30 Questions
What is the approximate thickness of the cell membrane in meters?
8 x 10^-9
What is the primary function of proteins in the cell membrane?
To regulate traffic and act as gatekeepers
What is the main reason why the lipid bilayer is impermeable to polar substances?
Because of the lipid bilayer's hydrophobic nature
What is the term that describes the movement of molecules from an area of higher concentration to an area of lower concentration?
Diffusion
What is the proportion of lipids and proteins in the cell membrane?
50% lipid and 50% protein
What is the term that describes the fluid mosaic model of membrane structure?
A sea of lipids in which proteins float like icebergs
What percentage of lipids in the phospholipid bilayer are comprised of phospholipids?
75%
What determines the fluidity of a membrane?
Lipid tail length, number of double bonds, and amount of cholesterol
What type of proteins have hydrophobic regions that span the hydrophobic core of the lipid bilayer?
Integral proteins
What is a characteristic of integral membrane proteins?
They have non-polar amino acids coiled into helices
What can be a function of membrane proteins?
To act as receptors
Why do lipids rarely flip-flop between membrane leaflets?
Because of the hydrophobic core of the lipid bilayer
What is the primary reason for the selective permeability of the membrane?
The molecular organisation of the lipid bilayer
Which of the following molecules is most likely to be impermeable to the lipid bilayer?
Glucose
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
What drives the random mixing of particles in a solution during diffusion?
The kinetic energy of the particles
What is the result of the diffusion process once equilibrium is reached?
The concentration of the substance is evenly distributed throughout the solution
What is the primary characteristic of a substance that is lipid soluble?
It is able to permeate the hydrophobic core of the lipid bilayer
What is the primary limitation on the size of cells?
The rate of diffusion sets a limit of about 20 µm
Which of the following would increase the rate of diffusion?
Increasing the concentration gradient
What is the primary factor that influences the movement of ions across the cell membrane?
Electrochemical gradient
What is the role of the selective permeability of the membrane?
To establish a difference in concentration or concentration gradient across the membrane
What is the analogy used to describe the ability of membranes to separate and store charge?
Capacitor
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
What percentage of resting energy do cells use to maintain concentration and electrical gradients?
30%
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
What determines the permeability of a cell membrane to water?
The combination of lipid bilayer and aquaporins
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
What is the effect of differences in osmolarity on water movement across membranes?
Move water into the cell
What is the characteristic of Pf, the permeability of aquaporins?
Large and mercury sensitive
Test your knowledge of cell membrane structure and function, including transport mechanisms and epithelial transport of glucose. Based on Tortora & Grabowski 9th edition.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
