Ions cannot cross directly through a lipid bilayer, yet we know they travel in and out of cells. Which of the following is/are true about how ions diffuse cross membranes?   a)  They diffuse down their concentration gradients.   b)  They diffuse through channels formed by integral membrane proteins.   c)  They diffuse down their electrical gradients.   d)  a and c   e)  a, b and c

Which of the following distinguishes osmosis from simple diffusion?  a) a concentration gradient  b) a solute  c) a selectively permeable membrane  d) water molecules

Whether in a gas, a liquid, or a semisolid, diffusion always occurs a). at the same rate. b). from high to low solute concentration. c). faster at lower temperaturesd). from low to high solute concentration.

An ionophore: A) increase the membrane potential B) transports ionic proteins across a membrane C) disrupts ion gradients D) forms channels when inserted into a membrane E) often has antibiotic properties because it can block the transport of ions

Which of these answers explains why synaptic vesicles only releasee their neurotransmitter cargo in response to a signal? A) the necessary Rab proteins are not synthesized until an action potential arrives B) vesicle formation at the trans-Golgi network cannot occur in the absence of plasma membrane depolarization C) an additional protein, synaptotagmin, makes vesicle fusion dependent on the calcium concentration D)a plasma membrane transporter is needed to actively pump neurotransmitter into the synaptic cleft. These are inactive until membrane depolarization

Membrane embedded Proteins: A) Why were the membrane embedded proteins important in the appearance of life? B) Why was it important to have a mechanism for the movement of molecules in to and out of the cell?  C) Describe the key structure and functional properties of the three types of cell membrane embedded transport proteins.