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Cell StructureChapter 6
IB Biology
Prokaryotes vs. Eukaryotes
• Prokaryotes have no nucleus or membrane bound organelles
•Most have a cell wall
•Many have flagella
• Very primitive
•Origin: 3.5 BYA Ex- Bacteria
Prokaryotes:
Eukaryotic Cells
• “Eu” = true “Karyo” = kernal (nucleus)
• “YOU are a Eukaryote”
• Have a nucleus
• Have membrane-bound organelles.
• First appeared in fossil records 1.5 bya
• All members of the following kingdoms have this type of cell: Protocista, Fungi, Plantae, Animalia.
Prokaryotes/Eukaryotes**
Prokaryotes Eukaryotes
No nucleus Nucleus
“Naked” DNA DNA associated with proteins
DNA in cytoplasm DNA in an envelope (nucleus)
No mitochondria Mitochondria
70s ribosomes 80s ribosomes
No organelles organelles
Reproduce by binary fission Reproduce by mitosis
Ex.- Bacteria Ex.- all other cells
Note: s = subunits
Prokaryotic CellBacterium:
Prokaryotic Cells
Escherichia coli
What do all cells have in common?•Cell membrane
•Cytoplasm/cytosol
•Genetic material
•Ribosomes
Cell Membrane
•A selectively permeable phospholipid bilayer that forms a barrier between the cell and its environment
Cytoplasm/cytosol
•Liquid substance that all chemical reactions of life take place in
•Has dissolved ions, macromolecules
Genetic Material- Chromosomes
•DNA is found as either organized chromosomes (eukaryotes) or single, loosely packed chromosome (prokaryotes)
Ribosomes• Two-piece protein-
based organelle that makes proteins in both major types of cell
• Varies structurally in prokaryotes (70S)and eukaryotes (80S).
Generalized Animal Cell
Generalized Plant Cell
Differences between cells
Plants Lack:1. Lysosomes
2. Centrioles
3. Flagella or Cilia
Animals Lack:1. Chloroplasts
2. Vacuoles
3. Cell Walls
4. Plasmodesmata
Eukaryotic Cell Organelles: Nucleus
• Contains cell’s genetic material in form of chromosomes
• Controls most of cell activities
• Site of transcription (1st step in protein synthesis)
• Has a double-membrane
Eukaryotic Cell Organelles: Nucleolus
•Smaller, dark body inside nucleus
•Responsible for ribosome synthesis
Eukaryotic Cell Organelles: ER
• ER =Endoplasmic reticulum
• Part of endomembrane system
• Smooth ER: no ribosomes, synthesizes lipids, detoxifies substances
• Rough ER: studded with ribosomes, transports proteins inside cell
Rough ER makes membrane and proteins
• The rough ER manufactures membranes• Ribosomes on its surface produce proteins
1 2
3
4Transport vesiclebuds off
Ribosome
Sugarchain
Glycoprotein
Secretory(glyco-) proteininside transportvesicle
ROUGH ER
Polypeptide
Eukaryotic Cell Organelles: Golgi Apparatus (not body)
• Part of endomembrane system
• The Golgi apparatus consists of stacks of membranous sacs These receive and modify ER
products, then send them on to other organelles or to the cell membrane
• Packages and exports cell chemicals such as proteins, carbohydrates and lipids
Eukaryotic Cell Organelles: Mitochondria
• Converts glucose into ATP during cell respiration
• Is thought to have been primitive prokaryote because: Has own genome (mtDNA) Directs own division
• Highly folded inner membrane• Found in cells that are motile
and contractible• Has a double membrane, with
inner membrane called the cristae.
MITOCHONDRIONOuter membrane
Inner membrane
Cristae
Matrix
Eukaryotic Cell Organelles: Chloroplast
• Found in plant cells and some protists• Contains chlorophyll• Responsible for converting carbon dioxide and
water into glucose during photosynthesis
Eukaryotic Cell Organelles: The Cytoskeleton
-Fibrous proteins (actin & tubulin)-Roles: Support, cell motility, biochemical
regulation, organelle movement-Microtubules:
•thickest (25 nm) •tubulin protein (hollow rods) •maintains shape, support, transport,
chromosome separation-Microfilaments: •thinnest ( 7 nm) •actin protein filaments; •motility, cell division, shape-Intermediate filaments: • middle diameter (8-12 nm)
•keratin; •shape, nucleus anchorage
MICROFILAMENT
Figure 4.17B
INTERMEDIATEFILAMENT
MICROTUBULE
Actin subunit Fibrous subunitsTubulinsubunit
7 nm 10 nm25 nm
The Cytoskeleton
Basic jobs of each
Microtubules Microfilaments Intermediate-give the cell rigidity -made of actin -reinforce the cell
-provide anchors for -enable cells to change -anchor certain organelles
organelles shape and move
-act as tracks for
organelle
movement
Eukaryotic Cell Organelles: Lysosome
• Vesicle that comes off of Golgi body containing hydrolytic digestive enzymes
• Responsible for digestion of old, worn out cell parts and cells
• Also digests nutrients **Found extensively in
Macrophages (WBC’s)
Eukaryotic Cell Organelles: Centriole
• Found only in animal cells
• Composed of microtubules in triplet arrangement
•Organizes microtubules that attach to chromosomes during cell division
Eukaryotic Cell Organelles: Vacuole
• Small ones in animal cells
• Large ones found in plant cells, stores water to maintain turgor pressure
• Can accumulate wastes, pigments in plant cells
Eukaryotic Cell Organelles: Peroxisomes
• Single membrane• Oxidative organelle ***strips e-’s (H’s) from
substances• Produce hydrogen peroxide
(H2O2) in cells• Metabolism of fatty acids;
detoxification of alcohol (liver)
• Hydrogen peroxide then converted to water
Eukaryotic Cell Organelles: Cell Wall
• Found only in plants
•Made of cellulose
• Non-living
• Has small pores called plasmodesmata, which allows materials in and out.
Eukaryotic Cell Organelles: Cilia/Flagella
•Cilia: short hairlike projections used in cellular movement
•Flagella: whiplike projection used in cellular movement Structure in
prokaryotes is slightly different
ECM: Extracellular Matrix**
•Extracellular matrix (ECM) composed of (located on outside of cell):
-Proteins & Carbodydrate
-Specifically:-glycoproteins
-glycolipids
-integrins
-fibronectins
-collagen (50% of all protein in the body)
Extracellular Matrix (ECM) - Pg. 118-120
Animal cells secrete or produce:
Glycoproteins: •proteins covalently bonded to carbohydrate
Collagen
(50% of protein in human body
•embedded in proteoglycan
(another glycoprotein-95% carbohydrate)
Fibronectins
bind to receptor proteins in plasma membrane called integrins
(cell communication?)
Functions: support, adhesion, movement**
ECM’s in Plants**
Cell Walls are an ECM.
-maintain shape
-prevents excessive water uptake, and
-holds the plant up against the force of gravity.
Samples of Various Types of Cells
•Protists may have contractile vacuoles
Figure 4.13B
Nucleus
Contractilevacuoles
– These pump out excess water
•Cell, stained for mitochondria, actin, and nucleus
Figure 4.1x
•Prokaryotic cells, Bacillus polymyxa
Figure 4.4x1
•Prokaryotic cell, E. coli
Figure 4.4x2
•Pili on a prokaryotic cell
Figure 4.4x3
•Prokaryotic flagella
Figure 4.4x4
•Prokaryotic and eukaryotic cells compared
Figure 4.4x5
• Paramecium, an animal cell
Figure 4.5Ax
•Plant cells
Figure 4.5Bx1
•Chloroplasts in plant cells
Figure 4.5Bx2
•Nuclei (yellow) and actin (red)
Figure 4.6x