Download Organelles - morescience

Cytology ~ The study of
cells
Organelles
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D. Two Types of Cells:
Prokaryotic Cells Eukaryotic Cells
1. Simple
2. Unicellular
3. Primitive ancestor
4. No nucleus
5. No membrane-covered
organelles
6. Circular DNA
7. Example - bacteria
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1. Complex
2. Unicellular or multicellular
3. Evolved from Prokaryotes
4. Has a Nucleus
5. Has MembraneCovered organelles (has
everything)
6. Linear DNA
7. Every other cell (plants/animals)
I. Organelles (means little organs)
1. Plasma Membrane (cell membrane)
- keeps cytosol (cytoplasm and organelles) inside; shape
- controls movement of substances in/out
- contains important components involved in cell signalling,
communication, and cell recognition
01_cell membrane.mov
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Q1. What dietary nutrients are necessary to generate a cell membrane?
A1. Phosphate, Lipids, Protein (Nitrates), Carbohydrates
Q2. Would water readily pass through the bilipid layer directly? Why?/Why not?
A2. Not readily. Water is hydrophilic and lipids are hydrophobic.
Facilitated diffusion through an aquaporins (integral proteins for water) is faster
Endocytosis:
Exocytosis:
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6. Mitochondria
• “Power House” of the cell
• Responsible for Cellular Respiration
~ converts food energy – ATP energy
~ reason we breath O2 = to make ATP
• Increased surface area by folds called cristae
means more places to make ATP
• cells more active=more mitochondria
Originated as an aerobic bacterium
- size and shape of a bacterium
- has its own, circular DNA
- has its own ribosomes
- divides by binary fission
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Q1. Why do we breath?…and what does that do?
A1. Breath to make ATP - which is the energy that runs the cell
Q2. How does the saying, “If you don’t use it, you’ll lose it,” apply here?
A1. If you are active - your muscles will make more mitochondria, if you become less
active, your body will recycle the extra, unnecessary mitochondria.
7. Chloroplasts
• in plants in algae
• contains chlorophyll (makes plants green)
• sunlight sugar = photosynthesis
Originated as a photosynthetic bacterium
- size and shape of a bacterium
- has its own, circular DNA
- has its own ribosomes
- divides by binary fission
With CHO you can make:
Carbs - CH2O
Lipids - CH>>O
Protein - CHON
Nucleic Acids - CHONP
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Q1. Plants can carryout photosynthesis to make what? And used for…(2)
A1. Carbohydrates - plant parts and energy
Q2. With CHO, what else can be made?
A2. Carbs - CH2O
Lipids - CH>>O
Protein - CHON
Nucleic Acids - CHONP
Theory of Endosymbiosis
internal
membrane
system
aerobic
bacterium
Eukaryotic cell with
mitochondrion
Ancestral eukaryotic cell
chloroplast
Eukaryotic cell with chloroplasts
mitochondrion
photosynthetic
bacterium
Claim: Evolutionary Biologists believe both mitochondria
and
chloroplasts where once prokaryotic cells that
were engulfed by another cell and formed a symbiotic (working
together) relationship.
Evidence: list 4 pieces of evidence
1. ______________________________________________
2. ______________________________________________
3. ______________________________________________
4. ______________________________________________
Justification: restate the claim & use your evidence!
_______________________________________________________
_______________________________________________________
_______________________________________________________
_______________________________________________________
_______________________________________________________
_______________________________________________________
_______________________________________________________
_______________________________________________________
2. Nucleus
• “Control Center” of the cell
• largest, most visible organelle
• stores DNA (deoxyribonucleic acid) - 3.2 billion nucleotides
Nucleolus
~ most prominent structure in an undividing cell
~ genetic info for ribosome assembly
Nuclear envelop
~ double membrane
~ pores for passage of large macromolecules and particles
Nuclear lamina
~ netlike lining inside nuclear envelop
~ made of protein filaments - maintain shape
Chromatin
~ loose organization of protein & DNA
Q1. Why doesn’t DNA leave the nucleus
Physically: double stranded and can’t exit the nuclear pores
Philosophically: keep the original (DNA) safe and protected
Q2. What can? How and why?
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mRNA, ribosomes - through the nuclear pores because they are single stranded, and small
Every cell starts with a nuclei, but not all cells keep their nuclei
1. As part of the maturation process, human red blood cells destroy their cell nuclei. They do this in order to carry
as much oxygen as possible and still stay small enough to fit through narrow blood capillaries, thereby maximizing
the oxygen delivery. In fact, humans have some of the smallest red blood cells of all vertebrates, thanks in part to
the destruction of the nucleus.
Most mammals have red blood cells without nuclei, while all other types of vertebrates do have nuclei in their RBC’s.
However, all red blood cells, including human, must start with DNA, as DNA contains the code that tells each cell
how to construct itself in the first place.
Human red blood cells simply destroy their nucleus once it is no longer needed as part of the maturation process.
A ring of actin within a maturing red blood cell pinches and splits the cell into two parts: one part with the DNA and
one part without. Red blood cell enucleation is therefore a special type of cell division. Macrophages then come along
and gobble up the parts containing DNA, leaving only the red blood cell parts that don’t have DNA. Note that there is
much more in blood than red blood cells. As a result, a blood sample does contain DNA due to the presence of other
kinds of cells.
2. Cornified cells in the skin, hair, and nails also contain no cell nucleus. Like red blood cells, these cells start out
with cell nuclei in order to develop properly, but then destroy their nuclei as part of the cornification process.
They do this in order to maximize the space in the cell filled with the structural protein keratin.
Keratin is a strong protein that gives hair, skin, finger nails, and toe nails their toughness. Cells that undergo
cornification experience a form of programmed, controlled cell death in order to achieve their strength. The cell
nucleus and other internal parts of the cell are destroyed and their space is filled by keratin. Once cornification is
complete, these cells are dead and carry out no biochemical processes. But dead does not mean useless. Cornified
cells fulfill their end purpose of giving structural strength and warmth to surrounding tissues despite being dead.
The fact that cornified cells are dead means that you can cut your hair, clip your nails, and rub off the outer layer
of skin without causing any damage or killing cells. The lack of nuclear DNA in cornified cells means that
forensic biologists can rarely extract DNA from hair clippings in order to help determine the culprit.
Aside from red blood cells and cornified cells, all other cells in the human body contain nuclear DNA. Also, all
cells start with nuclear DNA. The reason for this is that DNA contains the basic code that tells each cell how to
grow, function, and reproduce.
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Genetic Material
Prokaryotic DNA
• Circular in shape
• In the cell’s cytoplasm
• Not wrapped around proteins
• No introns
• Fewer average bp’s (base pairs)
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Eukaryotic DNA
• Linear in shape
• In the cell’s nucleus
• Wrapped around proteins
• Introns and exons
• More bp’s (base pairs)
3. Ribosomes
• smallest & most abundant organelle
• made of rRNA and protein
• Role - protein synthesis
(site of Translation)
Free Ribosomes:
~ suspended in the cytoplasm
~ ie. Make enzymes for sugar decomposition (cellular respiration = ATP)
Bound Ribosomes:
~ attached to the Endoplasmic Reticulum (Rough ER)
~ Site of Translation (mRNA, tRNA come here to assemble protein which
can be insertion into membranes, for packaging within vesicles for the
cell or to be exported out of the cell)
Free & bound ribosomes are identical in structure and can
alternate roles, depending on the needs of the cell.
In prokaryotes ribosomes are smaller, free in the cytoplasm,
simultaneous transcription/translation
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Q1. Since free & bound ribosomes can change roles, why would you expect to see more of both in a
dividing cell?
A1. Free ribosomes - allow for more sugar decomposition - cellular respiration = ATP for dividing cells
Bound ribosomes - important for protein production necessary for new cells
Ribosomes
Prokaryotic ribosomes
Eukaryotic ribosomes
• 70S (smaller)
• Synthesized and assembled
in the cytoplasm
• Transcription and translation
in the cytoplasm
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• 80S (larger)
• Synthesized in the nucleolus
• Assembled in the cytoplasm
(free) or (attached) on the
Rough Endoplasmic Reticulum
• Transcription in the nucleus
then translation in the cytoplasm
4. Endoplasmic Reticulum (ER)
• “Assembly & Delivery System” of the cell
• membrane-covered vesicles
• Internal folds - cisternal space
Smooth ER: (no ribosomes attached)
~ Makes lipids (oils, phospholipids, steroids),
~ Metabolism of carbohydrates
~ Stores calcium ions for muscle contraction
~ Detox Role - breaks down drugs & poisons
(induced proliferation of smooth ER and related enzymes is
related to drug & alcohol tolerance)
Rough ER: (ribosomes attached)
~ Makes proteins to be secreted
~ Critical in making membranes (protein & phospholipids)
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1. As the medical examiner, what would be your
determination if you saw excessive amounts of
Smooth
ER in the liver cells of the corpse?
2. Why would you look to the ER if a person is not
5. Golgi Apparatus
• “Packaging Center” of the cell
• Cis face - where vesicles from the ER
enter the Golgi Apparatus
• Trans face - side where vesicles leave
the Golgi Apparatus
• looks like ER, but closer to membrane
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Q1. What can you say about the membranes of the endoplasmic
reticulum,
golgi apparatus, and the plasma (cell) membrane?
Nucleolus
Golgi sorts & packages
proteins to export from cell
DNA has
instructions to
build proteins
Proteins are
assembled at
the ribosomes
attached to
Rough ER
*Known as the Central Dogma
8. Vacuoles
- very large membrane-covered (tonoplast) compartment
- plants wilt when vacuoles lose water.
Three types of vacuoles:
1. Central vacuole - only found in plant cells
storage for water & dissolved minerals/salts
2. Contractile vacuole - in algae & protists
involved in osmoregulation
3. Food vacuole - digestive function for
protozoans
Exocytosis - leave the cell
Endocytosis - go into the cell:
phagocytosis - “cell eating”
pinocytosis - “cell drinking”
cell receptor - lock & key
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9. Vesicles
- membrane-covered compartment
- pinches off from the ER or from the Golgi Apparatus.
Used as a means of transporting nutrients and cellular components
throughout and out of the cell.
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Q1. What can you say about the membrane-covered compartments?
A1. It is interchangeable btw ER, Golgi, Plasma membranes
Q2. What is it called when the vesicle fuses to the plasma membrane & excretes
its contents out of the cell? Engulfs and brings contents into the cell.
A2. Exocytosis
Q3. Why doesn’t the cell membrane get bigger…or smaller?
A3. Exocytosis adds membrane while Endocytosis - (pinocytosis & phagocytosis) pinches off to make
vesicles - a constant exchange of membrane
10. Lysosomes
- “Package of Destruction”
- specialized vesicles in animal cells
- contain digestive enzymes
11. Peroxisome
- various metabolic functions dealing
with lipids and polyamines
- * produces catalase which decomposes
hydrogen peroxide H2O2
(a by-product of cellular respiration)
2H2O2 into 2H2O + O2
Q1. When active people become sedentary - what happens to their numbers of
mitochondria? How does that happen?
A1. Mitochondria numbers are reduced; lysosomes digest the unnecessary ones
Q2. What do peroxisomes produce when they break down hydrogen peroxide?
A2. Catalase (produced by peroxisomes) breaks down hydrogen peroxide
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12. Centrosomes
(pair of centrioles)
- found in animal cells
- believed to have a role in cell division
- spindle fibers grow from the centrioles
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13. Cell Wall
- provides strength, support, shape
- eukaryotes – predominantly cellulose/chitin
- prokaryotes - predominantly of peptidoglycans
- in plants and algae
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(protein & sugar polymer)
Cell Communication
- Animal Cells - Gap Junctions
- Plants - Plasmosomes
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Desmosomes - act like adhesive connections resisting shear forces btw cells
Gap Junctions - connects the cytoplasm of cells, allowing the movement of molecules & ions btw cells
Plasmodesmata - analogous to gap junctions, but in plant cells
Found in Plant & Animal Cells
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Cell membrane
Cytoplasm
Nucleus
Endoplasmic Reticulum
Ribosomes
Mitochondria
Golgi Complex
Vacuoles
Only in Plant Cells
• Cell Wall
• Large Vacuoles
• Chloroplasts
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Only in Animal Cells
• Centrosomes
• Lysosomes