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The Cell
The smallest unit
of life that can
perform all life processes.
“Life is macromolecules that can perform unique
functions because they are enclosed in a structural
compartment that is separate from the external
environment. This separation allows living things to
maintain a constant internal environment
(homeostasis)”.
All living organisms are composed of cells
that can:
• Respond to their environment
• Grow, develop and reproduce
• Metabolize
• Maintain homeostasis
A little bit of history
“cells”
Robert Hooke
“little wretched beasties”
Antone van Leeuwenhoek - lenses
Anton van Leeuwenhoek (1673)
Made microscopes with
better magnification
First person to observe
living cells
Spirogyra
The Cell Theory
(3 parts)
Matthias Schleiden
Theodor Schwann
(botonist)
(zoologist)
1. All organisms are made of one or more cells.
2. The cell is the basic unit of all living things.
•
All organisms are made of one or more cells
• The cell is the basic unit of all living things
Redi – spontaneous
generation
3. All cells come from pre-existing cells
Pasteur – spontaneous generation
Cell Theory
1. The cell is the basic unit of life.
2. All life forms are made of one or more
cells.
3. Cells only arise from pre-existing cells.
Why are cells so special?
Able to differentiate



Stem cell = general, unspecialized cell
Becomes specialized with time
Examples: skin cells, macrophage cells,
neurons
Differentiation
You can use different terms to
describe the type of cell(s) you’re
looking at.
3 different sets of words:
1) Unicellular vs. Multicellular
Unicellular
Uni = one
One cell
Multicellular
Multi = many
Many cells
2) Prokaryote vs Eukaryote
prokaryote
Cells that DO NOT
have a cell membrane
around their nucleus.
example –
Bacteria
eukaryote
Cells that have a membrane
around their nucleus.
Plant and Animal
Cells
Eukaryote cells usually 10X larger than Prokaryote cells.
2) Prokaryote vs Eukaryote
Prokaryotic Cells
No nucleus- DNA unbound
No membrane-bound
organelles
All unicellular organisms
All microscopic
Eukaryotic Cells
Have nucleus with DNA
Organelles membranebound
Unicellular OR
multicellular organisms
microscopic OR
macroscopic
Amoeba sisters – pro & eukaryotes
3. Plant or Animal
Have cell walls
Have chloroplasts
Have large vacuoles
Tend to have a square
shape
Plant
Animal
No cell walls
Have small vacuoles, if
any
Not so square
Eukaryotic Cell structures:
structure and function
Hank – crash course
Organelles
Structures within cells that have specific
jobs
“Little organs”
plant cell wall
cellulose
cell wall
cell membranes
a dynamic structure –
model
fluid mosaic
functions:
Separates cell from its environment
Allows cell to maintain homeostasis
Acts as selectively permeable
membrane (regulates molecules entering and
leaving the cell)
Cell-cell communication
Surface markers - recognition
Amoeba sisters - homeostasis
Made of phospholipid bilayer with
embedded proteins
Harvard animation
Phospholipid bilayer
The protein part of the cell membrane provides:
communication, "I.D." tags, anchors to microtubules, gates
of exchange for large molecules and pumps for maintaining
ionic balance.
Special designs for specific function:
The “typical” cell membrane vs different types of
membranes better suited for function
In a “typical” membrane, there is the passive phospholipid
bilayer part (75-95%) and the active protein part (5-25%).
Those cells that have to do more exchanging of materials,
such as glandular cells, have more of the protein
membrane.
Those cells that have minimal exchange of materials, such
as fat cells, have less protein membrane.
the cell membrane
semi-fluid
Selectively
permeable
microfilaments & microtubules
structure
movement
Cytoskeleton
Function: Framework for the cellshape, organize, and support cell
Other: made of proteins
Cilia and Flagella
Function: assist in movement
Other:


Cilia- short, hair-like
Flagella- long, tail-like
centrioles
Molecular "tags" on microtubules
direct traffic inside cells
Cytoplasm
Function: fill the spaces between
organelles and the plasma membrane
the nucleus
contains the genetic material
Nucleus
Function: store and protect
genetic info (DNA)

NOT THE BRAIN- just stores the info
Other:


Chromosomes: DNA wound up
with proteins
Nuclear envelope:
double membrane with pores
endomembrane system
endoplasmic reticulum
rough ER
• transports
newly synthesized
proteins
• alters proteins
• folds into tertiary structures
smooth ER
• site for
synthesis of lipids
and steroids
• site for hydrolysis of glycogen
• modifies (detox.) small molecules
golgi apparatus
• recieves proteins
from ER – further
modifications
• Concentrates, packages, sorts proteins
• Polysacc. for plant cell walls synthesized
secreting side
receiving side
Vesicles and vacuoles
The function and importance of
vacuoles varies greatly according to
the type of cell in which they are
present.
functions of the vacuole include:
Isolating materials that might be harmful or a threat to
the cell.
Breaking down products taken into the cell to be used
in metabolism.
Exporting unwanted substances from the cell.
Allows plants to support structures such as leaves and
flowers.
Exporting manufactured products from the cell.
endocytosis
and
taking in
exocytosis
expelling
pinocytosis
phagocytosis
• Uses energy
• Encloses material in vesicles
exocytosis
Vesicle membranes are also phospholipid bilayer
special vesicles and vacuoles
peroxisomes
• the most common vesicle in cells
• found in all eukaryotes
• contain enzymes to rid the cell of hydrogen peroxide (convert
the hydrogen peroxide to water)
• some detoxify alcohol and other harmful compounds by
transferring hydrogen from the poisons to molecules of oxygen
(oxidation).
• others initiate production of phospholipids
special vesicles and vacuoles
lysosomes
contain hydrolytic enzymes - break
down cellular waste products, fats,
carbohydrates, proteins, and other
macromolecules into simple compounds,
which are then transferred back into the
cytoplasm as new cell-building materials
• autophagy - recycles the cell's organic material
special vesicles and vacuoles
Helps maintain
homeostasis for water
balance (osmotic
equilibrium)
contractile vacuole
central vacuole
central vacuole
(plants ONLY)
Maintaining
internal
hydrostatic
pressure or
turgor within
the cell
contractile vacuole
(animals ONLY)
found in certain unicellular organisms
pumps fluid from in the cell to the outside by
alternately filling and then contracting
ribosomes
site of protein synthesis
Mitochondria
Function: supply
energy by
converting food
to ATP
Other:


Highly folded
membranes
Has own DNA
and ribosomes
chloroplasts
Chloroplast
Function: carry out photosynthesis,
which turns light energy to chemical
energy
Other: has own DNA and ribosomes
Slide share
examples
The Cell is like……
CELL ANALOGY PROJECT
City 1
City 2
springfield
House analogy
Amusement park