Download Bio. Ch. 7 - NorthMacAgScience

Chapter 7
Cell Structure & Function
Section 7-1
Life is Cellular

What led to the discovery of the cell?
– The Microscope

Remember!
– Cells make up all living things.
The Discovery of the Cell
 Early
Microscopes:
– Scientists didn’t use microscopes until
the 1600’s.
– Robert Hooke -one of the 1st to look at
cells under a microscope.
 Gave
cells their name.
 P. 169, fig. 7-1
 He was looking at dead cork cells.
Cork Cells (Hooke)
Robert Hooke
 At
about the same time as Hooke,
Anton van Leeuwenhoek used a tiny
microscope to look at pond water.
 He
discovered the new world of
microorganisms.
The Cell Theory



In 1838, Matthias Schleiden stated that all
plants are made of cells.
In 1839, Theodore Schwann stated that all
animals were made of cells.
In 1855, Rudolf Virchow stated that cells
could only come from other cells.
The Cell Theory:
P. 170
1. All living things are made of cells.
2. Cells are the basic units of structure &
function in living things.
3. New cells are produced from existing
cells.
Exploring the Cell
Today, modern biologists use more
powerful microscopes & techniques.
 Some of the tools they use:

– Fluorescent labels & light microscopy
 Able
to follow molecules moving through a cell.
– Confocal light microscopy
 Scans
cells w/ a laser to make 3D images of cells &
their parts.
– High-resolution video
 Enables
us to make movies of cells as they grow,
divide, & develop.
 http://www.kent.edu/projects/cell/vi
deo/fatheadminnow2.mpg
Another New Method
 Electron
Microscopes (EM):
– Can view things 1 million times smaller
than that of a light microscope.
– 2 types of EM’s:
 Transmission
Electron Microscopes (TEM)
 Scanning Electron Microscopes (SEM)
 TEM:
– Lets us see cell structures & large
protein molecules.
– Cells & tx’s must be cut into ultra-thin
slices before they are examined.
– 2D cross sectional image.
 TEM
 SEM:
– 3D images of cells
– Objects don’t have to be thinly sliced to
view.
 SEM
 Remember!
– EM’s can only view the nonliving.
 In
the 1990’s, researches perfected a
new class of microscope.
– The Scanning Probe Microscope
– Produces images by tracing the surfaces
of samples w/ a fine probe.
– Can observe single atoms.
– Used to see DNA & protein molecules.

Scanning Probe
Microscope
Prokaryotes & Eukaryotes


Cells come in all shapes & sizes.
But, all cells have 2 characteristics
in common:
1.
2.
They have a cell membrane at some point
in their lives.
They contain DNA.
 Cells
fall into 2 categories based on if
they have a nucleus.
– Nucleus –large membrane bound
organelle.
 Contains
cell’s DNA.
 Controls many of the cell’s activities.
– Organelle –specialized structure that
performs important functions w/in the
cell.
 “Tiny
organs”
 The
2 categories are:
– Prokaryotes
 Cells
don’t contain a nucleus.
– Eukaryotes
 Cells
do contain a nucleus.
– Pro = before
– Eu = true
– Karyon =kernel
Prokaryotes
Generally smaller & simpler than
eukaryotic cells.
 Prokaryotes have DNA, but it’s not
contained in a nucleus.
 All are unicellular.
 Despite their simplicity, prokaryotes:

–
–
–
–

Grow
Reproduce
Respond to their env.
Some are mobile.
Ex:
– Bacteria
Eukaryotes
Generally larger & more complex than
prokaryotes.
 Eukaryotes contain membrane bound
organelles & a nucleus (DNA).
 Eukaryotes can be unicellular or
multicellular.
 Ex:

–
–
–
–
Plants
Animals
Fungi
Protists
Pro-k vs. Eu-k
Prokaryotes
Cell membrane
Contain DNA
Eukaryotes
Nucleus
Endoplasmic reticulum
Golgi apparatus
Lysosomes
Vacuoles
Mitochondria
Cytoskeleton
Plant vs. Animal Cell
Animal Cells
Centrioles
Plant Cells
Cell membrane
Ribosomes
Nucleus
Endoplasmic reticulum
Golgi apparatus
Lysosomes
Vacuoles
Mitochondria
Cytoskeleton
Cell Wall
Chloroplasts
Section 2
Eukaryotic Cell Structure
Comparing the Cell to a Factory
 Organelles
organs”.
–literally means “little
– Specialized structures that carry out
specific functions in a cell.
 Cell
biologist divide cells into 2 parts:
– The nucleus
– The cytoplasm
 Cytoplasm
–portion of the cell
outside the nucleus.
– Cytoplasm is a gelatinous-like material.
Cytoplasm:
Nucleus
 The
cell.
nucleus is the control center of the
– It contains almost all the cell’s DNA & w/ it
the coded instructions for making proteins
& other important molecules.
 Surrounding
the nucleus is a double
membrane called the nuclear envelope.
 On
the nuclear envelope you will find
nuclear pores.
– Allow materials to move in & out of the
nucleus.
 Ex:
– Proteins
– RNA
– Other molecules
 Chromatin
–a granular material
visible w/in the nucleus.
– It consists of DNA tightly coiled around
proteins.
– Most of the time chromatin is spread
throughout the nucleus.
– However, when a cell divides, chromatin
condenses to form chromosomes.
 Another
structure found in most
nuclei is a nucleolus.
– The nucleolus assembles ribosomes.
 P.
176, fig. 7-7
Ribosomes


Ribosomes –small particles of RNA &
protein found throughout the cytoplasm.
Ribosomes make proteins by following
coded instructions that come from the
nucleus.
– These instructions are RNA.

Cells that are major protein producers
often have numerous ribosomes.
Endoplasmic Reticulum (ER)
 Endoplasmic
Reticulum –an internal
membrane system in cells in which
lipid components of the cell
membrane are assembled & some
proteins are modified.

There are 2 portions to an ER:
– The rough ER
– The smooth ER

The rough ER
– Involved in the synthesis of proteins.
– It is said to be rough b/c it has ribosomes
found on its surface.
– Newly made proteins enter the rough ER & get
modified.
 The
Smooth ER
– No ribosomes found on the surface.
– Contains collections of enzymes that
perform special tasks such as:
 Synthesis
of membrane lipids
 Detoxification of drugs
– Liver cells tend to have a large amounts
of smooth ER.
 RER
 SER
Golgi Apparatus (GA)
 Proteins
made in the ER move to the
Golgi Apparatus (GA).
 The
GA looks like a stack of closely
apposed membranes.
 The
GA’s modifies, sorts, & packages
proteins & other materials from the
ER.
– These proteins can be stored in the cell
or secreted out of the cell.
 Kind
 P.
of like
UPS.
178, fig. 7-9
Lysosomes
 The
clean up crew.
 Lysosome
–small organelles filled w/
digestive enzymes.
 Lysosomes
are involved in:
– Breaking down old organelles.
– Digesting foreign matter in the cell.
 Tay-Sachs
-a disease is caused by
lysosomes that fail to properly do
their job.
– Fatal by the age of 4.
– More common in eastern European
Jews.
Vacuoles
 Vacuoles
–an organelle that stores
materials such as:
– Water
– Salts
– Proteins
– Carbs
 Plants
have large central vacuoles
that can hold, water & wastes.
– P. 179, fig. 7-10
Mitochondria & Chloroplasts
 The
power plants of a cell.
 Most cells get their energy (E) in 2
ways:
– Food (Heterotrophs)
– Sun (Autotrophs)
 Mitochondria:
– Can be found in almost all eukaryotic
cells.
 Including
plant cells.
– Converts chemical E into compounds
that are easy for the cell to use.
 Ex:
ATP (Adenosine Triphosphate)
 Mitochondria
membranes.
are enclosed by 2
– An outer membrane
– An inner membrane
 Highly
folded on itself.
 Creates more surface area for chemical
reactions.
 Chloroplasts:
– Found in plants & some other orgs.
– They capture sunlight & convert it into
chemical E by photosynthesis.
 This
chemical E is then converted to ATP by
mitochondria in the plant.
– Also surrounded by 2 membranes.
– Contains a green pigment called
chlorophyll.
 Chloroplasts
Organelle DNA
 Chloroplasts
& mitochondria contain
their own DNA.
– No other organelles do.
 It
is believed that both of these
organelles are ancient descendants
of prokaryotes.
 This
is called the endosymbiotic
theory.
Cytoskeleton
 Cytoskeleton
–a network of protein
filaments that helps the cell maintain
its shape.
– It is also involved in movement.
 The
cytoskeleton is made up of:
– Microfilaments
– Microtubules
 Microfilaments:
– Threadlike
– Made of actin
– Forms a tough, flexible framework that
supports the cell.
– Also responsible for cytoplasmic
movement of the cell.
 Microtubules:
– Hollow tube-like structures
– Made of tubulin
– Critical to maintaining cell shape.
– Also form structures called spindles
during cell division.
– Tubulin is also used to make centrioles.
 Located
near the nucleus.
 Help organize cell division.
 Microtubules
also help w/ movement.
– They make up cilia & flagella.
 P.
181, fig. 7-11
Section 7-3
Cell Boundaries
 All
cells are surrounded by a thin
barrier called the cell membrane.
 Many
cells also have a strong
supporting layer around that
membrane called the cell wall.
Cell Membrane
 Cell
membranes regulate what
enters & leaves a cell.
 They
also aid in protection & support.
 Nearly
all cell membranes are a
flexible, double layered sheet called
a lipid bilayer.
– P. 182, fig. 7-12
 Along
w/ lipids, the cell membrane
also has proteins & carbohydrates
embedded in it.
 The
lipid bilayer is often called a
mosaic, b/c it is made up of many
different parts.
 The
proteins form channels & pumps
for moving materials across the
membrane.
 The carbohydrates act like ID cards,
allowing individual cells to identify
one another.
 http://www.youtube.com/watch?v=Q
qsf_UJcfBc&feature=related
 http://www.youtube.com/watch?v=v
h5dhjXzbXc
Cell Walls (CW’s)
 Found
in:
– Plants
– Algae (Protists)
– Fungi
– Many prokaryotes
 CW’s
(not all)
lie outside the cell membrane.
 Most
cell walls allow certain
substances to pass through.
 Such as:
– H20
– CO2
– O2
 Its
main function is to support &
protect the cell.
 Most
CW’s are made of fibers of
carbohydrate & protein.
 Plant
CW’s are made of cellulose.
– Cellulose is a tough carbohydrate fiber.
– The fiber in your diet.
Diffusion Through Cell Boundaries
 The
movement of molecules from
one side of the cell membrane to the
other.
Measuring Concentration
 Recall
what a solution is.
– What’s a solute?
– What’s a solvent?
 Concentration
–the mass of solute in
a given volume of solution, or
mass/volume.
 Lets figure concentration of a
solution.
– If you dissolved 12g of salt in 3L of
water, the concentration would be:
12g/3L = 4 g/L
Diffusion
 Diffusion
–process of molecules
moving from an area of high
concentration to an area of low
concentration.
– Equilibrium –when the concentration of
a solute is the same throughout a
solution.
 Diffusion
reached.
will go on until EQ is
 What
does diffusion have to do w/ a
cell membrane?
– P. 184, fig. 7-14
 Diffusion
cell.
– It’s free!
requires no E output by the
Osmosis

Biological membranes are selectively
permeable.
– Some substances can pass & some can’t.

Water passes very easily.

However, many solutes can’t.

Osmosis –the diffusion of water through a
selectively permeable membrane.
How Osmosis Works
 H2O
moves from an area of high H2O
concentration to an area of low H2O
concentration.
 Water
moves across the membrane
until EQ is reached.
Osmosis
Section 7-3
 http://www.youtube.com/watch?v=s
diJtDRJQEc&feature=related
3 types of Osmotic Solutions:
P. 186, fig. 7-16

Isotonic
– Concentrations are equal on both sides of the
membrane.
– Normal looking cells

Hypertonic
– Solution outside the cell has a higher solute
concentration than the inside of the cell.
– Water leaves the cell.
–

Cells shrink
Hypotonic
– Solution has a lower solute concentration than the cell.
– Water enters the cell.
– Cells swell
Plant Cells
Plant Cells
 http://www.youtube.com/watch?v=G
OxouJUtEhE&feature=related
Turgid
Flaccid
Red Blood Cells
Osmotic Pressure



Osmosis exerts a pressure known as
osmotic pressure.
Osmotic pressure -the pressure exerted by
the flow of water through a semi
permeable membrane.
This can cause serious problems for a cell.
– Cells can swell to the point of bursting.
 Fortunately,
animal cells are in a
isotonic solution & don’t come into
contact w/ pure H2O.
– If they did they would burst.
 Also,
plant cells & bacterial cells have
cell walls that prevent the cell from
bursting.
Facilitated Diffusion
 Facilitated
diffusion –movement of
specific molecules across CM’s via
protein channels.
– P. 187, fig. 7-17
 There
are hundreds of protein
channels that allow only certain
substances to cross different
membranes.
 This
 It
process does not require E.
acts just as diffusion.
– It goes from high to low concentrations.
Facilitated Diffusion
 http://www.d.umn.edu/~sdowning/
Membranes/diffusionanimation.html
Active Transport
 When
cells move materials against
the concentration gradient, they are
using Active Transport.
– This process requires E.
 Active
transport is carried out by
transport proteins or pumps found in
the membrane.

Transport of larger molecules can
be done through 2 active transport
processes:
1. Endocytosis
–
P. 188, fig. 7-18
2. Exocytosis
– For each of these processes, the shape
of the membrane changes.
Endo & Exo
 http://www.youtube.com/watch?v=K
7yku3sa4Y8&feature=related
Molecular Transport

Endocytosis –process of taking material
into the cell by infolding or pocketing of
the CM.
– This process forms a vacuole in the
cell.
– This process works for:



taking in food
larger molecules
other cells
– 2 examples of endocytosis are:


Phagocytosis
Pinocytosis
 Phagocytosis
– extensions of
cytoplasm surround a particle &
package it w/in food vesicles.
– Amoebas use this method
 Fig.
7-18
 Pinocytosis
–the process of taking in
liquids from the surrounding env.
 Many
cells also release large
amounts of material from the cell.
 This process is called exocytosis.
 Ex:
– The removal of water by a contractile
vacuole is an example of this kind of
active transport.
 http://highered.mcgraw-
hill.com/sites/0072437316/student_
view0/chapter6/animations.html#
Section 7-4
The Diversity of Cellular
Life
Unicellular Organisms
 Unicellular
orgs. –made of one cell.
 Unicellular
orgs. can:
– grow
– respond to the env.
– reproduce
– transform E
 Unicellular
Earth.
 Examples
orgs. dominate life on
on P. 190, fig. 7-20
Multicellular Organisms



Orgs. made up of many cells.
Multicellular orgs. have cells that are
specialized.
Cell Specialization –process in which cells
develop in different ways to perform
different tasks.
– P. 191, fig. 7-21
Specialized Animal Cells
 Examples
animals:
of specialized cells in
– Red blood cells
 Transport
O2 throughout the body.
– Pancreatic cells
 Produce
enzymes that aid in digestion.
 Contain cells specialized for making
proteins.
– These cells have numerous ribosomes.
– Muscle cells
 Able
to contract & relax, causing movement
of our bones.
Specialized Plant Cells
 Guard
cells of the stomata:
– Monitor a plants internal conditions, &
makes changes accordingly.
Levels of Organization
 The
levels of organization in a
multicellular org. are as follows:
– Individual Cells
– Tissues
– Organs
– Organ systems
– Organism
 P.
192, fig. 7-22
Examples
neurons
(nerve cells)
nervous tissue
brain
central nervous system
human

Tissue –a group of similar cells that
perform a specific function.
– Ex:
 The
collection of cells in the pancreas that make
proteins.
– Most animals have 4 types of tx:
 Muscle
 Epithelial
 Nervous
 connective
 Organs
–many groups of tx’s working
together.
– Each muscle is an organ.
– However, it also contains nervous tx, &
connective tx.
 Organ
system –a group of organs
working together to perform a
specific function.
– Digestive system
– Reproductive system
– Nervous system
 Altogether,
organ systems make up
the organism.
Body Systems