Cell structure & Cell structure & functionsfunctions

Department of Applied ScienceDepartment of Applied Science

King Saud University/ Community King Saud University/ Community CollegeCollege

By: Murad SawalhaBy: Murad Sawalha

IntroductionIntroduction Eucaryotic cell structureEucaryotic cell structure Procaryotic cell structureProcaryotic cell structure Differences between Procaryotic Differences between Procaryotic & &

Eukaryotic cells.Eukaryotic cells. Reproduction of organisms & Reproduction of organisms & their their

cells.cells. Gram stain Gram stain

OutlineOutline

IntroductionIntroduction- Cell is defined as the fundamental living unit of any Cell is defined as the fundamental living unit of any

organism.organism.

- Cell is important to produce energy for metabolism (all Cell is important to produce energy for metabolism (all chemical reactions within a cell)chemical reactions within a cell)

- Cell can mutate (change genetically) as a result of Cell can mutate (change genetically) as a result of accidental changes in its genetic material (DNA).accidental changes in its genetic material (DNA).

- Some microrganisms are procaryotic, some are eucaryotic, Some microrganisms are procaryotic, some are eucaryotic, & some are not cells at all (Viruses)& some are not cells at all (Viruses)

- Viruses are composed of only a few genes protected by a Viruses are composed of only a few genes protected by a protien coat, & may contain few enzymes.protien coat, & may contain few enzymes.

- Cytology: the study of the structure and functions of cells.Cytology: the study of the structure and functions of cells.

Eucaryotic cell structureEucaryotic cell structure

• Eucaryotic cells: have a Eucaryotic cells: have a true nucleus, & the true nucleus, & the DNA is enclosed by a DNA is enclosed by a nuclear membrane.nuclear membrane.

• They are 10 times They are 10 times larger than Procaryotic larger than Procaryotic cells.cells.

Cell membraneCell membrane• It’s composed of large It’s composed of large

molecules of protiens & molecules of protiens & phospholipids (certain phospholipids (certain types of fats).types of fats).

• The cell membrane is The cell membrane is seperating the contents seperating the contents of the cell from the of the cell from the outside world.outside world.

• It has the property of It has the property of selective permiability: selective permiability: only certain substances only certain substances may enter & leave the may enter & leave the cellcell

Cell MembraneCell Membrane

• Phospholipid bi-layer Phospholipid bi-layer that separates the that separates the cell from its cell from its environment.environment.

• Selectively Selectively permeable to allow permeable to allow substances to pass substances to pass into and out of the into and out of the cell.cell.

NucleusNucleus

• Double membrane-control, Double membrane-control, & integrates the functions & integrates the functions of the entire cell. of the entire cell.

• Consider the command Consider the command center of the cell.center of the cell.

• Separates the genetic Separates the genetic material from the rest of material from the rest of the cell.the cell.

Parts of the nucleus:Parts of the nucleus:

• Chromatin - genetic material of cell in its non-Chromatin - genetic material of cell in its non-dividing state.dividing state.

• Nucleoplasm is the gelatenous matrix of the Nucleoplasm is the gelatenous matrix of the nucleus, like cytoplasm.nucleus, like cytoplasm.

• Nucleolus - dark-staining structure in the Nucleolus - dark-staining structure in the nucleus that plays a role in making ribosomes. nucleus that plays a role in making ribosomes.

• Nuclear envelope - double membrane structure Nuclear envelope - double membrane structure that separates nucleus from cytoplasm.that separates nucleus from cytoplasm.

CytoplasmCytoplasm

• Is a gel-like matrix of water, enzymes, Is a gel-like matrix of water, enzymes, nutrients, wastes, and gases and contains nutrients, wastes, and gases and contains cell structures (organelles).cell structures (organelles).

• Fluid around the organelles called Fluid around the organelles called cytosol.cytosol.

• Most of the cells metabolic reactions Most of the cells metabolic reactions occur in the cytoplasm.occur in the cytoplasm.

The Endoplasmic ReticulumThe Endoplasmic Reticulum

• The endoplasmic reticulum (ER)The endoplasmic reticulum (ER)– Accounts for more than half the total Accounts for more than half the total

membranes in many eukaryotic cellsmembranes in many eukaryotic cells– The ER membrane: is continuous with The ER membrane: is continuous with

the nuclear envelopethe nuclear envelope

• There are two distinct regions of ERThere are two distinct regions of ER– Smooth ER, which lacks ribosomesSmooth ER, which lacks ribosomes– Rough ER, which contains ribosomesRough ER, which contains ribosomes

Rough Endoplasmic Rough Endoplasmic ReticulumReticulum

• Network of continuous Network of continuous sacs, studded with sacs, studded with ribosomes.ribosomes.

• Manufactures, pro-Manufactures, pro-cesses, and transports cesses, and transports proteins for export proteins for export from cell (vesicles)from cell (vesicles)

• Continuous with Continuous with nuclear envelope.nuclear envelope.

Smooth Endoplasmic Smooth Endoplasmic ReticulumReticulum• Similar in appearance to rough ER, Similar in appearance to rough ER,

but without the ribosomes.but without the ribosomes.

• Involved in the production of lipids, Involved in the production of lipids, carbohydrate metabolism, and carbohydrate metabolism, and detoxification of drugs and poisons.detoxification of drugs and poisons.

• Stores calcium.Stores calcium.

RibosomesRibosomes

• Are the sites of protein synthesis.Are the sites of protein synthesis.

• Found attached to the Rough Found attached to the Rough endoplasmic reticulum or free in endoplasmic reticulum or free in the cytoplasm.the cytoplasm.

• 60% RNA and 40% protein.60% RNA and 40% protein.

• Protein released from the ER are Protein released from the ER are not mature, need further not mature, need further processing in Golgi complex processing in Golgi complex before they are able to perform before they are able to perform their function within or outside their function within or outside the cell.the cell.

Golgi ApparatusGolgi Apparatus• Modifies proteins and lipids Modifies proteins and lipids

made by the ER and made by the ER and prepares them for export prepares them for export from the cell (exocytosis).from the cell (exocytosis).

• Encloses digestive Encloses digestive enyzymes into membranes enyzymes into membranes to form lysosomes.to form lysosomes.

• Consists of flattened Consists of flattened membranous sacs called membranous sacs called cisternaecisternae

LysosomeLysosome

• Single membrane Single membrane bound structure.bound structure.

• Contains digestive Contains digestive enzymes that break enzymes that break down cellular waste down cellular waste and debris and and debris and nutrients for use by the nutrients for use by the cell.cell.

• Originate at the Golgi Originate at the Golgi complex.complex.

• Are the Are the

LysosomeLysosome

• They contain lysozymes & other digestive They contain lysozymes & other digestive enzymes that breakdown foreign material taken enzymes that breakdown foreign material taken into the cell by phagocytosis (e.g Amebas, and into the cell by phagocytosis (e.g Amebas, and certain types of WBCs “phagocyte”).certain types of WBCs “phagocyte”).

• Also these enzymes may breakdown parts of Also these enzymes may breakdown parts of the cell or destroy the entire cell by process the cell or destroy the entire cell by process called autolysis if the cell damaged or called autolysis if the cell damaged or deteriorated.deteriorated.

• They contain up to 40 enzymes for digestionThey contain up to 40 enzymes for digestion

PeroxisomesPeroxisomes

• They are similar to lysosome but They are similar to lysosome but smaller.smaller.

• Peroxisomes contain the enzyme Peroxisomes contain the enzyme catalase, which breakdown of hydrogen catalase, which breakdown of hydrogen peroxide into water and oxygen.peroxide into water and oxygen.

• Found mainly in liver and kidney cellsFound mainly in liver and kidney cells

• Main function is detoxification of toxic Main function is detoxification of toxic materials.materials.

MitochondrionMitochondrion

• Membrane bound Membrane bound organelles that are the organelles that are the site of cellular site of cellular respiration (ATP respiration (ATP production)production)

• Mitochondria are Mitochondria are enclosed by two enclosed by two membranesmembranes– A smooth outer A smooth outer

membranemembrane– An inner membrane An inner membrane

folded into cristaefolded into cristae

ChloroplastChloroplast

• Site of Site of photosynthesisphotosynthesis

• Membrane bound Membrane bound structure.structure.

• Contains Contains chlorophyllchlorophyll

• Found only in Found only in plantsplants

CytoskeletonCytoskeleton

• The cytoskeletonThe cytoskeleton– Is a network of fibers extending Is a network of fibers extending

throughout the cytoplasmthroughout the cytoplasmMicrotubule

0.25 µm Microfilaments

Roles of the Cytoskeleton: Roles of the Cytoskeleton: Support, Motility, and Support, Motility, and RegulationRegulation• The cytoskeletonThe cytoskeleton

– Gives mechanical support to the cellGives mechanical support to the cell– Is involved in cell motility, which utilizes motor Is involved in cell motility, which utilizes motor

proteinsproteins

Components of cytoskeleton: Components of cytoskeleton: 1) Microfilaments1) Microfilaments

• Solid rods of Solid rods of globular proteins.globular proteins.

• Important Important component of component of cytoskeleton which cytoskeleton which offers support to offers support to cell structure.cell structure.

Components of cytoskeleton: Components of cytoskeleton: 2) Microtubules2) Microtubules

• MicrotubulesMicrotubules– Shape the cellShape the cell– Guide movement of organellesGuide movement of organelles– Help separate the chromosome copies in Help separate the chromosome copies in

dividing cellsdividing cells

Components of cytoskeleton: Components of cytoskeleton: 2) Microtubules2) Microtubules

Centrosomes and CentriolesCentrosomes and Centrioles

• The centrosomeThe centrosome– Is considered to be a “microtubule-Is considered to be a “microtubule-

organizing center”organizing center”– Contains a pair of centriolesContains a pair of centrioles

Components of cytoskeleton: Components of cytoskeleton: 2) Microtubules2) Microtubules

CentriolesCentrioles

• Found only in Found only in animal cells.animal cells.

• Self-replicatingSelf-replicating

• Made of bundles of Made of bundles of microtubules.microtubules.

• Help in organizing Help in organizing cell division.cell division.

Cell WallCell Wall

• Protects and gives Protects and gives rigidity to plant rigidity to plant cellscells

• Formed from fibrils Formed from fibrils of cellulose of cellulose molecules in a molecules in a “matrix” of “matrix” of polysaccharides polysaccharides and glycoproteins.and glycoproteins.

Cilia and FlagellaCilia and Flagella

• External External appendages from appendages from the cell membrane the cell membrane that aid in that aid in locomotion of the locomotion of the cell.cell.

• Cilia also help to Cilia also help to move substance move substance past the membrane.past the membrane.

Animal Cell vs. Plant CellAnimal Cell vs. Plant Cell

Prokaryotic vs. EukaryoticProkaryotic vs. Eukaryotic

Procaryotic cell strucureProcaryotic cell strucure

• Are about 10 times smaller than Are about 10 times smaller than eucaryotic cells.eucaryotic cells.

• Reproduction of these cells by binary Reproduction of these cells by binary fission.fission.

• Binary fission: the simple division of Binary fission: the simple division of one cell into two cells, following DNA one cell into two cells, following DNA replication, & the formation of a replication, & the formation of a separating membrane & cell wall.separating membrane & cell wall.

Procaryotic cell strucureProcaryotic cell strucure

• Cytoplasm is surrounded by a cell Cytoplasm is surrounded by a cell membrane, a cell wall (usually), & membrane, a cell wall (usually), & sometimes a capsule or slime layer.sometimes a capsule or slime layer.