Download Chapter 4

A Tour of the Cell
 Every
living organism is composed of one or
more cells
 A cell is the smallest unit having the
properties of life
 The continuity of life directly arises from the
growth and division of single cells
 Plasma


membrane
Phospholipid bilayer
Regulates transport
in/out of cell
 Genetic


material (DNA)
Nucleus—eukaryotic
Nucleoid—prokaryotic
 Cytoplasm


Fills cell
Contains organelles or
cell structures
 Metabolic
activity related to cell volume and
surface area
 Volume increases faster than surface area
 The speed and amount of “stuff” (waste &
nutrients) across a cell membrane is
determined by the surface area
 Larger cell volume needs more nutrients and
produces more waste
 Eventually the cell becomes big enough that
the membrane can’t transport “stuff” fast
enough
 Prokaryotes




“Before the nucleus”—no
nucleus or membranecovered structures
(organelles)
Bacteria
Very small
Simplest cells
 Eukaryotes


Nucleus and other complex
organelles
Organelle—internal
membrane-bound
compartment that serves
specialized functions.
“Little organs”
 Nucleoid
region
 DNA (single loop)
 Cell membrane
 Cell wall (in some)
 Capsule (in some)
 Cytoplasm
 Ribosomes
 Pili
 Flagellum
 Most





kinds of living organisms
Protozoans
Algae
Fungi
Plants
Animals
 Organelles

allow compartmentalizing
Different areas of the cell can carry on reactions
without affecting the rest of the cell
 Complex
systems
 Nucleus


Control center
Nucleolus


Constructs ribosomes
Chromatin



All DNA in cell
Organized into
chromosomes
6 Feet of DNA in one
nucleus!!!
 Nucleus

Nuclear envelope/membrane



(cont.)
Regulates transport of molecules
Receptors for signaling
Nuclear pores

Allow communication with cytoplasm
 Endoplasmic

Rough



Reticulum (ER)
Ribosomes attach
Protein synthesis
Smooth



No ribosomes
Lipid synthesis
Carbohydrate synthesis
 Ribosomes


Synthesize proteins
On rough ER
 Golgi




Body/Apparatus
Package and process proteins & lipids
“Warehouse & finishing factory”
Receives vesicles from ER
Produces vesicles for finished products
 Endomembrane


system
Interconnecting membrane system
Nuclear membrane  Rough ER  Smooth ER  Golgi
apparatus  lysosomes/vacuoles  plasma membrane
 Vesicles—sacs

Lysosomes




containing enzymes
Intracellular digestion
Destroy bacteria in white blood cells
Breaks down damaged organelles
Peroxisomes


Break down fatty acids & proteins
Detoxify alcohol & other toxic substances
 Vacuoles—large
vesicles for storing food &
water

Only some eukaryotes
 Mitochondria




Forms ATP (energy) from
carbohydrates
Requires oxygen
Site of cellular respiration
Similar to bacteria: have
their own DNA & ribosomes

May be artifact of ancient
symbiotic relationship
between prokaryotes &
eukaryotes
 Plastids

Chlorloplasts



Amyloplasts



Photosynthesis (energy
from light)
Only in plant cells
Store starches
Specialized chloroplast
Like mitochondria, may
be artifact of ancient
symbiotic relationship
between prokaryotes &
eukaryotes
 Central

Vacuole
Storage (amino
acids, sugars, ions,
wastes)
 Centrioles—produce
cell division.
microfilaments during
 Protein
filaments between nucleus & plasma
membrane
 Internal shape & organization
 Can be permanent or temporary

Microtubules
Keep organelles & cell
structures in place or move
them
 Microfilaments
 Centrioles
 Thin filaments
 Compose cilia & flagellae
 Help in cell division
 Intermediate filaments
(contracts midsection)
 Ropelike structure
 Anchor membrane proteins
 Reinforce cell shape
 Help support cell shape
 Anchor some organelles
 Muscle contraction (actin
filaments)
 More permanent than other
cytoskeleton

 Motor
proteins move things within cells
 Flagella—long outer structures for movement

Usually only a few
 Cilia—short

outer structures for movement
Usually many
 Pseudopod

“False foot”
 Structures
outside of the plasma membrane
 Holds cells together in tissues
 Protects & supports plasma membrane
 Collagen


Glycoproteins
Strong fibers
 Plasma


(cell) membrane
Regulates movement of “stuff” in and out of cell
Phospholipid bilayer
 Animal

Tight junctions


Tight seal, prevents
leakage of fluids
Anchoring junctions



Cell Junctions
Rivets
Fasten cells together
Gap junctions




Channels, pores
Allow small molecules
to travel between
neighboring cells
Cell-to-cell
communication
Nutrient & waste
transfer
 Cell



wall
Strong, gives
permanent shape
to cell
Bacteria, protists,
fungi, plants
Not found in
animals
 Plasmodesmata


Junctions between
plant cell walls
Circulation and
communication
between cells