Cellular Transport– Maintaining homeostasis

SB1. Students will analyze the nature of the relationships between structures and functions in living cells.

a. Explain the role of cell organelles for both prokaryotic and eukaryotic cells, including the cell membrane, in maintaining homeostasis and cell reproduction.

d. Explain the impact of water on life processes (i.e., osmosis, diffusion).

A concentration gradient occurs when there is a strong concentration difference between two areas or spaces.

Passive Transport

• Does not require energy

• Movement is down the concentration gradient (high low)

• Diffusion

• Osmosis

• Facilitated diffusion

Active Transport

• Does require energy

• Movement is up the concentration gradient (low high)

• Membrane pumps

• Endocytosis

• Exocytosis

Transport– movement through the cell membrane

http://www.sumanasinc.com/webcontent/animations/content/diffusion.html

Diffusion• The movement of molecules or particles from an

area of high concentration to an area of low concentration

• Works for water and nonpolar solutes

http://highered.mheducation.com/sites/0072495855/student_view0/chapter2/animation__how_diffusion_works.html

Osmosis

http://highered.mheducation.com/sites/0072495855/student_view0/chapter2/animation__how_osmosis_works.html

• The diffusion of water

Words to compare solutions:

• Hypertonic– the area of higher solute concentration

• Hypotonic– the area of lower solute concentration

• Isotonic– when the concentrations are the same

Solution: hypotonic solution: isotonic solution: hypertonic

Cell: hypertonic cell: isotonic cell: hypotonic

Water moves in water moves in & out water moves out

Cell swells & bursts cell stays the same cell shrivels up & dehydrates

Turgor Pressure

Pressure against the cell wall keeps structure for the plant.

Cell is hypertonic to environment.

Plants like hypotonic environments.

Plasmolysis

Cell contents shrink away from the cell wall.

Cell is hypotonic to environment.

Plants wilt in hypertonic environments.

Facilitated Diffusion

• Moves materials across the cell membrane down the concentration gradient with the assistance of a transport protein

• Works for polar molecules (typically large molecules or ions)

http://highered.mheducation.com/sites/0072495855/student_view0/chapter2/animation__how_facilitated_diffusion_works.html

• Move substances up the concentration gradient with the assistance of a transport protein AND the use of energy (ATP)

• Usually associated with the cell’s accumulation of necessary substances

Membrane Pumps

Membrane Pumps

http://highered.mheducation.com/sites/0072495855/student_view0/chapter2/animation__how_the_sodium_potassium_pump_works.html

The cell membrane engulfs particles of food or other materials and brings them into the cell.

Endocytosis

The cell membrane lets things exit the cell.

http://www.classzone.com/cz/books/bio_07/book_home.htm

Exocytosis