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Chapter 4
Structure and
Function
of the Cell!!!
Cell - the smallest unit able to carry out
all the life activities of an organism.
The History (4-1)
The men you need to know about….
•1500-1600s
•Hans & Zacharias Jenseen – 1st to produce compound
microscope
•Robert Hooke -scientist who saw cork
(plant) through
microscope and called the
openings/pores
“CELLS”.
•Anton van Leeuwenhoek
–Worked with lenses to
create the most powerful
microscope up to that
time
•Better magnification
•Better resolution
•1st to observe living
cells. (bacteria, protists)
•Known as “Father of
Microbiology”
1800s
• Schleiden – all plants composed of
cells
• Schwann – all animals composed of
cells
• Rudolph Virchow – all cells come
from other cells
• These three men developed what we
now call the “cell theory”.
CELL THEORY
1. All living organisms are composed
of one or more cells.
2. Cells are the basic units of structure
and function in an organism.
3. Cells come only from the
reproduction of existing cells.
Cell Diversity
•Cells come in different shapes, sizes, and
internal organizations.
•Shape reflects function.
•Three Domains
of Life
•Eukarya
•Bacteria
•Archaea
• TWO BASIC
TYPES OF
CELLS:
• Eukaryotes
vs. Prokaryotes
Organelles –
intracellular bodies
that perform
specific functions.
“mini-organs”
Prokaryotic Cell
•
•
•
•
•
•
•
NO membrane bound nucleus
Simple – no membrane bound organelles
Have DNA in “nucleoid” region
Smaller in size
Unicellular
Bacteria
Primitive (old)
Eukaryotic Cell
• A “true” membrane bound NUCLEUS
• Complex -many membrane bound
organelles
• DNA contained in nucleus
• Larger in size
• Unicellular and multicellular
• Animal, Plants, Fungi, Protist
• Not as old as prokaryotes
• Presence of
nucleus
• Complexity
• Size
What do all cells have?
• Genetic Information
• Nucleic Acids –DNA/RNA!
• Eukaryotic Cell
– Contained in nucleus
– More complex, rod shaped
• Prokaryotic Cell
– Free floating
– Simple, circular shaped
What do all cells
have?
Plasma
membrane/cell
membrane
•Semi-permeable or Selectively-permeable
•Allows some materials to pass in/out of the cell
•It is composed of phospholipids bilayer. (nonpolar)
•Also has proteins embedded within that act as “bridges” to
allow larger materials to pass.
•Covers cell surface, barrier, support, protection
• Phospholipid bilayer behaves like fluid.
(called Fluid Mosaic Model)
• The lipids and proteins can move laterally
within the bilayer, like boat on ocean.
• Constantly changes
What do all cells have?
• Ribosomes
• Responsible for building protein
• Look like small dots.
• Some ribosomes are free in
cytoplasm and others attached to
“rough” ER.
DNARNAProtein
What do all cells have?
Cytoplasm
• Region within the plasma
membrane that suspends cell organelles
• The “filler”
What do all cells have?
• The 4 Macromolecules
• Nucleic Acids
– Genetic info
• Proteins
– Made by ribosomes (many different functions)
• Lipids
– In cell membranes
• Carbohydrates
– Energy (metabolism)
Nucleus
• Contains the DNA
– Chromatin/chromosomes
• Control center
(regulates instructions)
Most prominent structure
What makes up the Nucleus?
• Nuclear
Envelope
• Also called nuclear
membrane
• double membrane
surrounding nucleus
What makes up the Nucleus?
• Chromosomes
• chromatin strands that
coil up
• Genes
• Traits
• DNA
• “Code”
– ATTTGGCC
What makes up the Nucleus?
• Nuclear pores
• Small holes in the
nuclear envelope.
– Allows RNA and
other materials to
pass in/out of
membrane
What makes up the Nucleus?
• Nucleolus
• Inside the nucleus
• Synthesis of
Ribosomes
• The ribosomes then
pass through the
nuclear pores to the
cytoplasm.
Organelles
• Mitochondria
• Cellular Respiration takes
place in Mitochondria
• Produces useable form of
ENERGY for cell.
• Converts organic
molecules (carbs) to ATP..
• Have their own DNA
(genetic info) and
ribosomes
• Double membrane
organelle
Organelles
• Endoplasmic
Reticulum
“ER”
• System of
membranous tubes and
sacs
• Acts as a
“HIGHWAY”,
moving molecules
(proteins) inside cell
• Two types: rough and
smooth
Rough ER
• With Ribosomes
Smooth ER
• NO ribosomes
Organelles
• Golgi
Apparatus
• Function: processing,
packaging, and
sending molecules
such as proteins
• Surrounds materials in
“vesicle”.
The Golgi body is like ER in that it is system
of membranes/sacs. Works closely with
Smooth ER and looks similar to it.
Organelles
• Lysosomes
• Vesicles produced by
Golgi apparatus
• Contain digestive
enzymes
• Get rid of unwanted
materials, waste,
damaged cells, etc.
Organelles
• Cytoskeleton
• Network of long
protein strands located
in the cytoplasm
• Framework…support
for cell structure
• Give cell shape.
Parts of Cytoskeleton
• Microfilament
• Part of cytoskeleton
• Aid cell in movement
Parts of Cytoskeleton
• Microtubule
• Part of Cytoskeleton
• Hollow tubes made of
protein (tubulin)
• Maintain cell shape
• Act as tracks to guide
Parts of Cytoskeleton
• Intermediate
Filaments
• Rods that anchor
nucleus and other
organelles
How does a cell move?
Cilia - hairlike organelles that extend from
surface of the cell. There are many of these
short hairs on outside. You have cilia in
your respiratory tract!!
Flagella - when the hairlike organelles are
long and less numerous. Flagella found on
sperm cells!
Cilia
Flagella
Centrioles
• Help with cell division
• Only in animal cells
Choices:
A. Cell
membrane
B. Nucleus
C. Rough ER
D. Smooth
ER
E. Golgi
Apparatus
F. Mitochondria
G. Ribosomes
Unique Features of Plant Cells
• Cell Wall
•
Exterior/Outside layer
of protection and
support for…
– Plants
– Fungi
– Prokaryotes
• Animals do NOT have
cell wall!!!!!!!!!!!!
• Made of cellulose
(complex
carbohydrate).
Central Vacuole
• Vacuoles
• Storage units
– Water, enzymes,
wastes, etc.
• They are quite large in
plant cell..take up 90%
of cell.
• Rarely found in
animal cells but very
small and few.
• Responsible for turgor
pressure in plants
Chloroplasts
• Only in the PLANT CELL.
• WHERE PHOTOSYNTHESIS
OCCURS
• Convert light energy to make
carbohydrates (glucose) for the plant.
• Have their own DNA (genetic info)
and ribosomes.
• Double membrane organelle
• Contains pigment Chlorophyll.
– Main molecule that absorbs light for cell.
(like a solar panel)
Parts of Chloroplasts
Choices:
A. Vacuole
B. Chloroplasts
C. Nucleus
D. ER
E. Cell
membrane
F. Cell wall
Comparing Cells
• What do all cells have
in common?
•
•
•
•
Cell membrane
Cytoplasm
Ribosomes
Genetic material
How is prokaryote different from
eukaryote?
• Only eukaryotes have membrane bound
organelles…especially the nucleus.
• Prokaryotes do have nucleiod.
• Eukaryotes are bigger and more advanced.
• Prokaryotes were the first cells, bacteria.
How is PLANT cell different from
animal cell?
Plant cell summary…
•Usually more square in shape (animal more
circular) and more green in color.
•Cell wall, helps make it more rigid.
•Can make its own food (photosynthesis) due to
Chloroplasts (plastids).
•Large central vacuole.
This is real
picture of
what a plant
cell looks
like.
This is real
picture of
what an
animal cell
looks like.
CELL SIZE: Why are cells small?
Volume = How “big”, the amount of space
• The number of reactions must increase as the
volume of a cell increases. (The larger the volume
the larger the number of reactions needed to
support the bigger size)
• Surface Area = The area around the cell,
the cell membrane, the amount of area
that materials can enter and leave
• All raw materials necessary for a cell’s reactions
(metabolism) can enter the cell only through its
cell membrane.
• As a cell grows, its SA to V ratio decreases.
– Surface Area does not increase as fast as the
Volume
• If cell grows too large, the SA (the area of cell
membrane) is not sufficient enough to move
enough raw materials to support that volume. At
this point the cell cannot get larger.
• What will it do?
• Die if it continues to grow larger
• Divide
• Flatten out (change shape) shape to maximize SA