SC B- 2.5: Explain how active, passive, and facilitated transport serve to maintain the homeostasis of the cell.

Honors BiologyChapter 7Section 3Cell Boundaries

Cell Membrane

surround all cells is a thin, flexible barrier that

acts like the cell’s “gate keeper” made of lipid-bilayer

provides protection & support

Cell Membrane: Lipid-Bilayer

Fluid Mosaic Model phospholipids

Plasma MembraneFluid Mosaic Model

resembles an ever-moving sea of fluid lipids that has large proteins bobbing along throughout the lipids

Membrane Lipids

1. Phospholipids (~70% of membrane)

2. Cholesterol: changes fluidity of membrane

3. Glycolipids sugar molecule on lipid

Membrane Proteins

Integral Proteins go all the way thru the membrane channel proteins receptor proteins

Peripheral Proteins on inside or outside of membrane +/- attached to integral proteins

Cell Membrane

Cell Walls

found in: plant cells fungi cells algae bacteria

secreted by cell membraneallow O2, CO2, glucose, & H2O to

pass through

Cell Wall

Cell Wall

Diffusion Thru Cell Boundaries

all cells bathed in liquidsolutes dissolve in solvent

(water)concentration:

mass of the solute /vol of solution

Passive Transport

does not require cell to spend energy to move substances

substances moving from area where it is in higher concentration area where it is in lower concentration

Types of Passive Transport

1. simple diffusion2. osmosis3. facilitated diffusion

Diffusion

all particles have KEdue to the KE of particles they

will move about until they are evenly distributed in the space they occupy

what we see is particles moving from where they are in high concentration where they are in lower concentration

Diffusion

a form of passive transport cell not spending nrg to make it

happenmovement of particles continues

even after equilibrium reached

Equilibrium

when concentration of solutes equal thru out a system

since solute particles still moving it is also referred to as dynamic equilibrium

Diffusion

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_diffusion_works.html

Osmosis

is the diffusion of water across a semi-permeable membrane it‘s water moving from where

water is in high concentration water is in lower concentration

semi-permeable = selectively permeable

Osmosis

Predict what will happen in the container on other side

Osmosis

water will move down its concentration gradient until equilibrium is reached

when concentrations of solutes same on both sides of membranes : equilibrium reached

Osmosis

Isotonic Solutions

cells are in isotonic solutions when the concentration of solutes inside cell = concentration of solutes outside cell

for human cells isotonic soultions = 0.9% NaCl

RBCs in Isotonic Solutions

Hypertonic Solutions

“above strength”cells in ECF (extracellular fluid)

with a higher concentration of solutes than inside cell

water in higher concentration inside cell so water leaves cell by osmosis…..cell shrinks….called crenation

RBCs in Hypertonic Solution

Crenation in Cells with Cell Walls

called plasmolysis

Hypotonic Solutions

“below strength”water now in higher

concentration in ECF so water will move from outside cell inside cell…. cell swells and eventually pops….. called hemolysis if it is a RBC, other cells it is called: cytolysis

Hemolysis ofRBCs

Cells with Cell Walls in Hypotonic Solutions

In Review:

Facilitated Diffusion

some substances move in/out of cells by diffusion but require a transport protein to cross the cell membrane

substance still moving from side with higher concentration side with lower concentration

example: sugars move into cells by facilitated diffusion

Facilitated Diffusion

Facilitated Diffusion

http://programs.northlandcollege.edu/biology/Biology1111/animations/passive3.swf

Active Transport

moving substances in/out of cell that requires cells to spend energy (usually in form of ATP)

substances are moving against their concentration gradients (from where they are in low concentration high concentration)

Types of Active Transport

1. Pumps2. Endocytosis3. Exocytosis

Pumps

protein in cell membrane that “pumps” ion or molecule in/out of cell against its concentration gradient

most pumps use ATP as source of energy

most important pump is Na+/K+/ATPase pump

Na+/K+/ATPase Pump

Na+/K+/ATPasePump

http://www.brookscole.com/chemistry_d/templates/student_resources/shared_resources/animations/ion_pump/ionpump.html

Endocytosis

process of cell taking up material into cell by means of infolding pockets of cell membrane

Phagocytosis

cell “eating”done by unicellular organisms

and phagocytes in multicellular organisms macrophages

Phagocytosis

Pinocytosis

cell “drinking”cells take up liquid from

surroundings

Pinocytosis

Exocytosis

when cells need to expel larger amounts of materials than can be expelled thru transport protein

storage vacuole moves to cell membrane; its membrane fuses with cell membrane expelling contents into ECF

Exocytosis

Exocytosis

Endocytosis & Exocytosis

endocytosis is removing some membrane from cell membrane

exocytosis is adding some membrane to cell membrane

usually evens out