CELLULAR
STRUCTURE AND
FUNCTION
BIG IDEA

Cells are the structural and functional units of all
living organisms.
Cell Discovery and Theory

Section 7.1
MAIN IDEA #1

The invention of the microscope led to the
discovery of cells.
Important Discoveries



Robert Hooke- observed cork with the first
microscope and coined the term “cellulae”
meaning small rooms
Anton van Leeuwenhoek- first to observe living
organisms with a microscope
Both men led to many scientific discoveries
(scientific revolution)
Microscopes

Compound light microscope- uses visible light
and a series of lenses to create a magnified
image.
Microscopes

Electron microscope- uses magnets to beam
electrons at thin specimens.

Only nonliving cells and tissues can be observed
with electron microscopes
Cell Theory

1.
2.
3.
One of the fundamental ideas of modern biology and
includes the following three principles.
All living organisms are composed of one or more
cells
Cells are the basic unit of structure and organization
of all living organisms
Cells arise only from previously existing cells, with
cells passing copies of their genetic material on to
their daughter cells
Cell types



Prokaryotic- cells without a nucleus OR
membrane bound organelles (mostly unicellular).
Eukaryotic- have a true nucleus and membrane
bound organelles.
Both have plasma membranes!
Eukaryotic structures



Nucleus- distinct central organelle that contains
the cell’s genetic material in the form of DNA.
Organelles- enable specialized cell functions to
take place in different parts of the cell at the
same time.
Eukaryotes are thought to have evolved from
prokaryotes- Endosymbiont Theory
The Plasma Membrane

Section 7.2
MAIN IDEA #2

The plasma membrane helps to maintain a cell’s
homeostasis.
Functions of the Plasma Membrane


Creates a thin, flexible boundary that controls
the movement of substances into and out of the
cell
Selective permeability- capability to allow some
substances pass through while keeping others
out.
Plasma Membrane




Phospholipid bilayer- phospholipids are
arranged in a double layer, TAIL TO TAIL.
Phospholipids have a polar head and two nonpolar “tails.”
Creates the barrier that is polar
at its surface and non-polar
in the center.
Separates the inside and outside
environments of the cell.
THINK ABOUT IT!!!

How do hydrophobic substances cross a plasma
membrane?
Other membrane components



Transport proteins- move needed substances or
wastes through the membrane.
Cholesterol- non-polar molecule among the
phospholipids; keeps the “tails” from sticking
together- fluidity
Carbohydrates (sugars)- help with cell
identification
Fluid Mosaic Model



Phospholipids can move sideways across the
membrane
Other components can even move
through/among the bilayer.
The fluidity of the membrane allows a
scattered/random pattern arrangement of the
components- mosaic.
Structures and Organelles

Section 7.3
MAIN IDEA #3

Eukaryotic cells contain
organelles that allow the
specialization and the
separation of functions
within the cell.
Cytoplasm




semifluid environment
inside the plasma
membrane.
In ALL cells
Prokaryotic- all chemical
processes
Eukaryotic- processes take
place in organelles
Cytoskeleton




Framework for the cell within the cytoplasm
also aids in cell movement and other cellular
activities.
ALL Eukaryotic cells
Microtubules- long,
hollow protein cylinders
Microfilaments- thin
protein threads.
Cell Structures

Nucleus- control center of the cell that contains
coded directions for the production of proteins
and cell division.
Surrounded by a nuclear envelope
 ALL Eukaryotic

Cell Structures

Ribosomes- site of
protein synthesis




Made of 2 components
Can be free floating OR
attached to the ER
Manufactured by the
nucleolus
ALL cells
Cell Structures

Endoplasmic reticulum- highly folded membrane that is
the site of protein and lipid synthesis



ALL Eukaryotic
Smooth- does NOT have ribosomes attached
Rough- HAS ribosomes associated within
Cell Structures

Golgi apparatus- a flattened stack of tubular
membranes that
modifies proteins
and packages them
for distribution
outside the cell
ALL Eukaryotic
 Vesicles= packages; fuses with plasma membrane

Cell Structures

Vacuoles- a membrane- bound vesicle for the
temporary storage of materials
Plant cells- ONE large
 Animal cells- a FEW small

Cell Structures

Lysosomes- a vesicle that
contains digestive
enzymes for the
breakdown of excess or
worn-out cellular
substances.

Animal cells ONLY
Cell Structures

Centrioles- organelles that occur in pairs and are
important for cell division
Animal cells
 MOST protist

Cell Structures

Mitochondria- a membrane-bound organelle
that makes energy available to the rest of the
cell.

ALL Eukaryotic cells
Cell Structures

Chloroplasts- a doublemembrane organelle with
thylakoids containing
chlorophyll where
photosynthesis takes
place.

Plant cells ONLY
Cell Structures

Cell wall- an inflexible barrier that provides
support and protects the plant cell.
Plant cells
 Fungi cells
 SOME Prokaryotes

Cell Structures

Cilia and flagella- projections from cell surfaces
that aid in locomotion and feeding.
Cilia- tiny hairs; SOME animal cells, protists cells,
and Prokaryotes
 Flagella- tail like; SOME animal cells, Prokaryotes,
and some plant cells

Cellular Transport

Section 7.4
MAIN IDEA #4

Cellular transport moves
substances WITHIN the
cell and moves
substances INTO &
OUT of the cell.
Diffusion


The net movement of particles from an area of
high concentration to low concentration.
Dynamic equilibrium- condition, in which there
is continuous movement but NO overall change
Diffusion

Factors that affect diffusion rate
Concentration
 Temperature
 Pressure
Ex: more collision= faster diffusion


Diffusion does NOT require any energy!
Facilitated Diffusion


Uses transport proteins to move other ions and
small molecules across the plasma membrane.
Still from high concentration to low
concentration!
Osmosis


Diffusion of water across a selectively permeable
membrane.
Also exhibits dynamic equilibrium
Isotonic


Cell is in a solution that
has the same
concentration of water
and solutes.
Stable/Equilibrium
Hypotonic


Cell is in a solution that has a lower concentration of
solute.
Net movement of water INTO the cell
Hypertonic


The concentration of the
solute outside of the cell
is higher than inside.
Net movement of water
is OUT of the cell
Active Transport



The net movement of particles against a
concentration gradient.
Requires energy
Maintains homeostasis
Na+/K+ Pump

+
Uses ATP energy to
transport three sodium
ions out of the cell while
moving two potassium
ions into the cell.
Large Particles


Endocytosis- intake of a substance
Exocytosis- secretion of a substance