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