Transcript Notes for Cell Organelles

Cell Unit Notes
The Cell Theory
 All
living things are composed of cells
 Cells
are the basic functional units of life
 New
cells are produced from existing cells
Prokaryotes vs. Eukaryotes








Prokaryotes
smaller & simpler
Contain a cell
membrane &
cytoplasm
Sometimes a cell wall
Also have ribosomes
No nucleus
All bacteria are
prokaryotes
DNA is “free –
floating”


Eukaryotes
Have a nucleus
containing DNA
 Most have specialized
structures called
organelles
 All plants, animals,
protists, and fungi are
eukaryotes
 Larger and more
complex
Prokaryote vs. Eukaryote
Cell membrane
Cytoplasm
Prokaryotic Cell
Cell membrane
Eukaryotic Cell
Cytoplasm
Nucleus
Organelles
Prokaryotes
 Prokaryotes
are simple, living
organisms that can reproduce on
their own
 They have diverse ways of
obtaining nutrients:



Photosynthesis
Chemosynthesis
Heterotrophic consumers
Prokaryotes
 Bacteria
(prokaryotes)
live in every habitat
possible and are the
most numerous of all
living things on our
planet
 All living things depend
upon bacteria –
including, especially,
humans!
Prokaryotes
represent the “ancient bacteria” and
they live in extreme environments such as
boiling water or extremely salty environments
 They are the oldest living organisms on this
planet. Evidence suggests that they were
present during the early stages of Earth over
3.9 billion years ago
 Archea
Prokaryotes

Bacteria have cell
membranes and
most have a cell wall
 Their DNA is one
circular molecule
 They often have
many plasmids


Small circular rings of
DNA usually
containing one gene
Pili help bacteria
“stick” to things
Many bacteria have a
flagellum or many flagella
to help them move
Prokaryotes & Viruses
 Viruses
are extremely
small particles not
considered to be “alive”
 They act like parasites
because they can ONLY
reproduce in a host
 They consist of a protein
coat and contain either
DNA or RNA inside
Eukaryote Cell Structures
 Cell


Wall
Found in many
organisms including
plants, algae, fungi,
and nearly all
prokaryotes
Not found in animal
cells
Cell Wall
The main function
of the cell wall is
to provide support
and protection for
the cell
Plant cell walls are
made of cellulose
The Nucleus
 The
nucleus is the “control center” of the cell
 The
nucleus controls most cell processes
and contains the hereditary information of
DNA
 Almost
all eukaryotic cells, including plant
and animal, contain a nucleus
The Nucleus
Nucleolus – small
dense region in
nucleus where
ribosomes are
produced
 Nuclear envelope –
double membrane
layer surrounding
the nucleus (aka.
Nuclear membrane)

The Cytoskeleton

A network of protein
filaments that help the
cell maintain it’s
shape
 It is also involved in
many forms of
Microtubule
movement
Microfilament
The Cytoskeleton
 Made



up of three types of structures:
Microtubules – hollow tubes of protein that help
maintain cell shape and serve as “tracks” for
organelles to travel on
Intermediate Filaments – smaller than
microtubules – gives a cell its strength
Microfilaments – long thin fibers that support cell
movement and support
Organelles in the Cytoplasm

Ribosomes



Organelle that
“assembles” proteins
(Protein Synthesis)
A ribosome is made up
of 2 parts:
• a protein
• rRNA (ribosomal
RNA)
Ribosomes make
proteins from the “coded”
instructions of the DNA
inside the nucleus
Ribosomes
Endoplasmic Reticulum


An internal membrane
where parts of the cell
membrane are made and
some proteins are
modified
Rough
endoplasmic reticulum
The Rough
Endoplasmic Reticulum
is where protein synthesis
occurs
 Ribosomes are on it’s
surface making it
appear “rough”
Endoplasmic Reticulum
 The
Smooth
Endoplasmic
Reticulum does
not have any
ribosomes on it’s
surface

It contains
enzymes that
make lipids (fats)
Smooth endoplasmic
reticulum
Golgi Apparatus
Golgi apparatus

After proteins are assembled and produced by the
Rough ER they move to the Golgi Complex where :


Carbohydrates (sugars) and lipids (fats) are attached to the
protein
They are then sent to their final destination
Lysosomes
 Small
organelles that are
filled with digestive and
other enzymes



They break down lipids
(fats), carbohydrates
(sugars), and proteins from
food particles so it can be
used by the rest of the cell
Lysosomes also break
down “old” organelles that
have outlived their function
Basically, they “take out the
trash”
Vacuoles

Serve as a storage for
water, salts, proteins,
and “carbs” (plant and
animal cells)
 In Plants :

They usually have one
large vacuole filled
with water to support
structures like leaves
and flowers
Vacuole
Chloroplasts
 The


producer!
They use sunlight to
power a familiar
process called
Photosynthesis
The green pigment
(color) chlorophyll is
what gives leaves
their color and is
found inside
chloroplasts
Chloroplast
Mitochondria
 The
“powerhouse” of
the animal and plant
cell!



Mitochondria use energy
from food to make highenergy compounds (ATP)
The cell uses these highenergy compounds for
growth, development, and
movement
In that way, the
mitochondria makes “fuel”
for the cell
Typical Plant Cell
Typical Animal Cell
The Cell Membrane
 The
cell membrane regulates what enters
and leaves the cell
 It also provides support and protection
 The cell takes in food and water and
eliminates wastes through the cell
membrane
 The cell membrane is selectively
permeable
Selective Permeability
The Lipid Bilayer

Most cell membranes are made up of a doublemembrane layer called the lipid bilayer
 Along with lipids the membrane also has
proteins that are “stuck” in it (see below)
The Lipid Bilayer
Along with the proteins are “carbohydrate
chains” that are attached to the protein
 These “chains” act like an identification card or
“face” so the cell can be recognized

Carbohydrate
chains
Protein
channel
Diffusion

All living cells are surrounded
by and full of liquid
 Even a cactus in the desert
has moist cells in it’s living
tissue
 One of the most important
functions of the cell
membrane is to regulate the
movement of molecules
from one side of the
membrane to the other
Diffusion
Diffusion

The concentration
of a solution is the
relative “purity” of a
liquid
 There can be a high
concentration to a
low concentration
 A solution will move
in the direction of
high concentration
to low
concentration and
this is called
Diffusion
Diffusion
 Diffusion
allows
substances to cross
the cell membrane
without requiring the
cell to use energy
 This is very
important since
energy must be
conserved – even at
the cellular level!
What is Osmosis
 Osmosis
is the movement of water across
a semi-permeable membrane.

Important part of homeostasis
Osmosis

Selective permeability
means that only select
“things” can pass
through the membrane
 Osmosis is “the
diffusion of water across
a selectively permeable
membrane”
Osmosis (cont.)

Tonicity: Ability of a
solution to cause a cell to
gain or lose water.

Is dependent on the
concentration of solutes
that cannot cross a
membrane (nonpenetrating solutes). The
more of these solutes there
are, the higher the
tendency that water will exit
the cell and vice versa.

Isotonic solution: No net
movement of H2O occurs.



The concentration of
solutes is equal outside &
inside of cell.
This is an indicator of a
stable cell environment.
Water will still flow across
the membrane at the same
rate in both directions.
Osmosis (cont.)

Hypertonic solution:
H2O will move out of
the cell (lose H2O).
Concentration of
solutes is greater
outside of cell.

Increases in salinity
causes cells to lose
H2O such as a
freshwater plant
placed into saltwater.

Hypotonic solution:
H2O will enter cell.
Concentration of
solutes is greater
inside of cell.

This can cause cells to
lyse (burst) & die.
Osmosis (cont.)
Osmotic Pressure
Isotonic – means that on
both sides of the cell
membrane it is the same
“concentration”
 Hypotonic – the cell fills
up with water and is in
danger of “bursting”
 Hypertonic – the cell loses
much of its water
concentration and can
“shrink”
 (Animal Cells react
differently than plant cells
because of the cell wall
that plant cells have)

Osmotic
Pressure
Osmosis (cont.)

Osmoregulation:
Control of H2O
balance.

Paramecium lives in
pond water (hypotonic
to cell). It has a
plasma membrane
that is less permeable
to H2O to slow the
uptake of H2O.
• Also has a contractile
vacuole that pumps out
H2O as fast as it enters.
Osmosis (cont.)

Plant cells are very turgid
(very firm) when they are
surrounded by a
hypotonic solution.


Allows the plant to stay
upright = Healthy.
If plant cells are in an
isotonic environment, the
cells will become flaccid
(limp) = Unhealthy.

If plant cells are in a
hypertonic environment,
they will undergo
plasmolysis.


Causes the plant cell to
lose water & turgor
pressure, resulting in cell
death.
Bacteria & fungi cells can
also undergo plasmolysis.
Facilitated Diffusion

This is diffusion
across the cell
membrane with the
“help” of proteins

It still flows from a high to
low concentration
Facilitated
Active and Passive Transport
Active Transport

Active transport requires
“action” or energy in order
to move these particles
across the cell membrane
 The input of energy along
with special proteins on
the surface of the cell can
move any particles across
any “gradient”
 Gradient – relative
concentration of a solution
Endocytosis & Exocytosis
Exocytosis

The removal of large
amounts of material
from the cell is known
as exocytosis
 The vesicle fuses with
the cell membrane
and forces its
contents out of the
cell