Membrane Transport Flashcards
Movement of stuff down a gradient
simple diffusion
Osmosis
Simple diffusion of solvents (in our case its water)
What molecules can diffuse freely across the membrane?
GASES- O2 and CO2 can diffuse freely and it is essential for respiration
True or False: Water, ethanol, and urea cannot diffuse freely across a semipermeable membrane
False: they can diffuse freely but not as freely as gases
Why don’t bacteria grow in jams and jellies
the sugar present makes a hypertonic environment that kills them. Same goes for pickles.
How do you calculate osmotic pressure?
Van’t Hoff’s Law: pi=iMRT, similar to ideal gas law
M=concentration of solutes (TOTAL conc)
R= Ideal gas constant
T=temp in kelvin
i= vanthoff constant, 1 for glucose, 2 for NaCl
If you have 1 mole of NaCl, how many osmoles would you have?
2 osmoles per liter, 1 mol Na 1 mol Cl
What will be the net direction of water movement when there is 1M NaCl on the right side of a membrane and 2M glucose on the left side of the membrane?
There will be no net movement. For osmosis, it is the total concentration of solute molecules that matters, even if they’re chemically different. A 1M solution of NaCl will create 2M total ions - 1M of Na+ and 1M of Cl-. 2M of ions on one side of the membrane and 2M of glucose on the other side of the membrane results in no net movement of water across the membrane.
How would you expect the osmotic pressure of a 1M solution of dissolved oxygen gas to compare to a 1M solution of dissolved potassium chloride?
A 1M solution of potassium chloride is equal to a 2M solution of dissolved solutes because potassium chloride fully dissociates in water to form K+ and Cl-. Oxygen, although diatomic, does not dissociate in water so 1M of dissolved oxygen gas is equal to 1M of dissolved solutes. We would expect the solution of potassium chloride to generate more osmotic pressure as demonstrated by van‘t Hoff’s law π = iMRT, where i refers to the van‘t Hoff constant, which is the number of particles that result in solution per molecule of a substance.
Simple diffusion, facilitated diffusion, osmosis are all examples of
PASSIVE transport
Channels specific for passive water transport
Aquaporins
True or False: passive membrane transporters tend to be general in the solutes/ions/molecules they permit
False- they can be very specific even with ions that have the same charge
True or False: Solutes can move down a concentration gradient but against the osmotic gradient
TRUE- your membrane may still transport K across the cell if it is down the concentration gradient despite having high osmolar pressure
How does active differ from passive transport?
Active requires the use of energy to move something up its gradient/ against the gradient
Primary Active Transport
Transport that directly requires energy. Sometimes it uses transmembrane proteins that are powered by ATP hydrolysis or sometimes it uses redox reactions like with the ETC
True or False: the sodium potassium pump helps establish the concnetration gradients of K and Na with higher concentrations of K inside the cell
True
How many potassiums are transported in and how many sodiums are transported out in the sodium potassium pump?
2 K in, 3 Na out
Secondary Active Transport
Active transport coupled to passive transport
Antiporter and Symporter
In secondary active transport both transporters move one ion or substance against its gradient and other down its gradient. Anti just mean sin opposite directions and sym means in same direction
True or False: active transport always requires the direct consumption of ATP
Two types of active transport exist: primary and secondary active transport. Primary active transport involves transmembrane proteins that catalyze ATP hydrolysis to release energy, which is coupled with the movement of solutes across the membrane. The basic idea of secondary active transport is that it’s a combination of active and passive transport, where active transport generates a concentration gradient that powers the passive transport of something else. More specifically, the spontaneous transport of one substance (usually an ion) down its electrochemical or concentration gradient is coupled to the non-spontaneous transport of another substance against its gradient. In other words, an energetically favorable transport process is used to power what would otherwise be a non-energetically favorable one. In this way secondary active transport is not directly powered by ATP but rather indirectly powered by ATP.
True or False: the Na/K pump creates a negative charge within the cell
true
Glucose being transported into the cell with sodium is an example of…
Symporters use secondary active transport to move two solutes in the same direction. In this example, sodium is allowed to move down its concentration gradient (a gradient that was established by the sodium-potassium pump through primary active transport) and in this way provides the energy the cell needs to bring a large, polar molecule like glucose inside.
True or False: Pinocytosis takes place when a cell engulfs small particles into the cell
False, it takes in LIQUID substances
True or False: Endocytosis takes in large particles and is not specific in what it takes in
False: Endocytosis can be used for general uptake of molecules as well as uptake of specific molecules, like in receptor-mediated endocytosis. This basically means that a cell is targeting specific molecules of some sort for ingestion.
Endosome
While endosomes are responsible for sorting ingested material, they do not degrade anything. The main job of late endosomes is to deliver material to lysosomes, which are the metaphorical recycling facility of the cell. These highly-acidic organelles contain specialized enzymes that break molecules of biological waste down into small components that can be recycled and reused.
Secretion of insulin from pancreatic beta cells is an example of…
Exocytosis
True or False: endo and pino cytosis dont require energy
False. Both pinocytosis and phagocytosis are forms of endocytosis. Both endocytosis and exocytosis require energy.
True or False: LDL is taken in by receptor mediated endocytosis
True
True or False: Endosome digest
False Early endosomes are responsible for sorting endocytosed vesicles and identifying what to do with the contents. They are not responsible for the actual degradation themselves. Late endosomes are responsible for the identification and transport of substances that have been ingested via endocytosis and need to be degraded by lysosomes. Late endosomes are not responsible for the actual degradation themselves.
