Ch7 Membrane Structure and function Flashcards
Plasma membrane is
selectively permeable, allowing some substances to cross more easily than others.
Passive transport
diffusion of a substance across a membrane with no energy investment
Osmosis
- The diffusion of water across a selectively permeable membrane
Water diffuses across the membrane from
- lower solute concentration to higher solute concentration
- higher water concentration to lower water concentration
Tonicity
the ability of a surrounding solution to cause a cell to gain or lose water.
Isotonic
no net movement of water across the plasma membrane
- o Water diffuses across the membrane, but at the same rate in both directions
hypertonic
the cell loses water to its environment, shrivels, and probably dies
- an increase in the salinity (saltiness) of a lake can kill aquatic animals
Hypotonic
water enters the cell faster than it leaves, and the cell swells and lyses (bursts) like an overfilled water balloon
Cell survival depends on the balance between
water uptake and loss
Organisms without rigid cell walls have what problems?
osmotic problems in either a hypertonic or a hypotonic environment.
Osmoregulation
the control of water balance
- an adaptation fro animals and other organisms without rigid cell walls living in hypertonic or hypotonic environments
Facilitated diffusion
The passive movement of molecules down their concentration gradient with the help of transport proteins
What are the 3 types of transport proteins
Channel proteins, aquaporins, carrier proteins
Channel proteins
create a hydrophilic channel that some polar molecules and ions can use as a tunnel through the membrane
Aquaporins
facilitate the passage of water molecules in certain cells.
Carrier Proteins
hold on to their passengers and change shape in a way that shuttles them across the membrane.
Diffusion
the movement of particles of any substance so that they spread out into the available space
Active Transport
the movement of a substance across a cell membrane against its concentration or electrochemical gradient, mediated by specific transport proteins and require energy (ATP)
Exocytosis
cell secretes molecules by the fusion of vesicles
- to export products
Endocytosis
cell takes in molecules and particulat matter by forming new vesicles from the plasma membrane
