7.3: CELL TRANSPORT (across the cell membrane!)

Vocabulary Osmosis Diffusion Facilitated Diffusion Osmotic Pressure Isotonic Hypertonic Hypotonic Active Transport Endocytosis Exocytosis Protein Pumps

Background Info… Every living cell contains a liquid interior (cytoplasm) 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 cell membrane? –regulate the movement of molecules 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 membranes which allows some substances to pass more easily than others

Transport proteins: membrane proteins that transport SPECIFIC molecules or ions across biological membranes

GLUCOSE Binding TransportRecovery Dissociation

Movement across the cell membrane can be: 1) PASSIVE  cell does not have to spend energy  substance moves from where it is MORE concentrated to where it is LESS concentrated. 2) ACTIVE  cell “spends” energy to move a substance from where it is LESS concentrated to where it is MORE concentrated (“UPHILL”)

Passive Transport: 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

INSIDE THE CELL OUTSIDE 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

ENDOCYTOSISEXOCYTOSIS *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)

ENDOCYTOSISEXOCYTOSIS *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) Phagocytosis: solid particles (“cell eating”) 2) Pinocytosis: fluid droplets (“cell drinking”)

Phagocytosis

Pinocytosis

What are the 3 types of passive transport across a membrane? a)Diffusion, osmosis, and exocytosis b)Exocytosis, endocytosis, and phagocytosis c)Diffusion, facilitated diffusion, and osmosis d)Diffusion, osmosis, and endocytosis