Cell Structure and Function
Chapter 7
Biology
Miller • Levine
The Scientists…
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Robert Hooke (1665)
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Viewed cork under a
microscope
Called the chambers he
saw “cells”
Anton van
Leeuwenhoek (1674)
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First to see living
organisms in a drop of
water
The Scientists…
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Matthias Schleiden (1838)
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Theodor Schwann (1839)
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All plants are made of cells
All animals are made of cells
Rudolf Virchow (1855)
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All cells come from preexisting
cells
The Cell Theory
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All living things are composed of
cells
Cells are the basic units of
structure and function in living
things
New cells are produced from
existing cells
Unicellular vs. Multicellular
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Unicellular – single-celled
organism
Multicellular – many-celled
organism
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Cell specialization – cells are
specialized to perform certain
functions
Cells → Tissues → Organs → Organ
systems → Organism
Prokaryotes vs. Eukaryotes
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Prokaryotes
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Have a cell membrane &
cytoplasm, but do not have a
nucleus
Ex. Bacteria such as E.coli
Eukaryotes
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Have a nucleus, cell membrane,
cytoplasm & organelles
Ex. Plants, Animals, Fungi
Prokaryotes vs. Eukaryotes
Basic Cell Structures
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Cell membrane – thin, flexible
barrier around the cell; protects
the cell
Present in all cells
● Selectively permeable
● Contains floating layers
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SS
The Fluid Mosaic Model
Hydrophobic vs. Hydrophilic Hydro = water
Phobic = fear/hate
Philic = love
Cytoplasm –
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material inside the cell
membrane (not including the
nucleus)
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Prokaryotes & Eukaryotes
Cell Wall
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Found in many organisms,
including plants, algae, fungi
and nearly all prokaryotes
Not found in animal cells
Lies outside the cell membrane
but is porous
Main function is to provide
support & protection for the cell
Nucleus
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Almost all eukaryotic cells,
including plants and animals
have a nucleus
Prokaryotes do not have a
nucleus
Controls most cell process and
contains the DNA
Nucleolus and Nuclear Envelope
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Nucleolus:
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Inside the nucleus
Where ribosomes are made
Nuclear Envelope:
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Double-membrane layer around
the nucleus
Allows material to move into and
out of the nucleus
Nucleus
Cytoskeleton
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Found in all eukaryotic cells
Not found in prokaryotes
A network of protein filaments
that helps the cell maintain its
shape
It also is involved in cell
movement
Microfilaments and Microtubules
made of actin, tough and flexible,
functions for cell movement, assemble
and disassemble
the microtubules for cell movement
made of tubulis, maintain cell shape, used
in cell division with centrioles and build the
projections of cilia and flagella
Ribosomes
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Found in all cells
Main function is to make
proteins
Can be found floating in the
cytosol or attached to
endoplasmic reticulum
Endoplasmic Reticulum (ER)
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Found only in eukaryotic cells
Where components of the cell
membrane are assembled
Two kinds: Smooth ER & Rough
ER
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Smooth ER: no ribosomes; makes
lipids
Rough ER: has ribosomes; involved
in making proteins
Endoplasmic Reticulum
Golgi Apparatus
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Found only in
eukaryotic cells
Enzymes attach
carbohydrates &
lipids to proteins
Send proteins to
their final
destination
Lysosomes
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Found in
animal cells only
Break down lipids,
carbohydrates & proteins from
food into particles that can be
used by the cell
Also break down “dead”
organelles
Vacuoles
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Not found in prokaryotes
Animal cells have small or no
vacuoles
Plant cells have a large central
vacuole
Store materials such as water,
salts, proteins & carbohydrates
How endocytosis and exocytosis works in animal
cells: Note the food Vacuole and Lysosomes
Chloroplasts
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They have their own DNA
Found in all plant cells
Some prokaryotes have them,
but most do not
Use the energy from sunlight to
make energy-rich food
molecules (carbohydrates)
during photosynthesis
Mitochondria
● converts stored energy to a usable
form
● double membrane with folds to
increase surface area
● it also has its own DNA
Endosymbiotic Theory (CH 19)
Diffusion
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Molecules move from an area of
high concentration to an area of
low concentration
Movement continues until
equilibrium is reached
Many substances move across
the membrane by diffusion
Does not require energy
(passive transport)
Diffusion
concentration gradient
Rate of Diffusion
is affected by:
1. Temperature
1. Steepness of
the gradient
1. Size of
Molecules
Facilitated Diffusion
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Some molecules cannot cross the
membrane without help
Some of the proteins in the
membrane form protein channels
Materials still move from higher to
lower concentrations
No energy is required
Facilitated Diffusion
htlfacilitated diffusion (fast and specific but energy free)
Osmosis: A special name for a
special Molecule!
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The diffusion of water
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Isotonic – equal concentration
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Hypertonic – higher concentration
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osmosis
Water moves out of the cell (shrivels)
Hypotonic – lower concentration
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Nothing happens (normal)
Water moves into the cell (pops at the
extreme)
No energy is required
Effects of Osmosis on Cells
Osmotic Pressure
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In pure water, an animal cell
would burst
Plant cells are protected by their
cell wall
Some freshwater organism have
special structures like contractile
vacuoles to get rid of extra
water
Active Transport: Working to go
Uphill---Up the gradient.
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Materials move
from lower
concentration to
higher
concentration
Requires an
input of energy
Works kind of
like a pump
Transport of Large Amounts
Bulk Transport
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Endocytosis – movement into
the cell
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Phagocytosis – “cell eating” – solid
particles
Pinocytosis – “cell drinking” –
particles dissolved in water
Exocytosis – movement out of
the cell
Phagocytosis
http://www.youtube.com/watch?v=pvOz4V699gk
Pinocytosis
animation
Homeostasis and Cells
(homeo = same Stasis = state
SIngle and cells and Multicellular
organisms - maintain a certain level of
conditions in its environment
Multicellular organisms divide and
conquer tasks and jobs to maintain
homeostasis. This takes communication!
Cell to cell communication:
● cellular signals speed up or slow
down cell activities
● receptors (1)in the cell
membrane and (2) inside the
cytoplasm carry electrical and
chemical messages.
● review of phospholipid
membrane and receptor visual