The cell is the smallest unit of life. All organisms are composed one or more cells. New cells arise from previously existing cells.
Basic Cell Structure Each cell has four common components: 1.Plasma membrane 2.Region containing DNA 3.Cytoplasm 4.Biochemical molecules & biochemical pathways
Fluid mosaic model: Working model of the membrane Protein molecules bobbing in phospholipid sea Proteins determine membrane’s specific functions
Phospholipids Most abundant lipid Polar/hydrophilic head(attracted to water) Pair of nonpolar/hydrophobic tails(repelled by water)
Hydrophilic head Hydrophobic tails
Polar heads, outside & inside Nonpolar tails in the interior cell membranes
Microvilli- intestinal cells Membrane Junctions Tight junctions (impermeable) - stomach Desmosomes (anchor) - skin & heart muscle Gap junctions(communication/electrical activity) - heart & smooth muscle
Selectively permeable- allows certain substances to pass through By 2 ways: active or passive transport Passive- downhill Active- uphill (needs energy)
Passive: downhill reaction Simple diffusion Osmosis Facilitated diffusion Filtration Active: uphill reaction, needs ATP Exocytosis Endocytosis - Pinocytosis - Phagosytosis
No Barrier: Substances “spread out” High concentration to low concentration e.g.: Red dye placed in glass of water
Substances diffuse High concentration to low concentration Pores in membrane must be large “Down the concentration gradient” Dynamic equilibrium, equal rates in both directions Biological membrane:
Carrier proteins: Bind specific molecule & change shape Pass molecule through middle of protein
Osmosis- diffusion of a water through a semi- permeable membrane Moves down concentration gradient e.g., Two sugar solutions of different concentrations separated by porous membrane which lets water through but not sugar What will happen?
More concentrated to less concentrated Until concentration same on both sides: isotonic
Concentration of solute less: solution is hypotonic. Concentration of solute greater: solution is hypertonic.
Animal cells No cell walls Isotonic environment: Influx of water equals the efflux of water No change in cell shape
Hypotonic solution: Water enters cell Bursts, or lyses Hypertonic solution: Water leaves cell Shriveled, or crenate
Glomerular filtration
Passive transport & facilitated diffusion do NOT require ATP
DOES require the input of ATP Transport proteins AGAINST concentration gradient outside cell inside cell
ATP ADP + P i + Energy
nuclei mucus
Membrane Permeability Cell membrane: selectively permeable 4 factors that determine permeability lipid solubility molecular size polarity charge
Lipid solubility Most important factor Hydrophobic molecules Passively diffuse Hydrocarbons, carbon dioxide, & oxygen
Molecular Size and Polarity Larger molecules, less permeable Lower kinetic energy Small pore sizes in the membrane Polar molecules hydrophilic, less permeable Very small, polar uncharged (water) molecules can diffuse - + Molecular Size Polarity
Charge Charged molecules hydrophilic, less permeable Surrounded by coat of water (hydration shell), increases the size
Rough and Smooth ER
Digest food Autophagy Autolysis
Rid body of toxic substances Contains enzymes that can oxidize various organic substances Liver cell
Centriole pair Assemble microtubules Assist in cell division 9 clusters of microtubule triplets
Figure 3.23c (c) Microtubules Hollow tubes of spherical protein subunits called tubulins 25 nm Tubulin subunits Microtubules appear as gold networks surrounding the cells’ pink nuclei in this photo.
Cillia & Flagella- 9x2 arrangement 0.1 micrometer
Cillia & Flagella- 9x2 arrangement
Flagellum
Flagellar Movement
Ciliated Epithelium ciliated surface nuclei mucus
Ciliary Movement
Ameboid Movement Ex. WBC
INQUIRY 1.Define isotonic, hypotonic, and hypertonic. 2.What % saline is a cell? 3.Distinguish between active and passive transport. 4.What is the function of: Mitochondria Nucleus Golgi apparatus Lysozome Ribosomes Smooth and rough ER Cellular Visions: The inner life of a cell (video)