Download AP Biology Ch. 6 Cells


What is the difference between life and nonlife? Where does the line begin?




All organisms are made of cells
The cell is the simplest collection of matter
that can live
Cell structure is correlated to cellular function—The
contraction of muscle cells allows you to move your
eyes as you read this sentence.
All cells are related by their descent from earlier
cells—however, they have been modified in many
different ways throughout the history of life on
Earth.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings




Light Microscopes: visible light
is passed through the specimen
and then through glass lenses.
The lenses bend in the light in
such a way that the image is
magnified.
Magnification=the ratio of an
object’s image size to its real
size
Resolution=a measure of the
clarity of the image


Light microscopes
cannot resolve detail
finer than 200 nm, the
size of a small
bacterium—that’s
about 1,000 times the
size of the object.
Advantage: Light
Microscopes can
observe living
organisms
Red Blood Cells
Pollen grain



Above: Spider
shown with a
Scanning
Electron
Microscope

Electron Microscopes
were first invented in
the 1950s.
They focus a beam of
electrons through a
specimen or onto its
surface.
They have a resolution
100 X better than a light
microscope.
Disadvantage: Only
nonliving material can
be studied
10 m
Human height
Length of some
nerve and
muscle cells
0.1 m
Chicken egg
1 cm
Frog egg
100 µm
10 µm
Most plant and
animal cells
Nucleus
Most bacteria
Note:
The scale is
logarithmic,
each reference
mark is a
tenfold increase
in size from the
bottom to top
1 µm
Mitochondrion
100 nm
Smallest bacteria
10 nm
1 nm
0.1 nm
Viruses
Ribosomes
Proteins
Lipids
Small molecules
Atoms
Electron microscope
1 mm
Light microscope
Most cells are
between 1 and
100
micrometers in
diameter (see
light region of
chart to the
right .
1m
Unaided eye
The Size Range
of Cells:



All cells have a plasma membrane surrounding
the cytosol (a semifluid, jellylike substance in
which organelles are found.
All cells contain chromosomes and ribosomes
Variations in other components, however, can
be found between cells.

Prokaryotic cells are
characterized by having






No nucleus
DNA in an unbound
region called the
nucleoid
No membrane-bound
organelles
“Pro”=before
“karyo”=kernel/nucleus
Bacteria are Prokaryotic





Eukaryotic cells have
DNA enclosed by a
membrane in the
nucleus.
“Eu”= True
In addition, they have
other membrane-bound
organelles in the
cytoplasm
Generally, they are
much larger than
prokaryotic cells
All organisms except
bacteria have eukaryotic
cells



Size is a general aspect
of cell structure that
relates to function
Limits to cell size are
due to the logistics of
carrying out cell
functions
Having organelles to
move materials around
allows eukaryotic cells
to be larger than
prokaryotic cells.
Elephants don’t have larger cells
than other organisms—they just
have more cells!
Surface Area and Volume


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
Why is this
important to
cells?
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 6-9a
A Typical Animal Cell:
ENDOPLASMIC RETICULUM
(ER)
Rough ER Smooth ER
Flagellum
Nuclear
envelope
NUCLEUS
Nucleolus
Chromatin
Centrosome
Plasma
membrane
CYTOSKELETON:
Microfilaments
Intermediate
filaments
Microtubules
Ribosomes
Microvilli
Golgi
apparatus
Peroxisome
Mitochondrion
Lysosome
Fig. 6-9b
Nuclear envelope
NUCLEUS Nucleolus
Chromatin
Rough endoplasmic
reticulum
A Typical Plant Cell
Smooth endoplasmic
reticulum
Ribosomes
Central vacuole
Golgi
apparatus
Microfilaments
Intermediate
filaments
Microtubules
Mitochondrion
Peroxisome
Chloroplast
Plasma
membrane
Cell wall
Wall of adjacent cell
Plasmodesmata
CYTOSKELETON



Cells need to build proteins
Cells need energy
Cells need to make more cells








Proteins are macromolecules that are used by
organisms for many different things:
Building cell structures
Transporting nutrients such as oxygen
Enzymes speed up chemical reactions
Hormones regulate functions of systems
Defensive proteins guard against infection
Responsive proteins communicate with other
cells
WOW! Lots of Work!




The nucleus contains
most of the genes in the
eukaryotic cell
It is generally the most
conspicuous organelle in
a eukaryotic cell
The Nuclear Envelope
encloses the nucleus
Chromatin contains the
DNA of the cell—it is
organized into individual
chromosomes.
The nuclear envelope is a double
membrane. It is perforated with pore
structures. An intricate protein
structure called a pore complex
surrounds each pore.


The Nucleus is like
the “brain” of the
cell—controlling most
of the activities of the
cell. How does it do
this? By controlling
what proteins are
made.
Proteins are the
workhorse molecules
of the cell—they are
made by ribosomes.




The nucleus contains the
following organelles that
are needed for protein
synthesis:
Nucleolus—builds rRNA
and Ribosomes
Chromosomes/Chromatin
—contains strands of DNA
Nuclear Membrane—has
pores to allow mRNA to
leave nucleus and go to
ribosomes


Ribosomes are particles
made of ribosomal RNA
and protein
Ribosomes carry out
protein synthesis in two
locations:
In the cytosol (free
ribosomes)
 On the outside of the
endoplasmic reticulum or
the nuclear envelope
(bound ribosomes)

DNA Controls the
production of proteins
in a series of steps that
begins in the nucleus
and ends at
ribosomes.
Remember: Proteins do
the work of the cell.
DNA directs which
proteins are made.
Ribosomes build the
proteins.







Take in nutrients
Take in oxygen
Build cell structures
Remove wastes
Make ATP
Cells use many organelles to
obtain, store, and release
energy: plasma membrane,
ER, Golgi Apparatus,
Lysosomes, Mitochondria
and Chloroplasts
ATP


“Endo”=inside
Consists of: Nuclear Envelope, Endoplasmic
Reticulum, Golgi Apparatus, Lysosomes,
Vacuoles, and the Plasma Membrane


“Endo”=inside;
“plasm”=liquid;
“reticula”=intricate
network
ER is an intricate
network of
membranes that start
at the nuclear
membrane and
continue throughout
the cell to the plasma
membrane.
Smooth ER=no ribosomes
attached
Rough ER=ribosomes
attached





Smooth ER:
Makes lipids
Metabolizes
carbohydrates
Detoxifies poisons
Stores calcium




Rough ER:
Because ribosomes are
attached, many proteins
are made here, especially
glyco-proteins. (what are
these?)
Distributes proteins in
vesicles (little membranebound bundles of
proteins)
Makes membranes for the
cell





Golgi Apparatus is a
complex of flattened sacs
of membranes (called
cisternae).
Function:
Modifies products of the
ER
Manufactures certain
macromolecules
Sorts and packages
materials into transport
vesicles
The Golgi is like the UPS store: It
is the packaging and shipping
center of the cell.




“lysis”=to split
Lysosomes are sacs of
enzymes that can
digest large molecules
These enzymes can
digest proteins, fats,
polysaccharides, and
nucleic acids—
basically anything
that enters the cell!
They can even digest
organelles in the cell
Lysosomes
may be called
the
“Stomach” of
the cell; or
even “The
Suicide Sac”



Some types of cell can
engulf another cell by
phagocytosis; this
forms a food vacuole
A lysosome fuses with
the food vacuole and
digests the molecules
Autophagy: The
lysosome can also digest
damaged organelles




These enzymes work best at
pH 5
The lysosome makes its own
enzymes
The pH inside the lysosome
stays at ph 5 because the
transport proteins in the
membrane pump in H+ ions.
These enzymes don’t work
well in the pH of the rest of
the cell. Why? (so it won’t
digest the cell if it leaks)
White Blood Cells such as
this one contain many
lysosomes. They engulf
bacteria and digest them.



Lysosome diseases are often
fatal.
The enzymes in the lysosome
may be defective…if so, when
the lysosome takes in
macromolecules, they may not
get digested properly
Undigested material builds up
and lysosome gets larger &
larger, eventually disrupting
cells and organs.
Tay-Sachs disease is a
genetic disease that
causes fat molecules to
build up in the brain.
Affected children usually
die before age 3.



Lysosomes can be
used to kill cells when
they are supposed to
be destroyed
Some cells have to die
for proper
development in an
organism
Apoptosis= “autodestruct” process;
lysosomes break open
& kill the cell. Why?
Tadpoles lose their tails as they
mature
Fingers
are
fused in
the
human
embryo


Vacuoles are membrane-bound organelles
whose functions vary—but most are used for
storage of needed materials
Food vacuoles: formed by phagocytosis, then
store food to be broken down by lysosomes



The central vacuole of
mature plant cells develops
from smaller vacuoles that
come from the ER and Golgi
apparatus.
This organelle in plants
stores proteins, sugars, ions
and water. Some may
contain pigments to give
color to flowers.
They may contain
poisonous substances that
keep the plant from being
eaten.
The membrane around the central
vacuoles is called the tonoplast.


Protists are fresh-water single-celled
organisms. They live in an environment that
causes water to constantly diffuse into their
body. This could cause swelling and death.
Contractile Vacuoles act like water pumps,
continually pumping water out of the cell.
Contractile Vacuoles in a
Paramecium


Mitochondria and Chloroplasts change energy
from one form to another.
Mitochondria are the sites for cellular
respiration; Chloroplasts are the sites for
photosynthesis.
Mitochondrion
Chloroplasts



Mitochondria –where
cellular respiration
occurs.
Where the chemical
energy stored in sugars
such as glucose is
converted to ATP—a
molecule that stores
cellular energy.
The “Powerhouse” of
the cell
Mitochondria have 2 membranes; the
inner one is folded to increase the
surface area. Enzymes attached to the
membranes do the work of the
mitochondria.


Almost all eukaryotic cells have
mitochondria—either one very large
mitochondrion, or thousands of smaller ones.
Which types of cells would have lots of
mitochondria? Hint: Which cells need a lot of
energy?


Chloroplasts also have two
membranes; the inner
membranes form sacs that are
stacked. In these membranes,
chlorophyll (green pigment)
traps sunlight energy.

Chloroplasts, found in
plants and algae are
where photosynthesis
occurs
They convert the energy
from sunlight into
organic compounds
such as glucose.
“Little Green Sugar
Factories”




Both transform energy
from one kind to
another
Both make ATP
Both have double
membranes
Both are semiautonomous
organelles—they can
move, change shape,
and divide
Both have their own DNA and
ribosomes—almost like
independent cells-within-a-cell



A peroxisome is a
specialized metabolic
compartment.
Peroxisomes contain
special enzymes that
remove hydrogen from
various substrates to form
H2O2 (hydrogen
peroxide).
This process may detoxify
poisons, or break down
fuel for energy.
Peroxisomes produce H2O2 as a
by-product of many of the
reactions in a cell.
H2O2 is toxic, so the peroxisome
has an enzyme, catalase, that
breaks down H2O2.



Organelles involved
in organizing the cell
so that it can divide
are:
Cytoskeleton
Centrioles (in animal
cells)


The cytoskeleton is a
network of fibers that
organizes structures
and activities in the
cell.
It gives the cell shape
and support, much
like the framework of
a building holds it up
and divides it into
rooms.


Besides giving shape
to the cell, the
cytoskeleton anchors
the other organelles.
It can be quickly
dismantled in one
part of the cell, then
reassembled in a new
location, changing the
shape of the cell!
The cytoskeleton consists of
three types of structures:
Microtubules, Microfilaments,
and Intermediate filaments
Vesicle
ATP
Receptor for
motor protein
Motor protein Microtubule
(ATP powered) of cytoskeleton
Microtubule
Vesicles
0.25 µm
By interacting with motor proteins, the cytoskeleton can move whole cells or just
move parts of the cell around. Inside the cell, vesicles can travel to their
destinations along “monorails” provided by the cytoskeleton.
The cytoskeleton is
composed of three main
elements :
1.actin filaments (shown
in red); also called
microfilaments.
2.mictrotubules (gold)
3. intermediate filaments
(blue)
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings


Hollow tubes made of Tubulin
Function: maintains cell shape, cell motility (as
in cilia or flagella), chromosome movement in
cell division, organelle movement.
Cilia
Flagellum


Tiny thread-like fibers
made of 2 intertwined
strands of actin
Function: Maintains cell
shape, changes in cell
shape, muscle
contraction, cytoplasmic
streaming, cell motility
(as in pseudopodia),
and cell division
(cleavage furrow
formation)


Made of fibrous
proteins supercoiled
into thicker cables
Function:
maintenance of cell
shape, anchoring
nucleus and certain
organelles


In animal cells, microtubules grow out from a
centrosome which is located near the nucleus.
Within the centrosome is a pair of centrioles,
each made of 9 sets of triplet microtubules.
Centrioles in
animal cells
are essential
for cell division.
They are not
found in plant
cells.

Cilia are hairlike
extensions of certain
cells that enable the
cell to move or move
fluid across the
surface of the cell.


Flagellum are singular
long, tail-like
extensions that also
enable certaincells to
move.
Both cilia and flagella
are made of
microtubules.



The cell wall is found outside the plant cell.
Cell walls protect the plant cell, maintains its
shape, and prevents excessive uptake of water.
Cell walls are made mostly of microfibrils of
cellulose.


A young plant first
secretes a relatively
thin and flexible cell
wall called the
primary cell wall.
Between primary cell
walls of adjacent cells
is the middle lamela, a
thin layer rich in
sticky polysaccharides
called pectin.
Some cells will add a secondary cell
wall outside the primary cell wall. Wood
is primarily secondary cell walls
Plant cellulose cell walls from
the ragweed plant anther
(Ambrosia psilostachya).
The rigid cell wall of plants is
made of fibrils of cellulose
embedded in a matrix of
several other kinds of polymers
such as pectin and lignin.
Although each cell appears
encased within a box, in fact
primary cell walls are
perforated permitting
plasmodesmata to connect
adjacent cells.

Animal cells do not have cell walls, but they do have
an elaborate extracellular matrix. The main ingredients
are glycoproteins (the most abundant is collagen).
Proteoglycans are
proteins with many
carbohydrate chains
attached.
Integrins are proteins
embedded in the cell
membrane that attach
to the extracellular
matrix.
The main functions of
the ECM: adhesion,
support, regulation