Chapter 4

Most Cells Are Microscopic

Prokaryotic cells are structurally simpler than eukaryotic cells

Eukaryotic cells are partitioned into functional compartmentsHuman cells have three basic parts:

Plasma membrane—flexible outer boundary

Cytoplasm—intracellular fluid containing organelles

Nucleus—control center

Smooth endoplasmicreticulum

Roughendoplasmicreticulum

CYTOSKELETON:

NUCLEUS:

Nuclear envelope

Chromosomes

Nucleolus

Ribosomes

Golgiapparatus

Plasma membrane

Mitochondrion

Peroxisome

Centriole

Lysosome

Microtubule

Intermediatefilament

Microfilament

Smooth endoplasmicreticulum

Rough endoplasmicreticulum

CYTOSKELETON:

NUCLEUS:

Nuclear envelope

Chromosome

NucleolusRibosomes

Golgiapparatus

Plasma membrane

Mitochondrion

Peroxisome

Cell wall

Central vacuoleMicrotubule

Intermediatefilament

Microfilament

Cell wall ofadjacent cell

Chloroplast

Plasmodesmata

Plasma MembraneBimolecular layer of

lipids and proteinsConstantly changingDynamic role in cellular

activitySeparates intracellular

fluid (ICF) from extracellular fluid (ECF)

Outside cell

Inside cell

The nucleus is the cell’s genetic control center

Contains chromatinGenetic library with

blueprints for nearly all cellular proteins

Bound by a nuclear envelope with pores

Contains a nucleolus

The endoplasmic reticulum is a biosynthetic factory

Interconnected cisternaeContinuous with nuclear

membraneTwo varieties:

Rough ERSmooth ER

Lysosomes are digestive compartments within a cellSpherical membranous bags containing

digestive enzymes (acid hydrolases)

Mitochondria harvest chemical energy from food

Contains folds called cristae and its own DNA

Provide most of cell’s ATP

Chloroplasts convert solar energy to chemical energy

Chloroplasts: plant organelles ; site of photosynthesis

Found in: All green parts of a plant; leaves are main site of photosynthesis

Contain: green pigment chlorophyll involved in photosynthesis

Chloroplast

Stroma

Inner and outermembranes

Granum

Intermembranespace

Plasmamem-brane

Secretion byexocytosis

Vesicle becomeslysosome

Golgiapparatus

Rough ER ERmembrane

Phagosome

Extracellular fluid

Secretoryvesicle

The Golgi apparatus finishes, sorts, and ships cell products

Stacked and flattened membranous sacs (cisternae)

Protein processing

The cell’s internal skeleton helps organize its structure and activities

Elaborate series of rods throughout cytosolMicrotubules (hollow)Microfilaments (solid)Intermediate filaments (solid)

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Microfilament

Actin subunit

7 nm

Intermediate filament

Fibrous subunits

10 nm

Microtubule

Tubulin subunit

25 nm

Nucleus

Nucleus

Cilia and flagella move when microtubules bend

Cilia and flagellaFlagella - whiplike, tails

that move entire cell

Cilia -short, hairlike structures that move substances across cell surfaces

Membrane JunctionsThree types:Tight junctions- Prevent fluids and most

molecules from moving between cells

Desmosomes- Rivets” or “spot-welds” that anchor cells together

Gap junctions-Transmembrane proteins form pores that allow small molecules to pass from cell to cellFor spread of ions between cardiac or smooth

muscle cells

Tight junctions

Anchoring junction

Gap junctions

Plasma membranesof adjacent cells

Extracellular matrix