Chapter 4 Chapter 4 Life’s Home: The CellLife’s Home: The Cell

Discovery of CellsDiscovery of Cells• Robert Hooke

– cork – the term “cell”

• Anton van Leeuwenhoek– microscope

Cells are the Fundamental Units of LifeCells are the Fundamental Units of Life

• The cell theory– All organisms are composed

of one or more cells– The cell is the basic living unit

of life (organization) – All cells arise from preexisting

cells

Anatomy of the Generalized CellAnatomy of the Generalized Cell

The cell is the smallest unit that shows the properties of life

ALL cells share 3 general structures

DNA

Cytoplasm (pg. 68)

Plasma membrane

The Two Major Categories of CellsThe Two Major Categories of Cells

– Two major kinds of cells (pg. 65):

• PROKARYOTICPROKARYOTIC cells

–“before nucleus”

• EUKARYOTICEUKARYOTIC cells

–eu = “true”

–karyon = “nucleus”

Prokaryotic CellsProkaryotic Cells• Lack a membrane-bound nucleus

– DNA in nucleoid region

• Structurally smaller and simpler than eukaryotic cells (most are unicellular)

• Prokaryotic cells are placed in two taxonomic domains:

– Bacteria

– Archaea

• Live in extreme habitats

Prokaryotic Cells - BacteriaProkaryotic Cells - Bacteria

Eukaryotic Cells (Eukaryotic Cells (eueu = “true”) = “true”)

• Eukaryotic cells are members of the domain Eukarya

• Much larger than prokaryotic cells

• Cells contain a membrane bound nucleus

– DNA (genetic material)• Eukaryotic cells are compartmentalized

– They contain membrane bound structures called organelles

Figure 4.2Figure 4.2

Comparison of

prokaryotes and

eukaryotes

pg. 64

Two Main Types of Eukaryotic CellsTwo Main Types of Eukaryotic Cells

• Animal cells and Plant cells

The NucleusThe Nucleus

– The NUCLEUS is the control center of the cell (pg. 69).• Contains DNA (genetic

information)–chromatin

• Nuclear envelope• Nucleolus (pg. 72)

–rRNA

nucleus

nuclearpores

(b) Yeast cell

nuclearenvelope

nuclearpores

nucleolus

chromatin

(a) Structure of the nucleus

The nucleus contains chromatin which condenses and coils into chromosomes just before the cell divides

The Endomembrane SystemThe Endomembrane System

– An extensive system of interior membranes that divides the cell into compartments – pg. 73• Nuclear envelope• Endoplasmic reticulum (ER)• Golgi apparatus (complex)• Vesicles

Ribosomes & The Endoplasmic ReticulumRibosomes & The Endoplasmic Reticulum

– Two forms of ER:–Rough endoplasmic

reticulum (pg. 72)»ribosomes are the

sites of protein synthesis – pg. 71

–Smooth endoplasmic reticulum

»Lipids & detoxification»pg. 74

Endoplasmic Reticulum (ER) – pg. 70 & 71Endoplasmic Reticulum (ER) – pg. 70 & 71

nuclear enveloperibosomes

0.08 m

roughendoplasmic

reticulum

smoothendoplasmic

reticulum

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The Golgi Apparatus (Complex) The Golgi Apparatus (Complex)

• A specialized set of membranes derived from the endoplasmic reticulum (ER) that modifies, sorts, and packages important molecules into vesicles.

»receives vesicles from ER (acts as a transfer station) – pg. 73

Fig 4.8 pg. 73Fig 4.8 pg. 73

Lysosomes & Cellular RecyclingLysosomes & Cellular Recycling

– Contain digestive enzymes that digest warn-out organelles and foreign materials that enter the cell – pg. 74• Produced by the Golgi

apparatus• Waste disposal and

recycling

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Endomembrane System SummaryEndomembrane System Summary

Energy-Related OrganellesEnergy-Related Organelles

• Chloroplasts (pg. 84)

– Photosynthesis in plants (leaves)

• Capture energy from sunlight

• Mitochondria (pg. 76)

– Involved in cellular respiration

• Extract energy (ATP) from food molecules

– “powerhouse” of the cell

Mitochondria – pg. 76Mitochondria – pg. 76

The Cytoskeleton – pg. 76The Cytoskeleton – pg. 76

• Maintains cell shape and assists in movement of the cell and organelles

• Three types of macromolecular fibers

– Microfilaments

– Intermediate Filaments

– Microtubules

Cilia and Flagella – pg. 79Cilia and Flagella – pg. 79

– Slender, movable extensions of the plasma membrane.

– Used for movement

Compare and Contrast plant and animal cells.

Animal Cells Plant Cells

•Plasma membrane•Cytoplasm•Nucleus

•Cell wall•Plasma membrane•Cytoplasm•Central vacuole•Chloroplasts•Nucleus

The Eukaryotic CellThe Eukaryotic Cell

Figure 4.4

nuclear envelope

nuclear poresDNA

nucleolus

nucleussmooth endoplasmic

reticulum

free ribosomes

cytosol

mitochondria

lysosomes

Golgi complex

plasma membrane

transport vesicle

rough endoplasmic

reticulum

cytoskeleton

The Plant CellFigure 4.16

nuclear envelopenuclear pores

nucleolus

nucleus

plasma membrane

cytoskeleton

smooth endoplasmic reticulum

rough endoplasmic reticulum

free ribosomes

cytosol

chloroplast

mitochondrion

cell wall

centralvacuole

DNA

Golgi complex

Plant cells have a cell wall, chloroplasts, and a central vacuole, while animal cells do not.

Structures in Plant and Animal CellsStructures in Plant and Animal Cells

Table 4.1

Chapter 4 ReviewChapter 4 Review

• Review the 3 parts of the cell theory (pg. 63-64)• Compare & contrast a prokaryotic versus a

eukaryotic cell (pg. 64-65, Fig 4.2)• List the 3 components found in ALL cells• List the principle components of the eukaryotic cell

– what is the function of each component?– pg. 65-80 Table 4.1

• Compare and contrast a plant versus an animal cell (pg. 80-84)