Download Introduction to Cells

Cell Structure & Function
Cells: the basic units of life.
The cell theory, set forth in the 1850s,
says that:
 All living things are composed of
cells.
 The cell is the smallest unit that
retains the properties of life.
 Under current conditions, all cells
come from preexisting cells.
Question
A.
B.
C.
D.
Which of the following statements is NOT
part of the cell theory?
All living things are composed of cells.
All cells are surrounded by an outer
membrane.
The cell is the smallest unit that retains the
properties of life.
Under current conditions, all cells come
from pre-existing cells.
All cells DO have an outer membrane (called
the plasma membrane), but this observation is
not considered part of the cell theory.
Light Microscope
(LM)
Shows the entire cell and its interior
Scanning Electron Microscope
(SEM)
Shows a cell’s surface structure
Transmission Electron Microscope
(TEM)
Shows internal details of a preserved cell
Question
A.
B.
C.
D.
Biologists generally rely on the ________
microscope to study the surface structures of
cells and the ________ microscope to study the
internal structure of cells.
light; electron
light; transmission electron
scanning electron; transmission electron
transmission electron; scanning electron
Specimens for both types of electron microscopes must be killed
and preserved before they can be examined. For this reason,
light microscopes are still useful for observing living cells.
Basic Cell Structure
Question
A.
B.
C.
D.
Which of the following correctly labels the
three major parts of the cell shown below?
1-nucleus, 2-cytoplasm, 3-plasma membrane
1-cytoplasm, 2-plasma membrane, 3-nucleus
1-plasma membrane, 2-nucleus, 3-cytoplasm
1-nucleus, 2-plasma membrane, 3-cytoplasm
1
2
3
The plasma membrane
encloses the cytoplasm,
and the cytoplasm
surrounds the nucleus.
Plasma membrane
Internal Cell Structures
Cell membranes divide the
cytoplasm of eukaryotic cells
into functional compartments
called organelles.
Organelle = “mini organs”
Plant Cell Structures
Animal Cell Structures
Eukaryotic vs. Prokaryotic
Internal Cell Membranes
Organelle membranes physically
separate important chemical
reactions in the cytoplasm and
allow them to take place in an
orderly fashion.
Selective permeability
Cell membranes are said to
be selectively permeable
membranes, meaning that
they allow some, but not all,
materials to simply pass
through them.
Question
A.
B.
C.
D.
Which of the following is NOT an
accurate analogy for a cell
membrane?
a window screen
the US – Mexico border
the Kansas – Colorado border
a university admissions department
The Kansas – Colorado border is a permeable barrier—anyone can
cross the border at any time. All of the other barriers in the list are
selectively permeable because they allow some things but not
others to pass through.
Membrane Composition
A phospholipid bilayer forms the
basic unit of the cell membrane.
Question
Where in this diagram of a cell
membrane would you expect to find the
FEWEST water molecules?
A
B
C
The fatty acid “tails” of
the phospholipids are
hydrophobic. They
would repel any water
molecules that came
into that area of the
membrane.
Membrane Composition
Proteins embedded in the bilayer help the
cell transport materials in and out.
Carbohydrate chains attached to some
membrane proteins help the cell
communicate with other cells.
Structure of the Cell Membrane
Question
A.
B.
C.
D.
What type of membrane molecules are
responsible for cell-to-cell communication?
Carbohydrate chains act like
lipids
“ID tags.” Different cell types
have different kinds of
proteins
carbohydrate chains on their
surfaces.
phospholipids
carbohydrates
A “Fluid” Membrane
The lipid molecules have
hydrophilic (“water-loving”)
heads and hydrophobic
(“water-hating”) tails.
Therefore, if you puncture a
membrane, it will come
together and seal itself.
Cell Membrane Analogy
The cell membrane is similar to the
walls that surround a house.
Both help protect the inside
from the outside.
inside
outside
A house needs a way of receiving
fuel and power from the outside.
Supply lines pass through the
walls of the house to bring in
these materials.
A cell receives fuel and power
from the outside through protein
channels in the membrane.
Doors are sometimes needed
to bring in food and take out
the trash.
Channels in the membrane
allow the cell to bring in food
and get rid of waste.
People in a house also need to
communicate with the outside.
Carbohydrates in the
membrane allow the cell to
communicate with other cells.