Cell Structure and Function
 Smallest
 Can
unit of life
survive on its own or has potential to do
so
 Is
highly organized for metabolism
 Senses
 Has
and responds to environment
potential to reproduce
All start out life with:

Plasma membrane

Region where DNA is
stored

Cytoplasm
Two types:


Prokaryotic
Eukaryotic
Prokaryotic and Eukaryotic Cells
cytoplasm
DNA
plasma membrane
Fig. 4-3a, p.52
Prokaryotic
and
Eukaryotic
Cells
DNA in
nucleus
cytoplasm
plasma
membrane
Fig. 4-3c, p.52
Plasma Membrane
Defines the cell as a distinct entity (p52)
Fig. 4-4, p.52
Plasma Membrane
Recognition
protein
Receptor
protein
extracellular
environment
lipid
bilayer
cytoplasm
Protein
pump across
bilayer
Protein
channel across
bilayer
Protein pump
Fig. 4-5a, p.53
 Main
component of cell
membranes
 Gives
the membrane its
fluid properties
 Two
layers of
phospholipids
 Membrane




is a mosaic of
Phospholipids
Glycolipids
Sterols
Proteins
 Most
phospholipids and some proteins can
drift through membrane
 Adhesion
proteins
 Communication
 Receptor
proteins
proteins
 Recognition
proteins
 Surface-to-volume
 The
ratio
bigger a cell is, the less surface area
there is per unit volume
 Above
a certain size, material cannot be
moved in or out of cell fast enough
 Mid
1600s - Robert Hooke observed and
described cells in cork
 Late
1600s - Antony van Leeuwenhoek
observed sperm, microorganisms
 1820s
- Robert Brown observed and named
nucleus in plant cells
 Matthias
Schleiden
 Theodor
Schwann
 Rudolf
Virchow
1) Every organism is composed of one or more
cells
2) Cell is smallest unit having properties of life
3) Continuity of life arises from growth and
division of single cells
 Create
detailed images of
something that is otherwise too
small to see
 Light

microscopes
Simple or compound
 Electron

microscopes
Transmission EM or Scanning EM
Ocular lens enlarges
primary image formed
by objective lenses.
Objective lenses (those closest
to specimen) form the primary
image. Most compound light
microscopes have several.
path of light rays (bottom to top) to eye
prism that
directs rays to
ocular lens
stage (holds microscope
slide in position)
Condenser lenses
focus light rays
through specimen.
illuminator
source of illumination
(housed in the base
of the microscope)
Fig. 4-7a, p.54
 Uses
streams of accelerated electrons rather
than light
 Electrons
are focused by magnets rather than
glass lenses
 Can
resolve structures down to 0.5 nm
 Wavelengths
of light are 400-750 nm
 If
a structure is less than one-half of a
wavelength long, it will not be visible
 Light
microscopes can resolve objects down
to about 200 nm in size
 Different
microscopes reveal different aspects
of this Green Algae
Fig. 4-9, p.55
 Archaea
 DNA
and eubacteria
is not enclosed in nucleus
 Generally
 No
the smallest, simplest cells
organelles
 MOST
OF THESE ORGANELLE FUNCTIONS ARE
CARRIED OUT IN THE CYTOPLASM (CYTOSOL)
bacterial flagellum
plasma membrane
pilus
bacterial flagellum
Most prokaryotic cells have a cell
wall outside the plasma
membrane, and many have
a thick, jellylike capsule around
the wall.
cytoplasm, with
ribosomes
DNA in
nucleoid
region
 Have
a nucleus and other
organelles
 Eukaryotic organisms




Plants
Animals
Protistans
Fungi
Plant Cell
Fig. 4-13, p.58
CELL WALL CHLOROPLAST
CENTRAL
VACUOLE
NUCLEUS
CYTOSKELETON
RIBOSOMES
ROUGH ER
MITOCHONDRION
SMOOTH ER
PLASMODESMA
GOLGI BODY
PLASMA
MEMBRANE
LYSOSOMELIKE VESICLE
Fig. 4-14, p.58
NUCLEUS
CYTOSKELETON
RIBOSOMES
ROUGH ER
MITOCHONDRION
SMOOTH ER
CENTRIOLES
GOLGI BODY
PLASMA
MEMBRANE
LYSOSOME
 Keeps
the DNA molecules of eukaryotic cells
separated from metabolic machinery of
cytoplasm
 Makes
it easier to organize DNA and to copy
it before parent cells divide into daughter
cells
 The
changing appearance of a chromosome
p.61
 Group
of related organelles in which lipids
are assembled and new polypeptide chains
are modified
 Products
are sorted and shipped to various
destinations
 Endoplasmic
 Golgi
bodies
 Vesicles
reticulum
 Arranged
into flattened sacs
 Ribosomes
on surface give it a rough
appearance
 Some
polypeptide chains enter rough ER and
are modified
 Cells
that specialize in secreting proteins
have lots of rough ER
 Produce
proteins
 They are made in the nucleolus
 Bound ribosomes—bound to rough ER;
produce proteins that travel on to reach the
Golgi complex to be packaged as a
glycoprotein, may reach lysosome to act as a
digestive enzyme, fuse with cell membrane
to function as membrane proteins, or get
excreted from cell
 Free ribosomes—produced in cytosol
(cytoplasm); proteins can act as structural
proteins or messenger proteins
A
series of interconnected tubules
 No ribosomes on surface
 Lipids assembled inside tubules
 Smooth ER of liver inactivates
wastes, drugs
 Sarcoplasmic reticulum of muscle is a
specialized form
 Put
finishing touches on proteins and
lipids that arrive from ER
 Package finished material for shipment
to final destinations
 Material arrives and leaves in vesicles
 Membranous
sacs that move
through the cytoplasm
 Lysosomes
 Peroxisomes
 Fluid-filled
 Stores
organelle
amino acids, sugars, wastes
 As
cell grows, expansion of vacuole as a result of
fluid pressure forces cell wall to expand
 In
mature cell, central vacuole takes up 50-90
percent of cell interior
 ATP-producing
powerhouses
 Double-membrane
 Carry
system
out the most efficient energy-
releasing reactions
 These
reactions require oxygen
Outer
mitochondrial
membrane
outer
compartment
Inner
mitochondrial
membrane
Mitochondria
inner
compartment
Fig. 4-19b, p.64
 Outer
 Inner
membrane faces cytoplasm
membrane folds back on itself
 Membranes
 ATP-making
form two distinct compartments
machinery is embedded in the
inner mitochondrial membrane
Convert sunlight energy to ATP through
photosynthesis
chloroplast in the cytoplasm of
a plant cell
central vacuole
Thylakoid
membrane, a muchfolded single
flattened
compartment inside
the stroma
two outer membranes
stroma (semifluid
interior)
Fig. 4-20, p.65
 Two
outer membranes around semifluid interior
(stroma) – bathes inner membrane
 Often, this single membrane is folded back on
itself as a series of stacked, flattened disks
 Each stack is called a thylakoid, which contains
chlorophylls and other substances involved in
photosynthesis
 Both
mitochondria and chloroplasts resemble
bacteria
 Have
own DNA, RNA, and ribosomes
 Organelles
such as mitochondrion and
chloroplast are believed to have once been a
free living prokaryote that arose out of a
symbiotic relationship
 Evidence favoring this theory:
These organelles have their own DNA, it is
circular DNA like found in bacteria, their DNA
lack histone proteins like in bacteria, they
have a double membrane, they can selfreplicate
Plasma membrane
 Structural
component
that wraps around the
plasma membrane
 Occurs in plants, some
fungi, some protistans
Primary cell wall of a young
plant
Secondary cell wall
(3 layers)
Primary cell wall
 Cell
secretions and waxes accumulate at
plant cell surface
 Semi-transparent
 Restricts
water loss
thick, waxy
cuticle at leaf
surface
cell of leaf
epidermis
photosynthetic
cell inside leaf
Fig. 4-22a, p.67
 Plants
 Plasmodesmata
 Animals
 Tight
junctions
 Adhering junctions
 Gap junctions
plasmodesma
 Present
 Basis
in all eukaryotic cells
for cell shape and internal organization
 Allows
organelle movement within cells and,
in some cases, cell motility
microtubule
microfilament
intermediate
 Largest
elements
 Composed
of the protein tubulin
 Arise
from microtubule organizing centers
(MTOCs)
 Polar
and dynamic
 Involved
in shape, motility, cell division
 Thinnest
cytoskeletal elements
 Composed
 Polar
 Take
of the protein actin
and dynamic
part in movement, formation and
maintenance of cell shape
 Present
 Most
 Six

only in animal cells of certain tissues
stable cytoskeletal elements
known groups
Desmins, vimentins, lamins, etc.
 Different
kinds
cell types usually have 1-2 different
 Length
of microtubules or
microfilaments can change
 Parallel rows of microtubules
or microfilaments actively
slide in a specific direction
 Microtubules
or
microfilaments can shunt
organelles to different parts
of cell
 Structures
for
cell motility
9
+ 2 internal
structure
spokes, rings
of connective
system
central
sheath
one central pair
of microtubules
plasma
membrane
one of nine pairs of microtubules with
dynein arms down their length
microtubules near base of flagellum or cilium
basal body (embedded in the cytoplasm)
plasma
membrane
 Some
free-living cells, such as amoebas, form
pseudopods (“false feet”)
 These temporary, irregular lobes project from
the cell and function in locomotion and prey
capture
 Pseudopods move as microfilaments elongate
inside them – motor proteins attached to the
microfilaments drag the plasma membrane with
them
Cilia
Fig. 4-28a, p.70
Flagellum
Fig. 4-28b,c, p.70
False Feet
Fig. 4-28b,c, p.70
Cilia
Fig. 4-29a, p.71
 LYSOSOMES—
 PEROXISOMES—
 EXTRACELLULAR
 CENTRIOLES—
MATRIX—
http://www.youtube.com/watch?v=1Z9pqST72
is&feature=c4overview&playnext=1&list=TLXLPZXEDTy6g