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 Hydrophilic head phospholipid Hydrophilic head Hydrophobic tail outside inside

Microvilli- intestinal cells Membrane Junctions Tight junctionsDesmosomesGap junctions

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

mucus Goblet cell

Nerve Axon at Rest Na + /K + Pump

H + Pump in a Plant

Ion channels - Voltage gated - Chemically gated - Mechanically gated Porins -Larger -Less specific Aquaporins - water Channel Proteins

Channel Proteins: Ion Channels

Channel Proteins: Porins MAC Barrel shaped protein

Channel Proteins: Aquaporins H2OH2O

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)