ch 4 tour of the cell. cells smallest unit that shows properties of life – metabolizes –...
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Cells
• Smallest unit that shows properties of life– Metabolizes– Reproduces
• Cell Theory– All organisms consist of one or more cells– The cell is the smallest unit of life– New cells arise from old cells– Cells pass hereditary material to offspring
Microscopic Worlds
• Microscopes led to the discovery of the cell– Discovered “animalcules”
and wee “beasties”• Antoni van Leeuwenhoek• Robert Hooke
Cell Size
• House DNA, protein molecules and internal structures
• Obtain nutrients and diffuse nutrients and O2
• Smaller cells have a greater surface area to volume ratio than do larger cells– Surface area is significant for diffusion and
osmosis
Surface area : Volume
• Volume= 30 um *30 um* 30 um=27000um • SA (large)= 6*(30um*30um)=5,400 um• SA (small)=(6*(10um*10um))*27=16,200 um
30 m 10 m
30 m 10 m
Surface areaof one large cube 5,400 m2
Total surface areaof 27 small cubes 16,200 m2
Domains of Life
• The 3 domains of life – Bacteria (prokaryotic cells)– Archaea (prokaryotic cells)– Eukarya (all other life forms)
Cells• Prokaryotic
– Bacteria & Archaea• Eukaryotic
– Protists, fungi, plants, animals
Prokaryotic cells are simpler & usually smaller than Eukaryotic cells
Prokaryotic cell
Nucleoidregion
Nucleus
Eukar yotic cell Organelles
Co
loriz
ed
TE
M 1
5,0
00
Prokaryote• Do not have membrane
bound nucleus• Have a cell wall outside
their plasma membrane• Circular DNA strands• No membrane bound
organelles
Prokar yoticflagella
Ribosomes
Capsule
Cell wall
Plasmamembrane
Nucleoid region (DNA)
Pili
Eukaryote
• Membrane bound nucleus
• Linear DNA• Membrane
bound organelles
NucleusSmooth endoplasmicreticulumRough
endoplasmicreticulum
Ribosomes
Golgiapparatus
Plasma membrane
Mitochondrion
Flagellum
Not in mostplant cells Lysosome
Centriole
Microtubule
CytoskeletonIntermediatefilament
Microfilament
Peroxisome
Eukaryotic Cells• A typical animal cell:
• Contains a variety of membranous organelles (underlined)
NucleusSmooth endoplasmicreticulum
Roughendoplasmicreticulum
Ribosomes
Golgiapparatus
Plasma membrane
Mitochondrion
Flagellum
Not in mostplant cells Lysosome
Centriole
Microtubule
CytoskeletonIntermediatefilament
Microfilament
Peroxisome
Figure 4.4A
Eukaryotic Cells
• A typical plant cell Smooth endoplasmicreticulum
Rough endoplasmicreticulum
CYTOSKELETON:
NUCLEUS
Ribosomes
Golgiapparatus
Plasma membrane
Mitochondrion
Peroxisome
Cell wall
Central vacuole Microtubule
Intermediatefilament
Microfilament
Cell wall ofadjacent cell
Chloroplast
Plasmodesmata
Categories of Organelles• Structural support, movement, communication
– Cytoskeleton, plasma membrane, cell wall (plants)• Manufacturing
– Nucleus, ribosomes, endoplasmic reticulum, Golgi apparatus
• Energy processing– Mitochondria (animal), chloroplasts (plants)
• Hydrolysis– Lysosomes (animals), vacuoles (plants),
peroxisomes
Plasma Membrane• Forms boundary around cell• Controls and regulates material transport
-Semi permeable• Phospholipid bilayer
Plants and Cell Walls
• Cell wall– Cellulose
• Connect by plasmodesmata– Channels between adj. cells
Plasma membrane
Cytoplasm
Plasmodesmata
Vacuole
Layers of one plant cell wall
Walls of two adjacent plant cells
Cytoskeleton
• Cell’s internal skeleton – Helps organize structure and activities– Consists of network of protein fibers
Actin subunit
Microfilament
7 nm
Fibrous subunits
10 nm
Intermediate filament Microtubule
25 nm
Tubulin subunit
Cytoskeleton• Microfilaments (actin filiments)
– Enable cells to change shape and move
• Intermediate filaments – Reinforce the cell and anchor certain organelles
• Microtubules – give the cell rigidity, provide anchors for organelles,
act as tracks for organelle movement
Actin subunit
Microfilament
7 nm
Fibrous subunits
10 nm
Intermediate filament Microtubule
25 nm
Tubulin subunit
Nucleus• Contains most of the
cells DNA• Eukaryotic
chromosomes made of chromatin
• Enclosed by nuclear enveloper
• Nucleolus– rRNA synthesized
NucleusChromatin
Nucleolus
Pore
Ribosomes
Roughendoplasmicreticulum
Two membranesof nuclearenvelope
Endomembrane System• Interconnected structurally and functionally
– Physically connectedOR– Connected via vesicles
Nucleus
Smooth ER Nuclear envelope Golgi apparatus
Lysosome
Vacuole
Plasmamembrane
Rough ERTransport vesiclefrom ER to Golgi
Transport vesicle fromGolgi to plasma membrane
Rough Endoplasmic Reticulum• Membrane continuous
with nuclear envelope– Makes more membrane – Transferred via vesicles
• Bound ribosomes– Produces proteins– Transported or secreted
Smooth ER
Rough ER
Nuclearenvelope
Rough ER
Ribosomes
Smooth ER
TE
M 4
5,00
0
Figure 4.7
Fig. 4-9b
Transport vesiclebuds off
Secretoryproteininside trans-port vesicle
Glycoprotein
Polypeptide
Ribosome
Sugarchain
Rough ER
1
2
3
4
Smooth ER
• Lacks bound ribosomes• Involved in metabolic
processes– Synthesis of lipids,
hormones, enzymes
• Stores calcium
Golgi Apparatus• Vesicles from ER go to Golgi• Receives and modifies products
Golgi apparatus
TE
M 1
30
,00
0
Transportvesicle fromthe Golgi“Shipping” side
of Golgi apparatus
Golgiapparatus
“Receiving” side ofGolgi apparatus
Transportvesiclefrom ER
New vesicleforming
Lysosomes• Digestive enzymes enclosed by membrane sac• Destroy ingested bacteria, recycle damaged
organelles • Break down food
DigestiveenzymesLysosome
Plasmamembrane
Food vacuoleDigestion
Lysosome
Vesicle containingdamaged mitochondrion
Digestion
Lysosomes
Figure 4.10AFigure 4.10A
GolgiapparatusPlasma
membrane
“Food”
Foodvacuole
Lysosomes
Lysosomeengulfingdamagedorganelle
Digestion
Engulfmentof particle
Transport vesicle(containing inactivehydrolytic enzymes)
Rough ER
Vacuoles
• Membranous sac• Central Vacuole
– hydrolytic function
• Contractile• Food
Chloroplast
Centralvacuole
Nucleus
Col
oriz
ed T
EM
8,7
00
Peroxisomes
• Metabolize fatty acids & inactivate toxins• Enzymes that digest peroxides• Come only from ER
Mitochondria• Cellular respiration
– Converts chemical energy to ATP
– Phospholipid bilayer membrane
– Has own DNA and ribosomes
Mitochondrion
Outermembrane
Intermembranespace
Matrix
Innermembrane
Cristae
TE
M 4
4,8
80
Chloroplasts• Convert solar energy to chemical energy (photosynthesis)• Stroma
– Contains DNA, ribosomes and enzymes• Thylakoids
– Interconnected sacs that form stacks called granum
Endosymbosis
• Hypothesis of endosymbosis– Mitochondria and chloroplasts were once small
prokaryotes living independently– At some point, began living within larger cells
Movement• Cilia
– Short appendage, numerous– Move via coordinated beating– Stirs fluid around stationary cells
• Flagella– Long appendage, whip-like– Move via bending
• Pseudopods– Irregular long lobes– Bulge outward and drag cell
Extracellular matrix• Holds cells to tissues• Protect and support PM
– Integrins
• Regulate behavior, transmit information, coordinate cells
Cell Junctions•Tight junctions can bind cells together into leakproof sheets•Anchoring junctions link animal cells into strong tissues•Gap junctions allow substances to flow from cell to cell
Anchoring junction
Tight junctions
Gap junctions
Extracellular matrix
Space between cells
Plasma membranes of adjacent cellsFigure 4.18B
Videos• Overview• http://www.youtube.com/watch?v=NiiLS_ovLwM&feature=related• http://www.youtube.com/user/greatpacificmedia#p/u/56/vCqQLoRaTNA• Basic cell structure
http://www.youtube.com/watch?v=mphqugYoiQY&feature=related• Cytoskeleton• http://www.youtube.com/user/greatpacificmedia#p/u/55/5rqbmLiSkpk• Cell membrane and wall• http://www.youtube.com/user/greatpacificmedia#p/u/52/-aSfoB8Cmic