PSL300 Week 1 Exam Questions and Correct
Answers
What is the composition of the cell membrane?
The cell membrane is composed of a phospholipid bilayer.
What type of molecules can readily diffuse through the cell membrane?
Lipid-soluble molecules and gases can diffuse through readily.
What is the permeability of the cell membrane to organic anions?
The cell membrane is impermeable to organic anions (proteins).
What factors determine membrane permeability?
Membrane permeability depends on molecular size, lipid solubility, and charge.
What is simple diffusion?
Simple diffusion is the process where small, lipid-soluble molecules and gases pass through
the phospholipid bilayer or pores down their concentration gradient.
What is facilitated diffusion?
Facilitated diffusion is the process where molecules diffuse across membranes with the
assistance of carrier proteins.
How do carrier proteins function in facilitated diffusion?
Carrier proteins aid the movement of polar molecules by changing shape to allow the
molecule to cross the membrane.
What is active transport?
,Active transport is a mechanism that moves selected molecules across cell membranes
against their concentration gradient, requiring energy from ATP.
What is the role of ATPases in active transport?
ATPases, like the Na+/K+ pump, couple the hydrolysis of ATP with the movement of
substances across the membrane.
What is secondary active transport?
Secondary active transport occurs when the kinetic energy of one substance moving down its
concentration gradient powers the transport of another substance against its gradient.
What are membrane channels?
Membrane channels are proteins that form pores through the membrane, allowing specific
ions to diffuse.
What is the function of gated channels?
Gated channels can open or close based on specific conditions, allowing or blocking
diffusion.
What triggers ligand-gated channels to open?
The binding of a chemical agent (ligand) to the channel triggers it to open.
What is the significance of voltage-gated channels?
Voltage-gated channels respond to changes in membrane potential, allowing ions to diffuse
when the channel opens.
What is endocytosis?
, Endocytosis is the inward 'pinching' of the membrane to create a vesicle, usually to capture
proteins from outside the cell.
What is exocytosis?
Exocytosis is the process of vesicles fusing with the cell membrane to transport molecules
from inside to outside the cell.
What is 'Kiss and Run' exocytosis?
'Kiss and Run' exocytosis involves vesicles that dock and fuse with the plasma membrane,
partially releasing contents multiple times.
What is full exocytosis?
Full exocytosis involves complete fusion of the vesicle with the membrane, releasing all
contents at once.
What is membrane potential?
Membrane potential is the potential difference across the membrane of a cell, essential for
cell function.
What happens if the membrane potential difference is zero?
If the membrane potential difference is zero and not negative inside, the cell is likely dead.
What are the two conditions needed to generate membrane potential?
The two conditions needed to generate membrane potential are the presence of ions and a
selectively permeable membrane.
What is the function of an enzyme ion pump in creating a concentration gradient?
It actively transports certain ion species across the membrane.
Answers
What is the composition of the cell membrane?
The cell membrane is composed of a phospholipid bilayer.
What type of molecules can readily diffuse through the cell membrane?
Lipid-soluble molecules and gases can diffuse through readily.
What is the permeability of the cell membrane to organic anions?
The cell membrane is impermeable to organic anions (proteins).
What factors determine membrane permeability?
Membrane permeability depends on molecular size, lipid solubility, and charge.
What is simple diffusion?
Simple diffusion is the process where small, lipid-soluble molecules and gases pass through
the phospholipid bilayer or pores down their concentration gradient.
What is facilitated diffusion?
Facilitated diffusion is the process where molecules diffuse across membranes with the
assistance of carrier proteins.
How do carrier proteins function in facilitated diffusion?
Carrier proteins aid the movement of polar molecules by changing shape to allow the
molecule to cross the membrane.
What is active transport?
,Active transport is a mechanism that moves selected molecules across cell membranes
against their concentration gradient, requiring energy from ATP.
What is the role of ATPases in active transport?
ATPases, like the Na+/K+ pump, couple the hydrolysis of ATP with the movement of
substances across the membrane.
What is secondary active transport?
Secondary active transport occurs when the kinetic energy of one substance moving down its
concentration gradient powers the transport of another substance against its gradient.
What are membrane channels?
Membrane channels are proteins that form pores through the membrane, allowing specific
ions to diffuse.
What is the function of gated channels?
Gated channels can open or close based on specific conditions, allowing or blocking
diffusion.
What triggers ligand-gated channels to open?
The binding of a chemical agent (ligand) to the channel triggers it to open.
What is the significance of voltage-gated channels?
Voltage-gated channels respond to changes in membrane potential, allowing ions to diffuse
when the channel opens.
What is endocytosis?
, Endocytosis is the inward 'pinching' of the membrane to create a vesicle, usually to capture
proteins from outside the cell.
What is exocytosis?
Exocytosis is the process of vesicles fusing with the cell membrane to transport molecules
from inside to outside the cell.
What is 'Kiss and Run' exocytosis?
'Kiss and Run' exocytosis involves vesicles that dock and fuse with the plasma membrane,
partially releasing contents multiple times.
What is full exocytosis?
Full exocytosis involves complete fusion of the vesicle with the membrane, releasing all
contents at once.
What is membrane potential?
Membrane potential is the potential difference across the membrane of a cell, essential for
cell function.
What happens if the membrane potential difference is zero?
If the membrane potential difference is zero and not negative inside, the cell is likely dead.
What are the two conditions needed to generate membrane potential?
The two conditions needed to generate membrane potential are the presence of ions and a
selectively permeable membrane.
What is the function of an enzyme ion pump in creating a concentration gradient?
It actively transports certain ion species across the membrane.
