29 Questions
What is the primary function of the leaky K+ channel?
To control the resting membrane potential in neurons
Which type of channel is involved in the neuromuscular junction?
Ligand-gated channel
What is the primary function of GLUT4 transporter?
To regulate the movement of glucose into the cell
What happens to a cell when it is placed in a hypertonic solution?
Water moves out of the cell, causing it to crenate
What is the primary function of aquaporin protein channels?
To facilitate the movement of water molecules across the membrane
What type of channel is involved in generating graded potentials in response to mechanical vibration?
Mechanically gated channel
What is the term for the movement of water molecules from a solution with a high concentration of water molecules to a solution with a lower concentration of water molecules?
Osmosis
What happens when a cell is placed in an isotonic solution?
There is no net movement of water into or out of the cell
What is the primary function of the Na-K pump in the Na-glucose secondary transport mechanism?
To generate a high Na gradient across the cell membrane
What is the term for the process by which cells take in external solids?
Phagocytosis
What is the primary function of exocytosis?
To export intracellularly synthesized materials from the cell
What is the mechanism by which cholesterol enters cells?
Receptor-mediated endocytosis
What is the term for the uptake of extracellular fluids and dissolved solutes?
Pinocytosis
What is the function of the glucose-Na symport protein in the Na-glucose secondary transport mechanism?
To transport glucose through the Na gradient into the cell
What happens to the overall concentration of solutes on both sides of the cell membrane when there is no net movement of water particles?
The concentration of solutes on both sides remains constant
What type of solution has a lower solute concentration than another solution?
Hypotonic solution
What happens to the red blood cell in a hypertonic solution?
It appears to shrink
What is the primary function of primary active transport?
To move molecules from lower concentration to higher concentration
What is the Na-K pump an example of?
Primary active transport
What is the result of the Na-K pump's action?
Na+ moves from inside the cell to high concentration outside, and K+ moves in opposite direction
What is the role of ATPase in primary active transport?
To create a conformational change in the membrane protein
What is the effect of insulin and thyroid hormones (T3 and T4) on ATPase enzyme?
They increase ATPase enzyme
What is the primary function of the cell membrane?
To regulate the entry and exit of molecules
What is the direction of movement of particles in passive transfusion?
From an area of greater concentration to an area of lesser concentration
What type of molecules can traverse the cell membrane through simple diffusion?
Small and non-polar molecules
What is the role of proteins in facilitated diffusion?
To mediate diffusion through channels or carriers
Why can't glucose diffuse across the cell membrane?
Because it's a large molecule
What is the purpose of facilitated diffusion?
To facilitate the transfer of substances that cannot cross the membrane through simple diffusion
What is an example of facilitated diffusion?
K+ leaky channel in neurons
Study Notes
Cell Membrane Transport
- Cell membrane is a phospholipid bilayer that regulates the entry and exit of molecules
- Cell transport can be classified into passive and active transport
Passive Transport
- No energy required
- Movement of particles from an area of higher concentration to an area of lesser concentration
- Types of passive transport:
- Simple diffusion
- Facilitated diffusion
- Osmosis
Simple Diffusion
- Movement of small, non-polar molecules (e.g. O2, CO2, steroids, lipid-soluble drugs) from higher to lower concentration
- No energy required
- No protein-mediated transport
Facilitated Diffusion
- Movement of large or charged molecules (e.g. glucose, amino acids, nucleic acids) from higher to lower concentration
- Proteins required for transport (channel or carrier proteins)
- No energy required
- Types of facilitated diffusion:
- Leaky channels (e.g. K+ leaky channel in neurons)
- Voltage-gated channels (e.g. Na+ and Ca++ in neurons)
- Ligand-gated channels (e.g. acetylcholine in neuromuscular junction)
- Mechanically gated channels (e.g. sound waves or pressure in sensory receptors)
Osmosis
- Movement of water molecules from higher to lower concentration
- Depends on solute concentration (e.g. Na+, glucose)
- Types of solutions:
- Hypertonic solution (higher solute concentration)
- Isotonic solution (equal solute concentration)
- Hypotonic solution (lower solute concentration)
- Aquaporin protein channels facilitate water movement
Active Transport
- Movement of molecules from lower to higher concentration
- Energy required (typically from ATP hydrolysis)
- Types of active transport:
- Primary active transport
- Secondary active transport
Primary Active Transport
- Directly uses ATP energy
- Involves conformational change in membrane protein
- Examples:
- Na-K pump (antiport that transfers K+ and Na+ into and out of the cell)
- CaATPase
- Proton pump (H+)
Secondary Active Transport
- Uses energy from primary active transport
- Examples:
- Na-glucose secondary transport mechanism (uses Na-K pump to generate Na gradient)
- Glucose-Na symport protein transports glucose into the cell
Endocytosis
- Cell membrane wraps around external medium, forming endosomes
- Types of endocytosis:
- Pinocytosis (small vesicles with fluid)
- Phagocytosis (larger vesicles with solids)
- Receptor-mediated endocytosis (substances bind to specific receptors)
Exocytosis
- Export of intracellularly synthesized materials from the cell
- Vesicles fuse with the outer membrane
- Examples:
- Cell-specific protein products
- Neurotransmitters
- Various other molecules
Explore cell membrane transport, including passive and active transfusion, and how it regulates the entry and exit of molecules in the body.
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