Honors Biology Chapter 7 Section 3 Cell Boundaries

Honors Biology Chapter 7 Section 3 Cell Boundaries SC B- 2. 5: Explain how active, passive, and facilitated transport serve to maintain the homeostasis of the cell.

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 Membrane Fluid Mosaic Model �resembles an ever-moving sea of fluid lipids that has large proteins bobbing along throughout the lipids

Membrane Lipids Phospholipids (~70% of membrane) Cholesterol: 1. 2. changes fluidity of membrane Glycolipids 3. 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 membrane �allow O 2, CO 2, glucose, & H 2 O through to pass

Cell Wall

Cell Wall

Diffusion Thru Cell Boundaries �all cells bathed in liquid �solutes dissolve in solvent �concentration: (water) 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. 2. 3. simple diffusion osmosis facilitated diffusion

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

Diffusion �a form of passive transport cell not spending nrg to make it happen �movement 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_view 0/cha pter 2/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% Na. Cl

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 of. RBCs

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/biolog y/Biology 1111/animations/passive 3. 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. 2. 3. Pumps Endocytosis 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+/ATPase. Pump �http: //www. brookscole. com/chemistry_d/te mplates/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