CELL STRUCTURE & CELL STRUCTURE & FUNCTIONFUNCTION

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FUNCTIONFUNCTION

By By

Professor Dr.Professor Dr. Hosny FouadHosny Fouad

What Is a Cell ?What Is a Cell ?

•• Organisms are composed of cells.Organisms are composed of cells.

•• Cells are quite small and can only be Cells are quite small and can only be seen under the Microscope.seen under the Microscope.

•• When was the microscope invented?When was the microscope invented?

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•• When was the microscope invented?When was the microscope invented?

•• The cell is: The cell is: The basic unit of life.The basic unit of life.•• Nothing smaller than a cell is alive.Nothing smaller than a cell is alive.•• Humans are multicellular.Humans are multicellular.

3Light MicroscopeLight Microscope

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Cells Look Quite DifferentCells Look Quite Different

•• A blood cell, a nerve cell, a cartilage A blood cell, a nerve cell, a cartilage cell are all different.cell are all different.

•• Cells in an organism have certain Cells in an organism have certain parts in common (Animal cell & plant parts in common (Animal cell & plant

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parts in common (Animal cell & plant parts in common (Animal cell & plant cell).cell).

•• New cells arise from preNew cells arise from pre--existing existing cells.cells.

7Red Blood Cells (RBCs)Red Blood Cells (RBCs)

8Nerve CellNerve Cell

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Cartilage CellCartilage Cell

Internal Organization Internal Organization of Cellsof Cells

•• Electron MicroscopeElectron Microscope allowed allowed biologists to determine the biologists to determine the internal organization of cells.internal organization of cells.

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internal organization of cells.internal organization of cells.

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Electron MicroscopeElectron Microscope

1.1.Plasma membranePlasma membrane

2.2.The CytoskeletonThe Cytoskeleton

3.3.The Nucleus (& Nucleolus)The Nucleus (& Nucleolus)

4.4.The MitochondrionThe Mitochondrion

Cell Components include:Cell Components include:

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4.4.The MitochondrionThe Mitochondrion

5.5.LysosomesLysosomes

6.6.Endoplasmic Reticulum (Rough & Smooth)Endoplasmic Reticulum (Rough & Smooth)

7.7.RibosomesRibosomes

11. Plasma Membrane. Plasma Membrane

•• Surrounds the cellSurrounds the cell•• Keeps the cell intactKeeps the cell intact•• Regulates what enters and exits a Regulates what enters and exits a

cell.cell.

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cell.cell.•• Is a phosphoIs a phospho--lipid bilayer with lipid bilayer with

attached or embedded proteins.attached or embedded proteins.•• Selectively permeable (it allows Selectively permeable (it allows

certain molecules to enter the cell but certain molecules to enter the cell but not others).not others).

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Phospholipid bilayerPhospholipid bilayer

What is Phospholipid?What is Phospholipid?

•• A Phospholipid (PL) molecule has a A Phospholipid (PL) molecule has a polar head and nonpolar tails.polar head and nonpolar tails.

•• The polar head is charged and The polar head is charged and hydrophilic (loves water) facing hydrophilic (loves water) facing outward.outward.

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hydrophilic (loves water) facing hydrophilic (loves water) facing outward.outward.

•• The nonpolar tails are hydrophobic The nonpolar tails are hydrophobic (hates water) facing inward.(hates water) facing inward.

•• When PL placed in water form When PL placed in water form spherical bilayer.spherical bilayer.

Membrane StructureMembrane Structure

•• FluidFluid--mosaic structure.mosaic structure.•• Protein molecules can move freely.Protein molecules can move freely.•• Cholesterol is present to give support Cholesterol is present to give support

to the membrane.to the membrane.

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to the membrane.to the membrane.•• Sugar is attached to the outer Sugar is attached to the outer

surface of some protein (glycoprotein) surface of some protein (glycoprotein) and lipid (lipoprotein) molecules.and lipid (lipoprotein) molecules.

•• Carbohydrate chains are specific to Carbohydrate chains are specific to each cell (blood types)each cell (blood types)

Functions of Proteins in Cell Functions of Proteins in Cell MembraneMembrane

•• Some glycoSome glyco--proteins act as proteins act as receptorsreceptors..

•• Some proteins formSome proteins form channelschannels..

•• Some proteins are Some proteins are enzymesenzymes..

•• Some proteins areSome proteins are carrierscarriers for the for the

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•• Some proteins areSome proteins are carrierscarriers for the for the passage of molecules through the passage of molecules through the membrane.membrane.

Functions of Plasma MembraneFunctions of Plasma Membrane

•• Keeps a cell Keeps a cell intact.intact.

•• Allows certain molecules & ions to enter and Allows certain molecules & ions to enter and exit the cytoplasm freelyexit the cytoplasm freely (selectively (selectively permeable).permeable).

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permeable).permeable).

•• Small Small lipidlipid--soluble moleculessoluble molecules, e.g. oxygen , e.g. oxygen and carbon dioxide can and carbon dioxide can pass easilypass easily..

•• WaterWater cancan freely crossfreely cross the membrane.the membrane.

•• Ions and large moleculesIons and large molecules cannot cross cannot cross without assistance. without assistance.

Mechanisms of Transport Mechanisms of Transport through Cell Membranethrough Cell Membrane

1.1. Simple DiffusionSimple Diffusion

2.2. Facilitated DiffusionFacilitated Diffusion

3.3. Active TransportActive Transport

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3.3. Active TransportActive Transport

4.4. Endocytosis & ExocytosisEndocytosis & Exocytosis

a) Simple Diffusiona) Simple Diffusion

•• Diffusion is a passive way for Diffusion is a passive way for molecules to enter or exit a cellmolecules to enter or exit a cell(i.e. no energy is needed).(i.e. no energy is needed).

•• Molecules move from the area of Molecules move from the area of

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•• Molecules move from the area of Molecules move from the area of higherhigher concentration concentration toto the area of the area of lowerlower concentration, until they are concentration, until they are equally distributed.equally distributed.

b) Facilitated Transportb) Facilitated Transport

•• Needs a protein carrier.Needs a protein carrier.

•• Faster than passive diffusion.Faster than passive diffusion.

•• From the side of higher concentration to From the side of higher concentration to the side of lower concentration.the side of lower concentration.

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the side of lower concentration.the side of lower concentration.

•• Does not need energy.Does not need energy.

•• The protein carrier is called a transporter, The protein carrier is called a transporter, it binds to the molecule, e.g. glucose.it binds to the molecule, e.g. glucose.

•• Diabetes type Diabetes type 2 2 results when cells lack a results when cells lack a sufficient number of transporters.sufficient number of transporters.

c) Active Transportc) Active Transport

•• Occurs Occurs against concentration gradientagainst concentration gradient(i.e. from lower to higher (i.e. from lower to higher concentration).concentration).

•• Requires Requires a protein carrier.a protein carrier.

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•• Requires Requires a protein carrier.a protein carrier.

•• Needs cellular energy from Needs cellular energy from ATPATP..

•• ProteinsProteins used in the active transport used in the active transport are are called pumpscalled pumps, Na, Na++/K/K++ pumppump..

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d) Endocytosis & Exocytosisd) Endocytosis & Exocytosis

•• During endocytosis a part of the plasma During endocytosis a part of the plasma membrane membrane invaginates invaginates to engulf the to engulf the molecule.molecule.

•• The membrane then formsThe membrane then forms a vesiclea vesicle inside inside the cell.the cell.

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the cell.the cell.•• Some white blood cells take up pathogens Some white blood cells take up pathogens

by endocytosis, the process is called by endocytosis, the process is called phagocytosisphagocytosis..

•• Taking up molecules and fluids is calledTaking up molecules and fluids is calledpinocytosis.pinocytosis.

ExocytosisExocytosis

•• A vesicle fuses with the plasma A vesicle fuses with the plasma membrane as secretion occurs ,e.g. membrane as secretion occurs ,e.g. insulin secretion.insulin secretion.

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22. Cytoskeleton. Cytoskeleton

•• The cytoplasm is crissThe cytoplasm is criss--crossed by protein crossed by protein fibers called cytoskeleton.fibers called cytoskeleton.

•• It helps to keep shape of the cell and It helps to keep shape of the cell and assists movement of organelles.assists movement of organelles.

•• It consists of: microtubules, actin filaments It consists of: microtubules, actin filaments

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•• It consists of: microtubules, actin filaments It consists of: microtubules, actin filaments and intermediate filaments.and intermediate filaments.

•• Microtubules: keep the shape of ell and act Microtubules: keep the shape of ell and act as tracks along which organelles move. They as tracks along which organelles move. They are made of tubulin.are made of tubulin.

22. Cytoskeleton (Cont.). Cytoskeleton (Cont.)

•• Microtubules form spindle fibers Microtubules form spindle fibers during cell division, which assist during cell division, which assist movement of chromosomes.movement of chromosomes.

•• Actin filaments: made of the protein Actin filaments: made of the protein

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•• Actin filaments: made of the protein Actin filaments: made of the protein actin and occurs in cells in which actin and occurs in cells in which movement occurs (e.g. microvilli movement occurs (e.g. microvilli projecting from certain cells contain projecting from certain cells contain actin).actin).

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33. The Nucleus. The Nucleus

•• A large.A large.

•• Can be seen with the light Can be seen with the light microscope.microscope.

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•• Contains the chromosomes.Contains the chromosomes.

•• Is the control center of the cell.Is the control center of the cell.

•• Controls metabolism and structure Controls metabolism and structure of the cell.of the cell.

33. The Nucleus (Cont.). The Nucleus (Cont.)

•• Stores genetic information.Stores genetic information.

•• Every cell contains the same genes, Every cell contains the same genes, but each type has certain genes but each type has certain genes turned on and others turned off.turned on and others turned off.

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turned on and others turned off.turned on and others turned off.

•• Activated DNA (via RNA) specifies Activated DNA (via RNA) specifies the protein in a cell.the protein in a cell.

•• Proteins determine cell’s structure & Proteins determine cell’s structure & functions (as enzymes are proteins).functions (as enzymes are proteins).

33. The Nucleus (Cont.). The Nucleus (Cont.)

•• Chromatin is coiled in the form of Chromatin is coiled in the form of chromosome just before cell division.chromosome just before cell division.

•• The nuclear envelope surrounds the The nuclear envelope surrounds the nucleus.nucleus.

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nucleus.nucleus.

•• The nuclear envelope has nuclear The nuclear envelope has nuclear pores to permit passage of proteins pores to permit passage of proteins into the nucleus and ribosomes & into the nucleus and ribosomes & mRNA out of the nucleus.mRNA out of the nucleus.

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44. The Nucleolus. The Nucleolus

•• Nucleolus is present within the Nucleolus is present within the nucleus.nucleus.

•• In the nucleolus, ribosomal RNA In the nucleolus, ribosomal RNA is produced and joins with is produced and joins with

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is produced and joins with is produced and joins with proteins to form ribosomes.proteins to form ribosomes.

55. The Ribosomes. The Ribosomes

•• Ribosomes are organelles composed of Ribosomes are organelles composed of proteins and rRNA.proteins and rRNA.

•• Protein synthesis occurs at the Protein synthesis occurs at the ribosomes.ribosomes.

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ribosomes.ribosomes.

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RibosomesRibosomes

55. Mitochondria. Mitochondria

•• Mitochondria (singular, mitochondrion) Mitochondria (singular, mitochondrion) are called the powerhouses of he cell.are called the powerhouses of he cell.

•• Mitochondrion has a double membrane.Mitochondrion has a double membrane.

•• The inner membrane is folded to form The inner membrane is folded to form

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•• The inner membrane is folded to form The inner membrane is folded to form cristae.cristae.

•• The inner space is called the matrix.The inner space is called the matrix.

55. Mitochondria (Cont.). Mitochondria (Cont.)

•• Mitochondria convert the chemical Mitochondria convert the chemical energy of glucose products into the energy of glucose products into the chemical energy of ATP molecules.chemical energy of ATP molecules.

•• Mitochondria use up oxygen and give Mitochondria use up oxygen and give

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•• Mitochondria use up oxygen and give Mitochondria use up oxygen and give off carbon dioxide and water.off carbon dioxide and water.

•• Oxygen in breath enters cells and Oxygen in breath enters cells and then mitochondria.then mitochondria.

55. Mitochondria (Cont.). Mitochondria (Cont.)

•• The matrix contains a gelThe matrix contains a gel--like fluid, like fluid, and enzymes of the break down of and enzymes of the break down of glucose products and fatty acids.glucose products and fatty acids.

•• The respiratory chain is located in The respiratory chain is located in the inner membrane and produces the inner membrane and produces

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•• The respiratory chain is located in The respiratory chain is located in the inner membrane and produces the inner membrane and produces ATP.ATP.

•• ATP is used by cells for synthesis of ATP is used by cells for synthesis of molecules, contraction of muscles, molecules, contraction of muscles, conduction of nerve impulses.conduction of nerve impulses.

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MitodhondrionMitodhondrion

http://www.modares.ac.ir/elearning/Dalimi/Proto/images/Lec

tures/

66. Endoplasmic Reticulum . Endoplasmic Reticulum (ER)(ER)

A.A.Rough ERRough ER

B.B.Smooth ERSmooth ER

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A. Rough ERA. Rough ER

•• Carries ribosomes.Carries ribosomes.

•• Synthesis of ProteinsSynthesis of Proteins

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45Rough Endoplasmic ReticulumRough Endoplasmic Reticulum

B. Smooth ERB. Smooth ER

•• Does not carry ribosomes.Does not carry ribosomes.

•• Lipid synthesis & Drug MetabolismLipid synthesis & Drug Metabolism

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Smooth Endoplasmic Reticulum Smooth Endoplasmic Reticulum (sEPR)(sEPR)

77. The Cytoplasm. The Cytoplasm

•• Is the semiIs the semi--fluid medium between fluid medium between the nucleus and the plasma the nucleus and the plasma membrane.membrane.

•• It contains water, various It contains water, various

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•• It contains water, various It contains water, various molecules and proteins.molecules and proteins.

8. Lysosomes

•• Vesicles with digestive enzymesVesicles with digestive enzymes

•• Intracellular DigestionIntracellular Digestion

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50Golgi Apparatus & LysosomesGolgi Apparatus & Lysosomes

99. Golgi Apparatus. Golgi Apparatus

•• Membranous SacculesMembranous Saccules

•• Processing, Sorting & Packaging of Processing, Sorting & Packaging of proteins.proteins.

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FunctionFunctionComposition Composition NameNameStorage of Storage of Genetic Genetic InformationInformation

Envelope, chromatin Envelope, chromatin and nucleolus.and nucleolus.

NucleusNucleus

Ribosomal Ribosomal FormationFormation

Chromatin, RNA & Chromatin, RNA & ProteinsProteins

NucleolusNucleolus

Subcellular OrganellesSubcellular Organelles

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FormationFormationProteinsProteins

Protein SynthesisProtein SynthesisProtein & RNA in Protein & RNA in 2 2 subunitssubunits

RibosomeRibosome

Synthesis of Synthesis of ProteinsProteins

Carries ribosomesCarries ribosomesRough Rough EndoplasmicEndoplasmic Reticulum (ER)Reticulum (ER)

Lipid synthesis & Lipid synthesis & Drug MetabolismDrug Metabolism

No ribosomesNo ribosomesSmooth ERSmooth ER

FunctionFunctionComposition Composition NameName

Processing, Sorting & Processing, Sorting & Packaging of proteinsPackaging of proteins

Membranous Membranous SacculesSaccules

Golgi Golgi ApparatusApparatus

Intracellular Intracellular DigestionDigestion

Vesicles with Vesicles with digestive enzymesdigestive enzymes

LysosomesLysosomes

Subcellular OrganellesSubcellular Organelles

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DigestionDigestiondigestive enzymesdigestive enzymes

Cellular RespirationCellular RespirationInner & outer Inner & outer MembranesMembranes

MitochondrionMitochondrion

Shape of cell & Shape of cell & MovementMovement

Microtubules, Microtubules, actin filamentsactin filaments

Cytoskeleton Cytoskeleton

What are the What are the 7 7 Characteristics of life?Characteristics of life?

1.1. ReproductionReproduction2.2. Response to stimuli.Response to stimuli.3.3. HomeostasisHomeostasis4.4. Growth.Growth.

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4.4. Growth.Growth.5.5. Development.Development.6.6. Take in & use materials from the Take in & use materials from the

environment.environment.7.7. Adaptation with the environment.Adaptation with the environment.

CELL METABOLISMCELL METABOLISM

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ByBy

Prof Dr Hosny FouadProf Dr Hosny Fouad

Cell MetabolismCell Metabolism

Definition:Definition:

•• Means all the chemical reactions Means all the chemical reactions that occur in a cell. that occur in a cell.

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•• Metabolic reactions are catalyzed Metabolic reactions are catalyzed by enzymes.by enzymes.

Cellular RespirationCellular Respiration

•• Glucose breakdown requires Glucose breakdown requires 4 4 phases:phases:

1)1) GlycolysisGlycolysis

2)2) Preparatory reactionPreparatory reaction

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2)2) Preparatory reactionPreparatory reaction

3)3) The citric acid cycleThe citric acid cycle

4)4) The electron transport chainThe electron transport chain

Breakdown of Glucose Breakdown of Glucose (Cellular Respiration)(Cellular Respiration)

Glucose breakdown to Glucose breakdown to 6 6 COCO22, , 6 6 HH22O and energy (ATP) requires O and energy (ATP) requires 4 4 phases:phases:

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phases:phases:

11. Glycolysis. Glycolysis

a)a) This reaction occurs in the This reaction occurs in the cytoplasm.cytoplasm.

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b)b) Glucose (a Glucose (a 66--carbon molecule), is carbon molecule), is broken down to broken down to 2 2 molecules of molecules of pyruvic acid, pyruvic acid, 2 2 NADHNADH22 & & 2 2 ATP ATP molecules.molecules.

2.2. Preparatory ReactionPreparatory Reaction

a)a) Occurs in the matrix of Occurs in the matrix of mitochondria.mitochondria.

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mitochondria.mitochondria.

b)b) Pyruvic acid is converted to Pyruvic acid is converted to 2 2 molecules of acetylmolecules of acetyl--CoA, CoA, 2 2 COCO2 2

& & 2 2 NADHNADH2 2 ..

33. The Citric Acid Cycle. The Citric Acid Cycle

a)a) The acetyl group (acetylThe acetyl group (acetyl--CoA) CoA) enters the citric acid cycle.enters the citric acid cycle.

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b)b) As a result of the citric acid As a result of the citric acid cycle: cycle: 4 4 COCO22,,2 2 ATP, ATP, 6 6 NADHNADH22 and and 2 2 FADHFADH22 are produced.are produced.

44.The Electron Transport Chain.The Electron Transport Chain

1.1. Electrons are removed from the Electrons are removed from the hydrogen atoms (carried by NADHhydrogen atoms (carried by NADH22

and FADHand FADH22 coming from the citric acid coming from the citric acid cycle) are oxidized by the electron cycle) are oxidized by the electron

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cycle) are oxidized by the electron cycle) are oxidized by the electron transport chain by oxygen atom to transport chain by oxygen atom to form water.form water.

2.2. ATP molecules and water are formed.ATP molecules and water are formed.

The The 4 4 phases of complete cellular respirationphases of complete cellular respiration

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