Transcript Cell Membrane

Cells
By the end of this class you should understand:
• The three major parts of all cells
• The primary structures found in prokaryotic
and eukaryotic cells
• The major organelles found in all living things
• The basic functions of membrane-bound
organelles found in eukaryotes
Parts of a Cell
• There are two major types
of cells
– Prokaryotic cell
– Eukaryotic cell
• All cells have three parts:
– Cell membrane
– Genetic information
– Cytoplasm
Prokaryotic Cells
• Prokaryotic cells are cells
without a nucleus
– All genetic info is bundled
but not separated from
cytoplasm
• All known prokaryotes
are single-celled bacteria
– Prokaryotic cells are tiny!
Eukaryotic Cells
• If every cell was a
company:
– Prokaryotic cells are a 1man startup in a garage
– Eukaryotic cells are a large
corporation
• Eukaryotic cells have
organelles which each
perform separate jobs
• Genetic info stored in
nucleus
Eukaryotes
• Some eukaryotes are single
celled organisms
– One eukaryotic cell performs
all functions of life
• Some eukaryotes are
multicellular
– The different cells specialize
in different tasks
– Each cell is still individually
alive!
Key Parts of Eukaryotic Cells
• Nucleus
– Stores genetic information
• Cytoplasm
– Composed of a liquid called
cytosol
– Filled with various membranebound organelles
• Cell Membrane
– Often referred to as plasma
membrane
Key Parts of Prokaryotic Cells
• Cell membrane, nucleic
acids, and cytoplasm
– Same as eukaryotes
• Cytoplasm is much simpler
– Prokaryotes have NO
membrane-bound organelles
– They do have a cytoskeleton
and ribosomes!
Cell Membrane
• The cell membrane is a
flexible, selectively
permeable (or
semipermeable) barrier
• Boundary of cell, visible
under microscope only as
border of cell
• NOT the same as a cell wall
– Cell wall is rigid
Cell Membrane Structure
• The cell membrane is
composed of phospholipids
– Hydrophilic head,
hydrophobic tail
• The nonpolar tails orient
themselves into a
hydrophobic zone
surrounding the cell
– Essentially a thin bubble of
oil
Cell Membrane Structure
Cell Membrane Proteins
• Proteins are
macromolecules
constructed from many
linked amino acids
• Some amino acids are
hydrophobic and so mix
with the inside of the cell
membrane
• These proteins sit inside
the cell membrane
Membrane Protein Functions
• Cell membrane proteins
serve many vital functions:
– Markers
– Receptors
– Channels
• Transporting things in and
out of cells is a key
function of life!
– Will cover this more
tomorrow
Parts of the Eukaryotic Cell
(organelles)








Nucleus
Cell membrane
Cytoskeleton
Cytoplasm
Mitochondria
Ribosome
Endoplasmic Reticulum
Golgi Apparatus
Nucleus: The Library

The nucleus stores all the cell's
genetic information in massive
molecules of DNA


The DNA molecules are packed
into many pairs of
chromosomes
When a protein is needed, signals
enter the nucleus and cause
copies of the appropriate genes
to be made with RNA
Key Nucleus Facts:

Every complete human cell has one nucleus




Exception: red blood cells have no nucleus (also
have no other membrane-bound organelles)
Exception: muscle cells are many cell fused
together and so have many nuclei
Every nucleus has the complete human genome
The nucleus has its own envelope to keep
unwanted things out
Cytoskeleton: The City Streets



Every cell has long
strands of different kinds
of proteins running
through it
When organelles are
moved they move along
the cytoskeleton
If the cell moves under its
own power it uses the
cytoskeleton as well
Key Cytoskeleton Facts:



There are several different types of fibers and
they have different functions
All cells must produce each of these fibers
These fibers are made of different kinds of
proteins (keratin, collagen, actin, myosin, etc)


If the genes for any of these fibers are no
good, no cells can form and the organism will
never develop, grow or be born
This makes these genes essential for life
Cytoplasm: The Marketplace



The liquid of the cell is called
cytosol
Cytosol plus the organelles
are called cytoplasm
All the cell's chemical
reactions and growth take
place here


Many exchanges are made
Many chemicals are
stored in vesicles in the
cytoplasm
Key Cytoplasm Facts:


Cytosol is a clear liquid but it is filled with salts
and sugars
Cytoplasm is held within the cell membrane


If the cell membrane develops a hole,
cytoplasm can leak out and the cell can die
If the cell membrane bursts all at once, this is
called lysis and is instant cell death
Ribosome: The Machine Shop

Site of protein synthesis



Some are free floating in
cytoplasm
Some are attached to
membranes called the
endoplasmic reticulum
Made with a combination of
protein and RNA

Probably the first structure
in the original cells
Key Ribosome Facts

Ribosome is the site for proteins to be
synthesized




That process will be discussed next week
Cytoplasmic ribosomes make the cytoskeleton
and cell enzymes
Rough endoplasmic reticulum produces
proteins that will enter the membrane or leave
the cell
Smooth endoplasmic reticulum is for synthesis
of other macromolecules such as lipids
Golgi Apparatus: The Shipping Center
• Vesicles from the
endoplasmic reticulum
are organized here
• Different vesicles have
different destinations
– The chemical reactions
that determine where
these vesicles go occur
here
Key Golgi Facts
• The Golgi manipulates cell membrane
material into many types of vesicles
– Peroxisomes contain peroxides
– Lysosomes contain destructive enzymes (that can
lyse chemicals or even other cells)
– Secretory vesicles are designed for exocytosis
(they will secrete their contents)
Mitochondria: The Power Plant
• Mitochondria (singular:
mitochondrion) produce
the cell's supply of energy
molecules
– Cells use a molecule called
ATP
– Made using the energy from
blood sugar
• Must have oxygen to work
– Process that requires oxygen
is called aerobic
Key Mitochondria Facts:

Mitochondria were once bacteria


Mitochondria must have oxygen to burn sugar



Captured/adopted by animal cells billions of
years ago and now we work together
Produce CO2 as a waste product
This is why we breathe in oxygen and breathe
out carbon dioxide
Mitochondria sustain our high metabolic rate

Cyanide blocks mitochondrial activity, which is
why it is a lethal poison to us
Mitochondria Activity
• Mitochondria perform aerobic respiration
(requiring O2)
– This is the key part of cellular respiration that will
be covered next week
• Prokaryotes have no membrane-bound
organelles, therefore they do not have
mitochondria
– Some bacteria are aerobic, which means they
perform the same processes as a mitochondrion!
See you in lab!