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Chapter 7
Cell Structure &
Function
7-1: Life is Cellular
Discovery of the Cell:
- It began with the
development of the
microscope.
1665 – Robert Hooke used
an early compound
microscope to view cork
- He coined the term
“cell.”
1674 – Anton van
Leeuwenhoek used a
simple microscope to
view organisms in pond
water
- He called the
organisms
“animalcules.”
7-1: Life is Cellular
The Cell Theory: combination of the work of
3 German scientists in the 1800s.
1838 – Matthias Schleiden stated all plants
were made of cells.
1839 – Theodor Schwann stated that all
animals were made of cells.
1855 – Rudolf Virchow stated that all cells
came from preexisting cells.
7-1: Life is Cellular
The Cell Theory states:
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.
7-1: Life is Cellular
Modern Techniques for Studying Cells:
1. Compound Light Microscope – uses two
lenses to focus light that passes through the
object.
- 1st lens is nearest the object (objective lens)
- 2nd lens is near the eye (eyepiece or ocular
lens)
Total Magnification = eyepiece X objective
- the limit of resolution for light microscopes is
about 1000X
- make sure you memorize the microscope
parts on the following picture.
7-1: Life is Cellular
Modern Techniques for Studying
Cells:
2. Fluorescent Labels – tag
molecules so that researchers
can follow them through the
cell.
- helps discover the chemical
pathways used by the cell.
3. Transmission Electron
Microscopes (TEMs) – used to
view internal cell structures.
7-1: Life is Cellular
4. Scanning Electron Microscopes
(SEMs) – create 3-D images of the
surface of a cell.
7-1: Life is Cellular
All cells have 2 things in common:
1. Cell Membrane – controls what comes
in/out of the cell
2. DNA – contains the instructions for
making every protein used by the cell
7-1: Life is Cellular
There are 2 kinds of cells:
1. Prokaryotic – no
nucleus or membranebound organelles
- evolved first
- bacteria are
prokaryotic
7-1: Life is Cellular
There are 2 kinds of cells:
2. Eukaryotic – have a nucleus &
membrane-bound organelles
- most living things are made of
these cells including all
multicellular ones
7-2: Eukaryotic Cell Structure
Eukaryotic Cells have
two main parts:
1. Nucleus – contains
the DNA
2. Cytoplasm – jelly-like
substance between
the nucleus & the cell
membrane
- This is where the
organelles can be
found.
The Organelles
1. Nucleus – contains nearly all of the cell’s
DNA
Has 3 parts:
A. Nuclear Envelope – double membrane
structure that is dotted with openings
called nuclear pores
- the pores control what
comes in/out of the
nucleus
The Organelles
The Nucleus has 3 parts:
B. Chromatin – this is the DNA and its
associated proteins (histones)
- during cell division, it condenses
into chromosomes
The Organelles
Nucleus has 3 parts:
C. Nucleolus – darkest region of the
nucleus & it is where ribosomes
are made.
The Organelles
2. Ribosomes – 2-part structures that are
made of small particles of RNA and
proteins
- using other types of RNA, ribosomes
produce proteins in a process called
translation
The Organelles
3. Endoplasmic Reticulum (ER) – the
cell’s internal membrane system.
Two Kinds of ER:
A. Smooth ER – no ribosomes
- makes & transports lipids
- contains enzymes that
break down toxins
The Organelles
Two Kinds of ER:
B. Rough ER – has ribosomes
- makes & transports proteins
The Organelles
Both types of ER package their products
into membrane bubbles called vesicles.
The Organelles
4. Golgi Body – named
after Italian Camillo Golgi
- It is a stack of
membranes that
modify, sort, and
repackage cell
products made by the
ER.
- The new products are
repackaged into new
vesicles
The Organelles
5. Lysosomes – small
vesicles that contain
strong digestive
enzymes
They have two functions:
A. Breakdown
biomolecules to be
used by the cell.
B. Destroy worn out
organelles
The Organelles
6. Vacuoles –
membrane bags used
to store materials
- Bigger than vesicles
- Plants have a large
central vacuole for
storing H2O
- Paramecia have a
contractile vacuole
that removes excess
H 2O
The Organelles
7. Mitochondria – powerhouse of the cell
- helps turn glucose into the energy
molecule ATP
- has a double membrane; inner
membrane is where the ATP is made
- they have their own DNA;
undergo division;
mitochondria are inherited
from your mother
The Organelles
8. Chloroplasts – double membraned &
found in plants
- captures light energy to turn CO2 &
H2O into glucose
- like mitochondria,
they have their own
DNA
The Cytoskeleton
Functions:
1. Supports the shape of the cell.
2. Transports materials around the cell in a
process called cytoplasmic streaming.
Made of 2 Kinds of Protein Filaments:
1. Microfilaments – made of actin; responsible
for cytoplasmic streaming
2. Microtubules – made of tubulin; keeps cell’s
shape
- used in cell division by making up the
mitotic spindle
- also found in cilia & flagella
The Cytoskeleton
What is a centriole?
* It is an organelle that helps create the spindle during
cell ÷
* Found only in animal cells
* Made of microtubules arranged in a 9 x 3 pattern.
What are cilia & flagella?
• They are both made of microtubules that are arranged in
a 9 + 2 pattern.
• They are attached to the cell/plasma membrane
• They are used for moving the cell through its
environment (cilia & flagella) or to move materials
past the cell (cilia)
• Flagella = longer & fewer in number
• Cilia = shorter & much more numerous
Cell Boundaries
What is a cell wall?
• Structure that surrounds some
cells (bacteria, fungi, plants)
• Provides protection &
support
• Found outside of the
cell/plasma membrane
• Bacterial cell walls are made of
peptidoglycan
• Fungal cell walls are made of
chitin
• Plant cell walls are made of
cellulose
Cell Boundaries
The Cell Membrane:
Functions:
1. Regulate what goes in & out of the cell.
2. Cellular communication:
- identify each cell
- binding sites for hormones
The Cell Membrane
The Lipid Mosaic Model:
1. Lipid Bilayer – made of 2 layers of
phospholipids
2. Transport Proteins – channels that let
materials in/out
3. Marker Proteins – have carbohydrates
on them; works like a name tag for the
cell
4. Receptor Protein – many hormones
connect to these.
The Cell Membrane
Make sure you can
draw & label these
Passive Transport
Movement of materials without the use of energy.
How does this happen?
- molecules naturally move from an area of high
concentration to an area of low concentration
- this is called the concentration gradient
Types of Passive Transport:
1. Diffusion – any molecule moving down the
concentration gradient
2. Osmosis – diffusion of H2O molecules across a
membrane
3. Facilitated Diffusion – uses a protein to help move
material down a concentration gradient
Diffusion
What is it?
- Movement of molecules from [Hi] to [Lo]
until equilibrium is reached. [ ] = concentration
Osmosis
What is it?
- Diffusion of H2O across a biological
membrane.
- Biological membranes are selectively
permeable (let some stuff in/out).
Osmosis
The tonic words: used to describe solutions.
1. Hypotonic – [Hi] of water/[Lo] of solute; cells
placed in this kind of solution will expand.
2. Hypertonic – [Lo] of water/[Hi] of solute; cells
placed in this kind of solution will shrink.
3. Isotonic – same [H2O]/[solute]; cells placed in
this kind of solution will not change shape.
* Water molecules will move from hypo to
hyper in order to become iso.
Facilitated Diffusion
What is it?
- A way for large molecules to cross the
membrane without using energy
- Uses a carrier protein to move the
molecule from [Hi] to [Lo]. [ ] = concentration
Active Transport
What is it?
- Movement of molecules
from [Lo] to [Hi]
- Requires energy to move
against the
concentration gradient.
- Energy comes from
using ATP to change the
shape of the protein pump.
Endo & Exocytosis
Both are types of active transport (require energy).
Endocytosis: bringing large amounts of materials
into the cell
Types:
1. Phagocytosis – bringing in solids; white blood
cell eating a bacterium. (Cell Eating)
2. Pinocytosis – bringing in liquids (Cell
Drinking)
Endo & Exocytosis
Exocytosis: releasing materials from the cell
7-4: Diversity of Cellular Life
In multicellular organisms, cells become specialized.
- Specialized cells perform specific functions;
they only use the portion of their DNA that
deals with their function
Levels of Organization in multicellular organisms:
1. Individual Cells
2. Tissues – similar cells working on a common
function
3. Organs – similar tissues working on a common
function
4. Organ System – similar organs working on a
common function
5. Organism – many systems working together
Multicellular Life
Multicellular organisms have specialized
cells.
How do cells become specialized?
They express only the genes required to
do their function. Skin cells only express
the “skin cell” genes, not “heart cell” genes.
Skin cell
Cardiac
Muscle Cells