Bio 178 Lecture 7Cell Structure

Copyright: J. Elson-Riggins

Reading

• Chapter 5 (& P 550)

Quiz Material

• Questions on P 104

• Chapter 5 Quiz on Text Website (www.mhhe.com/raven7)

Outline

• Microscopy (Cntd.)

• Prokaryotes

• Eukaryotes

Characteristics of Principle Cell Types2 structurally different types of cells:

PROKARYOTE EUKARYOTE

True Nucleus? No Yes

Membrane bound organelles?

No Yes

KingdomsBacteria

Archaebacteria

Protista

Fungi

Plantae

Animalia

SEM - Dinoflagellate, Gonyaulax polyedra

http://www.mcb.harvard.edu/hastings/dino.html

Immunofluorescence Microscopy

Green = Anti-tubulin

Red = Anti-vimentin

http://www.img.cas.cz/dbc/gallery.htm

Prokaryotic Cells (Bacteria)

Prokaryotes

Characteristics

• Simple Organization

1. Little compartmentalization.

2. Nucleoid region with a simple circle of DNA.

3. Ribosomes.

• Size

~ 1 to 10 µm.

Prokaryote Characteristics (Cntd.)

• Support

Most prokaryotes have a strong cell wall (instead of internal support structures).

• Cell Shape

Variable - rod (bacillus), sphere (coccus), comma (vibrio), spiral (spirillum).

Staphylococcus epidermidis

Dr. Dennis Kunkel / Visuals Unlimited,

http://www.visualsunlimited.com/browse/vu285/vu285886.html

Spirillum

http://web.grcc.cc.mi.us/biosci/pictdata/103contents.htm

http://web.grcc.cc.mi.us/biosci/pictdata/103contents.htm

Bacillus

http://bioaulas.tioale.pro.br/aula_bacterias.php

VibrioVibrio cholerae

Prokaryote Cell Walls

• Bacteria have cell walls of peptidoglycan (protein-carbohydrate), but Archaebacteria use other materials.

• Gram Staining

Gram Positive:

A thick wall with many layers of peptidoglycan that blocks the escape of the gram stain Purple.

Gram Negative:

Only a thin peptidoglycan layer that allows the escape of the gram stain Red.

Prokaryote Cell Walls

Importance of Prokaryotes

• Decomposition

• Photosynthesis

• Disease

• Tools for molecular biology

Eukaryotic Cells

Key Characteristic:

COMPARTMENTALIZATION:

• Membrane-bound organelles (including the endomembrane system).

• Nucleus.

• Plasma membrane.

Eukaryote - Animal Cell

Eukaryote - Plant Cell

The NucleusFunction

Control center of cell.

Structure

• Nuclear Envelope

1. 2 phospholipid bilayers.

2. Internal bilayer continuous with ER.

3. Nuclear pores that allow selective passage of proteins and RNA.

Nuclear Envelope

Nuclear Structure (Cntd.)• Nucleolus

1. Dark staining region of nucleus.

2. Contains genes that encode rRNA.

3. Function - rRNA synthesis and assembly of ribosomal subunits.

• ChromosomesDNA and protein (histones).

Nucleolus

http://cellbio.utmb.edu/cellbio/nucleus3.htm

Chromosome Structure

RibosomesFunctionProtein synthesis.

Composition

2 subunits of rRNA and protein.

The Endomembrane systemStructureInterior membranes that are connected by either:

• direct physical continuity or

• vesicular transport

FunctionCompartmentalization, large surface area, and trafficking.

Components• Endoplasmic reticulum

• Golgi apparatus

• Lysosomes

The Endomembrane System

The Endomembrane System

Endoplasmic Reticulum

Structure

• Lipid bilayer with embedded proteins that forms an intracellular network.

• Cisternal space.

Intracellular Location

Continuous with nuclear envelope and concentrated around it.

Rough Endoplasmic Reticulum (RER)

Structure

ER with attached ribosomes.

Functions

• Lipid/membrane synthesis.

• Synthesis of proteins to be secreted from the cell - determined by the presence of a signal sequence on the polypeptide chain.

• Synthesis of proteins that will be embedded in the cell membrane or sent to lysosomes.

RER Structure

Synthesis of Secreted ProteinsSignal sequence composed of hydrophobic aa.

RER

http://trc.ucdavis.edu/mjguinan/apc100/modules/TermsCells&Tissues/structures/ER.html

Smooth Endoplasmic Reticulum (SER)

Structure

Few attached ribosomes.

Functions

• Lipid/membrane synthesis.

• Detoxification.

SER

http://cellbio.utmb.edu/cellbio/ser.htm