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Chapter 4
Cell Structure and Function
Do Now
What is the common structure that
makes up every living thing?
What instrument do you need to see
them?
The Discovery of the Cell
• Advances in
technology led
to the
discovery of
the cell:
INVENTION OF
MICROSCOPE.
1665: Robert Hooke
• English scientist that
used an early
compound
microscope to look at
cork.
• Noticed empty
“chambers” or
“boxes” in cork and
named them “cells.”
• He named them cells
because they
reminded him of the
small rooms where
monks lived
• He was looking at the
remains of dead
plant cells
Anton van Leeuwenhoek
• This Dutch
scientist was the
first person to
observe living
cells
• Used single-lens
microscope to
observe pond
water.
• Observed
microorganisms.
Making of the Cell Theory
• Proposed by 3 German scientists:
– In 1838, botanist Matthias Schleiden
concluded that “All plants are made
of cells”
– In 1839, zoologist Theodor
Schwann concluded that
“All animals are made of cells”
– In 1855, physician Rudolf Virchow
concluded that “New cells are
produced only from the division
of existing cells”
The proposals made by these 3 men
have been continually confirmed
by other biologists and make up
the:
Cell Theory
1. All living things are composed of one or
more cells.
2. Cells are the basic units of structure and
function in living things.
3. Cells come only from the reproduction
of existing cells.
CELL DIVERSITY - not all cells are
alike
Size:
•
•
•
•
2m (nerve cells in giraffe’s leg) to 0.2um
(bacteria)
Cell is limited in size by its surface area to
volume ratio
Food and oxygen must enter through its
surface
As a cell grows large, its surface area
becomes too small to maintain its life
functions
CELL DIVERSITY
Shape – cube, square, round, irregular
Form reflects function:
Nerve cell – reaches out to send impulses
Skin cell – flat and covers body
White blood cell – can change shape
Cell activity
• Structure and Function of Cells
Worksheet
• Finish for homework
Do Now
• Who named “cells” after looking at
cork cells?
• Who first examined living cells?
• What are the 3 points of the cell
theory?
2 Types of Cells
– Prokaryotes – lack:
• nucleus - for containing genetic
material
• membrane bound organelles - cell
compartments that carry out specific
cell functions – like our organs
– Eukaryotes – contain:
• a nucleus
• membrane bound organelles
Prokaryotes
• Smaller and simpler
than eukaryotic
cells.
• Genetic material is
not contained in a
nucleus.
• No organelles
• Bacteria
• First cells on earth –
prokaryotic
heterotrophs
Eukaryotes
• Larger and more
complex than
prokaryotes.
• Contain a nucleus
with DNA.
• Organelles
• Plants, animals,
fungi, and protists.
Do Now
• Name the 2 basic differences
between prokaryotic and eukaryotic
cells.
• Give an example of each type of cell.
Cell Membrane
• All cells have a cell membrane:
– A thin membrane that surrounds the
whole cell
– Selectively permeable – it regulates
what enters the cell (nutrients) and
leaves the cell (wastes)
– Provides protection and support
– Made of lipids and proteins
Cell Membrane
• Phospholipid bilayer: double-layered
sheet of lipids
– Hydrophilic phosphate heads love
water and are directed outward
toward the watery environments
– Hydrophobic lipid tails are afraid of
water and are directed inward
toward each other to get away from
the watery environments
Cell Membrane
– Gives cell flexible structure
– Forms strong barrier between the cell
and surroundings
Membrane Proteins
• Most cell membranes contain 2 types
of proteins:
– Peripheral proteins – located on both
the interior and exterior surface of the
cell membrane
– Integral proteins – embedded in the
lipid bilayer - can extend all the way
across from outside of the cell to inside
of the cell
Membrane Proteins
• Act as gates, channels, or pores
– Form channels and pumps that help
move material across membrane
• Carbohydrates are sometimes
attached to membrane proteins as
cell markers
– Carbs act as chemical ID cards,
allowing cells to identify one another
Fluid Mosaic Model
• Scientists used to think that the cell
membrane was static – didn’t move or
change
• New technology tells us that the lipid
bilayer behaves more like a liquid
(fluid) than a solid
• Lipids and proteins can move around
laterally and their pattern (mosaic) is
always changing
Do Now
• What is the term that describes the
gatekeeper duty of the cell
membrane?
• What is the cell membrane made of?
• What 2 types of proteins are in the cell
membrane?
Eukaryotic Cells
• Divided into two major parts:
– Nucleus
– Cytoplasm
with
organelles
Organelles
• Cytoplasm – area between the
nucleus and cell membrane which
contains organelles
• Organelles are membrane bound
structures that perform a specific
function
• Organelles are bathed in a gelatin-like
fluid called the cytosol that contains
salts, minerals and organic
compounds
Mitochondria
•Convert chemical energy
stored in food 
compounds that the cell can
use for energy (ATP)
•Enclosed by two
membranes:
•Inner membrane has folds
(cristae) to increase
surface area for chemical
reactions
Mitochondria
• Mitochondria are numerous in cells
with high energy requirements
(muscles)
• Mitochondria have their own DNA and
new ones only arise through growth
and division
• There is a theory that they developed
from prokaryotic cells living inside
eukaryotic cells (symbiosis)
•Small particles of RNA
Ribosomes
and protein – no
membrane
•Proteins are assembled
at ribosomes:
•Some are free in the
cytoplasm (proteins
used inside of cell)
•Some are attached to
endoplasmic reticulum
(proteins for use
outside of cell)
Endoplasmic Reticulum (ER)
•A system of
membranous tubes
and sacs
•Functions as an
intracellular highway
•Molecules can be
moved from one part
of cell to another
Rough ER
• Rough ER:
– covered with
ribosomes
– found in cells
which produce a
lot of proteins to
be exported from
cell
Smooth ER
• Smooth ER:
– not covered with
ribosomes
– Found in gland cells
that produce steroids
and liver cells that
breakdown toxic
substances
Cell Activity
• Cell Structure and Function worksheet
Do Now
• What is the function of the
mitochondria?
• What is the function of the ribosome?
• What are the 2 types of ER?
Golgi Apparatus
•Stack of flattened sacs
•Proteins move from ER to
Golgi
•Golgi customizes and
ships proteins to final
destinations
•Modifies, sorts, and
packages materials from
ER for:
•Storage in cell
•Secretion outside of cell
Lysosomes – not common in plant
cells
•Small, round organelles filled
with hydrolytic enzymes (suicide
sacs)
•Digestion of lipids, proteins,
carbs, DNA & RNA in the cell
•Digests old organelles, viruses
and bacteria
•May selectively destroy tissue
to shape bodies of animals
during development
Cytoskeleton
•Support
network of protein
strands
•Helps:
•maintain cell shape
•organelle movement
Microfilaments – part of
cytoskeleton
Smaller strands
made of actin protein
Produce a framework
that supports the cell
Helps cells move and
muscle cells to
contract
Microtubules – part of
cytoskeleton
•Larger strands made of
tubulin proteins
•Maintain cell shape
•Form cilia and flagella
•Important in cell division:
•form spindle fibers
•form centrioles
Cilia and Flagella
• Hair-like organelles that extend fro surface of
cell and assist in movement
• Cilia – short and present in large numbers
– Microorganisms – movement of cilia
propels them through water
– Respiratory tract – trap particles from air
and sweep them back to your throat to
be swallowed
• Flagella – long and less numerous
– Sperm cells – whip-like motion can propel
cells
•Contains nearly all cell DNA
Nucleus
in form of chromatin
(hereditary information)
•When cell is about to divide,
chromatin coils up and
becomes chromosomes
•Surrounded by nuclear
envelope
•lined with pores
•RNA, proteins, and
other molecules can
move into cell
Nucleus
Also contains the
nucleolus:
Site where
ribosomes are
synthesized
Do Now
• What is the function of the Golgi
apparatus?
• What are the parts of the
cytoskeleton?
• What is the function of the nucleus?
Plant cells
• May contain 3 additional
structures important to plant cell
function:
– Cell Walls
– Vacuoles
– Plastids
Cell Walls
Present in plants,
algae, fungi, and
many prokaryotes
Lie outside the cell
membrane
Pores let water,
oxygen, and carbon
dioxide pass
through easily
Cell Walls
• Provide support
and protection for cell
• Made from carbs
and protein.
– Cellulose –
carbohydrate fiber
– Principal component
of wood and paper
Vacuole
•Fluid filled organelles
that store enzymes and
wastes
•Plants have a single,
large, central vacuole
used for support
•Helps control water
content and maintain
homeostasis
•Surrounded by two
membranes
Plastids
•Can contain pigments that
capture energy from sunlight
•Chloroplasts have a system
of flattened membranous sacs
called thylakoids
•Chloroplasts contain
chlorophyll that converts the
sun’s energy into chemical
energy via photosynthesis
Do Now
• Name the 3 parts of a plant cell that
animal cells don’t have.
• What advantage do chloroplasts give
to plants?
Multicellular Organization
• Unicellular organisms – one cell carries
out all functions of life
• Multicellular organisms – cells are
specialized to perform one or a few
functions
– Specialization means that cells depend
on other cells for survival
Levels of Organization
• Cells: basic units of organization
• Tissues: similar cells grouped into units
to carry out specific functions
(epithelial tissue)
• Organs: several types of tissues that
work together to perform a function
(stomach)
• Organ systems: group of organs that
work together to perform a set of
related tasks (digestive system)
Evolution of Multicellular
Organization
• Fossil evidence suggests that the first
cells on earth were prokaryotes (like
bacteria)
• They couldn’t synthesize their own
nutrients
• Depended on organic nutrients in
environment
• Began to compete for limited
resources
• Cells with adaptations arose –
Colonial Organizations
• Some of the unicellular eukaryotes
began to live in groups or colonies
• Some of the cells may have
specialized in performing certain
functions
• Colonial Organisms – a collection of
genetically identical cells that live
together in a closely connected group
• Volvox – example of colonial organism
• Hollow sphere
containing 500 –
60,000 cells
• Each cell maintains its
own existence, but
many perform specific
functions that benefit
the whole colony
– Outer cells use flagella
to propel the colony
– Some cells are
specialized for
reproduction
Volvox
Colonial Organizations
• May be a link between unicellular
organisms and true multicellular
organisms
• They lack tissues and organs, but do
have specialized cells
• This may be how multicellular
organisms evolved:
– Cells became more specialized
– Less capable of living apart