Chapter 6
Cell Theory
cell |
fundamental unit of structure and function
for all living organisms
arise only from previously existing cell
Figure 5.4 The size range of cells
WHY are your brain
cells the same size
as hamster brain
cells?
– diffusion
– plasma membrane
1
• light - 0.1-0.2 um (most organelles smaller)
–compound (one plane at a time)
–magnify in stages using multiple lenses
DIFFERENTIAL INTERFERENCE
• confocal (eliminates blurring, 3D image)
FLUORESCENCE
Resolution - minimum distance two points can be apart and
still be distinguished as two separate points
• electron - 0.00001 um
–transmission (electrons absorbed differently, thin sections)
–scanning ATOMIC LEVEL!(electrons bounced off – 3D image)
• scanning tunneling (scans with electrons or ions)
2
prokaryotic cells – NO true nucleus – Bacteria and Archaea
nucleoid (no membrane);
ribosomes?
gram-positive or gram-negative
Susceptibility of bacteria to
antibiotics depends on cell wall
structure.
peptidoglycan
Cells walls of bacteria –complicated
peptidoglycan - sugars
• Gram negative (do not pick up stain - Ecoli)
• Gram positive (DO pick up stain - Staph)
• Penicillin inactivates enzyme in cell wall
• No new cells can form
• (gram negative bacteria resist penicillin )
Killing bacteria
• Penicillin - replication – cell wall can’t form
(bedpans, parachute silk and cantaloupe)
• H2O2 – replication DNA (bacteria have no
repair mechanism)
• Tetracycline - ribosomes
3
eukaryotic control center
The Nucleus
1 µm
Nucleus
Nucleolus
Chromatin
Nuclear envelope:
Inner membrane
Outer membrane
Nuclear pore
Rough ER
Surface of nuclear
envelope
Pore
complex
Ribosome
Close-up
of nuclear
envelope
Chromatin
1 µm
0.25 µ m
• DNA, chromatin,
chromosomes
• nuclear envelope: double
membrane | double lipid
bilayer
• DNA copied to mRNA,
which travels to cytoplasm,
where ribosomes make
proteins
• nucleolus | ribosomal RNA
(rRNA) and proteins form
ribosomal subunits
Pore complexes (TEM)
Nuclear lamina (TEM)
Figure 6.9
1 µm
Nucleus
Nucleolus
Chromatin
Nuclear envelope:
Inner membrane
Outer membrane
Nuclear pore
Rough ER
Surface of nuclear
envelope
Pore
complex
Ribosome
Chromatin
1 µm
0.25 µm
Close-up
of nuclear
envelope
Pore complexes (TEM)
Nuclear lamina (TEM)
• single DNA + proteins = chromatin, chromosome
• chromatin
chromosome before cell division
• nucleolus within nucleus
• site of ribosomal RNA (rRNA) synthesis
Nucleolus
Nucleus
Chromatin
• RNA, proteins
enter/exit via pores
• nuclear lamina
maintains shape
Nuclear envelope:
Inner membrane
Outer membrane
Nuclear pore
Rough ER
Pore
complex
Ribosome
Close-up
of nuclear
envelope
Chromatin
Figure 6.9a
4
ribosomes: protein factories
• Ribosomes - made of ribosomal RNA and protein
• proteins synthesis
– in cytosol (free ribosomes)
– on outside of endoplasmic reticulum (ER) or of
nuclear envelope (bound ribosomes)
Figure 6.10
Figure 6.10
0.25 µm
Free ribosomes in cytosol
Endoplasmic reticulum (ER)
Ribosomes bound to ER
Large
subunit
TEM showing ER and
ribosomes
Small
subunit
Diagram of a ribosome
endomembrane system
•
•
•
•
•
•
Nuclear envelope
Endoplasmic reticulum
Golgi apparatus
Lysosomes
Vacuoles
Plasma membrane
• Either continuous or connected via transfer by
vesicles
5
The Endoplasmic Reticulum:
Biosynthetic Factory
• more than half of total membrane in many eukaryotic
cells
• Continuous with nuclear envelope
– Smooth ER, few ribosomes
– Rough ER, studded with ribosomes
Figure 6.11
Smooth ER
Nuclear
envelope
Rough ER
ER lumen
Cisternae
Ribosomes
Transport vesicle
Smooth ER
Transitional ER
Rough ER
200 nm
Functions of Smooth ER
enzymes of smooth ER in
liver cells: detoxify drugs
and poisons
Smooth ER
– Synthesizes lipids
– Metabolizes
carbohydrates
– Stores calcium ions
6
Functions of Rough ER
secretory proteins,
proteins bound for
membrane via
transport vesicles
membrane factory
Rough ER
Golgi apparatus: shipping and
receiving center
• flattened membranous sacs - cisternae
– Modifies products of the ER
– Manufactures certain macromolecules
– Sorts and packages materials into transport vesicles
cis face
(“receiving” side of
Golgi apparatus)
0.1 µm
Cisternae
trans face
(“shipping” side of
Golgi apparatus)
TEM of Golgi apparatus
cis - faces ER
trans - exit, towards plasma membrane
Figure 6.12
cis face
(“receiving” side of
Golgi apparatus)
0.1 µm
Cisternae
trans face
(“shipping” side of
Golgi apparatus)
TEM of Golgi apparatus
7
Figure 6.15-3
Nucleus
Rough ER
Smooth ER
cis Golgi
Plasma
membrane
trans Golgi
Lysosomes: Digestive
Compartments
• membranous sac of hydrolytic enzymes - digests
macromolecules
• hydrolyze proteins, fats, polysaccharides, and
nucleic acids
• recycle defective
organelles
• work best at pH 5
• phagocytosis
• enzymes recycle cell’s own organelles and
macromolecules, autophagy
Nucleus
Vesicle containing
two damaged
organelles
1 µm
1 µm
Mitochondrion
fragment
Lysosome
Peroxisome
fragment
Digestive
enzymes
Lysosome
Lysosome
Plasma membrane
Peroxisome
Digestion
Figure 6.13
Food vacuole
(a) Phagocytosis
Vesicle
Mitochondrion
Digestion
(b) Autophagy
8
Figure 6.13
Vesicle containing
two damaged
organelles
1 µm
Nucleus
1 µm
Mitochondrion
fragment
Lysosome
Peroxisome
fragment
Digestive
enzymes
Lysosome
Lysosome
Plasma membrane
Peroxisome
Digestion
Food vacuole
Vesicle
(a) Phagocytosis
Digestion
Mitochondrion
(b) Autophagy
Vacuoles: Diverse Maintenance
Compartments
• one or several vacuoles, derived from ER and Golgi
Central vacuole
• food, contractile,
central vacuoles
• variety of functions
Cytosol
Nucleus
Central
vacuole
Cell wall
Chloroplast
5 µm
Figure 6.14
•central vacuole stockpiling proteins
• inorganic ions
•depositing metabolic
byproducts
•storing pigments
•storing defensive
compounds
• ALSO
increases
surface to volume
ratio for whole cell
tonoplast selective in transport into central vacuole
9
organelles with DNA
• mitochondria | cellular respiration
• chloroplasts | photosynthesis
• peroxisomes | oxidation, H2O2
The Evolutionary Origins of
Mitochondria and Chloroplasts
• Mitochondria and
chloroplasts similar to
bacteria
Endoplasmic
reticulum
Engulfing of oxygenNuclear
using nonphotosynthetic
envelope
prokaryote, which
becomes a mitochondrion
Nonphotosynthetic
eukaryote
Engulfing of oxygenusing nonphotosynthetic
prokaryote, which
becomes a mitochondrion
At least
one cell
Engulfing of
photosynthetic
prokaryote
Chloroplast
Mitochondrion
Photosynthetic eukaryote
Endoplasmic
reticulum
Figure 6.16
Ancestor of
eukaryotic cells
(host cell)
Mitochondrion
– double membrane
– free ribosomes,
circular DNA
– autonomous growth
and reproduction
Nucleus
Nucleus
Nuclear
envelope
Ancestor of
eukaryotic cells
(host cell)
Mitochondrion
Nonphotosynthetic
eukaryote
At least
one cell
Engulfing of
photosynthetic
prokaryote
Chloroplast
Mitochondrion
Photosynthetic eukaryote
10
Mitochondria: Chemical Energy
Conversion
• present in nearly all eukaryotic cells
• smooth outer membrane; inner membrane folded into
cristae
• enzymes in intermembrane space and mitochondrial
matrix - cellular respiration, ATP
10 µm
Intermembrane space
Mitochondria
Outer
membrane
DNA
Free
ribosomes
in the
mitochondrial
matrix
Inner
membrane
Mitochondrial
DNA
Cristae
Matrix
(a) Diagram and TEM of mitochondrion
Nuclear DNA
0.1 µm
(b) Network of mitochondria in a protist
cell (LM)
Figure 6.17
10 µm
Intermembrane space
Mitochondria
Outer
membrane
DNA
Inner
membrane
Free
ribosomes
in the
mitochondrial
matrix
Mitochondrial
DNA
Cristae
Matrix
(a) Diagram and TEM of mitochondrion
Nuclear DNA
0.1 µm
(b) Network of mitochondria in a protist
cell (LM)
Chloroplasts: Capture of Light
Energy
• found in leaves of plants and in algae
• chlorophyll, thylakoids, stroma
Figure 6.18
50 µ m
Ribosomes
Stroma
Inner and outer
membranes
Granum
DNA
Intermembrane space
Thylakoid
(a) Diagram and TEM of chloroplast
Chloroplasts
(red)
1 µm
(b) Chloroplasts in an algal cell
11
Peroxisomes: Oxidation
• specialized metabolic compartments bounded by a
single membrane
• produce hydrogen peroxide and convert it to water
1 µm
Chloroplast
Peroxisome
Mitochondrion
Figure 6.19
Cytoskeleton
• network of fibers throughout cytoplasm
• internal scaffolding for organelles, organellar activity
10 µm
– Microtubules
– Microfilaments
– Intermediate filaments
Figure 6.20
• support cell,
maintain shape
ATP
• motor proteins
Vesicle
Receptor for
motor protein
Motor protein Microtubule
(ATP powered) of cytoskeleton
(a)
• “monorails”
Microtubule Vesicles
0.25 µm
• may help regulate
biochemical
activities
(b)
Figure 6.21
12
• Three main types of fibers
– Microtubules are the thickest components
– Microfilaments, actin filaments, thinnest
components
– Intermediate filaments are fibers in a middle range
Table 6.1a
10 µm
Column of tubulin dimers
25 nm
α
β
Tubulin dimer
Centrosomes and Centrioles
• microtubules grow out from a centrosome near
nucleus
• The centrosome is a “microtubule-organizing center”
• animal centrosome has a pair of centrioles, each with
nine triplets of microtubules arranged in a ring
13
cilia and flagella
• locomotor appendages
Direction of swimming
• differ in their beating patterns
(a) Motion of flagella
5 µm
Direction of organism’s movement
Power stroke Recovery stroke
(b) Motion of cilia
15 µm
cell extensions
Cilia—Hair-like
growths
• move back and forth to propel
cell
• common in single-celled
organisms, cells of simple
animals (jellyfish, sponges), and
our cells (lining of lungs)
Flagella—tail-like
growths
– used for propulsion (sperm)
Figure 6.23
Direction of swimming
(a) Motion of flagella
5 µm
Direction of organism’s movement
Power stroke Recovery stroke
(b) Motion of cilia
15 µm
14
• common structure
– core of microtubules, plasma membrane sheath
– basal body anchor
– motor protein, dynein, drives the bending movements
0.1 µm
Figure 6.24
Outer microtubule
doublet
Dynein proteins
Central
microtubule
Radial
spoke
Microtubules
Plasma
membrane
(b) Cross section of
motile cilium
Plasma membrane
Cross-linking
proteins between
outer doublets
Basal body
0.1 µm
0.5 µm
(a) Longitudinal section
of motile cilium
Triplet
(c) Cross section of
basal body
Figure 6.24
0.1 µm
Outer microtubule
doublet
Dynein proteins
Plasma membrane
Central
microtubule
Radial
spoke
Microtubules
Plasma
membrane
(b) Cross section of
motile cilium
Cross-linking
proteins between
outer doublets
Basal body
0.1 µm
0.5 µm
(a) Longitudinal section
of motile cilium
Triplet
(c) Cross section of
basal body
•flagellum - undulatory
movement.
– Force generated
parallel to the
flagellum’s axis.
• Cilia – oars,
alternating power and
recovery strokes.
– force perpendicular to
the cilia’s axis.
15
•bending of both driven by arms of a motor
protein dynein
– Addition and removal of phosphate group (from
ATP) causes conformation changes dynein
Table 6.1b
10 µm
Actin subunit
7 nm
Table 6.1c
5 µm
Keratin proteins
Fibrous subunit (keratins
coiled together)
8−12 nm
16
Figure 6.26
Microvillus
Plasma membrane
Microfilaments (actin
filaments)
Intermediate filaments
0.25 µm
Extracellular components and
connections
– plant cell walls
– extracellular matrix (ECM) of
animal cells
Plant Cell Walls
• protects cell, maintains shape, limits water
absorption
• cellulose fibers embedded
in other polysaccharides and
protein
Secondary
cell wall
Primary
cell wall
Middle
lamella
1 µm
Central vacuole
Cytosol
Plasma membrane
Plant cell walls
Plasmodesmata
17
• multiple layers
– Primary: relatively thin and flexible
– Middle lamella: thin layer between primary walls of
adjacent cells
– Secondary (in some cells): added between the plasma
membrane and the primary cell wall
• Plasmodesmata channels between adjacent plant cells
Figure 6.28
Secondary
cell wall
Primary
cell wall
Middle
lamella
1 µm
Central vacuole
Cytosol
Plasma membrane
Plant cell walls
Plasmodesmata
Plant cell walls
continuous w/ neighbors
wood – lots of secondary walls
Note – not like walls of prokaryotes
Also other eukaryotes:
fungi
protists
(paramecium, slime molds, algae)
18
Plasmodesmata
• channels that perforate plant cell walls
• water and small solutes can pass from cell to cell
Cell walls
Interior
of cell
Interior
of cell
0.5 µm
Plasmodesmata
Plasma membranes
Figure 6.31
Animal Cells
• Animal cells lack cell walls
• extracellular matrix ECM
• provides support, strength, and resilience
Also problems
AD - tangles
Extracellular matrix (ECM) of an animal cell
glycoprotein (aka proteoglycan) collagen – 30-50% proteins in humans
19
Figure 6.30
Collagen
Polysaccharide
molecule
EXTRACELLULAR FLUID
Carbohydrates
Proteoglycan
complex
Fibronectin
Core
protein
Integrins
Proteoglycan
molecule
Plasma
membrane
Proteoglycan complex
Microfilaments
CYTOPLASM
• Functions of the ECM
– Support
– Adhesion
Collagen
– Movement
– Regulation
Polysaccharide
molecule
EXTRACELLULAR FLUID
Carbohydrates
Proteoglycan
complex
Fibronectin
Core
protein
Integrins
Proteoglycan
molecule
Plasma
membrane
Proteoglycan complex
Microfilaments
Tight junctions prevent
fluid from moving
across a layer of cells
Tight junction
TEM
0.5 µm
Tight junction
Intermediate
filaments
Desmosome
TEM
1 µm
Gap
junction
Ions or small
molecules
Space
between cells
Plasma membranes
of adjacent cells
Extracellular
matrix
TEM
Figure 6.32
CYTOPLASM
0.1 µm
20
The Cell: A Living Unit Greater
Than the Sum of Its Parts
5 µm
• Cell functions rely on integration of structures and
organelles
• example: coordination among cytoskeleton,
lysosomes, and plasma membrane enables
macrophage defense
5 µm
Figure 6.33
Figure 6.UN01
Nucleus
(ER)
(Nuclear
envelope)
21