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Systems and Surroundings
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mates_a_cell.html
A Tour of the Cell –CH 4
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Cell Theory
What all cells have
2 cell types- prokaryotes vs. eukaryotes
Eukaryotes
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Plasma membrane
Nucleus
Ribosomes
Endoplasmic Reticulum
Golgi Apparatus
Lysosomes
Peroxisomes
Vacuoles and vesicles
Endomembrane system
Mitochondria
Chloroplasts
Cytoskeleton
Cilia and flagella
Extra cellular matrix
Cell Theory
• 1. all living organisms are made up of at least
one cell
• 2. all cells arise from pre-existing cells
• 3. all cells are functional units of life
All cells have
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DNA
Cytoplasm
Plasma membrane (cell membrane)
Ribosomes
Two Cell Types
• Prokaryotic cells
• Eukaryotic cells
4.3 Prokaryotic cells (before kernel)
• Prokaryotic cells are structurally simpler than
eukaryotic cells.
• Bacteria and archaea are prokaryotic cells.
• They have one or more chromosomes and
ribosomes.
• Prokaryotes have a nucleoid and no true
organelles.
• Have cell walls
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Pili
Nucleoid
Ribosomes
Plasma membrane
Bacterial
chromosome
Cell wall
Capsule
Flagella
Different Shapes of Bacteria
10 m
100 mm
(10 cm)
Length of some
nerve and
muscle cells
Chicken egg
10 mm
(1 cm)
Unaided eye
Human height
1m
Frog egg
10 µm
1 µm
100 nm
Most plant
and animal
cells
Nucleus
Most bacteria
Mitochondrion
Mycoplasmas
(smallest bacteria)
Viruses
10 nm
Ribosome
Proteins
Lipids
1 nm
Small molecules
0.1 nm
Atoms
Electron microscope
100 µm
Light microscope
1 mm
Eukaryote ( true-kernel)
• Animal, Plant, Fungi, Protists
• Have a plasma membrane
• DNA (one or more chromosomes) is contained
in a nucleus
• Have membrane-bound organelles and other
structures
• 10-100 micrometers in size
• Animal cells and animal-like protists don’t
have cell walls
There are four life processes in eukaryotic cells
that depend upon structures and organelles:
• Manufacturing- nucleus, ribosomes, endoplasmic
reticulum, golgi apparatus
• Breakdown/hydrolysis- lysosomes, vacuoles,
peroxisomes
• Energy Processing/Power House- chloroplast,
mitochondria
• Structural support, communication, movementplasma membrane, cell wall, cytoskeleton
– A typical animal cell
• Contains a variety of membranous organelles (underlined)
Rough
endoplasmic
reticulum
Smooth endoplasmic
reticulum
Nucleus
Flagellum
Not in most
plant cells
Lysosome
Ribosomes
Centriole
Golgi
apparatus
Peroxisome
Microtubule
Cytoskeleton
Plasma membrane
Intermediate
filament
Mitochondrion
Figure 4.4A
Microfilament
Human blood cells
Other animal cells
• Cheek Cells
Muscle Cells
A typical plant cell has some structures that an
animal cell lacks
• Such as chloroplasts, a rigid cell wall, and central vacuole.
Figure 4.4B
Plasma Membrane
Fibers of the
extracellular
matrix
Carbohydrate
(of glycoprotein)
Glycoprotein
Glycolipid
Plasma
membrane
Phospholipid
Proteins
Microfilaments
of cytoskeleton
Cholesterol
Cytoplasm
4.5 The structure of membranes correlates with
their functions
• The plasma membrane controls the movement
of molecules into and out of the cell, a trait
called selective permeability
– The structure of the membrane with its component
molecules is responsible for this characteristic
– Membranes are made of lipids, proteins, and some
carbohydrate, but the most abundant lipids are
phospholipids
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Hydrophilic head
Phosphate
group
Symbol
Hydrophobic tails
Outside cell
Hydrophilic
heads
Hydrophobic
region of
protein
Hydrophobic
tails
Inside cell
Proteins
Hydrophilic
region of
protein
4.6 The nucleus is the cell’s genetic control center
• The nucleus controls the cell’s activities and is
responsible for inheritance
– Inside is a complex of proteins and DNA called
chromatin, which makes up the cell’s chromosomes
– DNA is copied within the nucleus prior to cell
division
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4.6 The nucleus is the cell’s genetic control center
• The nuclear envelope is a double membrane
with pores that allow material to flow in and out
of the nucleus
– It is attached to a network of cellular membranes
called the endoplasmic reticulum
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– The nucleus is the cellular control center (library)
• Containing the cell’s DNA, which directs cellular activities
Chromatin
Nuclear envelope
(2 membranes)
Nucleolus
Nucleus
Pore
Rough
endoplasmic
reticulum
Figure 4.5
Ribosomes
4.7 Ribosomes make proteins for use in the cell
and export
• Ribosomes are involved in the cell’s protein
synthesis
– Ribosomes are synthesized in the nucleolus, which is
found in the nucleus
– Cells that must synthesize large amounts of protein
have a large number of ribosomes
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4.7 Ribosomes make proteins for use in the cell
and export
• Some ribosomes are free ribosomes; others are
bound
– Free ribosomes are suspended in the cytoplasm
– Bound ribosomes are attached to the rough
endoplasmic reticulum (ER) associated with the
nuclear envelope
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Ribosomes
ER
Cytoplasm
Endoplasmic reticulum (ER)
Free ribosomes
Bound ribosomes
Large
subunit
TEM showing ER
and ribosomes
Diagram of
a ribosome
Small
subunit
4.9 The endoplasmic reticulum is a biosynthetic
factory
• There are two kinds of endoplasmic reticulum—
smooth and rough
• Smooth ER lacks attached ribosomes
• Rough ER lines the outer surface of membranes
– They differ in structure and function
– However, they are connected
– Has ribosomes
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Nuclear
envelope
Ribosomes
Smooth ER
Rough ER
4.9 The endoplasmic reticulum is a biosynthetic
factory
• Smooth ER is involved in a variety of diverse
metabolic processes
– For example, enzymes produced by the smooth ER
are involved in the synthesis of lipids, oils,
phospholipids, and steroids
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• Smooth endoplasmic reticulum (ER) has a variety of
functions
– Synthesizes lipids
– Processes toxins and drugs in liver cells
– Stores and releases calcium ions in muscle cells
Smooth ER
Rough ER
Nuclear
envelope
Ribosomes
Figure 4.7
Rough ER
TEM 45,000
Smooth ER
Rough ER
• Rough ER makes additional membrane for itself
and proteins destined for secretion
– Once proteins are synthesized, they are transported
in vesicles to other parts of the endomembrane
system
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Transport vesicle
buds off
4
Ribosome
Secretory
protein
inside transport vesicle
3
Sugar
chain
1
2 Glycoprotein
Polypeptide
Rough ER
The Golgi apparatus finishes, sorts, and ships cell
products
– Stacks of membranous sacs receive and modify ER
products then ship them to other organelles or the
cell surface
Golgi apparatus
TEM 130,000
“Receiving” side
Transport
vesicle
from ER
New vesicle
forming
Figure 4.9
“Shipping” side
Transport
vesicle
Lysosomes are sacs of digestive enzymes
• digestive functions in many single celled organisms
• In white blood cells, they destroy ingested bacteria
• Also recycle damaged organelles
Rough ER
1
Transport vesicle
(containing inactive
hydrolytic enzymes)
Golgi
apparatus
Plasma
membrane
2
Engulfment
of particle
“Food”
Lysosomes
Lysosome
engulfing
damaged
organelle
3
5
4
Food
vacuole
Figure 4.10A
Digestion
Digestive
enzymes
Lysosome
Plasma
membrane
Digestive
enzymes
Lysosome
Plasma
membrane
Food vacuole
Digestive
enzymes
Lysosome
Plasma
membrane
Food vacuole
Digestive
enzymes
Lysosome
Plasma
membrane
Digestion
Food vacuole
Lysosome
Vesicle containing
damaged mitochondrion
Lysosome
Vesicle containing
damaged mitochondrion
Lysosome
Digestion
Vesicle containing
damaged mitochondrion
4.12 Vacuoles function in the general
maintenance of the cell
• Vacuoles are membranous sacs that are found
in a variety of cells and possess an assortment
of functions
– Examples are the central vacuole in plants with
hydrolytic functions, pigment vacuoles in plants to
provide color to flowers, and contractile vacuoles in
some protists to expel water from the cell
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Chloroplast
Nucleus
Central
vacuole
Nucleus
Contractile
vacuoles
4.13 A review of the structures involved in
manufacturing and breakdown
• The following figure summarizes the
relationships among the major organelles of the
endomembrane system
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Nucleus
Nuclear
membrane
Rough ER
Smooth
ER
Transport
vesicle
Transport
vesicle
Golgi
apparatus
Lysosome
Vacuole
Plasma
membrane
4.8 Overview: Many cell organelles are connected
through the endomembrane system
• The membranes within a eukaryotic cell are
physically connected and compose the
endomembrane system
– The endomembrane system includes the nuclear
envelope, endoplasmic reticulum (ER), Golgi
apparatus, lysosomes, vacuoles, vesicles, and the
plasma membrane
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Energy Company of Cells
• Mitochondria- found in all eukaryotic cells
• Chloroplasts- found in plants and some
protists (unicellular eukaryotes)
Mitochondria
• Not part of the endomembrane system
• Carry out cellular respiration to convert
chemical energy in food to ATP for cellular use
• Has two layers of membrane: outer layer
smooth and inner layer folded, forming:
– Intermembrane space
– Mitochondrial matrix
• Which contains DNA, ribosomes, and enzymes
Figure 4.15
Chloroplast
• Found in plants and some protists
• Not part of the endomembrane system
• Site of photosynthesis
– Converts CO2, H2O, and solar energy into chemical
energy
• Has 2 layers of membrane (like mitochondria)
– Inner space contains stroma – thick fluid with
DNA, ribosomes, and enzymes
– Stacked thylakoid sacs are grana
• Packed with green pigments to absorb solar energy
Chloroplasts convert solar energy to
chemical energy
– Chloroplasts, found in plants and
some protists convert solar energy
to chemical energy in sugars
– Also has its own DNA
THE CYTOSKELETON AND RELATED
STRUCTURES
The cell’s internal skeleton helps organize its
structure and activities
– A network of protein fibers make up the cytoskeleton.
Tubulin subunit
Actin subunit
Fibrous subunits
25 nm
7 nm
Microfilament
10 nm
Intermediate filament
Microtubule
– Filaments
• Enable cells to change shape and move
• Reinforce the cell and anchor organelles
– Microtubules give the cell rigidity
• Act as tracks for organelle movement
Cilia & flagella move when microtubules bend
Figure 4.17A
LM 600
Colorized SEM 4,100
– Eukaryotic cilia and flagella are locomotor appendages
that protrude from certain cells
Figure 4.17B
Cilia
– Smaller in size, more in number
– Whip-like movement
– Inside trachea to move mucus
– Can also be used to capture food
Flagella
• Larger, usually one per cell
• Snake-like movement
• Sperm for swimming
The extracellular matrix of animal cells functions in
support, movement, and regulation
• Cells synthesize and secrete the extracellular
matrix (ECM) that is essential to cell function
– The ECM is composed of strong fibers of collagen,
which holds cells together and protects the plasma
membrane
– ECM attaches through connecting proteins that bind
to membrane proteins called integrins
– Integrins span the plasma membrane and connect to
microfilaments of the cytoskeleton
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Glycoprotein
complex with long
polysaccharide
EXTRACELLULAR FLUID
Collagen fiber
Connecting
glycoprotein
Integrin
Plasma
membrane
Microfilaments
CYTOPLASM
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