Download Cell Structure and Function

Biology
Sylvia S. Mader
Michael Windelspecht
Chapter 4
Cell Structure
and Function
Lecture Outline
See separate FlexArt PowerPoint slides
for all figures and tables pre-inserted into
PowerPoint without notes.
1
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
4.1 Cellular Level of
Organization
• Cell Theory:
 All organisms are composed of cells
• German botanist Matthais Schleiden (1804-1881)
• German zoologist Theodor Schwann (1810-1882)
 All cells come only from preexisting cells
• German physician Rudolph Virchow (1821-1902)
 Cells are the smallest structural and functional unit of
organisms
2
Cell Size
• The surface-area-to-volume ratio requires that
cells be small
 Large cells - surface area relative to volume
decreases
 Small cells – larger surface area to volume ratio is
advantageous for exchanging molecules
3
EK 2.A.3b: Surface area-to-volume ratios affect a
biological system’s ability to obtain necessary
resources or eliminate waste products.
Learning Objectives: (AP EXAM)
LO 2.6 The student is able to use calculated
surface area-to-volume ratios to predict which
cell(s) might eliminate wastes or procure nutrients
faster by diffusion.
LO 2.7 Students will be able to explain how cell
size and shape affect the overall rate of nutrient
intake and the rate of waste elimination.
4
Surface to Volume Ratio
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
One
4-cm cube
Total surface area
96 cm2
Eight
2-cm cubes
Sixty-four
1-cm cubes
192 cm2
384 cm2
(height × width × number of sides × number of cubes)
Total volume
64 cm3
64 cm3
64 cm3
(height × width × length × number of cubes)
Surface area:
1.5:1
3:1
6:1
Volume per cube (surface area ÷ volume)
5
Practice
• Surface Area to Volume Ratios Worksheet
6
Evidence of student learning is a demonstrated understanding of
each of the following:
1. As cells increase in volume, the relative surface area
decreases and demand for material resources increases;
more cellular structures are necessary to adequately
exchange materials and energy with the environment. These
limitations restrict cell size.
1. The surface area of the plasma membrane must be large
enough to adequately exchange materials; smaller cells have
a more favorable surface area-to-volume ratio for exchange
of materials with the environment.
7
4.2 Prokaryotic Cells
• Lack a membrane-bound nucleus
• Structurally smaller and simpler than eukaryotic
cells (which have a nucleus).
• Prokaryotic cells are placed in two taxonomic
domains:
 Bacteria
 Archaea
• Live in extreme habitats
 Domains are structurally similar but biochemically
different
8
The Structure of Prokaryotes
• Extremely small: 1–1.5 μm wide and 2–6 μm long
• Occur in three basic shapes:
 Spherical coccus,
 Rod-shaped bacillus,
 Spiral spirillum (if rigid) or spirochete (if flexible).
9
The Structure of
Prokaryotes
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
spirillum
spirochete
bacillus
coccus
10
Prokaryotic Cell Shape
• http://highered.mheducation.com/sites/007
337525x/student_view0/exercise9/procary
otic_cell_shapes.html
11
The Structure of Prokaryotes
• Cell Envelope includes:
 Plasma membrane - lipid bilayer with imbedded and peripheral
protein
 Form internal pouches (mesosomes)
 Cell wall - maintains the shape of the cell and is strengthened by
peptidoglycan
(EK 2.B.1.c Cell walls provide structural boundary as well as a
permeability barrier for some substances to the internal
environment.)
 Glycocalyx - layer of polysaccharides on the outside of the cell
wall
• Well organized and resistant to removal (capsule)
12
The Structure of Prokaryotes
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Ribosome:
site of protein synthesis
Inclusion body:
stored nutrients for
later use
Mesosome:
plasma membrane
that folds into the
cytoplasm and
increases surface area
Fimbriae:
hairlike bristles that
allow adhesion to
the surfaces
Conjugation pilus:
elongated, hollow
appendage used for
DNA transfer to other
bacterial cells
Nucleoid:
location of the bacterial
chromosome
Plasma membrane:
sheath around cytoplasm
that regulates entrance
and exit of molecules
Cell wall:
covering that supports,
shapes, and protects cell
Glycocalyx:
gel-like coating outside
cell wall; if compact, called
a capsule; if diffuse, called
a slime layer
Flagellum:
rotating filament present
in some bacteria that
pushes the cell forward
Escherichia coli
© Howard Sochurek/The Medical File/Peter Arnold, Inc.
13
Prokaryotic Cytoplasm and
Appendages
• Cytoplasm
 Semifluid solution
• Bounded by plasma membrane
• Contains water, inorganic and organic molecules, and enzymes
 Nucleoid is a region that contains the single, circular DNA
molecule
 Plasmids are small accessory (extrachromosomal) rings of DNA
14
Prokaryotic Cytoplasm and
Appendages
• Appendages
 Flagella – provide motility
 Fimbriae – small, bristle-like fibers that sprout from the cell
surface
 Conjugation pili – rigid tubular structures used to pass DNA
from cell to cell
15
Bacteria Locomotion
• http://highered.mheducation.com/sites/007
337525x/student_view0/exercises_3590/bacterial_locomotion.html
16
4.3 Introducing Eukaryotic
Cells
• Cells contain:
 Membrane-bound nucleus that houses DNA
 Specialized organelles
 Plasma membrane
• Much larger than prokaryotic cells
17
Origin of Eukaryotic Cells
• http://highered.mheducation.com/sites/983
4092339/student_view0/chapter4/animatio
n_-_endosymbiosis.html
• Essential knowledge 1.B.1: Organisms
share many conserved core processes
and features that evolved and are widely
distributed among organisms today.
b. Structural evidence supports the relatedness
of all eukaryotes.
18
Origin of Organelles
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Original
prokaryotic cell
DNA
1. Cell gains a nucleus by the
plasma membrane invaginating
and surrounding the DNA
with a double membrane.
Nucleus allows specific functions
to be assigned, freeing up cellular
resources for other work.
2. Cell gains an endomembrane
system by proliferation
of membrane.
Increased surface area allows
higher rate of transport of
materials within a cell.
3. Cell gains mitochondria.
aerobic
bacterium
Ability to metabolize sugars in
the presence of oxygen enables
greater function and success.
mitochondrion
4. Cell gains chloroplasts.
Ability to produce
sugars from sunlight
enables greater
function and success.
chloroplast
Animal cell
has mitochondria,
but not chloroplasts.
photosynthetic
bacterium
Plant cell
has both mitochondria
and chloroplasts.
19
Exam
Essential knowledge 2.B.3: Eukaryotic cells maintain
internal membranes that partition the cell into specialized
regions.
• Internal membranes facilitate cellular processes by
minimizing competing interactions and by increasing
surface area where reactions can occur.
• Membranes and membrane-bound organelles in
eukaryotic cells localize (compartmentalize) intracellular
metabolic processes and specific enzymatic reactions.
20
Eukaryotic Cells: Organelles
• Eukaryotic cells are compartmentalized
 They contain small structures called organelles
• Perform specific functions
• Isolates reactions from others
• Two classes of organelles:
 Endomembrane system
• Organelles that communicate with one another
– Via membrane channels
– Via small vesicles
 Energy related organelles
• Mitochondria and chloroplasts
• Independent and self-sufficient
21
Animal Cell Anatomy
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
mitochondrion
chromatin
nucleolus
nuclear
envelope
Plasma membrane:
outer surface that
regulates entrance and
exit of molecules
endoplasmic
reticulum
protein
2.5 µm
phospholipid
Nucleus: command center of cell
• Nuclear envelope: double
membrane with nuclear pores
that encloses nucleus
Cytoskeleton: maintains
cell shape and assists movement
of cell parts:
• Chromatin: diffuse threads
containing DNA and protein
• Nucleolus: region that produces
subunits of ribosomes
Endoplasmic reticulum:
protein and lipid metabolism
• Microtubules: protein
cylinders that move
organelles
• Intermediate filaments:
protein fibers that provide
stability of shape
• Rough ER: studded with
ribosomes that synthesize
proteins
• Actin filaments: protein
fibers that play a role in
cell division and shape
• Smooth ER: lacks
ribosomes, synthesizes
lipid molecules
Centrioles*: short
cylinders of microtubules
Peroxisome: vesicle
that is involved in
fattyacid metabolism
Centrosome: microtubule
organizing center that
contains a pair of centrioles
Ribosomes:
particles that carry
out protein synthesis
Lysosome*: vesicle that
digests macromolecules
and even cell parts
Vesicle: small membranebounded sac that stores
and transports substances
Polyribosome: string of
ribosomes simultaneously
synthesizing same protein
Mitochondrion: organelle
that carries out cellular respiration,
producing ATP molecules
Cytoplasm: semifluid
matrix outside nucleus
that contains organelles
Golgi apparatus: processes, packages,
and secretes modified proteins
*not in plant cells
© Dr. Dennis Kunkel/Visuals Unlimited
22
Plant Cell Anatomy
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
peroxisome
mitochondrion
nucleus
ribosomes
central vacuole
plasma membrane
cell wall
chloroplast
1 µm
Nucleus: command center of cell
Central vacuole*: large, fluid-filled
sac that stores metabolites and
helps maintain turgor pressure
• Nuclear envelope: double membrane with
nuclear pores that encloses nucleus
• Nucleolus: produces subunits of ribosomes
Cell wall of adjacent cell
• Chromatin: diffuse threads containing
DNA and protein
• Nuclear pore: permits passage of
proteins into nucleus and ribosomal
subunits out of nucleus
Middle lamella:
cements together the
primary cell walls of
adjacent plant cells
Ribosomes: carry
out protein synthesis
Chloroplast*: carries
out photosynthesis,
producing sugars
Centrosome:
microtubule organizing
center (lacks centrioles)
Granum*: a stack
of chlorophyllcontaining thylakoids
in a chloroplast
Endoplasmic
reticulum : protein
and lipid metabolism
• Rough ER: studded
with ribosomes that
synthesize proteins
Mitochondrion: organelle
that carries out cellular
respiration, producing
ATP molecules
• Smooth ER: lacks
ribosomes, synthesizes
lipid molecules
Microtubules: protein cylinders
that aid movement of organelles
Peroxisome: vesicle that
is involved in fatty acid
metabolism
Actin filaments: proteinfibers
that play a role in cell division
and shape
Golgi apparatus: processes,
packages, and secretes
modified proteins
Cytoplasm: semifluid matrix outside
nucleus that contains organelles
Plasma membrane: surrounds
cytoplasm, and regulates entrance
and exit of molecules
Cell wall*: outer surface that shapes,
supports, and protects cell
*not in animal cells
© Newcomb/Wergin/Biological Photo Service (FIRST USE)
23
4.4 The Nucleus and
Ribosomes
• The Nucleus
 Command center of cell, usually near center
 Separated from cytoplasm by nuclear envelope
• Consists of double layer of membrane
• Nuclear pores permit exchange between nucleoplasm &
cytoplasm
24
4.4 The Nucleus and
Ribosomes
• The Nucleus
 Contains chromatin in semifluid nucleoplasm
• Chromatin contains DNA of genes, and proteins
• Condenses to form chromosomes
– Chromosomes are formed during cell division
 Dark nucleolus composed of rRNA
• Produces subunits of ribosomes
25
Anatomy of the Nucleus
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
nuclear
envelope
nucleolus
Nuclear envelope:
inner membrane
outer membrane
nuclear pore
nuclear
pore
chromatin
nucleoplasm
phospholipid
(Bottom): Courtesy Ron Milligan/Scripps Research Institute; (Top right): Courtesy E.G. Pollock
26
Ribosomes
• Are the site of protein synthesis in the cell
• Composed of rRNA
 Consists of a large subunit and a small subunit
 Subunits made in nucleolus
• May be located:
 On the endoplasmic reticulum (thereby making it
“rough”), or
 Free in the cytoplasm, either singly or in groups,
called polyribosomes
27
4.5 The Endomembrane
System
• Series of intracellular membranes that
compartmentalize the cell
• Restrict enzymatic reactions to specific
compartments within cell
• Consists of:
 Nuclear envelope
 Membranes of endoplasmic reticulum
 Golgi apparatus
 Vesicles
• Several types
• Transport materials between organelles of system
28
Endoplasmic Reticulum and
Golgi Apparatus
• http://bcs.whfreeman.com/thelifewire/conte
nt/chp04/0402002.html
29
Endoplasmic Reticulum
• A system of membrane channels and saccules
(flattened vesicles) continuous with the outer membrane
of the nuclear envelope
• Rough ER
 Studded with ribosomes on cytoplasmic side
 Protein anabolism (Synthesizes proteins)
• Modifies and processes proteins
– Adds sugar to protein
– Results in glycoproteins
30
Endoplasmic Reticulum
• Smooth ER
 No ribosomes
 Synthesis of lipids
 Site of various synthetic processes, detoxification,
and storage
 Forms transport vesicles
31
Endoplasmic Reticulum
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
ribosomes
Nuclear envelope
rough
endoplasmic
reticulum
smooth
endoplasmic
reticulum
0.08 µm
© R. Bolender & D.Fawcett/Visuals Unlimited
32
The Golgi Apparatus
Golgi Apparatus
 Consists of flattened, curved saccules
 Resembles stack of hollow pancakes
 Modifies proteins and lipids
• Receives vesicles from ER on cis (or inner face)
• Packages them in vesicles
• Prepares for “shipment” and packages them in
vesicles from trans (or outer face)
– Within cell
– Export from cell (secretion, exocytosis)
33
Golgi Apparatus
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
secretion
transport saccules
vesicle
transport
vesicles
trans face
cis face
Golgi apparatus
Nucleus
0.1µm
Courtesy Charles Flickinger, from Journal of Cell Biology 49:221-226, 1971, Fig. 1 page 224
34
Lysosomes
• Membrane-bound vesicles (not in plants)
 Produced by the Golgi apparatus
 Contain powerful digestive enzymes and are highly
acidic
• Digestion of large molecules
• Recycling of cellular resources
• Some genetic diseases
 Caused by defect in lysosomal enzyme
 Lysosomal storage diseases (Tay-Sachs)
35
Lysososmes
• http://highered.mheducation.com/sites/007
2495855/student_view0/chapter2/animatio
n__lysosomes.html
36
Endomembrane System
Summary
• Proteins produced in rough ER and lipids from
smooth ER are carried in vesicles to the Golgi
apparatus.
• The Golgi apparatus modifies these products
and then sorts and packages them into vesicles
that go to various cell destinations.
• Secretory vesicles carry products to the
membrane where exocytosis produces
secretions.
• Lysosomes fuse with incoming vesicles and
digest macromolecules.
37
Endomembrane System
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Consumption
Secretion
5. Secretion
plasma
membrane
4. Secretory vesicle
fuses with the plasma
membrane as secretion
occurs.
Incoming vesicle
brings substances
into the cell that are
digested when the
vesicle fuses with a
lysosome.
enzyme
3. Golgiapparatus
modifies lipids and proteins
from the ER; sorts them
and packages them in
vesicles.
Lysosome
Contains digestive enzymes
that breakdown worn-out
cell parts or substances
entering the cell at the
plasma membrane.
protein
2. Transport vesicle
shuttles proteins to
various locations such as
the Golgi apparatus.
Transport vesicle
shuttles lipids to various
locations such as the
Golgi apparatus.
lipid
1. Rough endoplasmic
reticulum
synthesizes proteins and
packages them in vesicles;
vesicles commonly go to
the Golgi apparatus
Smooth endoplasmic
reticulum
synthesizes lipids and
also performs various
other functions.
ribosome
Nucleus
38
4.6 Other Vesicles and
Vacuoles
• Peroxisomes
 Similar to lysosomes
• Membrane-bounded vesicles
• Enclose enzymes
 However
• Enzymes synthesized by free ribosomes in cytoplasm
(instead of ER)
• Active in lipid metabolism
• Catalyze reactions that produce hydrogen peroxide H2O2
– Toxic
– Broken down to water & O2 by catalase
39
Peroxisomes
40
Vacuoles
• Membranous sacs that are larger than vesicles
 Store materials that occur in excess
 Others very specialized (contractile vacuole)
• Plants cells typically have a central vacuole
 Up to 90% volume of some cells
 Functions in:
• Storage of water, nutrients, pigments, and waste products
• Development of turgor pressure
• Some functions performed by lysosomes in other eukaryotes
41
Plant Cell Central Vacuole
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
100 nm
© Newcomb/Wergin/Biological Photo Service
42
4.7 Energy-Related Organelles
• Chloroplasts
 Bounded by double membrane
 Inner membrane infolded (why?)
• Forms disc-like thylakoids, which are stacked to form grana
• Suspended in semi-fluid stroma
 Green due to chlorophyll
• Green photosynthetic pigment
• Found ONLY in inner membranes of chloroplast
43
Chloroplasts
• Serve as the site of photosynthesis
• Captures light energy to drive cellular machinery
• Photosynthesis
 Synthesizes carbohydrates from CO2 & H2O
 Makes own food using CO2 as only carbon source
 Energy-poor compounds converted to energy-rich compounds
solar energy + carbon dioxide + water → carbohydrate + oxygen
 Only plants, algae, and certain bacteria are capable of conducting
photosynthesis
44
Chloroplast Structure
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
a.
500 nm
outer
membrane
double
membrane
inner
membrane
grana
thylakoid
stroma space thylakoid membrane
b.
Courtesy Herbert W. Israel, Cornell University
45
Mitochondria
•
Smaller than chloroplast
•
Contain ribosomes and their own DNA
•
Surrounded by a double membrane

Inner membrane surrounds the matrix and is convoluted (folds) to
form cristae.

Matrix – Inner semifluid containing respiratory enzymes
•
Break down carbohydrates
•
Involved in cellular respiration
•
Produce most of ATP utilized by the cell
46
Mitochondrion Structure
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
a.
double
membrane
200 nm
outer
membrane
inner
membrane
cristae
matrix
b.
Courtesy Dr. Keith Porter
47
Origin of Mitochondria and
Chloroplasts
• http://www.sumanasinc.com/webcontent/a
nimations/content/organelles.html
• http://highered.mheducation.com/sites/983
4092339/student_view0/chapter4/animatio
n_-_endosymbiosis.html
48
4.8 The Cytoskeleton
• Maintains cell shape
• Assists in movement of cell and organelles
• Three types of macromolecular fibers
 Actin filaments
 Intermediate filaments
 Microtubules
• Assemble and disassemble as needed
49
Actin Filaments
• Extremely thin filaments like twisted pearl
necklace
• Dense web just under plasma membrane
maintains cell shape
• Support for microvilli in intestinal cells
• Intracellular traffic control
 For moving stuff around within cell
 Cytoplasmic streaming
• Function in pseudopods of amoeboid cells
• Important component in muscle contraction
(other is myosin)
50
Actin Filament Operation
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
actin filament
ADP +
ATP
tail
myosin
molecules
P
head
membrane
51
Intermediate Filaments
• Intermediate in size between actin filaments and
microtubules
• Rope-like assembly of fibrous polypeptides
• Vary in nature
 From tissue to tissue
• Function:
 Support nuclear envelope
 Cell-cell junctions, like those holding skin cells tightly
together
52
Microtubules
• Hollow cylinders made of two globular proteins
called a and b tubulin
• Interacts with proteins kinesin and dynein to
cause movement of organelles
53
Microtubule Operation
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
ATP
vesicle
kinesin
kinesin
receptor
vesicle moves, not microtubule
54
Centrioles
• Short, hollow cylinders
• One pair per animal cell
 Located in centrosome of animal cells
 Oriented at right angles to each other
 Separate during mitosis to determine plane of division
• May give rise to basal bodies of cilia and
flagella
55
Centrioles
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
empty center
of centriole
one microtubule
triplet
one centrosome: one pair of centrioles
two centrosomes: two pairs of centrioles
200 nm
(Middle): Courtesy Kent McDonald, University of Colorado Boulder; (Bottom): Journal of Structural Biology, Online by Manley McGill et al. Copyright 1976 by Elsevier
Science & Technology Journals. Reproduced with permission of Elsevier Science & Technology Journals in the format Textbook via Copyright Clearance Center
56
Cilia and Flagella
• Hair-like projections from cell surface that aid in
cell movement
• Very different from prokaryote flagella
 Outer covering of plasma membrane
• In eukaryotes, cilia are much shorter than
flagella
 Cilia move in coordinated waves like oars
 Flagella move like a propeller or cork screw
57
Structure of a Flagellum
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
outer
microtubule
doublet
Flagellum
radial
spoke
central
microtubules
The shaft of the
flagellum has a ring
of nine microtubule
doublets anchored
to a central pair of
microtubules.
shaft
dynein
side arm
Flagellum cross section
Sperm
plasma
membrane
triplets
25 nm
The side arms
of each doublet
are composed
of dynein, a
motor molecule.
dynein
side arms
Basal body
ATP
Basal body cross section
100 nm
The basal body of a flagellum has
a ring of nine microtubule triplets
with no central microtubules.
In the presence of
ATP, the dynein side
arms reach out to
their neighbors,
and bending occurs.
(Flagellum, Basal body): © William L. Dentler/Biological Photo Service
58
Review – Bozeman Biology
• http://www.bozemanscience.com/043cellular-organelles
59
Mini-Lab Cell Size
1. Calculate the surface area and volume of the 2
cubes and the SA/V ratio. Record in notes.
2. Place each of the 2 cubes into a beaker and
cover them with 0.1M NaOH for 10 minutes.
3. Remove the cubes and blot them dry.
4. Cut each cube in half and measure the pale
yellow area in the center.
5. Calculate the volume of this region. Record in
your notes.
6. Subtract the volume of the yellow region from the
volume of the cube to get the volume of the pink
region.
7. Calculate (Vol. Pink/Vol. Cube) X 100%