sign in sign up
<<
Home , Facilitated diffusion

7.3: TRANSPORT (across the cell !) Vocabulary • • • • • • Facilitated Diffusion • Protein Pumps • Osmotic Pressure • Isotonic • Hypertonic • Hypotonic Background Info… • Every living cell contains a liquid interior () and is surrounded by a liquid .

• The cell (plasma) membrane separates what is inside the cell from what is outside of the cell

• What is the MAJOR function of ? – regulate the movement of from one side of the membrane to the other. • In other words—control what gets in and what gets out!

Selectively permeable : • property of biological which allows some substances to pass more easily than others Transport proteins : • membrane proteins that transport SPECIFIC molecules or ions across biological membranes

Binding

Recovery Transport

Dissociation S S concentrated(“UPHILL”) energy is concentrated. LESS it concentratedwhereto isit MORE celldoes not have spendto substancemoves from where it MORE isconcentrated whereto substancefrom where isLES it cell “spends” energy moveto a Movement across membrane thecell be: can 1) PASSIVE   ACTIVE 2)  : DIFFUSION

• movement of a substance from where it is conc. to where it is less conc. (“ down a concentration gradient ”)

Passive Transport : OSMOSIS

• diffusion of WATER across a selectively permeable membrane; water moves DOWN its concentration gradient OUTSIDE INSIDE THE CELL THE CELL

– the direction of water movement water can be described/predicted based on if the cell’s environment is:

• ISOTONIC : equal solute concentration compared to inside a cell • HYPERTONIC : greater solute concentration than inside a cell

• HYPOTONIC : lower solute concentration compared to inside a cell WATER MOVES FROM HYPO TO HYPERTONIC!!!

In animal cells: • in a HYPERTONIC environment, water exits the cell; cells shrivel and usually die

• in a HYPOTONIC environment, water moves into cell, causing it to swell and possibly burst

In cells with cell walls (i.e. plant cells): • in a HYPERTONIC environment, water exits the cell; cells shrivel and usually die

• in a HYPOTONIC environment, water moves into cell, causing it to swell; cells become more TURGID .

Passive Transport : FACILITATED DIFFUSION

• diffusion of solutes across a membrane, with the help of transport proteins (passive transport because it is movement down a concentration gradient; cell does not need to spend any energy) ACTIVE TRANSPORT : energy-requiring process; molecules are moved across the cell membrane AGAINST their concentration gradient (“uphill”)

ACTIVE TRANSPORT : ENDOCYTOSIS & EXOCYTOSIS

• transport of large molecules (e.g. proteins and polysaccharides ) into or out of the cell ENDOCYTOSIS EXOCYTOSIS

*importing large molecules by forming vesicles out of the cell membrane **vesicle forms in a small region of cell membrane ***used by cells to bring in larger, extracellular substances (e.g. proteins )

ENDOCYTOSIS EXOCYTOSIS

*exporting large molecules by vesicles fusing w / the cell membrane **vesicle buds from ER or Golgi and migrates to cell membrane ***used by cells to export products (e.g. cells in pancreas secreting insulin)

2 types of Endocytosis:

1) : solid particles (“cell eating”)

2) : fluid droplets (“cell drinking”) Phagocytosis Pinocytosis What are the 3 types of passive transport across a membrane? a)a)Diffusion, osmosis, and exocytosis b)b) Exocytosis , endocytosis , and phagocytosis c)c)Diffusion, facilitated diffusion, and osmosis d)d) Diffusion, osmosis, and endocytosis