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Chapter 4
Most Cells Are
Microscopic
Effect of Cell Size on Surface Area
Scanning & Transmission Electron Microscopes
Prokaryotic cells are structurally
simpler than eukaryotic cells
Eukaryotic cells are partitioned into
functional compartments
 Human cells have three basic parts:
 Plasma membrane—flexible outer
boundary
 Cytoplasm—intracellular fluid containing
organelles
 Nucleus—control center
NUCLEUS:
Nuclear envelope
Smooth endoplasmic
reticulum
Chromosomes
Nucleolus
Rough
endoplasmic
reticulum
Lysosome
Centriole
Ribosomes
Peroxisome
CYTOSKELETON:
Microtubule
Intermediate
filament
Microfilament
Golgi
apparatus
Plasma membrane
Mitochondrion
NUCLEUS:
Rough endoplasmic
reticulum
Nuclear envelope
Chromosome
Ribosomes
Nucleolus
Smooth
endoplasmic
reticulum
Golgi
apparatus
CYTOSKELETON:
Central vacuole
Microtubule
Chloroplast
Cell wall
Intermediate
filament
Plasmodesmata
Microfilament
Mitochondrion
Peroxisome
Plasma membrane
Cell wall of
adjacent cell
Plasma Membrane
 Bimolecular layer of lipids
and proteins
 Constantly changing
 Dynamic role in cellular
activity
 Separates intracellular fluid
(ICF) from extracellular fluid
(ECF)
Outside cell
Inside cell
The nucleus is the cell’s genetic control
center
 Contains chromatin, a complex of
proteins and DNA
 Genetic library with blueprints for
nearly all cellular proteins
 Bound by a nuclear envelope with
pores
 Contains a nucleolus, darkstaining spherical bodies w/in
nucleus (ribosome assembly)
The endoplasmic reticulum is a biosynthetic factory
 Interconnected tubes & parallel
membranes (cisternae)
 Continuous with nuclear
membrane
 Two varieties:
 Rough ER-external surface studded
with ribosomes
 Ribosomes are the platform for
protein synthesis
 Smooth ER-lacks ribosomes; functions
in lipid synthesis and detoxification of
drugs, synthesis of steroid sex
hormones
Lysosomes are digestive compartments within a cell
 Spherical membranous bags containing digestive
enzymes (acid hydrolases)
 Digest unwanted material for the cell
Mitochondria harvest chemical energy from food
 Double-membrane
structure with shelflike
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
Chloroplasts convert solar energy to chemical energy
Chloroplast
Stroma
Inner and outer
membranes
Granum
Intermembrane
space
The Golgi apparatus finishes, sorts, and ships cell
products
Stacked and
Rough ER
flattened
membranous
sacs (cisternae)
Phagosome
ER
membrane
Plasma
membrane
Protein
processing
Vesicle becomes
lysosome
Golgi
apparatus
Secretory
vesicle
Secretion by
exocytosis
Extracellular fluid
The cell’s internal skeleton helps organize its
structure and activities
 Elaborate series of rods throughout cytosol
 Microtubules (hollow)
 Microfilaments (solid)
 Intermediate filaments (solid)
Nucleus
Nucleus
Actin subunit
10 nm
7 nm
Microfilament
Tubulin subunit
Fibrous subunits
25 nm
Intermediate filament
Microtubule
Copyright © 2010 Pearson Education, Inc.
Cilia and flagella move when microtubules bend
 Cilia and flagella
 Flagella - whiplike, tails
that move entire cell
 Cilia -short, hairlike
structures that move
substances across cell
surfaces
Membrane Junctions
 Three 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 cell
 For spread of ions between cardiac or smooth muscle
cells
Tight junctions
Anchoring junction
Gap junctions
Plasma membranes
of adjacent cells
Extracellular matrix