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CELLULAR STRUCTURE AND BIOLOGICAL MEMBRANES Outline - Cells

• Cell Theory • Modern cell concept• Cell Size and function• Methods -Microscopes• Prokaryotic Cells• Eukaryotic Cells• Cell Membranes

• 1665 - Robert Hooke – Describes small rooms in tree bark

• 1838-39 Matt Schleiden & Ted Schann– All organisms are composed of one or more cells.– Cells are the smallest living units of all living organisms.

• Late 1800’s Rudolf Virchow’s contribution– Cells arise only by division of a previously existing cell.– Life on earth represents a continuous line of descent

Cell Theory

Cell Theory1. All organisms are composed of cells.2. Cells are the smallest living things.3. Cells arise only from pre-existing cells.4. All cells today represent a continuous line of descent

from the first living cells.5. Cells contain a mechanism for protein synthesis

Modern Cell Concept

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Surface area to volume ratio 3:1 0.3:1

Small cells have an optimum surface area to volume ratio

Why Are Cells Small?Cell size

Electron microscopesresolve structures 0.2nm apart.

Light microscopesresolve structures 200nm apart.

• Magnification – “enlarge” objects

• Resolution - minimum distance two points can be distinguished as separate points

– Light microscopes– Electron microscopes

• Transmission (TEM) • Scanning (SEM)• Scanning Tunneling (STEM)

Microscope Properties Light Microscopy

67 µm

Compound Light Microscope Phase Contrast Microscope

Dark-field Microscope Fluorescence Confocal Microscope

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LM 1,000×

Light microscope

TEM 2,800×

Transmission Electron Microscope

SEM 2,000×

Scanning Electron Microscope

Views through a microscope - Euglena

Transmission Electron

Microscope Image of 1 Cilium

Scanning Electron Microscope

67 µm

Electron Microscopy

SEM

TEM

Light micrograph

Corral of iron atoms on Corral of iron atoms on a copper surfacea copper surface

DNADNA

2 nm

Scanning Tunneling Electron Microscopy

All cells have certain structures in common.

1. genetic material – in a nucleoid or nucleus2. cytoplasm – a semifluid matrix3. plasma membrane – a phospholipid bilayer

Cell Structure

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Types of Cells

1. ProkaryoticBacteriaArchaebacteria

2. EukaryoticPlantsAnimalsFungiProtists

Prokaryotic Cell Structure

Gram Positive

Gram Negative

Bacterial Cell Walls Prokaryotic Cells - Summary

• Simplest organisms – all bacteria– Plasma Membrane – barrier & regulates

– Inside the Plasma Membrane• Cytoplasm

– Ribosomes– DNA

– Outside the Plasma Membrane• Cell wall – Peptidoglycan layer(s)

– gram-positive or gram-negative• Capsule – Polysaccharide: Adhesion & Hydration• Pili - cell adhesion or DNA transfer

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Eukaryotic Cell Structure

• Characterized by compartmentalization

– Nucleus– Plasma Membrane– Cytoplasm

Plasma Membrane

Nucleus

Cytoplasm

Plasma Membrane

Nucleus

Cytoplasm

Centriole

Lysosome

Mitochondrion

Ribosomes

Roughendoplasmicreticulum

CytoplasmNucleus

Nucleolus

Nuclearenvelope

Smoothendoplasmicreticulum

Golgiapparatus Plasma

membrane

Microvilli

Peroxisome

CytoskeletonActin filament

Intermediatefilament

Microtubule

Eukaryotic Cell Structure

Central vacuole

Chloroplast

Cell wall

Plasma membrane

Plant Cell• Central vacuole

– Large compartments in mature plant cells,– Storage facility for water & other materials– Produce turgor (pressure) for cell rigidity

• Cell wall– Cellulose & other polysaccharides– Support of Cells, Tissues, Organs, Whole Plant

• Chloroplasts– Membranes: 2 in envelope & many internal– Semiautonomous: DNA & ribosomes– Photosynthesis

Plant Cell Unique Characteristics

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Plant Cells - Vacuole

Chloroplasts

Plant Cell Walls

Plasmodesmata

Eukaryotic Cell Structure – Nucleus

Nuclear pores

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Nucleus

Nucleus1. Repository of genetic information2. Synthesis of RNA

for ribosome constructionfor protein synthesis

• Ribosomes– RNA-protein complexes

composed of two subunits– Site of protein synthesis– Assembled in nucleoli

Ribosomes

Fig. 4.11

Ribosomes and Endoplasmic Reticulum

Rough endoplasmic

reticulum

Rough endoplasmic

reticulum

Smooth endoplasmic

reticulum

Endoplasmic Reticulum

Forms compartmentsLarge surface area for metabolism

Rough ERProtein synthesis by ribosomesTransport

Smooth ER Lipid synthesisDetoxification

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Golgi viewed with fluorescence microscopy

Golgi Apparatus

Golgi viewed with fluorescence microscopy

Incoming Transport Vesicles

Outgoing Vesicles

Collect, package, and distribute molecules

Endomembrane System

Lysosomes - membrane-bound digestive vesicles

LysosomesEndomembrane System & Lysosomes

Golgiapparatus

Transport vesiclePlasmamembrane

“Food”

Food vacuole

Lysosomes

Digestion

1

2

54

3Engulfmentof particle

Rough ER

Lysosome animation

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Mitochondrion

Outermembrane

Intermembrane space

MatrixInnermembrane

Cristae

TEM 44,880×

Mito

chon

drio

nMovie

http://www.sci.sdsu.edu/TFrey/MitoMovie.htm

Energy converting organelle: MitochondrionExterior and interior membranes

Semi-autonomousDNARibosomes

Function: ATP synthesis Energy MetabolismAerobic respiration

Mitochondrion

Energy Converting Organelle: Chloroplast

Chloroplast structureTwo external membranesInternal membranesDNARibosomes

Function: Photosynthesis 36

Cytoskeleton

• Network of protein fibers supporting cell shape and anchoring organelles– Actin filaments

• cell movement– Microtubules

• centrioles– Intermediate filaments

• cell structure

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Cytoskeleton

Amoeboid Movement

http://video.google.com/videoplay?docid=4349197081937999314&q=elodea&total=23&start=0&num=10&so=0&type=search&plindex=0http://video.google.com/videoplay?docid=-

5522357274832025243&q=mitosis&total=329&start=0&num=10&so=0&type=search&plindex=4

SE

M 4

,100×

LM 6

00×

Cilia and Flagella

Flagellum

Basal body

TEM

206

,500×

TEM

206

,500×

Plasmamembrane

Protein Fibers of the cytoskeleton

Actin subunit

Microfilament

7 nm

Fibrous subunits

10 nm

Intermediate filament

Microtubule

25 nm

Tubulin subunit

Network of protein fibers supporting cell shape, movement and anchoring organelles

Actin and Microfilaments

Actin Microfilaments

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Microtubules Intermediate Filaments

Intermediate Filaments Rat epithelial cell

Red blood cellsKeratins: Hair & Nails

• Network of protein fibers – Shape– Movement– anchoring organelles

Microfilaments - made of Actin protein• Cell shape & movement

Microtubules - made of tubulin protein• Organelle & chromosome movement

Intermediate filaments – fibrous protein• Structural stability

Cytoskeleton - Summary