Overview of Cells Prokaryotic All bacteria Most have cell wall No membrane-bound organelles...
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Transcript of Overview of Cells Prokaryotic All bacteria Most have cell wall No membrane-bound organelles...
Overview of Cells Prokaryotic
All bacteria Most have cell wall No membrane-bound
organelles Biochemical reactions take
place in cytoplasm or cell membrane
Typically very small
Eukaryotic Protist, fungi, plant and
animal cells Some have cell walls Possess membrane-bound
organelles Biochemical reactions
take place in specialized compartments
Much larger than bacteria
Prokaryotic Cell
Fimbriae
Nucleoid
Ribosomes
Plasma membrane
Cell wall
Capsule
Flagella
Bacterialchromosome
(a) A typical rod-shaped bacterium
(b) A thin section through the bacterium Bacillus coagulans (TEM)
0.5 µm
Animal Cells
Surrounded by plasma membrane Allows certain molecules in or out of the cell Does not have a cell wall
ENDOPLASMIC RETICULUM (ER)
Smooth ERRough ERFlagellum
Centrosome
CYTOSKELETON:
Microfilaments
Intermediatefilaments
Microtubules
Microvilli
Peroxisome
MitochondrionLysosome
Golgiapparatus
Ribosomes
Plasma membrane
Nuclearenvelope
Nucleolus
Chromatin
NUCLEUS
Plant Cells
Have plasma membrane and cell wall Cell wall gives support Has chloroplasts (contain chlorophyll) and large vacuole
Fig. 6-9b
NUCLEUS
Nuclear envelopeNucleolus
Chromatin
Rough endoplasmic reticulum
Smooth endoplasmic reticulum
Ribosomes
Central vacuole
Microfilaments
Intermediate filaments
Microtubules
CYTO-SKELETON
Chloroplast
PlasmodesmataWall of adjacent cell
Cell wall
Plasma membrane
Peroxisome
Mitochondrion
Golgiapparatus
Why Small Cells?
Cells obtain nutrients (gases, water other molecules) from the environment through the cell membrane
High surface area:volume ratios maximizes the amount of cell/environment interaction Large cells would starve
Cell MembraneClip
Lipid bilayer Integral proteins “float” in fluid
Hydrophobic region of proteins reside in fatty acid layer of membrane
Hydrophilic regions are on cytoplasmic and extracellular surfaces
Membrane fluidity may be altered by adjusting fatty acid chains
Fig. 7-3
Phospholipidbilayer
Hydrophobic regionsof protein
Hydrophilicregions of protein
Membranes are complex
Membranes are embedded with:Integral proteinsPeripheral proteinsGlycoproteinsProteoglycansCarbohydrates
Membranes are connected to cytoskeleton on the Cytoplasmic surface
Fig. 7-7
Fibers ofextracellularmatrix (ECM)
Glyco-protein
Microfilamentsof cytoskeleton
Cholesterol
Peripheralproteins
Integralprotein
CYTOPLASMIC SIDEOF MEMBRANE
GlycolipidEXTRACELLULARSIDE OFMEMBRANE
Carbohydrate
Roles of Membranes Gatekeeper of cell
Determines what goes in or out of cell
Compartmentalization Every membrane-bound organelle is isolated
Transport Actively move molecules into cell
Signal transduction Environmental conditions trigger genetic and
biochemical changes in cell via receptors
Cell-cell communication and interaction
Diffusion Starts with a gradient System will eventually reach equilibrium (even
distribution) Happens passively without selective barriers Many small molecules diffuse through cell
membrane
Fig. 7-11Molecules of dye Membrane (cross section)
WATER
Net diffusion Net diffusion Equilibrium
(a) Diffusion of one solute
Net diffusion
Net diffusion
Net diffusion
Net diffusion
Equilibrium
Equilibrium
(b) Diffusion of two solutes
Osmosis
Requires a gradient and a selectively permeable membrane Solute is unable to pass through membrane to reach equilibrium Water will move to area of greater solvent concentration until
equilibrium is reached
Lowerconcentrationof solute (sugar)
Fig. 7-12
H2O
Higher concentrationof sugar
Selectivelypermeablemembrane
Same concentrationof sugar
Osmosis
Facilitated diffusion
An integral protein helps molecules across the membrane
Often act as a revolving door (carrier) or tunnel (channel)
Fig. 7-15
EXTRACELLULAR FLUID
Channel protein
(a) A channel protein
Solute CYTOPLASM
Solute Carrier protein
(b) A carrier protein
Active Transport
Cell expends energy to move molecule or atom inside Often forms gradients to accomplish this
Entry into Cell Summarized
Diffusion and Facilitated diffusion are passive transport because no energy is required
Facilitated diffusion and active transport can be very selective processes
Membrane Pumps
Can be used to remove unwanted molecule from cytoplasm (like sump pump)
Can also be used to form a gradient across the membrane which can drive other transports (protomotor force)
Fig. 7-17
Passive transport
Diffusion Facilitated diffusion
Active transport
ATP