Cellular Classification & Organelles:
A Look at the Endomembrane System
Biology 111
Holyoke Walsh
Cells
• http://www.youtube.com/watch?v=IcevP5tk
WH0&feature=related
COMPARING CELLS
• The size & shape of a
cell relates to its
function.
Cells
• All cells are classified as either
1. Prokaryote
2. Eukaryote
Prokaryote Cells
• no membrane bound nucleus, chromosomes
grouped together in an area called the "nucleoid"
• no membrane bound organelles
• smaller than eukaryotes
• have cell wall and cell
membrane, some have a
capsule on the outside
• ribosomes make protein
• consist of bacteria and
archaebacteria
• Appendages
include: fimbriae/pili,
flagella
*pili are usually longer and fewer than fimbriae, both
function for attachment and recognition of host cells
(pili has a function for sexual reproduction)
Figure 4.4a
E. coli
Eukaryotes
•
•
•
•
has a membrane bound nucleus
has membrane bound organelles in cytoplasm
Organelles perform specific functions
much larger than prokaryotes
Organisms within the animal, plant, fungi and
protista kingdoms are all eukaryotes
We will be spending a lot of time on
organelles and their functions.
Figure 4.6b
Figure 4.7b
Prokaryote vs Eukaryote Cells
Endosymbiosis theory:
All organelles seem to share many properties with bacteria. Lynn
Margulis proposed endosymbiont hypothesis: that organelles
derived from ancient colonization of large bacteria (became the
eukaryotic cell) by smaller bacteria (became the mitochondria,
chloroplast, etc.) Symbiosis = "living together".
*Mitochondria & Chloroplasts have their own DNA
Animation at Microbiological Concepts
Commonalities…of all cells!!
•
•
•
•
Plasma Membrane
Cytoplasm
Chromosomes (DNA)
Ribosomes
Key Differences?
• The location of their DNA; membrane bound
organelles
• Prokaryote = nucleoid region
• Eukaryote = nucleus
Prokaryote vs. Eukaryote
Prokaryote or Eukaryote??
Prokaryote or Eukaryote??
Prokaryote or Eukaryote??
Eukaryotes
• In addition to the plasma membrane at its outer
surface, a eukaryotic cell has extensive & elaborately
arranged internal membranes, which divide the cell
into compartments.
• These provide different local environments that
facilitate specific metabolic functions, so
incompatible processes can go on simultaneously in
a single cell
• The plasma and organelle membranes participate
directly in the cell’s metabolism b/c many enzymes
are built right into the membranes themselves.
Cell Membranes..in general
• Phospholipid bilayer
• Embedded proteins
• Each type of membrane has a unique
composition of lipids and proteins suited to
that membrane’s specific function
Ex: enzymes embedded in the mitochondrial
membrane function in cellular
respiration…which creates the ATP energy our
cells need to function!
Cell Membrane
Pg 64
Eukaryotes…genetic info…
• Two cellular components involved with the
genetic control of the cell are the NUCLEUS &
the RIBOSOMES
NUCLEUS
The Nucleus
The Nucleus
• Nuclear envelope contains nuclear pores for some things to enter and
exit (nucleoplasm within)
• Chromatin is DNA and proteins, when the cell begins to divide, chromatin
condenses and forms chromosomes
• DNA remains in the nucleus, it sends instructions to the cytoplasm via
messenger RNA
• RNA directs the synthesis of proteins on ribosomes in the cytoplasm
• Nucleolus assembles ribosomes within the nucleus, ribosomes contain
the "tools" to construct proteins
Chromosomes – made of
DNA/Protein!
• DNA: Polymer of millions of nucleotides
Nucleotide = Deoxyribose Sugar (pentose)
+Phosphate + Nitrogen Base
One Strand of DNA
• The backbone of
the molecule is
alternating
phosphates and
deoxyribose sugar
• The teeth are
nitrogenous bases.
phosphate
deoxyribose
bases
29
DNA Double Helix
Bases:
Cytosine
Thymine
Adenine
Guanine
T
G
http://www.youtube.com/watch?v=qy8dk5iS1f
0
C
T
A
G
Ribosomes
• Made of some RNA (genetic info) and Protein
• each is composed of two subunits, one large
and one small
• Non-membranous organelles
• Vary in size (smaller in prokaryotes)
• Main function is to carry out protein
synthesis.
Ribosomes cont…
• Cells that have high rates of protein synthesis have
particularly high rates of ribosomes
• Located in the cytoplasm/ER (structurally identical)
• Free ribosomes – function within the cytosol (ie.
enzymes that catalyze reactions)
• Attached ribosomes – generally destined for
insertion into organelles membranes or for export
(cells that secrete enzymes)
• Why does the human pancreas have millions of
ribosomes?