Cell Theory
 Cells are the basic living units of
organization and function
 All cells come from other cells
 Work of Schleiden, Schwann,
and Virchow contributed to this
theory
 Each cell is a microcosm of life
Biological Size and Cell Diversity
 Cell surface area-to-volume ratio
 Plasma membrane must be large
enough relative to cell volume to
regulate passage of materials
 Volume increases faster than
surface area so cells must divide
 Cell size and shape related to
function
Cell Surface Area-to-Volume Ratio
 Microscopes
 Light microscope, referred to as
compound microscope, used by most
students
 Two features determine how clearly
an object is viewed
 Magnification
 Resolution
 Light microscope has 500 times more
resolution than human eye
Electron microscope
 Developed in the 1950s
 Allows study of the
ultrastructure of cells
 10,000 times more resolution
than human eye
Types of electron microscope
 Transmission electron microscope
TEM

Used to view internal cell structures
 Scanning electron microscope SEM
 Produces 3-D picture of cell surface
 Can’t be used to view living cells
Comparing light and electron microscopy
 Cell fractionation
 Used to determine isolate & tell
function of organelles
 Cells broken apart and the resulting
cell extract spun in a centrifuge
 Centrifugal force separates extract
 Pellet – heavier cell organelles
 Supernatant – liquid poured off
Cell fractionation
 Prokaryotic
 Bacteria and Archaea (ancient
bacteria)
 DNA not enclosed in a nucleus
 Eukaryotic
 All other known organisms
 Highly organized membraneenclosed organelles
 Cytoplasm
 Nucleoplasm
 Functions of cell or plasma
membranes
 Divide cell into compartments,
allowing for specialized activities
 Interacting membranes form
endomembrane system
 Vesicles transport materials
between compartments (ER 
Golgi, Golgi  plasma
membrane…)
Diagram
of
a plant
cell
Diagram
of
an
animal
cell
 The cell nucleus
 Contains DNA
 Bounded by
Nuclear envelope
 Double membrane perforated with
nuclear pores
 DNA forms chromatin, which is
organized into chromosomes
 Nucleolus
 RNA synthesis and ribosome
assembly

The cell
nucleus
 Endoplasmic reticulum (ER)
 Network of folded internal membranes
in the cytosol
 Connected to Nuclear envelope
 Smooth ER




Site of lipid synthesis
Site of detoxifying enzymes
Detoxifies drugs & alcohol
Stores Ca++ in muscle cells
 Rough ER
 Ribosomes on surface manufacture
secretory proteins
 Proteins may be moved into the ER lumen
(interior)
Endoplasmic
reticulum
(ER)
 Golgi complex
 Cisternae that process, sort, and
modify proteins
 In animal cells, Golgi complex also
manufactures lysosomes
 Glycoproteins
 Transported to the cis face
(receiving side)
 Golgi modifies carbohydrates and
lipids and packages into vesicles
that pinch off the trans face
(shipping side)
Golgi complex
 Lysosomes break down worn-out
cell structures, bacteria, and
other substances

Responsible for cell death &
recycling
 Peroxisomes
 Involved in lipid metabolism and
detoxification
 Contain enzymes (catalase) that
produce and degrade hydrogen
peroxide H2O2  H2O + O2
Lysosomes
 Mitochondria
 Sites of aerobic respiration
 Organelles enclosed by a double
membrane
 Has its own genome
 Place important role in apoptosis
 Cristae (internal folds) and matrix
(innermost space) contain enzymes for
aerobic respiration


Nutrients broken down and energy
packaged in ATP
Carbon dioxide and water by-products
Mitochondria
 Chloroplasts
 Plastids that carry out
photosynthesis
 Inner membrane of chloroplast
encloses the stroma gel-like liquid)
 Contains stacks of interconnected
sacs called thylakoids
 Stack of thylakoids called grana
 During photosynthesis, chlorophyll
traps light energy (sunlight)
 Energy converted to chemical energy
in ATP
Chloroplast
Cellular respiration and photosynthesis
 Cytoskeleton
 Internal framework made of
Microtubules - tubulin
 Microfilaments - actin
 Intermediate filaments - keratin
 Provides structural support
 Involved with transport of materials
in the cell
 Make up cilia, flagella, and
centrioles

The
Cytoskeleton
 Cilia and flagella
 Thin, movable structures that
project from cell surface
 Function in movement
 Microtubles anchored in cell by
basal body
Structure
of cilia
 Glycocalyx
 Cell coat formed by
polysaccarides extending from
plasma membrane
 Many animal cells also
surrounded by an extracellular
matrix (ECM)
 Most bacteria, fungi, and plant
cell walls made of carbohydrates
Extracellular matrix
Plant
cell walls