answer

watching

views

24 Nov 2018

Which of the following scenarios, a molecule can cross the plasma membrane WITHOUT using a carrier protein?

a. A polar molecule moving against the gradient.

b. A polar molecule moving with the gradient.

c. A non-polar molecule moving against the gradient.

d. A non-polar molecule moving with the gradient.

e. All of these need a carrier protein.

Any kind of short explanation would be appreciated, thanks!

answer

watching

279

views

For unlimited access to Homework Help, a Homework+ subscription is required.

You have 0 free answers left.
Get unlimited access to 3.8 million step-by-step answers.

Get unlimited access

Already have an account? Log in

Bunny GreenfelderLv2

26 Nov 2018

Unlock all answers

Get 1 free homework help answer.

Already have an account? Log in

Related questions

Are the following correct?

1. Which type of lipids do not make up a membrane?

a. Triglycerides <--

b. Glycerophospholipids

c. Sphingolipids

d. Chloesterol

2. A lipid bilayer becomes a membrane with the addition of _____.

a. Polar heads

b. Hydrophobic tails

c. Cholesterol

d. Proteins <--

3. A transporter protein has to have how many polar regions (minimum) on a hydropathy plot?

a. 3

b. 1-2 <--

c. 4

d. 0

4. Molecule X goes down its gradient molecule Y goes against its gradient using the same transporter. This is an example of ___ and ___ if they are both entering the cell.

a. Active, antiport <--

b. Active, symport

c. Facilitated, antiport

d. Facilitated, symport

5. Facilitated and active transport have all in common except _____.

a. Sigmoidal graphs

b. Ability to find Km

c. The use of ATP <--

d. Higher rates compared to diffusion

orangecicada796

1A.

A <---> B

You measure the amount of molecules A and B for the reversible reaction above at a particular time point and find more of molecule A than of B. Your colleague believes that the reaction is at equilibrium. Which of the following statements about this reaction is correct? (select all that apply)

A	A --> B is exergonic
B	B --> A is exergonic
C	B --> A is endergonic
D	A --> B is endergonic
E	Your colleague must be wrong. If the reaction were at equilibrium, there must be equal amounts of molecule A and B.

1B. Which of the following is/are true of energy and chemical gradients? (select all that apply)

A	A concentration gradient represents a form of potential (stored) energy.
B	Movement of a molecule down a concentration gradient across a membrane releases energy that can be used to do work.
C	If a molecules cross a membrane at equal rates in both directions (is at equilibrium) this movement is neither exergonic or endergonic.
D	Moving molecules against a concentration gradient is an endergonic process.

sapphireant197

It's a pretty elementary concept, and when I first learned of itI don't think I had the foundations to even think of such aquestion, but I found myself the other day thinking about theamphipathic nature of the phospholipids in the plasma membrane andwhy it might be that lipid-soluble molecules don't stay in betweenthe layers (of the bilayer).

I know that simple diffusion is a response to a concentrationgradient, but consider a case where equilibrium is being restoredand lipid-soluble molecules are diffusing from whateverextracellular matrix through the membrane and into the cytosol.Towards the end of this process, when equilibrium is nearlyrestored and the last few molecules are making their way into thecell, the rate of diffusion for these last couple molecules will beslower than those that diffused when the concentration differencewas greater. Since the polar heads on the outside and inside of thebilayer are hydrophilic but the inner part, where the fatty acidtails are, is hydrophobic, what drives a molecule to leave thecozy, accepting, lipophilic environment of the middle (of thebilayer) to cross through the cytosolic-side rejecting polar headsand enter the cytosol?

I understand that initially these molecules were moving into thecell in response to a difference in intracellular vs extracellularconcentration, but I'm asking whether we would ever see a casewhere the gradient is nearly zero and a molecule in transit simplydecides to reside in between the layers instead of crossing all theway into the cell; as if moving through the cytosolic polar headside is not worth the effort to reduce a nearly-zero gradient tozero.

Please ask me if I can clarify my question in any way -- I'mfinding it difficult to phrase. I asked my professor (who has herdoctorate in toxicology & pharmacology) and she understood whatI was asking but didn't have an answer.