Chapter 4
A Tour of the Cell
Laura Coronado
Bio 10
Chapter 4
Biology and Society:
Drugs That Target Bacterial Cells
– Antibiotics were first isolated from mold in 1928.
– The widespread use of antibiotics drastically
decreased deaths from bacterial infections.
• Most antibiotics kill bacteria while minimally
harming the human host by binding to structures
found only on bacterial cells.
• Some antibiotics bind to the bacterial ribosome,
leaving human ribosomes unaffected.
• Other antibiotics target enzymes found only in the
bacterial cells.
Laura Coronado
Bio 10
Chapter 4
Colorized TEM
Laura Coronado
Bio 10
Chapter 4
Figure 4.00
The Microscopic World of Cells
– Organisms are either
• Single-celled, such as most prokaryotes and
protists or
• Multicelled, such as plants, animals, and most
fungi
Laura Coronado
Bio 10
Chapter 4
Microscopes as Windows on the World
of Cells
– Light microscopes can be used to explore the
structures and functions of cells.
– When scientists examine a specimen on a
microscope slide
• Light passes through the specimen
• Lenses enlarge, or magnify, the image
– Magnification is an increase in the specimen’s
apparent size.
– Resolving power is the ability of an optical
instrument to show two objects as separate.
Laura Coronado
Bio 10
Chapter 4
Cell Theory
– Cells were first described in 1665 by Robert
Hooke.
– The accumulation of scientific evidence led to
the cell theory.
• All living things are composed of cells.
• All cells come from other cells.
Laura Coronado
Bio 10
Chapter 4
TYPES OF MICROGRAPHS
Light micrograph of a protist, Paramecium
Colorized TEM
Transmission Electron Micrograph (TEM)
(for viewing internal structures)
Colorized SEM
Scanning Electron Micrograph (SEM)
(for viewing surface features)
LM
Light Micrograph (LM)
(for viewing living cells)
Scanning electron micrograph of Paramecium
Laura Coronado
Bio 10
Chapter 4
Transmission electron micrograph of Paramecium
Figure 4.1
Electron Microscopes
– The electron microscope (EM) uses a beam of
electrons, which results in better resolving
power than the light microscope.
• Magnify up to 100,000 times
• Distinguish between objects 0.2 nanometers apart
– Scanning electron microscopes examine cell
surfaces.
– Transmission electron microscopes (TEM) are
useful for internal details of cells.
Laura Coronado
Bio 10
Chapter 4
Laura Coronado
Bio 10
Chapter 4
Figure 4.2
10 m
Human height
Length of some
nerve and
muscle cells
Unaided eye
1m
10 cm
Chicken egg
1 cm
Frog eggs
Light microscope
1 mm
100 mm
Plant and
animal cells
1 mm
100 nm
Nucleus
Most bacteria
Mitochondrion
Electron microscope
10 mm
Smallest bacteria
Viruses
Ribosomes
10 nm
Proteins
Lipids
1 nm
0.1 nm
Small molecules
Atoms
Laura Coronado
Bio 10
Chapter 4
Figure 4.3
The Two Major Categories of Cells
– The countless cells on earth fall into two
categories:
• Prokaryotic cells — Bacteria and Archaea
• Eukaryotic cells — plants, fungi, and animals
– All cells have several basic features.
• They are all bound by a thin plasma membrane.
• All cells have DNA and ribosomes, tiny structures
that build proteins.
Laura Coronado
Bio 10
Chapter 4
Differences Between Prokaryotic &
Eukaryotic Cells
– Prokaryotic and eukaryotic cells have
important differences.
– Prokaryotic cells are older than eukaryotic
cells.
• Prokaryotes appeared about 3.5 billion years ago.
• Eukaryotes appeared about 2.1 billion years ago.
Laura Coronado
Bio 10
Chapter 4
Prokaryotes
– Are smaller than
eukaryotic cells
– Lack internal
structures
surrounded by
membranes
– Lack a nucleus
– Have a rigid cell
wall
Laura Coronado
Bio 10
Chapter 4
Plasma membrane
(encloses cytoplasm)
Cell wall (provides rigidity)
Capsule (sticky coating)
Prokaryotic
flagellum
(for propulsion)
Ribosomes
(synthesize
proteins)
Nucleoid
(contains DNA)
Pili (attachment
structures)
Bio 10 Chapter 4
Laura Coronado
Figure 4.4a
Eukaryotes
– Eukaryotes
• Only eukaryotic cells have organelles,
membrane-bound structures that perform
specific functions.
• The most important organelle is the
nucleus, which houses most of a eukaryotic
cell’s DNA.
Laura Coronado
Bio 10
Chapter 4
An Overview of Eukaryotic Cells
– Eukaryotic cells are fundamentally similar.
– The region between the nucleus and plasma
membrane is the cytoplasm.
– The cytoplasm consists of various organelles
suspended in fluid.
– Make up animal & plant cells
– Unlike animal cells plant cells have
• Protective cell walls
• Chloroplasts, which convert light energy to the
chemical energy of food
Laura Coronado
Bio 10
Chapter 4
Centriole
Lysosome
Ribosomes
Cytoskeleton
Flagellum
Not in most
plant cells
Plasma
membrane
Nucleus
Mitochondrion
Rough
endoplasmic
reticulum (ER)
Smooth
endoplasmic
reticulum (ER)
Golgi
apparatus
Idealized animal cell
Laura Coronado
Bio 10
Chapter 4
Figure 4.5a
Cytoskeleton
Central
vacuole
Cell wall
Chloroplast
Mitochondrion
Nucleus
Not in
animal cells
Rough endoplasmic
reticulum (ER)
Ribosomes
Plasma
membrane
Smooth
endoplasmic
reticulum (ER)
Channels between
cells
Golgi apparatus
Idealized plant cell
Laura Coronado
Bio 10
Chapter 4
Figure 4.5b
MEMBRANE STRUCTURE
– The cell membranes are composed mostly of
• Phospholipids & Proteins
– Phospholipids form a two-layered membrane,
the phospholipid bilayer.
– The plasma membrane separates the living cell
from its nonliving surroundings.
– The plasma membrane is a fluid mosaic:
• Fluid because molecules can move freely past one
another
• A mosaic due to the diversity of proteins membrane
Laura Coronado
Bio 10
Chapter 4
Outside of cell
Hydrophilic
region of
protein
Hydrophilic
head
Hydrophobic
tail
Proteins
Outside of cell
Hydrophilic
head
Phospholipid
bilayer
Hydrophobic
tail
Phospholipid
Cytoplasm (inside of cell)
(a) Phospholipid bilayer of
membrane
Hydrophobic
regions of
protein
Cytoplasm (inside of cell)
(b) Fluid mosaic model of
membrane
Laura Coronado
Bio 10
Chapter 4
Figure 4.6
Cell Membrane Proteins
– Most membranes have specific proteins
embedded in the phospholipid bilayer.
– These proteins help regulate traffic across the
membrane and perform other functions.
Laura Coronado
Bio 10
Chapter 4
The Process of Science:
What Makes a Superbug?
– Observation: Bacteria use a protein called PSM
to disable human immune cells by forming
holes in the plasma membrane.
– Question: Does PSM play a role in MRSA
infections?
– Hypothesis: MRSA bacteria lacking the ability
to produce PSM would be less deadly than
normal MRSA strains.
Laura Coronado
Bio 10
Chapter 4
The Process of Science:
What Makes a Superbug?
– Experiment: Researchers infected
• Seven mice with normal MRSA
• Eight mice with MRSA that does not produce PSM
– Results:
• All seven mice infected with normal MRSA died.
• Five of the eight mice infected with MRSA that
does not produce PSM survived.
Laura Coronado
Bio 10
Chapter 4
The Process of Science:
What Makes a Superbug?
– Conclusions:
• MRSA strains appear to use the membranedestroying PSM protein, but
• Factors other than PSM protein contributed to the
death of mice
Laura Coronado
Bio 10
Chapter 4
Colorized SEM
MRSA bacterium
producing PSM
proteins
Methicillin-resistant
Staphylococcus aureus (MRSA)
PSM proteins
forming hole
in human
immune cell
plasma
membrane
PSM
protein
Plasma
membrane
Pore
Cell bursting,
losing its
contents
through
the pores
Laura Coronado
Bio 10
Chapter 4
Figure 4.7-3
Cell Wall
– Plant cells have rigid cell walls surrounding
the membrane.
– Plant cell walls
• Are made of cellulose
• Protect the cells
• Maintain cell shape
• Keep the cells from absorbing too much water
Laura Coronado
Bio 10
Chapter 4
Animal Cells
– Animal cells
• Lack cell walls
• Have an extracellular matrix, which
–Helps hold cells together in tissues
–Protects and supports them
– The surfaces of most animal cells contain cell
junctions, structures that connect to other
cells.
Laura Coronado
Bio 10
Chapter 4
THE NUCLEUS
– The nucleus is the chief executive of the cell.
• Genes in the nucleus store information necessary
to produce proteins.
• Proteins do most of the work of the cell.
Laura Coronado
Bio 10
Chapter 4
Nucleus Structure and Function
– Nuclear envelope borders the nucleus and is a
double membrane.
– Pores in the envelope allow materials to move
between the nucleus and cytoplasm.
– The nucleus contains a nucleolus where ribosomes
are made.
– Chromatin are long DNA molecules and associated
proteins that form fibers.
• Stored in the nucleus
• Each chromatin fiber equals one chromosome.
Laura Coronado
Bio 10
Chapter 4
Nuclear
envelope
Nucleolus
Pore
TEM
Chromatin
TEM
Ribosomes
Surface of nuclear envelope
Laura Coronado
Nuclear pores
Bio 10
Chapter 4
Figure 4.8
DNA molecule
Proteins
Chromatin
fiber
Chromosome
Laura Coronado
Bio 10
Chapter 4
Figure 4.9
Ribosomes
– Ribosomes are responsible for protein
synthesis.
– Ribosome components are made in the
nucleolus but assembled in the cytoplasm.
– Ribosomes may assemble proteins:
• Suspended in the fluid of the cytoplasm or
• Attached to the outside of an organelle called the
endoplasmic reticulum
Laura Coronado
Bio 10
Chapter 4
Ribosome
mRNA
Protein
Laura Coronado
Bio 10
Chapter 4
Figure 4.10
TEM
Ribosomes in
cytoplasm
Ribosomes attached
to endoplasmic
reticulum
Laura Coronado
Bio 10
Chapter 4
Figure 4.11
How DNA Directs Protein Production
– DNA directs protein production by transferring its
coded information into messenger RNA (mRNA).
– Messenger RNA exits the nucleus through pores in
the nuclear envelope.
– A ribosome moves along the mRNA translating the
genetic message into a protein with a specific amino
acid sequence.
Laura Coronado
Bio 10
Chapter 4
DNA
Synthesis of
mRNA in the
nucleus
mRNA
Nucleus
Cytoplasm
Movement of
mRNA into
cytoplasm
via
nuclear pore
mRNA
Ribosome
Synthesis of
protein in the
cytoplasm
Laura Coronado
Protein
Bio 10
Chapter 4
Figure 4.12-3
THE ENDOMEMBRANE SYSTEM
– Many membranous organelles forming the
endomembrane system in a cell are
interconnected either
• Directly or
• Through the transfer of membrane segments
between them
– The endoplasmic reticulum (ER) is one of
the main manufacturing facilities in a cell.
• Produces an enormous variety of molecules
• Is composed of smooth and rough ER
Laura Coronado
Bio 10
Chapter 4
Nuclear
envelope
Ribosomes
Smooth ER
TEM
Rough ER
Laura Coronado
Bio 10
Ribosomes
Chapter 4
Figure 4.13
Endoplasmic Reticulum
– Rough ER (RER) is due to ribosomes that stud
the outside of the ER membrane.
• RER produce membrane proteins and secretory
proteins.
• After the rough ER synthesizes a molecule, it
packages the molecule into transport vesicles.
– Smooth ER (SER) lacks surface ribosomes
• Produces lipids, including steroids
• Helps liver cells detoxify circulating drugs
Laura Coronado
Bio 10
Chapter 4
Proteins are
often modified in
the ER.
Secretory
proteins depart in
transport vesicles.
Ribosome
Vesicles bud off
from the ER.
Transport
vesicle
Protein
A ribosome
links amino acids
into a
polypeptide.
Rough ER
Polypeptide
Laura Coronado
Bio 10
Chapter 4
Figure 4.14
The Golgi Apparatus
– The Golgi apparatus
• Works in partnership with the ER
• Receives, refines, stores, and distributes
chemical products of the cell
Video: Euglena
Laura Coronado
Bio 10
Chapter 4
“Receiving” side of
Golgi apparatus
Transport vesicle
from rough ER
“Receiving” side
of Golgi
apparatus
New
vesicle
forming
Transport
vesicle
from the
Golgi
“Shipping” side
of Golgi
apparatus
Plasma
membrane
New vesicle forming
Laura Coronado
Bio 10
Chapter 4
Figure 4.15
Transport vesicle
from rough ER
“Receiving” side of
Golgi apparatus
New
vesicle
forming
Transport
vesicle
from the
Golgi
“Shipping” side of
Golgi apparatus
Laura Coronado
Bio 10
Chapter 4
Plasma
membrane
Figure 4.15a
Lysosomes
– A lysosome is a sac of digestive enzymes found
in animal cells.
– Enzymes in a lysosome can break down large
molecules such as
• Proteins
• Polysaccharides
• Fats
• Nucleic acids
Laura Coronado
Bio 10
Chapter 4
Lysosome Functions
– Lysosomes have several of digestive functions.
• Many cells engulf nutrients in tiny cytoplasmic sacs
called food vacuoles.
• These food vacuoles fuse with lysosomes, exposing
food to enzymes to digest the food.
• Small molecules from digestion leave the lysosome
and nourish the cell.
– Lysosomes can also
• Destroy harmful bacteria
• Break down damaged organelles
Laura Coronado
Bio 10
Chapter 4
Plasma membrane
Digestive enzymes
Lysosome
Lysosome
Digestion
Food vacuole
Vesicle containing
damaged organelle
(a) Lysosome digesting food
Digestion
(b) Lysosome breaking down the molecules of damaged
organelles
Organelle fragment
Vesicle containing two
damaged organelles
TEM
Organelle fragment
Laura Coronado
Bio 10
Chapter 4
Figure 4.16
Plasma membrane
Digestive enzymes
Lysosome
Digestion
Food vacuole
(a) Lysosome digesting food
Laura Coronado
Bio 10
Chapter 4
Figure 4.16a
Lysosome
Digestion
Vesicle containing
damaged organelle
(b) Lysosome breaking down the molecules of damaged organelles
Laura Coronado
Bio 10
Chapter 4
Figure 4.16b
Vacuoles
– Vacuoles are membranous sacs that bud from:
• ER
• Golgi
• Plasma membrane
– Contractile vacuoles of protists pump out excess
water in the cell.
– Central vacuoles of plants
• Store nutrients
• Absorb water
• May contain pigments or poisons
Laura Coronado
Bio 10
Chapter 4
LM
Vacuole filling with water
LM
Vacuole contracting
Central vacuole
Colorized TEM
(a) Contractile vacuole in Paramecium
(b) Central
vacuole in a plant cell
Laura Coronado Bio 10 Chapter 4
Figure 4.17
TEM
Vacuole filling with water
TEM
Vacuole contracting
(a) Contractile vacuole Laura
in Paramecium
Coronado Bio 10
Chapter 4
Figure 4.17a
Endomembrane System
– To review, the endomembrane system interconnects
the
•
•
•
•
•
•
Nuclear envelope
ER
Golgi
Lysosomes
Vacuoles
Plasma membrane
Video: Chlamydomonas
Blast Animation : Vesicle Transport Along Microtubules
Laura Coronado
Bio 10
Chapter 4
Golgi
apparatus
Rough ER
Transport
vesicle
Transport vesicles
carry enzymes and
other proteins from
the rough ER to the
Golgi for processing.
Transport
vesicle
Plasma
membrane
Secretory
protein
Some products
are secreted
from the cell.
Vacuole
Lysosome
Lysosomes carrying
digestive enzymes can
fuse with other vesicles.
Vacuoles store some
cell products.
Laura Coronado
Bio 10
Chapter 4
Figure 4.18a
CHLOROPLASTS AND MITOCHONDRIA:
ENERGY CONVERSION
– Cells require a constant energy supply to perform the
work of life.
Laura Coronado
Bio 10
Chapter 4
Chloroplasts
– Most of the living world runs on the energy provided
by photosynthesis.
– Photosynthesis is the conversion of light energy from
the sun to the chemical energy of sugar.
– Chloroplasts are the organelles that perform
photosynthesis.
– Chloroplasts have three major compartments:
• The space between the two membranes
• The stroma, a thick fluid within the chloroplast
• The space within grana, the structures that trap
light energy and convert it to chemical energy
Laura Coronado
Bio 10
Chapter 4
Inner and outer
membranes
Space between
membranes
Granum
Laura Coronado
Bio 10
Chapter 4
TEM
Stroma (fluid in chloroplast)
Figure 4.19
Mitochondria
– Mitochondria are the sites of cellular
respiration, which produce ATP from the
energy of food molecules.
– Mitochondria are found in almost all
eukaryotic cells.
– An envelope of two membranes encloses the
mitochondrion. These consist of
• An outer smooth membrane
• An inner membrane that has numerous infoldings
called cristae
Laura Coronado
Bio 10
Chapter 4
TEM
Outer
membrane
Inner
membrane
Cristae
Matrix
Space between
membranes
Laura Coronado
Bio 10
Chapter 4
Figure 4.20
Mitochondria & Chloroplasts
– Mitochondria and chloroplasts contain their own
DNA, which encodes some of their proteins.
– This DNA is evidence that mitochondria and
chloroplasts evolved from free-living prokaryotes in
the distant past.
Laura Coronado
Bio 10
Chapter 4
THE CYTOSKELETON
– A network of fibers extending throughout the
cytoplasm.
• Provides mechanical support to the cell
• Maintains its shape
• Contains several types of fibers made from different
proteins:
–Microtubules are straight and hollow & guide the
movement of organelles and chromosomes
–Intermediate filaments and microfilaments are
thinner and solid.
Laura Coronado
Bio 10
Chapter 4
LM
(a) Microtubules
in the cytoskeleton
LM
(b) Microtubules
and movement
Laura Coronado
Bio 10
Chapter 4
Figure 4.21
Cilia and Flagella
– Cilia and flagella aid in movement.
• Flagella propel the cell in a whiplike motion.
• Cilia move in a coordinated back-and-forth motion.
• Cilia and flagella have the same basic architecture.
– Cilia may extend from nonmoving cells.
– On cells lining the human trachea, cilia help sweep
mucus out of the lungs.
Video: Prokaryotic Flagella (Salmonella typhimurium)
Video: Paramecium Cilia
Animation: Cilia and Flagella
Laura Coronado
Bio 10
Chapter 4
Colorized SEM
Colorized SEM
Colorized SEM
(b) Cilia on a protist
(a) Flagellum of a human sperm cell
Laura Coronado
Bio 10
(c) Cilia lining the
respiratory tract
Chapter 4
Figure 4.22
Evolution Connection:
The Evolution of Antibiotic Resistance
– Many antibiotics disrupt cellular structures of invading
microorganisms.
– Introduced in the 1940s, penicillin worked well against
such infections.
– But over time, bacteria that were resistant to
antibiotics were favored.
– The widespread use and abuse of antibiotics continues
to favor bacteria that resist antibiotics.
Laura Coronado
Bio 10
Chapter 4
Laura Coronado
Bio 10
Chapter 4
Figure 4.23
CATEGORIES OF CELLS
Prokaryotic Cells
Eukaryotic Cells
• Smaller
• Simpler
• Most do not have organelles
• Found in bacteria and archaea
Laura Coronado
• Larger
• More complex
• Have organelles
• Found in protists, plants,
fungi, animals
Bio 10
Chapter 4
Figure 4.UN12
Outside of cell
Phospholipid
Hydrophilic
Hydrophobic
Protein
Hydrophilic
Cytoplasm (inside of cell)
Laura Coronado
Bio 10
Chapter 4
Figure 4.UN13
Mitochondrion
Chloroplast
Light energy
PHOTOSYNTHESIS
Laura Coronado
Chemical
energy
(food)
Bio 10
Chapter 4
CELLULAR
RESPIRATION
Figure 4.UN14
ATP