THE CELLTHE CELL

Carsonella ruddiCarsonella ruddi

160Kb <200 genes160Kb <200 genes

Mycoplasma laboratorium – Mycoplasma laboratorium – 381 genes , 580kb381 genes , 580kb

Biological size and cell diversityBiological size and cell diversity

I. The history of cell studyI. The history of cell study

A. Robert Hooke—1665A. Robert Hooke—1665—coined the word cell, —coined the word cell, looked at cork cellslooked at cork cells

B. Robert Brown—1831B. Robert Brown—1831—discovered the —discovered the "nucleus""nucleus"

Robert Hooke's sketches of cork cells.

Credit: © Science VU/Visuals Unlimited 9470

Cell theoryCell theory• 1. All living things are 1. All living things are

composed of one or more composed of one or more cellscells

• 2. Cells are the basic unit of 2. Cells are the basic unit of structure and functionstructure and function

• 3. All cells come from 3. All cells come from preexisting cellspreexisting cells

T4 Bacteriophage Virus. T4 bacteriophages are parasites of E. coli, a bacteria common in the human gut. The virus attaches itself to the host bacteria cell wall by its tail fibers. The sheath then contracts, injecting the contents of the head (DNA) into the host. The viral DNA makes the bacteria manufacture more copies of the virus. TEM X450,000.

Credit: © Dr. Harold Fisher/Visuals Unlimited

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T4 Bacteriophages on Escherichia coli bacteria. T4 bacteriophages are parasites of E. coli, a bacteria common in the human gut. The virus attaches itself to the host bacteria cell wall by its tail fibers. The sheath then contracts, injecting the contents of the head (DNA) into the host. The viral DNA makes the bacteria manufacture more copies of the virus. TEM X60,000.

Credit: © Dr. George Chapman/Visuals Unlimited

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Paramecium, a ciliated protozoan. SEM X130.

Credit: © Dr. Dennis Kunkel/Visuals Unlimited 283885

E. coli dividing. Note the fibrillar DNA nucleoid. These bacteria are a part of human and animal microbiota that can cause urinary tract infections, traveler's diarrhea, and nosocomial infections. TEM.

Credit: © Dr. Dennis Kunkel/Visuals Unlimited 350484

BASIC - FunctionsBASIC - Functions- Boundaries – regulate environment- Boundaries – regulate environment

- Movement and/or transport- Movement and/or transport

- Energy production/capture- Energy production/capture

- Protein synthesis- Protein synthesis

- Waste production and removal- Waste production and removal

- Communication- Communication

And most importantly And most importantly reproduction!reproduction!

Cell sizeCell size• 1. 1–100µm1. 1–100µm• 2. Why is there a limit to cell 2. Why is there a limit to cell

size?size? a. Surface-to-volume ratioa. Surface-to-volume ratio b. Distance from surface to b. Distance from surface to

centercenter

BASICALLY…..BASICALLY…..

Diffusion limits cell sizeDiffusion limits cell size Diffusion would be too Diffusion would be too slow to meet demands slow to meet demands of cell if they were of cell if they were larger larger

Eg oxygen consumptionEg oxygen consumption

ProkaryoticProkaryotic•Bacteria and archaea Bacteria and archaea •DNA not enclosed in a DNA not enclosed in a nucleusnucleus

•No cytoskeletonNo cytoskeleton•No No compartmentalizationcompartmentalization

EukaryoticEukaryotic•Highly organized Highly organized membrane-membrane-enclosed enclosed organellesorganellesCytoplasmCytoplasmNucleoplasmNucleoplasm

CellsCellsA)A) Plasma membranePlasma membrane

boundaryboundary

regulates trafficking into regulates trafficking into and out of celland out of cell

communication with other communication with other cellscells

HypercholesterolemiaHypercholesterolemia

Eukaryotic CellEukaryotic CellB) CytoplasmB) Cytoplasm

•Cytosol (the fluid part)Cytosol (the fluid part)

WaterWater

SaltsSalts

Organic moleculesOrganic molecules

•OrganellesOrganelles

Freeze Etched MicrographFreeze Etched MicrographPlasmaPlasma

MembraneMembrane

NucleusNucleus

NuclearNuclearPoresPores

VesiclesVesicles

C) NucleusC) Nucleus•Contains DNAContains DNA•Bounded byBounded by

Nuclear envelopeNuclear envelopeDouble membrane Double membrane perforated with nuclear perforated with nuclear porespores

- Progeria linked to Lamin - Progeria linked to Lamin

Hutchinson-Gilford progeria syndrome (HGPS) is a childhood disorder Hutchinson-Gilford progeria syndrome (HGPS) is a childhood disorder caused by a caused by a point mutation in position 1824 of the in position 1824 of the LMNA gene, gene,

replacing cytosine with thymine, creating an unusable form of the replacing cytosine with thymine, creating an unusable form of the protein protein Lamin A. Lamin A is part of the building blocks of the nuclear . Lamin A is part of the building blocks of the nuclear

envelope.envelope.

•DNA forms DNA forms chromatin, which is chromatin, which is organized into organized into chromosomeschromosomes

D) NucleolusD) NucleolusRNA synthesis and RNA synthesis and ribosome assemblyribosome assembly

Freeze-fracture technique used to show nuclear pores. Nuclear pores are structures in the nuclear envelope that allow passage of certain materials between the cell nucleus and the cytoplasm. TEM X100,000.

Credit: © Dr. Richard Kessel & Dr. Gene Shih/Visuals Unlimited 900007

2 chromosomes not 1!2 chromosomes not 1!

F) Endoplasmic reticulum (ER)F) Endoplasmic reticulum (ER)•Network of folded internal Network of folded internal membranes in the cytosolmembranes in the cytosol

I) Smooth ER I) Smooth ER Site of lipid synthesisSite of lipid synthesisSite of detoxifying enzymes Site of detoxifying enzymes (addicts)(addicts)

•II) Rough ERII) Rough ERRibosomes Ribosomes manufacture manufacture proteinsproteins

Proteins may be Proteins may be moved into the ER moved into the ER lumenlumen

RibosomesRibosomes

FREE RIBOSOMES FREE RIBOSOMES protein protein prod. Stay in cell prod. Stay in cell

ie ATPsynthaseie ATPsynthase

BOUND RIBOSOMES (RER) BOUND RIBOSOMES (RER) excreted (exocytosis) ie excreted (exocytosis) ie insulin, antibodiesinsulin, antibodies

H) Golgi complexH) Golgi complex process, sort, and modify process, sort, and modify

proteins proteins •In animal cells, Golgi In animal cells, Golgi complex also prod. complex also prod. lysosomes lysosomes

modifies carbohydrates and modifies carbohydrates and lipids and packages into lipids and packages into vesiclesvesicles

CDG (congenital disorders of CDG (congenital disorders of glycosolation – also in ER)glycosolation – also in ER)

H) VesiclesH) Vesicles

- - generic name for generic name for hundreds of small, hundreds of small, membrane bound membrane bound organelles in a cellorganelles in a cell

Functions in transport Functions in transport and storageand storage

I) Lysosomes break down I) Lysosomes break down worn-out cell structures, worn-out cell structures, bacteria, and other bacteria, and other substancessubstances

involved in apoptosis involved in apoptosis removal of webbing between removal of webbing between digitsdigits

Tay Sachs diseaseTay Sachs disease

J) PeroxisomesJ) Peroxisomes•Involved in lipid Involved in lipid metabolism and metabolism and detoxificationdetoxification

•Contain enzymes that Contain enzymes that produce and degrade produce and degrade hydrogen peroxidehydrogen peroxide

•Adrenoleukodystrophy Adrenoleukodystrophy (can’t break down long fatty (can’t break down long fatty acid chains)acid chains)

Peroxisomes are organelles in eukaryotic cells that contains enzymes that produce or degrade hydrogen peroxide. TEM.

Credit: © Dr. Donald Fawcett/Visuals Unlimited 900015

K) Mitochondria K) Mitochondria •Sites of aerobic respirationSites of aerobic respiration•Organelles enclosed by a double Organelles enclosed by a double membranemembrane

•role in apoptosisrole in apoptosis•contain enzymes for aerobic contain enzymes for aerobic respiration to produce ATPrespiration to produce ATP

Mitochondrial cytopathies (mtDNA or Mitochondrial cytopathies (mtDNA or DNA) incl Mitochondrial myopathyDNA) incl Mitochondrial myopathy

L) Chloroplasts L) Chloroplasts •Plastids that carry out Plastids that carry out photosynthesisphotosynthesis

•During photosynthesis, During photosynthesis, chlorophyll traps light chlorophyll traps light energyenergy

•Energy converted to Energy converted to chemical energy in ATPchemical energy in ATP

M) Cytoskeleton M) Cytoskeleton •Internal frameworkInternal framework

MicrotubulesMicrotubulesMicrofilamentsMicrofilamentsIntermediate filamentsIntermediate filaments

•Provides structural supportProvides structural support•Involved with transport of materials in Involved with transport of materials in the cellthe cell

•ALS (motor proteins)ALS (motor proteins)

Cytoskeleton intermediate fibers in a human cell.

Credit: © Dr. K.G. Murti/Visuals Unlimited 304144

Cilia and flagella Cilia and flagella •Thin, movable structures Thin, movable structures that project from cell that project from cell surfacesurface

•Function in movementFunction in movement•Microtubles anchored in Microtubles anchored in cell by basal bodycell by basal body

Thin cross-section cut through the isolated axoneme. Chlamydomonas algae flagella have the 9+2 structure characteristic of all eukaryotic cells. The axoneme has a central unit containing two single microtubules and nine peripheral doublet microtubules. Dynein sidearms project from the A tubule of each doublet. Also visible are the radial spokes and the inner sheath. TEM.

Credit: © RMF/Visuals Unlimited

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This image of Chlamydomanas algae is a longitudinal section through the flagellar apparatus. In the cell apex are the basal body regions that are the anchoring sites for the flagella. The two flagella form a V and they are connected at their bases by a transversely striated fiber. This connection is thought to play a part in the coordination of flagellar movement. TEM.

Credit: © RMF/Visuals Unlimited

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ANCHORING IN MULTI’SANCHORING IN MULTI’S GlycocalyxGlycocalyx, cell coat formed , cell coat formed by polysaccarides extending by polysaccarides extending from plasma membranefrom plasma membrane

Many animal cells also Many animal cells also surrounded by an surrounded by an extracellular matrix (ECM)extracellular matrix (ECM)

Extracellular matrixExtracellular matrix

PlantPlantcell wallscell walls

N) CELL WALLN) CELL WALL

Protection; maintains Protection; maintains shape; protection shape; protection from bursting; holds from bursting; holds plant up;plant up;

Also found in fungi, Also found in fungi, bacteriabacteria

Plant cells!!!Plant cells!!!

- - cell wallcell wall

- central vacuole- central vacuole

- chloroplasts- chloroplasts

O) Central Vacuoles in PlantsO) Central Vacuoles in Plants Large, water-filled Large, water-filled spaces spaces

storage (pigments, storage (pigments, salts, wastes)salts, wastes)

•maintain turgiditymaintain turgidity

CELL-CELL JUNCTIONSCELL-CELL JUNCTIONS

DESMOSOMES DESMOSOMES

- “SPOT WELDS”- “SPOT WELDS”

- strength- strength

- ie neck of uterus- ie neck of uterus

TIGHT JUNCTIONSTIGHT JUNCTIONSBelts around Belts around epithelial cells to epithelial cells to prevent leakage ie prevent leakage ie intestinal epithelium, intestinal epithelium, urinary bladderurinary bladder

GAP JUNCTIONS & GAP JUNCTIONS & PLASMODESMATAPLASMODESMATA

Direct passage of Direct passage of materials between cellsmaterials between cells

Ie ion flow between Ie ion flow between cardiac cellscardiac cells

QuestionsQuestions 1.Which organelle would be missing from 1.Which organelle would be missing from

plant cells in the root of the plant?plant cells in the root of the plant? 2. A scientist samples an unknown cell’s 2. A scientist samples an unknown cell’s

genetic information and compares it to the genetic information and compares it to the genetic information of a photosynthetic genetic information of a photosynthetic prokaryote and a eukaryotic cell (from a prokaryote and a eukaryotic cell (from a human). The scientist ran several tests human). The scientist ran several tests and observed conflicting results – some and observed conflicting results – some tests revealed a greater similarity to the tests revealed a greater similarity to the prokaryotic cell while some revealed a prokaryotic cell while some revealed a greater similarity to the eukaryotic cell. greater similarity to the eukaryotic cell. Why?Why?

The following results were obtained The following results were obtained from the cellular analysis of an from the cellular analysis of an individual:individual:

- Accumulation of very long chain fatty Accumulation of very long chain fatty acidsacids

- Lack of bile productionLack of bile production

Which organelle is malfunctioning?Which organelle is malfunctioning?