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Cells
• First discovered and named by
Robert Hooke in 1665
• Saw them in cork samples
• Looked like rooms where monks
stayed
• 1673 Anton van Leewenhoek saw
first live cells
Cells
• 1838 Max Schleiden…all plants
made of cells
• 1839 Theodor Schwann…all
animals made of cells
• Rudolf Virchow…all cells come
from other cells
Cell Theory
• All living things are made of cells
• Cells come from other cells
• Cells are the basic unit of life (i.e.
life functions happen at cell
level; cells can do all life
functions)
Cells
• Have different shapes, according to
their functions
• Limited in size by the ratio of surface
area to volume
• As a cell gets bigger, it’s volume
increases faster than surface
area
• Bigger cells need more substances
(water, oxygen, etc.) but don’t have
enough surface area to let
everything in/out
Cell shapes
2 kinds of cells
• Prokaryotic
– Have no membranes around nucleus or
organelles
– Still have DNA, just not in a nucleus
– Still perform life functions (use energy,
make proteins), but they’re done in
cytoplasm
– e.g. bacteria, Archaea
2 kinds of cells
• Eukaryotic
– Have nucleus with membrane and
organelles (with membrane)
– A few life functions go in cytoplasm, most
in specialized organelles
– e.g. plants, animals, fungi, protists
Cell membrane
• Also called plasma membrane
• Allows only certain things to enter
and leave the cell (selectively
permeable).
• Membrane around organelles has
similar structure.
• Phospholipid bilayer:
– 2 layers of phospholipids (phosphate
group (PO4) and two fats (lipids))
Cell membrane
• Fluid Mosaic:
– Bilayer also contains proteins
(mark the cell as one of yours
and help things move in and
out of cell)
– Things in the cell membrane move
around, they don’t stay
still…it’s dynamic, not static
– https://www.youtube.com/watch?v=LKN5sq5dtW4
– https://www.youtube.com/watch?v=Pfu1DE9PK2w
Cell membrane
Cytoplasm
• Jelly-like substance inside of cells,
does have a structure
(cytoskeleton)
• Contains all the organelles
• A few cell processes take place here
• Also has things dissolved in it
– Protein
– Water
– Salts
Microtubules/
Microfilaments
• Part of the cytoskeleton
• Microtubules hold the cell’s shape
and act as tracks as
organelles move around
• Microfilaments contribute to the
whole cell moving
Microtubules /
Microfilaments
Nucleus
• Controls the functions of the cell (by
helping to make proteins that
control chemical processes)
• Holds DNA (genetic info)
• Surrounded by a double membrane
called the nuclear envelope or
nuclear membrane
• Dark area called the nucleolus
– Makes ribosomes
Nucleus
Mitochondria
• Change energy from food into ATP
(energy for your cell)
• More mitochondria a cell has, the
more energy it uses
• Has a 2-layer membrane
• Has folds inside of it called cristae
• Has its own DNA
Mitochondria
Ribosome
• Build proteins
• No membrane, actually is made of
RNA (similar to DNA) and protein
• Made of two parts, a large and
small subunit that come together
• Some float freely around the
cytoplasm, others are attached to
endoplasmic reticulum
Ribosome
Endoplasmic reticulum
• System of tubes and sacs
• Make proteins and transports
things from one part of the
cell to another
• Rough ER
– Has ribosomes on surface, makes
proteins
• Smooth ER
– No ribosomes
Endoplasmic reticulum
Golgi Apparatus
• Flattened sacs near the nucleus
• Modifies proteins and moves
things from the ER either to the
rest of the cell or outside the
cell
Golgi Apparatus
Lysosome
• Contains digestive enzymes
– Break down food brought into the
cells
– Break down the cell when it dies
Lysosome
Cilia/Flagella
• Both help cells move (which, btw,
most cells don’t)
• Found on cell surface, but usually one
or the other, not both.
• Cilia
– Short hair-like structures
– Usually many of them
• Flagella
– Long, whip-like structure on cell
surface
– Usually only 1
Cilia/Flagella
(This is a bacteria, not an animal cell)
Centrioles
• Two cylinders of microtubules at
right angles to each other
• Only in animal cells
• Help in cell division by lining up
so things can move when cell
divides
Centrioles
Cell wall
• Rigid layer outside cell membrane
• Only in plants
• Made of lots of sugar molecules
put together (cellulose)
• Not digested by us = fiber!
• Gives strength and support to the
plant
Cell wall
Central Vacuole
• Large central area
• For storage
– Mostly water
• Can take up 90% of plant cell
volume!
• Animal cells have them, too, but
they are much smaller.
Central Vacuole
Chloroplasts
• Only in plant cells
• Surrounded by membrane
• Contains chemical chlorophyll
• Where photosynthesis takes place
(make food (sugars) for plant)
• Those sugars are used to build
the plant or go to mitochondria
to make energy
Chloroplasts
Like your body
• Cell membrane? Skin
• Nucleus? Brain
• ER? Circulatory system
• Lysosome? Digestive system
• Microtubules/Microfilaments (cell
wall for plants?
Bones and muscles
• Cilia/Flagella? Arms/legs