Download plasma membrane

Chapter 6
A Tour of the Cell
PowerPoint® Lecture Presentations for
Biology
Eighth Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 6-1
Microscopy
• Scientists use microscopes to visualize cells too small to
see with the naked eye
• In a light microscope (LM), this is the type of scope you
use, which magnifies about up to 1,000x the actual size
• The quality of an image depends on 3 things:
– Magnification
– Resolution (clarity)
– Contrast (visible differences), can be enhanced with
stains
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
10 m
1m
Human height
Length of some
nerve and
muscle cells
0.1 m
Chicken egg
1 cm
Unaided eye
Frog egg
100 µm
Most plant and
animal cells
10 µm
Nucleus
Most bacteria
1 µm
100 nm
10 nm
Mitochondrion
Smallest bacteria
Viruses
Ribosomes
Proteins
Lipids
1 nm
Small molecules
0.1 nm
Atoms
Electron microscope
1 mm
Light microscope
Fig. 6-2
Fig. 6-3
TECHNIQUE
RESULTS
(a) Brightfield (unstained
specimen)
Cheek
epithelial cells
50 µm
(b) Brightfield (stained
specimen)
(c) Phase-contrast
(d) Differential-interferencecontrast (Nomarski)
(e) Fluorescence
50 µm
(f) Confocal
50 µm
• Electron microscopes (EMs) are used to
study subcellular structures
• Scanning electron microscopes (SEMs)
focus e- onto the surface of a specimen,
providing images that look 3-D
• Transmission electron microscopes (TEMs)
focus e- through a specimen, used to study
internal cellular structures
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 6-4
TECHNIQUE
(a) Scanning electron
microscopy (SEM)
RESULTS
Cilia
1 µm
(b) Transmission electron Longitudinal Cross section
section of
of cilium
microscopy (TEM)
1 µm
cilium
What do you remember about Prokaryotic and
Eukaryotic Cells?????
Eukaryote
Prokaryote
Both
Concept 6.2: Eukaryotic cells have internal
membranes that compartmentalize their functions
• Prokaryotic = bacteria and Archaea
• Eukaryotic = everything else
• Basic features of all cells:
– Plasma membrane
– Semifluid substance called cytosol (aka
cytoplasm)
– Chromosomes (carry genes)
– Ribosomes (make proteins)
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
• Prokaryotic cells are
characterized by having
– No nucleus
– DNA in an unbound
region called the
nucleoid
– No membrane-bound
organelles
– Cytoplasm
– Circular chromosome
called a plasmid
• Eukaryotic cells are
characterized by having
– DNA in a nucleus that
is bounded by a
membranous nuclear
envelope
– Membrane-bound
organelles
– Cytoplasm Eukaryotic
cells are generally much
larger than prokaryotic
cells
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 6-6
Which class of cell is this?
Fimbriae
Nucleoid
Ribosomes
Plasma membrane
Bacterial
chromosome
Cell wall
Capsule
0.5 µm
(a) A typical
rod-shaped
bacterium
Flagella
(b) A thin section
through the
bacterium
Bacillus
coagulans (TEM)
• The plasma membrane is a selective barrier
that allows sufficient passage of oxygen,
nutrients, and waste to service the volume of
every cell
• Generally made up of a bilayer of
phospholipids
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 6-7
Outside of cell
Inside of
cell
0.1 µm
(a) TEM of a plasma
membrane
Carbohydrate side chain
Hydrophilic
region
Hydrophobic
region
Hydrophilic
region
Phospholipid
Proteins
(b) Structure of the plasma membrane
• The logistics of carrying out cellular metabolism
sets limits on the size of cells (what does this
mean????)
• The surface area to volume ratio of a cell is
critical
• As the surface area increases by a factor of n2,
the volume increases by a factor of n3
• Small cells have a greater surface area relative
to volume
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 6-9a
Nuclear
envelope
ENDOPLASMIC RETICULUM (ER)
Flagellum
Rough ER
NUCLEUS
Nucleolus
Smooth ER
Chromatin
Centrosome
Plasma
membrane
CYTOSKELETON:
Microfilaments
Intermediate
filaments
Microtubules
Ribosomes
Microvilli
Golgi
apparatus
Peroxisome
Mitochondrion
Lysosome
BioFlix: Tour Of An Animal Cell
Fig. 6-9b
NUCLEUS
Nuclear envelope
Nucleolus
Chromatin
Rough endoplasmic
reticulum
Smooth endoplasmic
reticulum
Ribosomes
Central vacuole
Golgi
apparatus
Microfilaments
Intermediate
filaments
Microtubules
CYTOSKELETON
Mitochondrion
Peroxisome
Chloroplast
Plasma
membrane
Cell wall
Plasmodesmata
Wall of adjacent cell
BioFlix: Tour Of A Plant Cell
You should know the major components of the cell and
their fxns, do you?
• Is there any organelle you are unclear about
from your pre-reading?
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 6-10
Nucleus
1 µm
Nucleolus
Chromatin
Nuclear envelope:
Inner membrane
Outer membrane
Nuclear pore
Pore
complex
Surface of
nuclear envelope
Rough ER
Ribosome
1 µm
0.25 µm
Close-up of nuclear
envelope
Pore complexes (TEM)
Nuclear lamina (TEM)
• Pores regulate the entry and exit of molecules
from the nucleus
• The shape of the nucleus is maintained by the
nuclear lamina, which is composed of protein
– A net-like array of protein filaments that
maintains the shape of the nucleus by
mechanically supporting the nuclear envelope
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Concept 6.4: The endomembrane system regulates
protein traffic and performs metabolic functions in
the cell
• Components of the endomembrane system:
– Nuclear envelope
– Endoplasmic reticulum
– Golgi apparatus
– Lysosomes
– Vacuoles
– Plasma membrane
• These components are either continuous or
connected via transfer by vesicles
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
How are they related?
• We mentioned that all of these are part of
the endomembrane system, so what does
that mean? Can you determine any
similarities that there may be between
them? What would they be made of?
The Endoplasmic Reticulum: Biosynthetic Factory
• The endoplasmic reticulum (ER) accounts for
more than half of the total membrane in many
eukaryotic cells
• The ER membrane is continuous with the
nuclear envelope
• There are two distinct regions of ER:
– Smooth ER, which lacks ribosomes
– Rough ER, with ribosomes studding its
surface
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 6-12
Smooth ER
Rough ER
ER lumen
Cisternae
Ribosomes
Transport vesicle
Smooth ER
Nuclear
envelope
Transitional ER
Rough ER
200 nm
Functions of Rough ER
• The rough ER
– Has bound ribosomes, which secrete
glycoproteins (proteins covalently bonded to
carbohydrates)
– Distributes transport vesicles, proteins
surrounded by membranes
– Is a membrane factory for the cell
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Functions of Smooth ER and Golgi Apparatus
• The smooth ER
– Synthesizes lipids
– Metabolizes carbohydrates
– Detoxifies poison
– Stores calcium
• Functions of the Golgi apparatus:
– Modifies products of the ER
– Manufactures certain macromolecules
– Sorts and packages materials into transport vesicles
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 6-13
cis face
(“receiving” side of
Golgi apparatus)
0.1 µm
Cisternae
trans face
(“shipping” side of
Golgi apparatus)
TEM of Golgi apparatus
Fig. 6-14a
Nucleus
1 µm
Phagocytosis –
“ingestion” of
food/solid materials
into the cell thru
vesicles
Lysosome
Lysosome
Digestive
enzymes
Plasma
membrane
Digestion
Food vacuole
(a) Phagocytosis
Vacuoles: Diverse Maintenance Compartments
• A plant cell or fungal cell may have one or
several vacuoles
• Food vacuoles are formed by phagocytosis
• Contractile vacuoles, found in many
freshwater protists, pump excess water out of
cells
• Central vacuoles, found in many mature plant
cells, hold organic compounds and water
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 6-16-3
Nucleus
Rough ER
Smooth ER
cis Golgi
Endomembrane
system
trans Golgi
Plasma
membrane
Other Organelles
• Peroxisomes are oxidative organelles
• Mitochondria and chloroplasts
– Are not part of the endomembrane system
– Have a double membrane
– Have proteins made by free ribosomes
– Contain their own DNA
• Question: anyone know why mitochondria
and chloroplasts contain their own DNA?
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Peroxisomes: Oxidation
• Peroxisomes are specialized metabolic
compartments bounded by a single membrane
• Peroxisomes produce hydrogen peroxide and
convert it to water
• Oxygen is used to break down different types
of molecules
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 6-19
Chloroplast
Peroxisome
Mitochondrion
1 µm
Concept 6.6: The cytoskeleton is a network of fibers
that organizes structures and activities in the cell
• The cytoskeleton is a network of fibers
extending throughout the cytoplasm
• It organizes the cell’s structures and activities,
anchoring many organelles
• It is composed of three types of molecular
structures:
– Microtubules
– Microfilaments
– Intermediate filaments
• Use motor proteins (dynein) to move
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 6-20
Video?
Microtubule
0.25 µm
Microfilaments
Components of the Cytoskeleton
• Three main types of fibers make up the
cytoskeleton:
– Microtubules – thickest, shape cell, guide
organelle mvmt, separate chroms during cell
division
– Microfilaments, also called actin filaments, are
the thinnest components (make up micro-villi in
your intestines)
– Intermediate filaments are fibers with
diameters in a middle range, more permanent,
fix organelles in place and help with cell shape
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Cilia and Flagella
• Microtubules control the beating of cilia and
flagella, locomotor appendages of some cells
• Cilia and flagella differ in their beating patterns
Video: Chlamydomonas
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Video: Paramecium Cilia
Fig. 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
• Cilia and flagella share a common
ultrastructure: (what would this suggest?)
– A core of microtubules sheathed by the plasma
membrane
– A basal body that anchors the cilium or
flagellum
Animation: Cilia and Flagella
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 6-24
Outer microtubule
doublet
0.1 µm
Plasma
membrane
Dynein proteins
Central
microtubule
Radial
spoke
Protein crosslinking outer
doublets
Microtubules
Plasma
membrane
(b) Cross section of
cilium
Basal body
0.5 µm
(a) Longitudinal
section of cilium
0.1 µm
Triplet
(c) Cross section of basal body
Notice the
arrangement
of the
microtubules
Cell Wall
• Plant cell walls may have multiple layers:
– Primary cell wall: relatively thin and flexible
– Middle lamella: thin layer between primary
walls of adjacent cells
– Secondary cell wall (in some cells): added
between the plasma membrane and the
primary cell wall
• Plasmodesmata are channels between
adjacent plant cells
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 6-28
Secondary
cell wall
Primary
cell wall
Middle
lamella
1 µm
Central vacuole
Cytosol
Plasma membrane
Plant cell walls
Plasmodesmata
The Extracellular Matrix (ECM) of Animal Cells
• Animal cells lack cell walls but are covered by
an elaborate extracellular matrix (ECM)
• The ECM is made up of glycoproteins such as
collagen, proteoglycans, and fibronectin
• ECM proteins bind to receptor proteins in the
plasma membrane called integrins
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 6-30
Collagen
Proteoglycan
complex
EXTRACELLULAR FLUID
Polysaccharide
molecule
Carbohydrates
Fibronectin
Core
protein
Integrins
Proteoglycan
molecule
Plasma
membrane
Proteoglycan complex
Microfilaments
CYTOPLASM
• Functions of the ECM:
– Support
– Adhesion
– Movement
– Regulation
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Intercellular Junctions
• Neighboring cells in tissues, organs, or organ systems
often adhere, interact, and communicate through direct
physical contact
• Intercellular junctions facilitate this contact
• There are several types of intercellular junctions
– Plasmodesmata (cell with cell walls) – perforate cell
walls
– Tight junctions -membranes of neighboring cells are
pressed together, preventing leakage of extracellular
fluid
– Desmosomes – anchoring junctions
– Gap junctions – communicating junctions
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 6-31
Cell walls
Interior
of cell
Interior
of cell
0.5 µm
Plasmodesmata Plasma membranes
Fig. 6-32a
Tight junctions prevent
fluid from moving
across a layer of cells
Tight junction
Intermediate
filaments
Desmosome
Gap
junctions
Space
between
cells
Plasma membranes
of adjacent cells
Extracellular
matrix
You should now be able to:
1. Distinguish between the following pairs of
terms: magnification and resolution;
prokaryotic and eukaryotic cell; free and
bound ribosomes; smooth and rough ER
2. Describe the structure and function of the
components of the endomembrane system
3. Briefly explain the role of mitochondria,
chloroplasts, and peroxisomes
4. Describe the functions of the cytoskeleton
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
5. Compare the structure and functions of
microtubules, microfilaments, and
intermediate filaments
6. Explain how the ultrastructure of cilia and
flagella relate to their functions
7. Describe the structure of a plant cell wall
8. Describe the structure and roles of the
extracellular matrix in animal cells
9. Describe four different intercellular junctions
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings