Physiology: Cell Membrane Transport

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Questions and Answers

What is the primary function of the leaky K+ channel?

To generate graded potentials in response to mechanical vibration
To regulate the action potential in neurons
To control the resting membrane potential in neurons (correct)
To facilitate the movement of glucose into the cell

Which type of channel is involved in the neuromuscular junction?

Mechanically gated channel
Ligand-gated channel (correct)
Voltage-gated channel
Channel-mediated molecule

What is the primary function of GLUT4 transporter?

To facilitate the movement of ions across the membrane
To facilitate the movement of water molecules across the membrane
To regulate the movement of glucose into the cell (correct)
To generate action potentials in neurons

What happens to a cell when it is placed in a hypertonic solution?

Water moves out of the cell, causing it to crenate (B) Signup and view all the answers

What is the primary function of aquaporin protein channels?

To facilitate the movement of water molecules across the membrane (C) Signup and view all the answers

What type of channel is involved in generating graded potentials in response to mechanical vibration?

Mechanically gated channel (C) Signup and view all the answers

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 (D) Signup and view all the answers

What happens when a cell is placed in an isotonic solution?

There is no net movement of water into or out of the cell (A) Signup and view all the answers

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 (C) Signup and view all the answers

What is the term for the process by which cells take in external solids?

Phagocytosis (B) Signup and view all the answers

What is the primary function of exocytosis?

To export intracellularly synthesized materials from the cell (B) Signup and view all the answers

What is the mechanism by which cholesterol enters cells?

Receptor-mediated endocytosis (D) Signup and view all the answers

What is the term for the uptake of extracellular fluids and dissolved solutes?

Pinocytosis (A) Signup and view all the answers

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 (C) Signup and view all the answers

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 (D) Signup and view all the answers

What type of solution has a lower solute concentration than another solution?

Hypotonic solution (D) Signup and view all the answers

What happens to the red blood cell in a hypertonic solution?

It appears to shrink (B) Signup and view all the answers

What is the primary function of primary active transport?

To move molecules from lower concentration to higher concentration (A) Signup and view all the answers

What is the Na-K pump an example of?

Primary active transport (B) Signup and view all the answers

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 (A) Signup and view all the answers

What is the role of ATPase in primary active transport?

To create a conformational change in the membrane protein (C) Signup and view all the answers

What is the effect of insulin and thyroid hormones (T3 and T4) on ATPase enzyme?

They increase ATPase enzyme (D) Signup and view all the answers

What is the primary function of the cell membrane?

To regulate the entry and exit of molecules (C) Signup and view all the answers

What is the direction of movement of particles in passive transfusion?

From an area of greater concentration to an area of lesser concentration (D) Signup and view all the answers

What type of molecules can traverse the cell membrane through simple diffusion?

Small and non-polar molecules (B) Signup and view all the answers

What is the role of proteins in facilitated diffusion?

To mediate diffusion through channels or carriers (C) Signup and view all the answers

Why can't glucose diffuse across the cell membrane?

Because it's a large molecule (D) Signup and view all the answers

What is the purpose of facilitated diffusion?

To facilitate the transfer of substances that cannot cross the membrane through simple diffusion (C) Signup and view all the answers

What is an example of facilitated diffusion?

K+ leaky channel in neurons (B) Signup and view all the answers

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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

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