hw 6 bio 110

How does lipid composition affect membrane fluidity?

- Saturated fatty acids tend to make the membrane less fluid because they pack together well. -Sphingolipids tend to make the membrane less fluid.

Place the following molecules in order according to their capability to cross the lipid bilayer of the plasma membrane without the help of transport proteins. Start with molecules that cross most easily on top.

1. non polar molecules 2. small polar molecules 3. large polar molecules

describe the relationship between solute concentration and rate of diffusion during facilitated diffusion by carrier proteins?

As solute concentration increases, the rate of diffusion increases but eventually it remains constant once it reaches a maximum rate.

During facilitated diffusion, how do carrier proteins transport solutes across the membrane?

During facilitated diffusion, how do carrier proteins transport solutes across the membrane?

The rate of diffusion of a substance across the plasma membrane depends on which of the following?

How easily the substance can cross the membrane The concentration of the substance outside the cell The concentration of the substance inside the cell

How do active and passive transport differ?

Only active transport can move a substance against its concentration gradient.

How do carrier proteins differ from channel proteins?

Only carrier proteins actually bind to the substance being transported.

They have a hydrophilic interior through which polar molecules can pass.

Which of the following is true of channel proteins?

________transport requires the cell to expend some of its own energy, ___________, transport does not.

active passive

oxygen diffuses across the plasma membrane due to which of the following?

all oxygen molecules are in constant random motion

Of the 2 types of transport proteins that mediate facilitated diffusion, _______________proteins actually bind with the substance being transported, while ____________proteins simply provide a hydrophilic space for the substance to move through.

carrier channel

ransport proteins that actually bind to the specific substance being transported across the membrane are called

carrier proteins

Transport proteins that have a hydrophilic interior space with an aqueous environment through which specific substances can move across the membrane in either direction are called

channell proteins

when the concentration of a substance varies from one region to another, the substance is exhibiting a ____________________

concentration gradients

Net movement of a substance from a region where it has a higher concentration to a region where it has a lower concentration is called?

diffusion

When a channel protein or carrier protein assists in diffusion, which of the following is observed?

facillitated diffusion

The lack of double bonds in phospholipids with saturated fatty acids allow them to pack together tightly, and therefore the membrane is ________ fluid. Kinks introduced by double bonds in lipids with unsaturated fatty acids prevent them from packing together tightly, and therefore the membrane is __________ fluid

less more

Cellular __________ , are said to be selectively ________ because they allow some substances to pass through easily while other substances pass through very slowly or not at all.

membrane permeable

During facilitated diffusion by carrier proteins, when solute concentrations are low, increasing the solute concentration causes a linear increase in the rate of diffusion. However, at high solute concentrations, further increases in the solute concentration no longer increase the rate of diffusion. This means that carrier proteins exhibi _______

saturation

diffusion is caused by what?

the constant random motion of all atoms and molecules

What is the permeability of a typical cell membrane to a large polar molecule (assume there are no special transporter proteins for that molecule)?

very limited permeability