Post on 08-Jul-2020
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Cell Membrane and Membrane Transport
Cell Membrane & Membrane transport
Cells· cells are the basic unit of life· 75 trillion in an adult human· vary greatly in size, shape, contents, and function
· 3 basic partscell membrane - encloses the cellsnucleus - houses genetic materials and controls
cellular activitiescytoplasm - fills out cell and houses organelles
A Composite Cell The Cell Membrane· a.k.a. plasma membrane· functions
a. maintains cell integrity (distinct inside and distinct outside)
b. controls passage of materials into and out of cell (selectively permeable - only certain substances can enter or leave)
· structurea. phospholipid bilayerb. cholesterol - helps stabilize membranec. proteins - channels, transporters, receptor for
hormones d. carbohydrates - cell markers
A. phospholipidA1 - hydrophilic headA2 - Hydrophobic tails
C, F, G. ProteinsD. CarbohydratesE. Cholesterol
Membrane Transport· interstitial fluid - extracellular fluid rich in nutrients· to maintain homeostasis cells must extract the exact amount of substances it needs at specific times· 2 ways
passive - does not require cellular energyactive - ATP needed to move substances across
membrane
Cell Membrane and Membrane Transport
Diffusion· passive process· characteristics
a. diffusion - molecules or ions move down their conc. gradient (high conc. to low conc.)
b. 3 requirements1. molecule/ion must be lipid soluble2. small enough to pass through membrane channels
(simple diffusion)3. or, assisted by a carrier molecule (facilitated
diffusion)· source of energy - kinetic energy of molecules· example - exchange of CO2 and O2 in the lungs· drawing -
· passive process· characteristics
facilitated diffusion - carrier proteins move molecules through a membrane from high to low conc.
limitations - # of carrier proteins in cell membranes
· energy - kinetic energy of molecules· example - movement of glucose through cell membrane· drawing -
Facilitated Diffusion
Osmosis· passive process· characteristics
osmosis - H2O moves from high to low conc. through a selectively permeable mem.· energy - kinetic energy of molecules· examples -
a. isotonic - conc. of H2O equal inside and out
b. hypertonic - conc. of H2O high inside cell
c. hypotonic - conc. of H2O high outside cell· drawing -
· active transport (requires ATP)· characteristics
carrier molecules move molecules or ions from regions of low conc. to regions of higher conc. (move up concentration gradient)· energy - cellular energy (ATP)· example - movement of ions, sugars, and amino acids through mem.· drawing -
Active Transport
endocytosis· active process (requires ATP)· characteristics
bringing materials into the cell· energy - cellular energy (ATP)· examples
pinocytosis (cell drinking) - mem. engulfs droplets of liquid from surroundings
phagocytosis (cell eating) - mem. engulfs solid particles from surroundings· drawing -
exocytosis· active process (requires ATP)· characteristics
vesicles fuse with mem. to expel substances from the cell· energy - cellular energy (ATP)· example - release of neurotransmitter from neurons· drawing -