Chapter 3

CELLS

A. The Early Years Robert Hooke (1660)

1st person to see the outlines of cells Antonie van Leeuwenhoek (1673)

developed high magnification lenses1st record of microorganisms

Matthias Schleiden & Theodore Schwann (1839) & Rudolph Virchow (1855)contributed to the cell theory

Cell Theory1. All living things are composed

of cells. [Schleiden & Schwann]2. All cells come from

preexisting cells. [Virchow]

B. Cell Size Most are 1-100m in diameter Smallest? Largest? Why can’t cells grow to be as large

as a car?- surface area/volume ratio- as cell grows, its volume increases

more rapidly than its surface area

C. Types of Cells3 basic types:BacterialArchaean ProkaryoticEukaryotic

1. Bacterial cells 1-10 m in diameter NO membrane-bound organelles1 circular DNA molecule located in nucleoid region

plasma membrane, cytoplasm & ribosomes

most have a cell wall (peptidoglycan)may have a polysaccharide capsuleEx. bacteria & cyanobacteria

2. Archaean cells1-10 m in diameterNO membrane-bound organellescell walls lack peptidoglycanhave characteristics of both

bacteria & eukaryotic cells

Ex. methanogens, extreme halophiles & extreme thermophiles

3. Eukaryotic cells10-100 m in diameter nucleus & other membrane-bound

organelles2 or more linear DNA molecules

located in nucleusplasma membrane, cytoplasm &

ribosomessome have a cell wall (cellulose or chitin) Ex. plants, animals, fungi, protista

Generalized Generalized Animal Cell Plant Cell

D. Organelles of Eukaryotic CellsOrganelles compartmentalize a

cell’s activities.1. Nucleus

surrounded by a double membrane (nuclear envelope), perforated with nuclear pores

contains DNA & nucleolus (stores RNA nucleotides)

functions to separate DNA from rest of cell

Nucleolus

2. Endoplasmic reticulum (ER) interconnected network of

membranes extending from nucleus to plasma membrane

Rough ER - studded with ribosomes site of protein synthesis (most will

be exported out of the cell)Free ribosomes in the cytoplasm synthesize proteins that remain in cell.

Smooth ER - lacks ribosomessite of lipid synthesiscontains enzymes that detoxify

drugs & poisons

3. Golgi apparatus stacks of membrane-enclosed

sacs

Functions: links simple carbohydrates

together to form starch links simple carbohydrates to

proteins (glycoprotein) or lipids (glycolipid)

completes folding of proteins temporarily stores secretions (milk)

Organelle interaction in a mammary gland cell.

#/cell variescontain DNA inherited from female parentsite of cellular respiration (production

of ATP)

4. Mitochondriadouble-membrane

outer is smooth inner is highly

folded (cristae)

5. Chloroplastspossess 3 membranes

outer/inner membranes surround stroma 3rd membrane system folded into

flattened sacs (thylakoids)

#/cell varies contain DNA found in plants & protists function in photosynthesis

6. Lysosomes (suicide sacs)vesicles containing > 40 types of

digestive enzymes

function to recycle damaged organelles, break down cellular byproducts & destroy invading microbes

7. Peroxisomesvesicles containing several types

of enzymes (produced in cytoplasm) found in all eukaryotic cells function to help cell use oxygen &

metabolize potentially toxic compounds

E. The Endosymbiont TheoryProposes that chloroplasts and

mitochondria evolved from once free-living bacteria engulfed by larger archaea.

Based on fact that mitochondria & chloroplasts resemble certain bacteria (size, shape, membrane structure & method of making proteins).