Transcript Cellular Organelles - holyoke

Cellular Classification &
Organelles:
A Look at the Endomembrane System
Biology 111
Holyoke Walsh
Prokaryotes vs Eukaryotes
• The basic structural & functional unit of
every organism is one or two types of cells
– pro or eukaryote.
• Prokaryotes are archaebacteria &
eubacteria
• Eukaryotes include protists, fungi, animals
and plants.
Typical Eukaryotic Cell
Typical Prokaryotic Cell
Commonalities…of all cells!!
•
•
•
•
Plasma Membrane
Cytosol
Chromosomes
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
Eukaryotes…genetic info…
• Two cellular components involved with the
genetic control of the cell are the
NUCLEUS & the RIBOSOMES
NUCLEUS
Chromosomes – made of DNA!
• 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
17
DNA Double Helix
Bases:
Cytosine
Thymine
Adenine
Guanine
T
G
http://www.youtube.com/wat
ch?v=qy8dk5iS1f0&feature=r
elated
C
T
A
G
Ribosomes
• Made of some RNA (genetic info) and
Protein
• 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?
Protein Synthesis Summary
Protein Synthesis
1. The DNA double helix unwinds to expose a sequence of
nitrogenous bases. (A,T,C,G)
2. A copy of one of the strands is made in a process known as
transcription. The copy is made of messenger ribonucleic acid
(mRNA) which, following transcription, travels out of the
nucleus into the main body of the cell, where protein synthesis
occurs.
3. The mRNA couples with the protein synthesis apparatus
(the ribosome). Another type of RNA, known as transfer RNA
(tRNA), brings free amino acids to the ribosome.
4. The anticodon present on the tRNA recognises the codon
present on the mRNA, and the ribosome adds the amino acid
to the growing chain of linked amino acids (polypeptides),
cleaving it away from the tRNA. This process is known as
translation.
5. As the polypeptide chain grows, it folds to form a protein.
http://www.youtube.com/watch?v=983lhh20rGY
Endomembrane System
• Many of the different membranes of the eukaryotic cell
are part of this system which carry out a variety of tasks
in the cell. i.e. synthesis of proteins, metabolism and
movement of lipids, & detoxification of poisons
• The membranes of this system are related either through
physical continuity or by the transfer of membrane
segments as tiny vesicles (sacs made of membrane)
• This system includes: nuclear envelope, the
endoplasmic reticulum, golgi apparatus, lysosomes,
various vacuoles, and the plasma membrane
Endomembrane System
Endoplasmic Reticulum
• Extensive network accounting for more than half
the total membrane in eukaryotic cells
• Consists of a network of membranous tubules
and sacs called cisternae
• The ER membrane separates the internal
compartment of the ER, called the ER lumen
(cavity) or cisternal space, from the cytosol.
• The ER membrane is continuous with the
nuclear membrane
ER cont…
Two types of ER: smooth and rough
1. Smooth ER – lacks ribosomes and
involved in diverse metabolic processes
such as lipid synthesis, metabolism of
carbohydrates, and detoxification of
drugs and poisons
2. Rough ER – has ribosomes and is
involved in protein synthesis
Golgi Apparatus – Shipping &
Receiving Center
See Handout*
Lysosomes
• Membranous sac of enzymes that an animal cell uses to
digest macromolecules.
• Lysosomal enzymes work best in an acidic environment
found in lysosomes. If a lysosome breaks or leaks the
enzymes are not very active b/c cytosol has a neutral pH
• Lysosomes carry out intracellular digestion in a variety
of ways. ie. amoebas use phagocytosis…food vacuole
fuses with lysosome and enzymes will then digest the
food.
FYI: humans use phagocytosis: WBC called
macrophage that engulfs and destroys bacteria &
other invaders.
http://www.youtube.com/watch?v=Jg8Dob35Rp4
Vacuoles
Types:
1. Food vacuoles – formed by phagocytosis
http://www.youtube.com/watch?v=W6rnhiMxtKU
2. Contractile vaculoes – pump excess water
out of the cell
http://www.youtube.com/watch?v=kkPiRT2ewVA
3. In plants & Fungi – Central vacuole: stores
food, nutrients, water and waste…maintains
turgor pressure (prefer a hypotonic state)