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Chapter 4
Cell Structure and
Function
1. What is a cell?
 A cell is the smallest unit that can carry
on all of the processes of life.
2. Early scientists that led to the
cell theory:
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Anton van Leeuwenhoek (1600s) – given credit for
developing the 1st mini microscope, looked at pond water
and made detailed drawings
Robert Hooke – coined the term “cell” when he looked at
slices of cork and dead plant cells
Robert Brown (1833) – observed a dark structure near the
center of the cell (we now know this is the nucleus)
Matthias Schleiden (1838) – stated all plants are made of
cells
Theodor Schwann (1839) – discovered all animals are made
of cells
Rudolph Virchow (1855) - stated all cells come from the
division of preexisting cells
3. Cell Theory
 All living things are composed of cells.
 Cells are the basic units of structure and
function in living things.
 All cells come from preexisting cells.
4. 8 Characteristics that
all living things share
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Consist of organized parts (cells)
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Obtain energy from their surroundings
Perform chemical reactions
Change with time (evolution)
Respond to their environments
Reproduce
Maintain constant internal environment (homeostasis)
Share a common history
5. Relationship between a cell’s
shape and it’s function
Nerve cells: communication
 Diversity of shape reflects
diversity of functions
 Can be simple or complex
depending on its function
 Cell shape evolved to allow
the cell to perform its
function effectively
Blood cells:
transport
Skin cells: protection
6. What factor limits the size
that most cells are able to
obtain?
 Limited by the relationship of the
cell’s outer surface area to its
volume
 Most cells range from 10 -100µm
7. What is the problem with
cells getting too large?
As a cell grows, it’s volume increases
much faster than its surface area
The surface area (the membrane) would
not allow materials to enter or leave the
cell quickly enough to meet the cell’s
needs.
Therefore, most cells are microscopic in
size.
8. Three Basic Parts of the Cell:
 Plasma Membrane –
and leaves the cell
 Cytoplasm –
the cell
regulates what enters
site of many chemical reactions of
 Material between the cell membrane and the nucleus
 Contains the organelles of the cell
 Control Center –
activities
controls all of the cells
 Either free-floating DNA in center of the cell
(Prokaryotes) OR a membrane bound organelle called a
nucleus (Eukaryotes)
9. Two basic types of cells
 Prokaryotes – organisms whose cells lack
nuclei and other organelles (i.e. bacteria)
 Eukaryotes – organism whose cells contain
nuclei and other organelles
Pro- = before
Eu- = true
-karyon = kernel/nucleus
10. What is an organelle?
 A well-defined, intracellular body that
performs specific functions for the cell.
 Ex/mitochondrion produces energy (in
the form of ATP) for the cell
Prokaryote vs. Eukaryote
Typical Prokaryote (a bacterium):
11. Prokaryote vs. Eukaryote
Characteristic
Prokaryotic
Eukaryotic
Cell membrane
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Cytoplasm
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Genetic Material
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Nucleus
Organelles
Archaea
Bacteria
Plants, animals, fungi, & protists
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(only ribosomes)
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11. Units of Organization
CELLS  TISSUE  ORGANS  ORGAN
SYSTEM  ORGANISM
12. PROKARYOTIC CELL DIAGRAM
PILI – used for
attachment to surfaces
CELL MEMBRANE –
Regulates what enters and leaves
CELL WALL –
protection
RIBOSOME –
makes proteins
DNA – controls all cells activities
FLAGELLA – moves the cell
Animal Cell
Nucleolus
Rough ER
lysosome
Nucleus
cytoplasm
Nuclear envelope
mitochondria
ribosomes
(dots)
Cell (Plasma) membrane
Golgi apparatus
Smooth ER
Plant Cell
*’s = organelles only found in plant cells, NOT animal cells
Nuclear envelope
Nucleolus
Nucleus
Golgi Apparatus
* Cell Wall *
Rough ER
Smooth ER
* Central Vacuole *
Mitochondria
Cytoplasm
Cell (Plasma) membrane
* Chloroplast *
Cell Membrane –
outer boundary
 In plants & animals
 Structure:
 Phospholipid bilayer
•
hydrophilic heads, hydrophobic tails
 Contains lipids (bilayer), proteins (channels), and
carbohydrate chains (identification cards)
 Function:
 Regulates what enters and leaves the cell
 Semi-permeable membrane
 Protection and support
Nucleus - control center
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In plants and animals
Structure:
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Genetic material called
chromatin (DNA +
proteins)
Function:
 Information center
of the cell
 Protects DNA
 Directs/controls
cell activities
Nucleolus  In plants &
animals
 Structure:
 Made of RNA +
proteins
 Small, darkened
region inside of
nucleus
 Function:
 where ribosomes
are made
Mitochondria
 In plants & animals
 Structure:
Double membrane
Cristae - inner folds, increase surface area
Outer membrane for protection of organelle
 Function:
“Powerhouse” of the cell – produces ATP’s (cell energy)
Able to self-replicate ( # in cells with high energy need)
Releases energy from food for the organism to use in the
process of cellular respiration
Ribosomes
 In plants & animals
 Structure:
Little “dots”
Small (25 nm) ball-like
structures
Found free-floating in cytoplasm
or attached to rough
endoplasmic reticulum
Composed of RNA and protein
 Function:
Synthesis of proteins (where
proteins are made)
Endoplasmic Reticulum
 In plants & animals
 Structure:
Network of flattened sacs
Can be rough (w/ ribosomes) or
smooth (w/o ribosomes)
 Function:
Transport materials within or out of
cell – intracellular highway
Synthesis of macromolecules
Rough - proteins, lipids, carbs
Smooth - lipids
Lysosome
 In animals only
 Structure:
 Small, circular structures
 Found only in animal cells
 Contain digestive enzymes
 Function:
 Digestion of:
Worn out organelles
Debris
Large ingested particles
 Lysosomes are responsible for your hands not being webbed!!
Golgi Apparatus
 In plants & animals
 Structure:
 Flattened stacks of membranes that are not
connected
 Vesicles fuse with Golgi and get released from
Golgi
 Function:
 Collection, modification, packaging of proteins
and other substances
Vesicles attach, deposit materials
Golgi modifies materials based on needs
Vesicles attach to membrane and distribute
modified substances
Vacuole
 In plants - 1 large, central
 In animals – several small
 Function:
 Storage of water, salts, proteins,
carbohydrates, waste products
 Pressure system for plants, prevents
wilting
 Special vacuole: contractile vacuole prevents excess water intake,
leading to cell-bursting found in
freshwater PROTISTS like a
paramecium
Cell Wall –
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Only in plants, bacteria, fungi
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Structure -
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Lies outside the cell membrane
Made of fibers of cellulose
(plants)
Very porous
Function
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Helps to protect and support the
cell
Gives rectangular shape to plant
cells
Chloroplasts
 Only in plants
 Structure:
Inner membranes (thylakoids)
surrounded by an outer
membrane
 Function:
 Conversion of light energy (sun)
into chemical energy
(glucose/food) during the process
of PHOTOSYNTHESIS
 Other Plastids:
 Chromoplasts – Store pigments (ex. carrot
root cells, flower petals)
 Amyloplasts - Store food/starch
Cytoskeleton -
framework
 In plants
– microtubules, intermediate filaments,
microfilaments
 In animals
– all
 Function: maintains cell shape and
provides internal support
 Microtubules - hollow tubes of proteins, hold
organelles in place, maintain shape, act as
tracks that guide organelle movement
 Intermediate filaments – rods that anchor
organelles in place
 Microfilaments – long & threadlike, used for
cell movement
 Cilia – short, hairlike projections used for cell
movement
 Flagella – long, taillike projections used for
movement
 Centrioles – organize microtubules during cell
division
Who Am I?
(quick review)
I stated all plants are made of cells
I stated all cells come from the division of
preexisting cells
I coined the term “cell” when I looked at
slices of cork and dead plant cells
I am given credit for developing the 1st mini
microscope and I looked at pond water and
made detailed drawings
I discovered all animals are made of cells
List 3 organelles you learned about
today.
Describe the function of each of the
organelles you listed.
Yes, you should write your name on the
paper