CellsThe smallest unit of life

Discovering the Cell

1665 - Robert Hooke

Anton van Leeuwenhoek - late

17th, early 18th centuries

• 1839 – Cell Theory is proposed independently by Theodore Schwann and Matthias Jakob Schleiden.

• Cell Theory:

• The cell is the fundamental structure of all living things.

• All living things are made of cells.

• Cells arise from pre-existing cells through cell division.

Ernst Ruska - 1938

Light micrograph

Scanning electron micrograph

Paramecium

Cell Membrane

Transmission electron micrograph

Scanning electron micrograph

Prokaryotic Cells

Prokaryotic Features

• No _______________ ___________, such as a nucleus.

• DNA in one large ring-shaped chromosome

• An enormous variety of metabolic pathways.

• Highly successful and adaptable.

External structure

_______ (spherical)

_________ (spiral) ___________ (rod-shaped)

Internal Structure____________(nucleoid region)

______________cytosol

___________________

______________

________orslime layer

prokaryoticflagellum

food granule

ribosomes

pili

True or False: A virus is a kind of bacteria.

1 2

50%50%1. True2. False

Viruses• A virus is usually

not considered living.

• A virus consists only of a protein coat (sometimes with a lipid outer layer) and a piece of genetic material (DNA or RNA).

Bacteria vs. Virus

FeaturesBacteri

aVirus

Reproduces independently?

Has genetic material?

Has cell membrane?

Has metabolism?

Living?

Eukaryotic Cells

Eukaryotic Features

• Cells contain ________________ ________________.

• _________ holds multiple strands of _____, which condense into _______________ during cell division.

• May be single-celled or multi-cellular organisms.

Figure 4-3 Biology: Life on Earth 8/e ©2008 Pearson Prentice Hall, Inc.

___________________

_________________

cytosol

lysosome

ribosomes onrough ER

centriole

___________________

________________

nuclear pore

nuclear envelope

chromatin (DNA)

nucleolus

______________________________

___________________

free ribosome

_________

Animal cell

Plant Cell - same organelles as an animal cell, plus a few more

ribosomes free ribosome

nuclear pore

nuclear envelope

chromatin (DNA)

nucleolus______

smoothendoplasmicreticulum

vesicle

roughendoplasmicreticulum

Golgi apparatus

_______________________________________plastid

__________________________

plasmodesma

_________________

central vacuole

cytosol

Things we will see in cells

• First let’s focus on things we can see using a light microscope and ordinary stains:

• Cell nucleus

• Cell membrane

• Cell wall

• Plastids (Chloroplast, amyloplast, chromoplast)

• Plant cell vacuole

Figure 4-9a Biology: Life on Earth 8/e ©2008 Pearson Prentice Hall, Inc.

nuclearpores

nuclearenvelope

chromatin

____________

Nucleus

Cell Wall

_________cell wall

middle_________

__________________

_______cell wall

Chloroplast

_______

________membrane

________membrane

channelinterconnecting

thylakoids

1 micrometer

______

granum(stack of thylakoids)

Amyloplasts and other plastids

starchglobules

0.5 micrometer

plastid

Protein-making Machinery

• Information for making proteins is in _____, stored in the ___________.

• An ______ copy is made in the nucleus and sent out to the rough Endoplasmic Reticulum (ER).

• Proteins leave the ER and are finished and packaged in the _____ ___________.

___________

____________ER

____________ER

____________

Endoplasmic Reticulum

Figure 4-13 Biology: Life on Earth 8/e ©2008 Pearson Prentice Hall, Inc.

Protein-carryingvesicles from ERmerge with Golgiapparatus

Golgiapparatus

Vesicles carryingmodified proteinleave Golgi apparatus

Golgi Apparatus

Figure 4-14 Biology: Life on Earth 8/e ©2008 Pearson Prentice Hall, Inc.

1 A protein issynthesized in the rough ER.

5 Vesicles merge with theplasma membrane andrelease protein byexocytosis.

4 Completed proteinis packaged intovesicles.

3 Vesicles fuse with Golgi. The protein may be altered and finished.

2 Protein is packagedinto vesicles and travelsto Golgi apparatus.

ER and Golgi function

Organelles in Cell Energy

• Chloroplasts capture energy from the sun and use that energy to manufacture sugars (chemical energy storage).

• Mitochondria break the bonds in sugars and release the energy that was stored there.

Mitochondrion

_________

___________membrane

__________membrane

intermembranecompartment

0.2 micrometer

_______

Single-Celled Organisms

• Single-celled organisms carry out the same functions that our multicellular bodies do, but all within a single cell. How do they do it?

One-celled Eukaryotic organisms have unique challenges.

A Paramecium must:

ingest food

excrete waste

sense and respond to the environment

(a) Cilium

(b) Flagellum

propulsion of fluid

return strokepower strokeplasma membrane

direction of locomotion propulsion of fluid

continuous propulsion

ciliumParamecium0.1 micrometer

protein"arms"

central pair ofmicrotubules

section of cilium(transmission EM)

basal body

plasma membrane

contractilevacuole

full reservoir

contracted reservoir

pore

collectingducts

centralreservoir

Reservoir contracts, expellingwater through pore.

Water enters collecting ducts,fills central reservoir.

Recap

• Prokaryotic cells have no membrane-bound organelles.

• Eukaryotic cells have membrane-bound organelles, which compartmentalize processes for better efficiency.

• ALL cells have a cell membrane and DNA.