VCE Biology Question Thread

[MM1]

I was also wondering, does bipolar refer to chemical substances that possess both polar and non-polar properties such as alcohol?

No and alcohol is polar.

[MM1]

How do substances like detergent disrupt the bilayer?

[nerdmmb]

How do substances like detergent disrupt the bilayer?

Please quote me if I'm wrong but the phospholipid bilayer is primarily composed of phospholipids however it has large amounts of protein embedded in it. If you've washed dishes before, you may have noticed that once you add the detergent, the oils suddenly begin to evacuate as far as possible. Similarly, the polarity of detergents puts huge amounts of pressure onto the bilayer causing it to disintegrate - I'm guessing this happens because the phospholipids try to get away from the detergent and in the process, separate from one another. (especially since the bilayer has LOTS of protein channels/pumps which makes the job easier) it's also important to note that the phospholipids aren't actually stuck to together and are instead flexible.

[nerdmmb]

How is a breathalyser able to give an accurate indication of blood alcohol concentration?

Also, since blood cells don't have a nucleus, does this mean that they don't produce proteins?

And, can blood cells absorb the molecules that any other cell in the body can absorb such as alcohol?

[howlingwisdom]

Also, since blood cells don't have a nucleus, does this mean that they don't produce proteins?

Blood cells do actually have a nucleus at some point in lifetime - so I assume that they do produce proteins then, but because of the blood cells' function (to predominately carry oxygen ) they get rid of their nucleus as they become mature, in order to increase surface area which allows them to hold more haemolglobin (therefore carry more oxygen), and improve flexibility when passing through thin diameters such as capillaries.

[vox nihili]

Please quote me if I'm wrong but the phospholipid bilayer is primarily composed of phospholipids however it has large amounts of protein embedded in it. If you've washed dishes before, you may have noticed that once you add the detergent, the oils suddenly begin to evacuate as far as possible. Similarly, the polarity of detergents puts huge amounts of pressure onto the bilayer causing it to disintegrate - I'm guessing this happens because the phospholipids try to get away from the detergent and in the process, separate from one another. (especially since the bilayer has LOTS of protein channels/pumps which makes the job easier) it's also important to note that the phospholipids aren't actually stuck to together and are instead flexible.

That's pretttttty much it, but not quite.

Detergent disrupts the phospholipid bilayer because it's made of lipids. So it's kind of like mixing coke with water, you'd expect them to just mix around. So it actually has the effect of diluting the bilayer. Because it doesn't have the same structural properties as bilayers, this means that wherever the detergent has mixed in (essentially) the bilayer won't be a layer anymore, instead, just free, happy phospholipids.

[Tyleralp1]

If a fresh water frog is placed in salt water:

Is it right to say that sodium ions move via facilitated diffusion into the cell, causing the concentration of ions to increase in the cell. Then, in an attempt to combat this, the frog will actively pump out the ions.

OR

Due to the new hypertonic environment, the frog will loose water via osmoisis. As it does, the concentration of ions within it increases, causing a need to expel the ions, which is done via active transport?

If neither of these are correct, what would be correct in terms of what occurs via osmosis and with the sodium ions. THANKS

[nhmn0301]

If a fresh water frog is placed in salt water:

Is it right to say that sodium ions move via facilitated diffusion into the cell, causing the concentration of ions to increase in the cell. Then, in an attempt to combat this, the frog will actively pump out the ions.

OR

Due to the new hypertonic environment, the frog will loose water via osmoisis. As it does, the concentration of ions within it increases, causing a need to expel the ions, which is done via active transport?

If neither of these are correct, what would be correct in terms of what occurs via osmosis and with the sodium ions. THANKS

If the frog is placed in salt water, the environment outside has a lower water concentration than the evironment inside the frog's cells. Hence, due to osmosis, the water will move from a high concentration of water, the frog's cells, to a region of low water concentration, salt water, to create an equilibrium effect. However, this would cause too much water leaving the cell and the frog will shrink/dehydrate and die.
Hope this helps.

[nerdmmb]

If a fresh water frog is placed in salt water:

Is it right to say that sodium ions move via facilitated diffusion into the cell, causing the concentration of ions to increase in the cell. Then, in an attempt to combat this, the frog will actively pump out the ions.

OR

Due to the new hypertonic environment, the frog will loose water via osmoisis. As it does, the concentration of ions within it increases, causing a need to expel the ions, which is done via active transport?

If neither of these are correct, what would be correct in terms of what occurs via osmosis and with the sodium ions. THANKS

If I'm not wrong, there will be a net movement of water molecules out of the frog since it is hypertonic to the surrounding medium. Cell's don't lose ions in a hypertonic solution, instead, they shrivel because water diffuses out of the cell via osmosis to enable the two solutions to reach equilibrium. If this is not regulated, the frog may die.

[alchemy]

If a fresh water frog is placed in salt water:

Is it right to say that sodium ions move via facilitated diffusion into the cell, causing the concentration of ions to increase in the cell. Then, in an attempt to combat this, the frog will actively pump out the ions.

OR

Due to the new hypertonic environment, the frog will loose water via osmoisis. As it does, the concentration of ions within it increases, causing a need to expel the ions, which is done via active transport?

If neither of these are correct, what would be correct in terms of what occurs via osmosis and with the sodium ions. THANKS

The net movement of fresh water will be going outside the cell. Some salt water does move inside, but this is minimal and I don't think active transport comes into play here; even if it did, the frog wouldn't survive for long. The frog would eventually dehydrate and die in these conditions. If it was a plant cell, however, it would develop a contractile vacuole in order to expel excess salt water.

[alchemy]

Also, I think you meant hypotonic

He means hypertonic, doesn't he?

Due to the new hypertonic environment, the frog will lose water via osmoisis...

[nerdmmb]

He means hypertonic, doesn't he?

woops!! I'm SO sorry! lol

[aqple]

He means hypertonic, doesn't he?

Hypertonic environment as in the intracellular environment contains more solvent than solute relative to the salt water, the frog loses water and dies

[Tyleralp1]

How do non-polar substances pass through the plasma membrane? I knot it's via diffusion, but does it occur as they are attracted to the phosphate head as they are non-polar, or are small enough to pass through the pores, and aren't repelled by the fatty acids as they too are non-polar?

Essentialy, how does non-polar substances get passed a negatively charged phosphate head?

[nerdmmb]

How do non-polar substances pass through the plasma membrane? I knot it's via diffusion, but does it occur as they are attracted to the phosphate head as they are non-polar, or are small enough to pass through the pores, and aren't repelled by the fatty acids as they too are non-polar?

Essentialy, how does non-polar substances get passed a negatively charged phosphate head?

You're right- there are pores in between the phospholipids so they can get through