Transcript chapter4_Sections 8-13.ppt

Cecie Starr
Christine Evers
Lisa Starr
www.cengage.com/biology/starr
Chapter 4
Cell Structure
(Sections 4.8 - 4.13)
Albia Dugger • Miami Dade College
4.8 The Endomembrane System
• The endomembrane system includes rough and smooth
endoplasmic reticulum (ER), vesicles, and Golgi bodies
• This system makes and modifies lipids and proteins; it also
recycles and disposes of molecules and particles
• endomembrane system
• Series of interacting organelles (endoplasmic reticulum,
Golgi bodies, vesicles) between nucleus and plasma
membrane; produces lipids, proteins
The Endomembrane System
The Endomembrane System
Rough ER
Modifies proteins made by
ribosomes attached to it
Smooth ER
Makes lipids, breaks down
carbohydrates and fats,
inactivates toxins
Golgi Body
Finishes, sorts, ships lipids,
enzymes, and proteins
Lysosome
Digests, recycles materials
Stepped Art
p. 62
Endoplasmic Reticulum
• endoplasmic reticulum (ER)
• Organelle that is a continuous system of sacs and tubes
• An extension of the nuclear envelope
• Site where many new polypeptide chains are modified
• Rough ER is studded with ribosomes that make
polypeptides that enter the ER as they are assembled
• Smooth ER has no ribosomes: Enzymes assemble lipids
that form cell membranes, and break down substances
A Variety of Vesicles
• Small, membrane-enclosed, saclike vesicles form in a variety
of types, either on their own or by budding
• Many vesicles transport substances from one organelle to
another, including endocytic vesicles and exocytic vesicles
• Other vesicles include peroxisomes, lysosomes, and
vacuoles (including central vacuoles)
Key Terms
• vesicle
• Small, membrane-enclosed, saclike organelle; different
kinds store, transport, or degrade their contents
• lysosome
• Enzyme-filled vesicle that functions in intracellular
digestion
• peroxisome
• Enzyme-filled vesicle that breaks down amino acids, fatty
acids, and toxic substances
Key Terms
• vacuole
• A fluid-filled organelle that isolates or disposes of waste,
debris, or toxic materials
• central vacuole
• Fluid-filled vesicle in many plant cells
Golgi Bodies
• Enzymes in a Golgi body finish proteins and lipids that are
delivered by vesicles from the ER
• Golgi body
• Modifies polypeptides and lipids; attaches phosphate
groups or oligosaccharides, and cuts certain polypeptides
• Sorts and packages the finished products into vesicles
that carry them to lysosomes or to the plasma membrane
Functions of
the Endomembrane System
polypeptide
nucleus
RNA
1
Rough ER
Some of the RNA
in the cytoplasm
is translated into
polypeptide chains
by ribosomes
attached to the
rough ER. The
chains enter the
rough ER, where
they are modified
ribosome
into final form.
attached to ER
3
Vesicles Vesicles
that bud from the rough
ER carry some of the
new proteins to Golgi
bodies. Other proteins
migrate through the
interior of the rough
ER, and end up in the
smooth ER.
vesicle budding
from ER
Fig. 4.16.1,3, p. 62
Functions of
the Endomembrane System (cont.)
Smooth ER
Some proteins from
the rough ER are
packaged into new
vesicles and
shipped to Golgi
bodies. Others
become enzymes of
the smooth ER.
These enzymes
assemble lipids and
inactivate toxins.
2
protein in
smooth ER
Golgi
body
Proteins
arriving in
vesicles from
the ER are
modified into
final form and
sorted. New
vesicles carry
them to the
plasma
membrane or
to lysosomes.
4
Plasma
membrane
A vesicle’s
membrane fuses
with the plasma
membrane, so the
contents of the
vesicle are
released to the
exterior of the
cell.
5
Fig. 4.16.2,4,5, p. 62
ANIMATION: The endomembrane system
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4.9 Mitochondria and Plastids
• Mitochondria make ATP by breaking down organic
compounds in the oxygen-requiring pathway of aerobic
respiration
• Chloroplasts are plastids that produce sugars by
photosynthesis
Function of Mitochondria
• mitochondrion
• Double-membraned organelle that produces ATP by
aerobic respiration in eukaryotes
• During aerobic respiration, hydrogen ions accumulate
between the two membranes
• The buildup causes the ions to flow across the inner
mitochondrial membrane, through membrane transport
proteins that drive the formation of ATP
Mitochondrion
outer membrane
outer
compartment
inner compartment
inner membrane
Fig. 4.17a, p. 64
Mitochondrion
Fig. 4.17b, p. 64
Mitochondrion
Energy powerhouse;
produces many ATP
by aerobic respiration
Fig. 4.17c, p. 64
ANIMATION: Structure of a mitochondrion
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Origins of Mitochondria
• Theory of endosymbiosis: Mitochondria evolved from aerobic
bacteria that took up permanent residence inside a host cell
• Resemble bacteria in size, form, and biochemistry
• Have their own DNA, which is similar to bacterial DNA
• Divide independently of the cell, and have their own
ribosomes
Chloroplasts and Other Plastids
• plastid
• An organelle that functions in photosynthesis or storage,
e.g. chloroplast, amyloplast
• chloroplast
• Organelle of photosynthesis in the cells of plants and
many protists
Chloroplast Structure
• Two outer membranes enclose a semifluid interior (stroma)
that contains enzymes and chloroplast DNA
• In the stroma, a highly folded stack of membrane
(grana/granum ) forms a single, continuous compartment
• Photosynthesis takes place at the thylakoid membrane, which
incorporates pigments such as chlorophylls, which are green
Photosynthesis
• Chlorophylls and other molecules in the thylakoid membrane
use the energy in sunlight to synthesize ATP
• ATP is used in the stroma to build carbohydrates from carbon
dioxide and water
Chloroplasts
Chloroplast
Specializes in
photosynthesis
Fig. 4.18a, p. 65
Plant Cell
Chloroplast
Specializes in
photosynthesis
Mitochondrion
Fig. 4.18b, p. 65
Chloroplast Structure
two outer
membranes
stroma
thylakoids
(inner membrane
system folded into
flattened disks)
Fig. 4.18c, p. 65
Other Plastids
• Chromoplasts are plastids that make and store pigments
other than chlorophylls
• Red, orange, and yellow pigments color many flowers,
leaves, fruits, and roots
• Amyloplasts store starch grains
• Abundant in starch-storing cells of stems, tubers
(underground stems), and seeds
4.10 The Dynamic Cytoskeleton
• A cytoskeleton includes microtubules, microfilaments, and
intermediate filaments
• cytoskeleton
• Dynamic framework of protein filaments that support,
organize, and move eukaryotic cells and their internal
structures
Key Terms
• microtubule
• Cytoskeletal element involved in cellular movement;
hollow filament of tubulin subunits
• microfilament
• Reinforcing cytoskeletal element; a fiber of actin subunits
• intermediate filament
• Cytoskeletal element that locks cells and tissues together
Microtubules
• Microtubules assemble,
separate the cell’s
duplicated
chromosomes, then
disassemble
Examples of Microtubules
• Microtubules (yellow)
support and guide the
growing ends of
young nerve cells
Examples of Microfilaments
• Myosin and actin
microfilaments interact in
contraction of muscle cells
• cell cortex
• Reinforcing mesh of
microfilaments under a plasma
membrane
Examples of Intermediate Filaments
• The nuclear envelope is
supported by an inner
layer of intermediate
filaments called lamins
• Intermediate filaments
connect to structures
that lock cell
membranes together in
tissues
tubulin
subunit
actin
subunit
one
polypeptide
chain
Intermediate filament
Microtubule
Microfilament
Fig. 4.19b, p. 66
ANIMATION: Cytoskeletal components
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Accessory Molecules
• Motor proteins move cell parts when energized by a
phosphate-group transfer from ATP
• motor protein
• Energy-using protein that interacts with cytoskeletal
elements to move the cell’s parts or the whole cell
Motor Proteins
• Kinesin (tan) drags a pink vesicle along a microtubule
ANIMATION: Motor proteins
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Motor Proteins
• Dynein interacts with
arrays of microtubules
to bring about
movement of eukaryotic
flagella and cilia
Flagella and Cilia
• A 9+2 array of microtubules extends lengthwise
through a flagellum or cilium
• The microtubules grow from a barrel-shaped
centriole, which remains below the finished array as
a basal body
Key Terms
• cilium
• Short, movable structure that projects from the plasma
membrane of some eukaryotic cells
• centriole
• Barrel-shaped organelle from which microtubules grow
• basal body
• Organelle that develops from a centriole
Flagella and Cilia
• 9+2 array: a ring of nine pairs of microtubules plus one pair at
its core
protein
spokes
pair of microtubules
in a central sheath
pair of
microtubules
plasma
membrane
dynein arms
A Sketch and micrograph of one
eukaryotic flagellum, crosssection. Like a cilium, it contains
a 9+2 array: a ring of nine pairs of
microtubules plus one pair at its
core. Stabilizing spokes and
linking elements that connect to
the microtubules keep them
aligned in this radial pattern.
Fig. 4.22a, p. 67
Flagella
and Cilia
B Projecting from each pair of
microtubules in the outer ring are
“arms” of dynein, a motor protein that
has ATPase activity. Phosphate-group
transfers from ATP cause the dynein
arms to repeatedly bind the adjacent
pair of microtubules, bend, and then
disengage. The dynein arms “walk”
along the microtubules. Their motion
causes adjacent microtubule
pairs to slide past one another
C Short, sliding strokes occur in a
coordinated sequence around the ring,
down the length of each microtubule
pair. The flagellum bends as the array
inside bends:
basal body, a microtubule organizing
center that gives rise to the 9+2 array and
then remains beneath it, inside the
cytoplasm
Fig. 4.22b, p. 67
ANIMATION: Flagella structure
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False Feet
• Pseudopods move the
cell and engulf prey
• Motor proteins attached
to microfilaments drag
the plasma membrane
ANIMATION: Phosphorus cycle
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4.11 Cell Surface Specializations
• Most cells of multicelled organisms are surrounded by a
complex mixture of fibrous proteins and polysaccharides
called extracellular matrix, or ECM
• extracellular matrix (ECM)
• Complex mixture of cell secretions
• Supports cells and tissues
• Has roles in cell signaling
ECM: Cuticle
• cuticle
• Secreted covering at a body surface
• Chitin covering protects arthropods
• Waxy coat protects plant’s exposed surfaces
thick, waxy
cuticle at
leaf surface
cell of leaf
epidermis
photosynthetic
cell inside leaf
Fig. 4.23, p. 68
Animal ECM
• ECM in animals consists of various carbohydrates and
proteins; it is the basis of tissue organization, and provides
structural support
• Example: Bone is mostly extracellular matrix composed of
collagen, a fibrous protein, hardened by mineral deposits
Plant ECM
• Plant cell wall is a type of ECM: Pliable primary walls
enclose secondary walls strengthened with lignin
• primary wall
• The first cell wall of young plant cells
• secondary wall
• Lignin-reinforced wall inside the primary wall of a plant cell
• lignin
• Material that stiffens cell walls of vascular plants
Plant
Cell Walls
A Plant cell secretions
form the middle lamella,
a layer that cements
adjoining cells together.
B In many plant tissues,
cells also secrete
materials that are
deposited in layers on
the inner surface of their
primary wall. These
layers strengthen the
wall and maintain its
shape. They remain after
the cells die, and become
part of pipelines that
carry water through the
plant.
middle
lamella
plasma
membrane
cytoplasm
primary
cell wall
secondary
cell wall
(added in
layers)
primary
cell wall
pipeline
made of
abutting
cell walls
Fig. 4.24a, p. 68
ANIMATION: Plant cell walls
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Plant Cell Junctions
• In plants, open channels called plasmodesmata
(plasmodesma) extend across cell walls, connecting the
cytoplasm of adjoining cells
• plasmodesmata
• Cell junctions that connect the cytoplasm of adjacent plant
cells
• Allow water, nutrients, and signaling molecules to flow
quickly from cell to cell
Plasmodesmata
middle lamella
C Plasmodesmata are
channels across the cell
walls and the plasma
membranes of living cells
that are pressed against
one another in tissues.
plasmodesma
middle lamella
Fig. 4.24c, p. 68
Cell Junctions in Animals
• In animal tissues, cells are connected to their neighbors and
to ECM by cell junctions
• cell junction
• Structure that connects a cell to another cell or to
extracellular matrix
• Cells send and receive ions, molecules, or signals through
some junctions
• Other kinds help cells recognize and stick to each other
and to extracellular matrix
Types of Cell Junctions
• tight junctions
• Arrays of fibrous proteins; join epithelial cells and
collectively prevent fluids from leaking between them
• adhering junction
• Cell junction that anchors cells to each other or to
extracellular matrix
• gap junction
• Cell junction that forms a channel across the plasma
membranes of adjoining animal cells
free surface
of epithelial
tissue
tight junctions
gap junction
Types of Cell
Junctions
basement membrane
(extracellular matrix)
adhering
junction
Fig. 4.25, p. 69
ANIMATION: Animal cell junctions
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4.12 Summary: Plant Cells
4.12 Summary: Plant Cells
Cell Wall Chloroplast
Protects, structurally Specializes in
supports cell photosynthesis
Cytoskeleton
Structurally
supports,
imparts shape
to cell; moves
cell and its
components
microtubules
microfilaments
intermediate
filaments
(not shown)
Mitochondrion
Energy powerhouse;
produces many ATP by
aerobic respiration
Plasmodesma
Communication junction
between adjoining cells
Plasma Membrane
Selectively controls the
kinds and amounts of
substances moving into
and out of cell; helps
maintain cytoplasmic
volume, composition
Central Vacuole
Increases cell
surface area; stores
metabolic wastes
Nucleus
Keeps DNA
separated from
cytoplasm; makes
nuclear envelope
ribosome subunits;
nucleolus
controls access to
DNA in
nucleoplasm DNA
Ribosomes
(attached to rough ER
and free in cytoplasm)
Sites of protein synthesis
Rough ER
Modifies proteins
made by ribosomes
attached to it
Smooth ER
Makes lipids, breaks
down carbohydrates and
fats, inactivates toxins
Golgi Body
Finishes, sorts, ships
lipids, enzymes, and
proteins
Lysosome-like Vesicle
Digests, recycles materials
A Typical plant cell components
Fig. 4.26a, p. 70
ANIMATION: Common eukaryotic
organelles
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Summary: Animal Cells
Cytoskeleton
Structurally
supports,
imparts shape
to cell; moves
cell and its
components
Nucleus
Keeps DNA
separated from
nuclear
cytoplasm;
envelope
makes ribosome
nucleolus
subunits;
DNA in
controls access
nucleoplasm to DNA
microtubules
microfilaments
Intermediate
filaments
Mitochondrion
Energy powerhouse;
produces many ATP by
aerobic respiration
Centrioles
Special centers that produce
and organize microtubules
Plasma Membrane
Selectively controls the kinds
and amounts of substances
moving into and out of cell;
helps maintain cytoplasmic
volume, composition
Ribosomes
(attached to rough ER
and free in cytoplasm)
Sites of protein synthesis
Rough ER
Modifies proteins
made by ribosomes
attached to it
Smooth ER
Makes lipids, breaks
down carbohydrates and
fats, inactivates toxins
Golgi Body
Finishes, sorts, ships
lipids, enzymes, and
proteins
Lysosome
Digests, recycles
materials
B Typical animal cell components.
Fig. 4.26b, p. 70
Summary: Cell Components
Key Concepts
• Eukaryotic Cells
• Cells of protists, plants, fungi, and animals are eukaryotic
• They have a nucleus and other membrane-enclosed
compartments
• Cells differ in internal parts and surface specializations
4.13 The Nature of Life
• Life is a property that emerges from cellular components, but
a collection of those components in the right amounts and
proportions is not necessarily alive
• Characteristics of life:
• A set of properties unique to living things
• Collectively, these properties characterize living things as
different from nonliving things
Characteristics of Living Things
1. They make and use organic molecules of life
2. They consist of one or more cells
3. They engage in self-sustaining biological processes such as
metabolism and homeostasis
4. They change over their lifetime by growing, maturing, and
aging
5. They use DNA as hereditary material
6. They have the collective capacity to change over successive
generations by adapting to environmental pressures
Food for Thought (revisited)
• Meat, poultry, milk, and fruits sterilized by exposure to
radiation are available in supermarkets
• By law, irradiated foods must be marked with a special
symbol:
• Foods sterilized with chemicals are not currently required to
carry any disclosure