I need help with my homework questions ! [chem/bio]

[carryon]

1. A cell is placed in saltwater solution of 0.2 mM NaCl. Neither Na+ nor Cl- can permeate the plasma membrane. What happens to the cell?

2. Assuming that = +60 mV, = -90 mV, and = -70 mV, find the direction of the electrochemical driving forces acting on Na+ and Cl- ions. In which direction will the ions move if they are transported passively? If they are transported actively?(Extra challenge: From the sign of , determine the direction of the concentration gradient of Cl- ions.) Please explain how you got the answer so I can do a similar one on my own

Explain the mechanism of glucose absorption by intestinal epithelial cells. Include a discussion of the significance of cellular polarity.

Ion channels can be regulated to open or close, changing the permeability of the membrane to a specific ion. Assume that a cell at a membrane potential of -70 mV has few open sodium channels. Knowing that the equilibrium potential for sodium is +60 mV, predict what would happen to the membrane potential if many sodium channels suddenly went from a closed state to an open state. Explain your answer.

Oubain is a drug that blocks the Na+/K+ pump. Describe and explain the effects you would expect oubain to have on (1) sodium concentration gradients across cell membranes, (2) potassium concentration gradients across cell membranes, and (3) movement of molecules by secondary active transport coupled with sodium.

Please answer what you know. I'm struggling with those questions even though I read all the chapter and took notes

 

[fiveworlds]

A cell is placed in saltwater solution of 0.2 mM NaCl. Neither Na+ nor Cl- can permeate the plasma membrane. What happens to the cell?

 

Passive transport

[imatfaal]

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Moderator Note

 

Homework Help Rules

 

A simple reminder to all: this is the "Homework Help" forum, not the "Homework Answers" forum. We will not do your work for you, only point you in the right direction. Posts that do give the answers may be removed.

 

So carryon would you explain where you have got to in solving this problem and what has stopped your progress - hopefully members can then help you to overcome your difficulties yourself.

 

 

1. Fiveworlds has already made a suggestion - although not a direct answer. But if you read up the wiki on passive transport you will be a lot closer to being able to answer this an others

2. question seems malformed

[fiveworlds]

Passive transport is a movement of biochemicals and other atomic or molecular substances across cell membranes.

 

Following a wiki error

Passive transport is a movement of biochemicals and other atomic or molecular substances across a semi-permeable membrane.

[Essay]

I'd suggest answering #3 and then #5 (about glucose and then the toxin Oubain), second; after you answer #1, but before answering #2 and #4.

 

What is the book title and author and date, that you're studying?

 

The book must talk about glucose and the sodium/potassium pump specifically, or is that wrong, and only in your notes? Is a particular sentence, about your information on glucose or the toxin, unclear or confusing?

 

Can you easily answer #1, and tell what would happen to the cell ...or at least what would first happen to the water inside the cell?

~

Edited September 6, 2014 by Essay

[imatfaal]

Following a wiki error

Passive transport is a movement of biochemicals and other atomic or molecular substances across a semi-permeable membrane.

 

Nope - passive transport can be either diffusion across a permeable membrane or osmosis across a semi-permeable (or various other methods) - is it just transport that requires no energy or work from "pumps" in the membrane.

[fiveworlds]

permeable membrane? Can you provide an example please.

Edited September 6, 2014 by fiveworlds

[imatfaal]

permeable membrane? Can you provide an example please.

permeable to the particular ion/molecule we are discussing.

[fiveworlds]

permeable to the particular ion/molecule we are discussing.

 

As in a permeable membrane example.

[imatfaal]

As in a permeable membrane example.

Oxygen can generally diffuse through a cell membrane. The cell membrane is permeable to oxygen

[fiveworlds]

Oxygen can generally diffuse through a cell membrane. The cell membrane is permeable to oxygen

 

Yes but a cell membrane is a selectively permeable(semi permeable membrane) not a permeable membrane.