Cell Membrane Structure & Function Quiz

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What is the approximate thickness of the cell membrane in meters?

8 x 10^-8

8 x 10^-9 (correct)

8 x 10^-11

8 x 10^-10

What is the primary function of proteins in the cell membrane?

To regulate traffic and act as gatekeepers (correct)

To act as a barrier to polar substances

To facilitate diffusion across the cell membrane

To store energy in the fluid compartments

What is the main reason why the lipid bilayer is impermeable to polar substances?

Because of the membrane's selective permeability

Because of the hydrogen bonds between lipids and proteins

Because of the lipid bilayer's hydrophobic nature (correct)

Because of the presence of proteins in the membrane

What is the term that describes the movement of molecules from an area of higher concentration to an area of lower concentration?

Diffusion Signup and view all the answers

What is the proportion of lipids and proteins in the cell membrane?

50% lipid and 50% protein Signup and view all the answers

What is the term that describes the fluid mosaic model of membrane structure?

A sea of lipids in which proteins float like icebergs Signup and view all the answers

What percentage of lipids in the phospholipid bilayer are comprised of phospholipids?

75% Signup and view all the answers

What determines the fluidity of a membrane?

Lipid tail length, number of double bonds, and amount of cholesterol Signup and view all the answers

What type of proteins have hydrophobic regions that span the hydrophobic core of the lipid bilayer?

Integral proteins Signup and view all the answers

What is a characteristic of integral membrane proteins?

They have non-polar amino acids coiled into helices Signup and view all the answers

What can be a function of membrane proteins?

To act as receptors Signup and view all the answers

Why do lipids rarely flip-flop between membrane leaflets?

Because of the hydrophobic core of the lipid bilayer Signup and view all the answers

What is the primary reason for the selective permeability of the membrane?

The molecular organisation of the lipid bilayer Signup and view all the answers

Which of the following molecules is most likely to be impermeable to the lipid bilayer?

Glucose Signup and view all the answers

What is the primary function of membrane proteins in relation to transport?

To mediate the transport of substances that cannot permeate the hydrophobic core of the lipid bilayer Signup and view all the answers

What drives the random mixing of particles in a solution during diffusion?

The kinetic energy of the particles Signup and view all the answers

What is the result of the diffusion process once equilibrium is reached?

The concentration of the substance is evenly distributed throughout the solution Signup and view all the answers

What is the primary characteristic of a substance that is lipid soluble?

It is able to permeate the hydrophobic core of the lipid bilayer Signup and view all the answers

What is the primary limitation on the size of cells?

The rate of diffusion sets a limit of about 20 µm Signup and view all the answers

Which of the following would increase the rate of diffusion?

Increasing the concentration gradient Signup and view all the answers

What is the primary factor that influences the movement of ions across the cell membrane?

Electrochemical gradient Signup and view all the answers

What is the role of the selective permeability of the membrane?

To establish a difference in concentration or concentration gradient across the membrane Signup and view all the answers

What is the analogy used to describe the ability of membranes to separate and store charge?

Capacitor Signup and view all the answers

What is the characteristic of the concentration of Na+ and K+ ions across the cell membrane?

High concentrations of Na+ and low concentrations of K+ outside the cell Signup and view all the answers

What percentage of resting energy do cells use to maintain concentration and electrical gradients?

30% Signup and view all the answers

What is the direction of net water movement through a selectively permeable membrane?

From an area of high water concentration to an area of low water concentration Signup and view all the answers

What determines the permeability of a cell membrane to water?

The combination of lipid bilayer and aquaporins Signup and view all the answers

What is the term for the pressure applied to a solution to prevent the inward flow of water across a semi-permeable membrane?

Osmotic pressure Signup and view all the answers

What is the effect of differences in osmolarity on water movement across membranes?

Move water into the cell Signup and view all the answers

What is the characteristic of Pf, the permeability of aquaporins?

Large and mercury sensitive Signup and view all the answers