made of canals with membranous walls and flat, Made of canals with membranous walls and flat, curving sacs arranged in parallel rows throughout curving sacs arranged in parallel rows throughout the cytoplasm; extend from the plasma membrane the cytoplasm; extend from the plasma membrane to the nucleusto the nucleus

Proteins move through the canalsProteins move through the canals



Endoplasmic reticulum (cont.)Endoplasmic reticulum (cont.)

Two types of endoplasmic reticulum:Two types of endoplasmic reticulum:

• Rough endoplasmic reticulumRough endoplasmic reticulum

Ribosomes dot the outer surface of the membranous wallsRibosomes dot the outer surface of the membranous walls

Ribosomes synthesize proteins, which move toward the Ribosomes synthesize proteins, which move toward the Golgi apparatus and then eventually leave the cellGolgi apparatus and then eventually leave the cell

Function in protein synthesis and intracellular Function in protein synthesis and intracellular transportationtransportation



Two types of endoplasmic reticulum (cont.) Two types of endoplasmic reticulum (cont.)

• Smooth endoplasmic reticulumSmooth endoplasmic reticulum

No ribosomes border membranous wallNo ribosomes border membranous wall

Functions are less well established and probably more Functions are less well established and probably more varied than for rough endoplasmic reticulumvaried than for rough endoplasmic reticulum

Synthesizes certain lipids and carbohydrates and creates Synthesizes certain lipids and carbohydrates and creates membranes for use throughout cellmembranes for use throughout cell

Removes and stores CaRemoves and stores Ca++++ from cell’s interior. from cell’s interior.



Ribosomes (Figure 3-6)Ribosomes (Figure 3-6)

Many are attached to the rough endoplasmic Many are attached to the rough endoplasmic reticulum and many lie free, scattered through the reticulum and many lie free, scattered through the cytoplasmcytoplasm

Each ribosome is a nonmembranous structure made Each ribosome is a nonmembranous structure made of two pieces, a large subunit and a small subunit; of two pieces, a large subunit and a small subunit; each subunit is composed of rRNAeach subunit is composed of rRNA

Ribosomes in the endoplasmic reticulum make Ribosomes in the endoplasmic reticulum make proteins for “export” or to be embedded in the proteins for “export” or to be embedded in the plasma membrane; free ribosomes make proteins plasma membrane; free ribosomes make proteins for the cell’s domestic usefor the cell’s domestic use



Golgi apparatusGolgi apparatus

Membranous organelle consisting of cisternae Membranous organelle consisting of cisternae stacked on one another and located near the stacked on one another and located near the nucleus (Figure 3-7)nucleus (Figure 3-7)

Processes protein molecules from the Processes protein molecules from the endoplasmic reticulum (Figure 3-8)endoplasmic reticulum (Figure 3-8)

Processed proteins leave the final cisterna in a Processed proteins leave the final cisterna in a vesicle; contents may then be secreted to outside vesicle; contents may then be secreted to outside the cellthe cell



Lysosomes (Figure 3-9)Lysosomes (Figure 3-9)

Made of microscopic membranous sacs that have Made of microscopic membranous sacs that have “pinched off” from Golgi apparatus“pinched off” from Golgi apparatus

The cell’s own digestive system; enzymes in The cell’s own digestive system; enzymes in lysosomes digest the protein structures of lysosomes digest the protein structures of defective cell parts, including plasma membrane defective cell parts, including plasma membrane proteins, and particles that have become trapped proteins, and particles that have become trapped in the cellin the cell



Proteasomes (Figure 3-10)Proteasomes (Figure 3-10)

Hollow, protein cylinders found throughout the Hollow, protein cylinders found throughout the cytoplasmcytoplasm

Break down abnormal/misfolded proteins and Break down abnormal/misfolded proteins and normal proteins no longer needed by the cellnormal proteins no longer needed by the cell

Break down protein molecules one at a time by Break down protein molecules one at a time by tagging each one with a chain of ubiquitin tagging each one with a chain of ubiquitin molecules and unfolding it as it enters the molecules and unfolding it as it enters the proteasome, then breaking apart peptide bondsproteasome, then breaking apart peptide bonds



PeroxisomesPeroxisomes

Small membranous sacs containing enzymes that Small membranous sacs containing enzymes that detoxify harmful substances that enter the cellsdetoxify harmful substances that enter the cells

Often seen in kidney and liver cellsOften seen in kidney and liver cells



Mitochondria (Figure 3-11)Mitochondria (Figure 3-11)

Made up of microscopic sacs; wall composed of Made up of microscopic sacs; wall composed of inner and outer membranes separated by fluid; inner and outer membranes separated by fluid; thousands of particles make up enzyme molecules thousands of particles make up enzyme molecules attached to both membranesattached to both membranes

The “power plants” of cells; mitochondrial enzymes The “power plants” of cells; mitochondrial enzymes catalyze series of oxidation reactions that provide catalyze series of oxidation reactions that provide about 95% of cell’s energy supplyabout 95% of cell’s energy supply

Each mitochondrion has a DNA molecule, allowing it Each mitochondrion has a DNA molecule, allowing it to produce its own enzymes and replicate copies of to produce its own enzymes and replicate copies of itselfitself


NucleusNucleus

Definition—spherical body in center of cell; Definition—spherical body in center of cell; enclosed by an envelope with many poresenclosed by an envelope with many pores


NucleusNucleus

StructureStructure

Consists of nuclear envelope (composed of two Consists of nuclear envelope (composed of two membranes each with essentially the same membranes each with essentially the same molecular structure as plasma membrane) molecular structure as plasma membrane) surrounding nucleoplasm; nuclear envelope has surrounding nucleoplasm; nuclear envelope has holes called nuclear pores (Figure 3-12)holes called nuclear pores (Figure 3-12)


NucleusNucleus

Structure (cont.)Structure (cont.)

Contains DNA (heredity molecules), which appear Contains DNA (heredity molecules), which appear as the following:as the following:

• Chromatin threads or granules in nondividing cellsChromatin threads or granules in nondividing cells

• Chromosomes in early stages of cell divisionChromosomes in early stages of cell division

• Functions of nucleus are functions of DNA molecules; Functions of nucleus are functions of DNA molecules; DNA determines both structure and function of cells and DNA determines both structure and function of cells and heredityheredity


CytoskeletonCytoskeleton

The cell’s internal supporting framework The cell’s internal supporting framework made up of rigid, rodlike pieces that provide made up of rigid, rodlike pieces that provide support and allow movement and support and allow movement and mechanisms that can move the cell or its mechanisms that can move the cell or its parts (Figure 3-13)parts (Figure 3-13)



Cell fibersCell fibers

Intricately arranged fibers of varying lengths that Intricately arranged fibers of varying lengths that form a three-dimensional, irregularly shaped latticeform a three-dimensional, irregularly shaped lattice

Fibers appear to support the endoplasmic Fibers appear to support the endoplasmic reticulum, mitochondria, and “free” ribosomesreticulum, mitochondria, and “free” ribosomes



Cell fibers (cont.)Cell fibers (cont.)

Smallest cell fibers are microfilaments Smallest cell fibers are microfilaments (Figure 3-14)(Figure 3-14)

• ““Cellular muscles”Cellular muscles”

• Made of thin, twisted strands of protein molecules that lie Made of thin, twisted strands of protein molecules that lie parallel to the long axis of the cellparallel to the long axis of the cell

• Microfilaments can slide past each other, causing Microfilaments can slide past each other, causing shortening of the cellshortening of the cell



Cell fibers (cont.)Cell fibers (cont.)

Intermediate filaments are twisted protein strands Intermediate filaments are twisted protein strands slightly thicker than microfilaments; they form slightly thicker than microfilaments; they form much of the supporting framework in many types much of the supporting framework in many types of cellsof cells

Microtubules are tiny, hollow tubes that are the Microtubules are tiny, hollow tubes that are the thickest of the cell fibers; they are made of protein thickest of the cell fibers; they are made of protein subunits arranged in a spiral fashion; their function subunits arranged in a spiral fashion; their function is to move things around in the cellis to move things around in the cell



CentrosomeCentrosome

An area of the cytoplasm near the nucleus that An area of the cytoplasm near the nucleus that coordinates the building and breaking of coordinates the building and breaking of microtubules in the cellmicrotubules in the cell

Nonmembranous structure also called the Nonmembranous structure also called the microtubule-organizing center (MTOC)microtubule-organizing center (MTOC)

Plays an important role during cell divisionPlays an important role during cell division

The general location of the centrosome is The general location of the centrosome is identified by the centriolesidentified by the centrioles



Cell extensionsCell extensions

Cytoskeleton forms projections that extend the Cytoskeleton forms projections that extend the plasma membrane outward to form tiny, fingerlike plasma membrane outward to form tiny, fingerlike processesprocesses



There are three types of these processes; each There are three types of these processes; each has specific functions (Figure 3-15):has specific functions (Figure 3-15):

• Microvilli—found in epithelial cells that line the intestines Microvilli—found in epithelial cells that line the intestines and other areas where absorption is important; they help and other areas where absorption is important; they help to increase the surface area manyfoldto increase the surface area manyfold

• Cilia and flagella—cell processes that have cylinders Cilia and flagella—cell processes that have cylinders made of microtubules at their core; cilia are shorter and made of microtubules at their core; cilia are shorter and more numerous than flagella; flagella are found only on more numerous than flagella; flagella are found only on human sperm cellshuman sperm cells


Cell ConnectionsCell Connections

Cells are held together by fibrous nets that Cells are held together by fibrous nets that surround groups of cells (e.g., muscle cells), surround groups of cells (e.g., muscle cells), or cells have direct connections to each otheror cells have direct connections to each other

There are three types of direct cell There are three types of direct cell connections (Figure 3-16)connections (Figure 3-16)



DesmosomeDesmosome

Fibers on the outer surface of each desmosome Fibers on the outer surface of each desmosome interlock with each other; anchored internally by interlock with each other; anchored internally by intermediate filaments of the cytoskeletonintermediate filaments of the cytoskeleton

Spot desmosomes, connecting adjacent Spot desmosomes, connecting adjacent membranes, are like “spot welds” at various pointsmembranes, are like “spot welds” at various points

Belt desmosomes encircle the entire cell like Belt desmosomes encircle the entire cell like a collara collar



Gap junctions—membrane channels of Gap junctions—membrane channels of adjacent plasma membranes adhere to each adjacent plasma membranes adhere to each other; have two effects:other; have two effects:

Form gaps or “tunnels” that join the Form gaps or “tunnels” that join the cytoplasm of two cellscytoplasm of two cells

Fuse two plasma membranes into a single Fuse two plasma membranes into a single structurestructure



Tight junctionsTight junctions

Occur in cells that are joined by “collars” of tightly Occur in cells that are joined by “collars” of tightly fused materialfused material

Molecules cannot permeate the cracks of tight Molecules cannot permeate the cracks of tight junctionsjunctions

Occur in the lining of the intestines and other parts Occur in the lining of the intestines and other parts of the body, where it is important to control what of the body, where it is important to control what gets through a sheet of cellsgets through a sheet of cells

mosby items and derived items © 2007, 2003 by mosby, inc. slide 1 chapter 3 anatomy of cells

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