Types of Cells and Cellular Organization

Two Basic Cell TypesProkaryotes:• “Pro”= before; “karyon”= nucleus

• Cells that do not contain any membrane-bound organelles

• Most unicellular (one cell) organisms; bacteria

• 0.5 -5 μm diameter; smaller ribosomes

Prokaryote StructuresAll prokaryotes have:

• Cell wall, plasma membrane, cytoplasm,

ribosomes, and nucleoid (circular DNA)

Additional structures:

• Flagellum tail for locomotion

• Capsule protective layer;prevents

dehydration

• Mesosome aid cell wall formation

• Plasmid small rings of extra DNA

• Pili sticky points that help cell stick to

surfaces; pass plasmids to other prokaryotes

Two Basic Cell TypesEukaryotes :

• Cells that do contain membrane-bound organelles

• Most multicellular (many cells) organisms; plants,

animals, fungi, etc.

• Some unicellular organism too; protoctists

• 10-100 μm; larger ribosomes

Prokaryote Vs. EukaryoteProkaryote Eukaryote

No membrane-bound organelles

Membrane-bound organelles

No nucleus NucleusSmall (0.5- 5 μm) Large (10-100μm)Small Ribosomes Large Ribosomes

Small, normally circular DNA Large, linear DNA

Practice1) A toxin deadly to humans is being tested in a lab. The toxin binds

to ribosomes and prevents them from making proteins. The toxin is

introduced to a colony of E. coli, a common bacteria used in labs.

What kind of result could you expect a day after the toxin is added?

Why?

•2) Will protective masks with 0.007mm filters help stop the spread

of an airborne toxic bacterium? Why?

The bacteria will grow as normal. The ribosomes of bacteria are too small to be affected

No. Bacteria are too small (0.5- 5 μm)

Organizing an Organism•Cell compartmentalize to divide labor

• How are organisms the same?

• Organs designed for specific jobs

CellsTissueOrganSystemOrganism

•Tissue cells of same type or mixed type

• Histology study of tissues

•Organ formed from tissues to do a specific

job (digest, move blood, see, etc.)

•System organs working together for a whole

body function (respiration, excretion, etc.)

Observing Tissues•Plan diagram mapping out tissues in a

section of an organism

• Focus is tissues not cells

•Plant tissue:

•Upper epidermis water proof outer

covering; covered with cuticle

•Palisade mesophyll photosynthetic cells

•Spongy mesophyll space for CO2 circulation

•Phloem transport solutes

•Xylem transport water and salts

•Lower epidermis stomata for gas exchange

Observing Tissues•How would you plan out a cross section of plant stem?

•Pith food storage cells

•Cortex main growth cells in stem; various other jobs

•Cambium produce specialized cells

•Why no mesophyll?

• No photosynthesis in the stem

Animal Tissue Layers•3 Major Layers

•Ectoderm outer layer; skin, nerves, pigments

•Mesoderm middle layer; muscles, bones, connective tissue,

organs

•Endoderm inner layer; digestive tract, respiratory tract, excretion

Homework

•Read pages 21- 28

•Answer questions 1.5

and 1.6

•Finish Cell Analogy

worksheet