Download cells - District 196

CHAPTER 6 - CELLS
Section 6.1 & 6.2
Importance of cells


An organism’s basic unit of structure & function is the
cell
Everything we do occurs fundamentally at the
cellular level
 Thinking
 Moving
 Maintaining

homeostasis
Cells discovered by Robert Hooke in 1665
Studying Cells



How do we understand cells if we can’t see them?
Microscopes allow us to see the inner workings of
cells
Two main types of Microscopes
 Light
Microscope (LM) – 1665-present
 Electron Microscope (EM) – 1950’s-present
Light Microscopes





Allow us to see plant & animal cells and the nucleus.
Can also see bacteria cells.
Light passes through the specimen and lenses, bends
the light to magnify the image.
Magnification: ratio of an object’s image to its real
size (max. about 1,000x)
Resolution: measure of the clarity of the image
(max. about 200nm – size of bacteria)
Electron Microscopes



Rapidly advance our understanding of cells
because we could see subcellular structures
Focuses a beam of electrons through the specimen
Two types:
 Scanning
 Gives
electron microscope (SEM)
a 3D image of the surface of the specimen
 Transmission
 Used
electron microscope (TEM)
to study internal stux – gives a cross section
Advantages & Disadvantages

Light Microscopes
 Advantage:
Can study living organisms
 Disadvantage: Can’t see organelles in detail

Electron Microscopes
 Advantage:
Can see organelles in detail
 Disadvantage: Specimens are killed in preparation
process (not for living tissues)
Cell Fractionation


Goal: take cells apart and separate the major
organelles from one another
Process:
 Centrifuge
spins test tubes at various speeds
 Cell components separate by size and density

Result:
 Bulk
quantity of cellular organelles to study composition
and function
Section 6.2

Two types of cells
 Prokaryotic
found in Domain _______ & _______
 Eukaryotic found in Domain _______

What 4 Kingdoms contain organisms with Eukaryotic
cells?
 1.
Animal
 2. Plant
 3. Protist
 4. Fungi
Similarities & Differences

All Cells contain:
 Plasma
membrane made up of a __________
 Phospholipid
 Cytosol
bilayer
(cytoplasm)
 DNA
 Ribosomes

Differences:
 Eukaryotic
cells contain membrane bound organelles
and the DNA is contained in the nucleus.
Prokaryotic cells:







DNA located in nucleoid region
Prefix: pro means “before”
Suffix: karyon means “kernel” (nucleus)
No membrane bound organelles in cytoplasm
Smaller & simpler
Cilia and flagella for locomotion
Some have cell wall surrounding plasma membrane
Prokaryotic cells
Cell Size




Cellular metabolism sets a limit on how large a cell
can get
The cell needs to bring in oxygen & nutrients and
needs to get rid of waste
Cell needs to maintain a high surface area to
volume ratio to exchange the materials it needs to
Larger organisms do not have larger cells just more
of them (we have trillions of cells!)
Surface area to volume ratio
Plasma membrane
Eukaryotic cells




Contain membrane bound organelles
Larger than prokaryotic cells and more complex
Animal & Plant cells
Draw a diagram of an animal and a plant cell