Honors Biology Chapter 7Section 3 Cell Boundaries

 surround all cells  is a thin, flexible barrier that acts like the cell’s “gate keeper”  made of lipid-bilayer  provides protection & support

 Fluid Mosaic Model  phospholipids

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

1. Phospholipids (~70% of membrane) 2. Cholesterol:  changes fluidity of membrane 3. Glycolipids  sugar molecule on lipid

 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

 found in:  plant cells  fungi cells  algae  bacteria  secreted by cell membrane  allow O 2, CO 2, glucose, & H 2 O to pass through

 all cells bathed in liquid  solutes dissolve in solvent (water)  concentration:  mass of the solute /vol of solution

 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

1. simple diffusion 2. osmosis 3. facilitated diffusion

 all particles have KE  due 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

 a form of passive transport  cell not spending nrg to make it happen  movement of particles continues even after equilibrium reached

 when concentration of solutes equal thru out a system  since solute particles still moving it is also referred to as dynamic equilibrium

 hill.com/sites/ /student_view0/cha pter2/animation__how_diffusion_works.html hill.com/sites/ /student_view0/cha pter2/animation__how_diffusion_works.html

 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

 Predict what will happen in the container on other side

 water will move down its concentration gradient until equilibrium is reached  when concentrations of solutes same on both sides of membranes : equilibrium reached

 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

 “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

 called plasmolysis

 “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

 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

 y/Biology1111/animations/passive3.swf y/Biology1111/animations/passive3.swf

 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)

1. Pumps 2. Endocytosis 3. Exocytosis

 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

 mplates/student_resources/shared_resources /animations/ion_pump/ionpump.html mplates/student_resources/shared_resources /animations/ion_pump/ionpump.html

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

 cell “eating”  done by unicellular organisms and phagocytes in multicellular organisms  macrophages

 cell “drinking”  cells take up liquid from surroundings

 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

 endocytosis is removing some membrane from cell membrane  exocytosis is adding some membrane to cell membrane  usually evens out