Cells
• 2 Basic Cell Types:
• Prokaryotes
• Eukaryotes
• Cell Organelles Structure and Function
• The Cell Membrane
The Cell Theory
1. All living things are composed of cells.
2. Cells are the basic unit of structure and function
in living things.
3. All cells are produced from other cells.
Two Basic Cell Types:
Prokaryotic vs. Eukaryotic
Cells
Two Basic Types
• Remember….cells are the basic unit of life
for ALL living things.
• There are two basic types of cells:
1. Prokaryotic cells – found in bacteria
2. Eukaryotic cells – found in protists, fungi,
plants and animals
Characteristics Shared
• Perform the same basic functions
• Surrounded by plasma membrane to control
what enters and leaves the cell
• “Filled” with cytoplasm
• Contain ribosomes to make protein
• Contain DNA to give the general
instructions for the cell’s life
What Makes Eukaryotic Cells
Different?
• Much larger
• Much more complex
• Contain a true nucleus to house the genetic material
(DNA)
• Linear DNA packaged into chromatin found inside
the nucleus
• Contains specialized structures in the cytoplasm
called organelles to carry out various functions
• Not all have a cell wall
Eukaryotic Cells
What Makes Prokaryotic Cells
Different?
• Much smaller
• Less complex
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No true nucleus
Circular DNA that is found in the cytoplasm
No organelles found in the cytoplasm
Surrounded by a cell wall
Prokaryotic Cell
What does size have to do with
it?
• Prokaryotic cells are much smaller than
eukaryotic cells. Why?
– Smaller surface area to volume allows nutrients to
easily and quickly reach inner parts of the cell.
– Eukaryotic cells are larger and can not pass
nutrients as quickly. They require specialized
organelles to:
• carry out metabolism
• provide energy
• transport chemicals throughout the cell
Prokaryotic Cell
http://www.cellsalive.com/
cells/bactcell.htm#top
Cell Organelles
Review
• No organelles in prokaryotic cells
• Both plants and animals are eukaryotic
cells!
Animal Cell
Plant Cell
Organelles Found in Plant and
Animal Cells
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Cell Membrane
Nucleus
Nucleolus
Mitochondria
Endoplasmic reticulum
Ribosomes
Golgi apparatus
Vacuoles (small in animals; large in plants)
Lysosomes
The Cell Membrane
• Location: Around the outside of the cell
• Function: Controls what substances enter and
leave the cell
• Aka: “plasma membrane”
Nucleus
• Location: In the cytoplasm
• Function: Directs all of the cell’s activities; stores
the chromatin
• Aka: “control center”
Nucleolus
• Location: In the nucleus
• Function: Makes ribosomes
• Aka: “little nucleus”
Mitochondria
• Location: In the cytoplasm
• Function: Produces energy
• Aka: “Powerhouse” or “Mighty
Mitochondria”
Ribosomes
• Location: In the cytoplasm and on the
rough ER
• Function: Makes protein
• Aka: “Protein packs”
Endoplasmic Reticulum (ER)
• Location: In the cytoplasm around the nucleus
• Function: Modifies materials needed in the cell
• Aka: “Fashion designers”
Smooth ER (no ribosomes)
Rough ER (has ribosomes)
Golgi Apparatus
• Location: In the cytoplasm
• Function: Sorts and ships materials to the correct
parts of the cell
• Aka: “the post office”
Vacuoles
• Location: In the cytoplasm (large in plants;
small in animals)
• Function: Storage
• Aka: “the closet”
Animal Cell Vaculole = small
Plant Cell Vaculole = large
Lysosome
• Location: In the cytoplasm
• Function: Destroys worn out cell parts
• Aka: “the death chamber:
Cilia / Flagella
• (*animal cells only: not all cells have one of
these)
• Location: on the cell membrane
• Function: help the cell move
• AKA: the “motor”
Organelles Found in Only Plant
Cells
• Cell Wall
• Chloroplast
Cell Wall
• Location: Around the cell membrane of
plant cells
• Function: Gives the cell shape and
protection
• Aka: “plant cell armor”
Chloroplast
• Location: In the cytoplasm
• Function: Photosynthesis: Makes sugar
from sunlight (also takes in carbon dioxide
and gives off oxygen)
• Aka: “mean green sugar machine”
See the Cell in Action!
• http://www.youtube.com/watch?v=1Z9pqST72is
&feature=related
(14 min.)
• Visit this link to see the cell in action, just click
on the various organelles to get a better idea of
how they work!
http://www.johnkyrk.com/CellIndex.html
http://www.cellsalive.com/cells/cell_model.htm
http://waynesword.palomar.edu/lmexer1a.htm
Plant Cell
•
http://waynesword.palomar.edu/lmexer1a.htm
Animal Cell
Prokaryotic Cell
http://www.cellsalive.com/c
ells/bactcell.htm#top
http://waynesword.palomar.edu/lmexer1a.htm
Plant Cell
Name_________________
•
http://waynesword.palomar.edu/lmexer1a.htm
Animal Cell
Name_________________
Prokaryotic Cell
http://www.cellsalive.com/c
ells/bactcell.htm#top
Name_________________
Movement Through
the Cell Membrane
http://programs.northlandcollege.edu/biology/bi
ology1111/animations/passive1.swf
Selectively-Permeable Membranes
• A selectively-permeable membrane will allow
certain molecules to pass through it, but not
others.
• Generally, small
particles can pass
through…
Partially permeable
membrane
…but large
particles
cannot
Structure of the Plasma/Cell
Membrane
• Plasma Membranes consist of 2 types of
molecules – phospholipids and proteins
Diagram of a Phospholipid
Phospholipids have 2 regions:
• Polar head region:
– attracts water molecules (hydrophilic)
– Phosphorous group
• Non-polar tail region:
– nonpolar tails repel water molecules
(hydrophobic).
– Made of long carbon chains (fatty acids)
Phospholipid bilayer
• Due to the hydrophobic and hydrophilic nature of the
phospholipid, a double layer is formed where the heads
protect the tails from the water. This is called the
phospholipid bilayer. The bilayer is fluid, not a hard shell.
Proteins are Embedded Within the Bilayer
• Proteins act as passageways for nonpolar
(hydrophobic) molecules to pass through.
• Without proteins embedded in the bilayer, essential
molecules needed for communication, energy, etc.,
would not reach the interior of the cell.
• Carbohydrates are attached to the proteins.
– Allow for cell recognition and communication.
Proteins are Embedded Within the
Bilayer (continued)
• The model of the lipid bilayer with embedded
proteins is called the Fluid Mosaic Model.
TWO Types of Transport Through a
Cell Membrane
1. Active Transport – the movement of molecules
through a cell membrane using energy
2. Passive Transport – the movement of molecules
through a cell membrane without the expenditure
of energy
3 Types of Passive Transport
1. Diffusion - Movement of molecules from areas
of high concentration to low concentration
2. Osmosis - Diffusion of water molecules from
higher concentration of water to lower
concentration of water
3. Facilitated Diffusion - Diffusion through pores
or channel proteins
DIFFUSION
• Molecules tend to move from areas where there is more
of them to where there is less
high concentration  low concentration
– This is called moving WITH the concentration gradient.
• Diffusion continues until equilibrium is reached, or
where molecules are equally distributed.
– Some solutes will be able to move through when others will
not.
Diffusion (continued)
OSMOSIS
• Water passes through cell membranes rapidly.
• Osmosis is a specialized form of diffusion that
moves water molecules through membranes.
• Osmotic pressure – when more water molecules
accumulate inside a cell, pressure increases. This
pressure is called osmotic pressure.
– when osmotic pressure is high inside the cell, water will
want to leave the cell.
OSMOSIS
3 Types of Solutions
hypertonic solution -solute concentration is HIGHER in
the solution than in the cell.
• Water will move out of the cell- cell will shrivel
hypotonic solution - solute concentration is LOWER in
the solution than in the cell.
• Water will move into the cell- cell will swell
isotonic solution - EQUAL solute concentrations in the
solution and in the cell.
• Water will move in and out of the cell at equal rates.
FACILITATED DIFFUSION
– some molecules cannot diffuse through on their own
(membrane is impermeable to them), and will need
assistance (facilitate).
– Passive transport aided by proteins. Each are very
specific to the size/shape/polarity of solute.
-transport proteins
-channel proteins
*aquaporins- facilitated diffusion of water
*ion channels- open and close in
response to a stimulus (gated channels)
Active Transport
• Some molecules exist in low amounts on one side of a
membrane and need to be moved to areas of high
amounts
• active transport- the use of energy to move molecules
from LOW concentration to HIGH concentration
(against or opposite the concentration gradient)
• Cell membranes have mechanisms to move these
molecules against their concentration gradients:
1. ion/molecular pumps
2. endocytosis
3. exocytosis
Types of Active Transport
1. ion/molecular pumps
-Molecules can be moved through the membrane by specific
proteins embedded in the membrane
-Na, K, Ca ions are transported in this manner
-sodium-potassium pump is the major pump of animal cells
-proton pump is main pump of plants, fungi, and bacteria
2. endocytosis- process of cells engulfing large particles by
forming a vesicle around them
-different names for different sizes of particles:
pinocytosis (cell drinking)
-occurs if the particles have been partially broken down into
a liquid of tiny dissolved molecules
phagocytosis (cell eating)
- If the particles are cell fragments or organic matter
3. exocytosis -process by which wastes or secretions
(hormones) are brought to the cell membrane, packaged
into vesicles and sent out of the cell
– the reverse of endocytosis
Unicellular vs. Multicellular
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Unicellular organisms – single celled.
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Include both prokaryotes and eukaryotes.
Maintain homeostasis by growing, responding to the
environment, transforming energy, and reproducing.
Multicellular organisms – many cells working
together to create an organism.
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Cells are specialized – different cell types play
different roles.
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Ex. Move, respond, communicate, substance production.
Cells communicate with one another to maintain
homeostasis for the organism.
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The organization allows them to divide labor in order to maintain
homeostasis.
Cellular communication
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Cells in large organisms must communicate with
one another in order to work together to maintain
homeostasis!
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Occurs via chemical signals that influence the behavior of the
cells receiving the signals.
Receptors are often found on the outside of cells where they
bind chemical signaling molecules and influence cellular
activity.