Movements Through Cell Membrane Flashcards
passive transport
-Physical process that requires no cellular energy
4 examples of passive transport
- Simple diffusion
- facilitated diffusion
- osmosis
- filtration
Active transport
Physiological process that requires energy
3 examples of active transport
- endocytosis
- exocytosis
- transcytosis
Simple diffusion
Movement of substances from regions of higher concentration to regions of lower concentration (no energy required)
In what 3 substances does simple diffusion occur?
Oxygen, carbon dioxide, and lipid-soluble substances
What is another way to explain going from high concentration to low concentration?
Going down/along the concentration gradient
Facilitated Diffusion
Diffusion across a membrane with help of a channel or carrier molecule (no energy required)
Phenomenon
Event you observe; either good/bad
Saline
salt
Osmosis
Simple diffusion; movement of water through a selectively permeable membrane from regions of higher concentration to regions of lower concentration.
In what direction does water move during osmosis?
Toward a higher concentration of solutes; (high concentration of WATER to low concentration of WATER)
Osmotic Pressure
Ability of osmosis to generate enough pressure to move a volume of water
Osmotic pressure _____________ as the concentration of non permeable solutes increases
Osmotic pressure INCREASES
Isotonic
Same osmotic pressure
RBC: normal physiological saline (0.85% NaCl)
Hypertonic
Higher osmotic pressure
RBC: crenation (i.e., 1.5% NaCl)
Hypotonic
Lower osmotic pressure
RBC: hemolysis (i.e., 0.25% NaCl)
Filtration
Smaller molecules are forced through porous membranes.
Hydrostatic pressure is important in the body
Hydrostatic pressure
Pressure a fluid exerts on the wall of its container
Filtrate
Substances you collect after filter
Active transport
*Requires energy (ATP)
Carrier molecules transport substances across a membrane from regions of lower concentration to regions of higher concentration
(against concentration gradient)
What molecules are usually involved in active transport? (4)
Sugars, amino acids, sodium ions, potassium ions
Molecules the cell really needs
Endocytosis
Cell engulfs a substance by forming a vesicle around the substance
Receptor-mediated endocytosis
requires the substance to bind to a membrane-bound receptor
What are two factors that affect the rate of diffusion?
- Temperature (warmer=happen faster)
2. Size
Exocytosis
Reverse of endocytosis
Substances in a vesicle fuse with cell membrane; contents released outside of the cell
i.e., release of neurotransmitters from nerve cells
Transcytosis
Endocytosis followed by exocytosis; transports a substance rapidly through a cell
i.e., HIV crossing a cell layer
