Ch 4 – A Tour of the Cell The cell is the basic unit of structure and

function in the body. Prokaryote v. Eukaryote

• Are smaller than eukaryotic cells

• Lack internal structures surrounded by membranes

• Lack a nucleus

There are three principal parts:– plasma membrane (plasmalemma)– cytoplasm and organelles– nucleus..

Prokaryoticflagella

Nucleoid region (DNA)

RibosomesPlasmamembrane

Cell wall

Capsule

Pili

Cytoskeleton

RibosomesCentriole

LysosomeFlagellum

Not in mostplant cells

Nucleus

Smoothendoplasmicreticulum (ER)Golgi

apparatus

Roughendoplasmicreticulum (ER)

Mitochondrion

Plasmamembrane

Cytoskeleton

Mitochondrion

Nucleus

Rough endoplamsicreticulum (ER)

Ribosomes

Smoothendoplasmicreticulum (ER)

Golgi apparatus

Plasmodesmata

Plasmamembrane

Chloroplast

Cell wall

Centralvacuole

Not in animal cells

• The plasma membrane is composed of a phospholipid bilayer with embedded proteins.

Hydrophilicregion ofprotein

Phospholipidbilayer

Hydrophobicregion of protein

(b) Fluid mosaic model of membrane

• The functions of plasma membrane include:– selectively permeable and surrounds the

cellular contents.– regulates the passage of materials into and out

of the cell.– participates in intercellular communications..

Transport of materials across the plasma membrane

• In general:– large macromolecules cannot cross the

membrane– charged molecules cannot cross the membrane– small, non-charged molecules can cross– water can cross..

• The cytoplasm (cytosol) is the gelatinous material inside the cell membrane but outside the nucleus.

• The cytoplasm contains organelles which are sub-cellular structures that perform discrete functions. True organelles are bounded by a phospholipid membrane..

• The nucleus is a double-membrane organelle containing the nucleic acids (DNA) and at least one nucleolus (contains ribosomal RNA).

• This organelle stores the genetic infor-mation and contains the blueprints for almost all protein syntheses.– DNA RNA protein..

Ribosomes ChromaticNuclearenvelope

Nucleolus Pore

Organelles of a Typical Cell

Storage..Vacuole & vesicle

Packages material for export & processes macromolecules

Golgi Apparatus

Passageway for materials

Produces proteins & processes molecules for secretion

Produces lipids & detoxifies drugs & stores Ca++

Endoplasmic

Reticulum (ER) *Rough

*Smooth

Production of proteins – located attached to ER or free-floating

Ribosome

Aerobic cellular respiration:C6H12O6 + 6O2 6CO2 + 6H2O +ATP

Mitochondria

Carries out photosynthesis:6CO2 + 6H2O C6H12O6 + 6O2

Chloroplasts

Contains digestive enzymes. Each contains one specific enzyme.

Lysosome

Surface projections – increase surface area & produce movement..

Cilia, flagella, microvilli

• Plant cells are encased by cell walls

– These provide support for the plant cells

Walls of two adjacentplant cells

Vacuole

Plasmodesmata(channels between cells)

CELL-CELL INTERACTIONS

• Animal cells lack cell walls– They secrete a sticky covering called the extracellular

matrix– This layer helps hold cells together

• Animal cells connect by various types of junctions– Tight junctions– Adhering junctions– Communicating junctions

Extracellular matrix

(a) Tight junctions

(b) Anchoring junctions

(c) Communicating junctions

Plasma membranesof adjacent cells

Extracellular matrix