Membrane Transport Quiz

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Questions and Answers

What is the primary function of the SGLT-1 transporter?

Transport glucose against its concentration gradient from the intestinal lumen into epithelial cells (correct)

Transport glucose from the kidney filtrate back into the bloodstream

Transport sodium ions out of the epithelial cells into the lumen

Transport glucose into the bloodstream via facilitated diffusion

What role does the Na+/K+ ATPase play in secondary active transport?

It directly transports glucose into the cells.

It creates a sodium gradient that provides energy for transport. (correct)

It prevents sodium from re-entering the cells.

It facilitates glucose diffusion into the bloodstream.

Which of the following statements correctly describes antiport transport?

One substance is pumped into the cell while another is expelled out. (correct)

It only applies to the transport of ions.

It utilizes ATP to drive the transport process.

Both substances are moved in the same direction across the membrane.

What characterizes the mechanism of the SGLT-2 transporter in the kidneys?

It facilitates the cotransport of glucose and sodium from the filtrate into epithelial cells. Signup and view all the answers

Which transport process uses the energy stored in a sodium gradient?

Cotransport of glucose and sodium ions via SGLT-1 Signup and view all the answers

What is the primary function of the sodium-potassium pump?

To maintain the electrochemical gradient of sodium and potassium ions Signup and view all the answers

Which cardiac glycoside is derived from Digitalis purpurea?

Digoxin Signup and view all the answers

Which subunits compose the sodium-potassium ATPase?

2 alpha and 2 beta subunits Signup and view all the answers

How does inhibition of the sodium-potassium ATPase affect intracellular calcium levels?

It increases intracellular sodium concentration, causing an increase in calcium influx Signup and view all the answers

What is a characteristic of primary active transport mechanisms?

They use the energy derived from ATP hydrolysis Signup and view all the answers

What does the ABC transporter protein family primarily do?

Pumps non-polar molecules out of the cell Signup and view all the answers

Which of the following correctly describes secondary active transport?

It uses ion gradients to drive the transport of other molecules Signup and view all the answers

What effect does cardiac glycoside inhibition have on cardiac myocytes?

It enhances cardiac contractility Signup and view all the answers

What is the primary function of active transport in cells?

To maintain ion concentrations against their electrochemical gradient Signup and view all the answers

Which of the following correctly describes primary active transport?

It directly uses ATP to transport solutes. Signup and view all the answers

What condition occurs if ATP production is inhibited in a cell?

Cells may die due to the loss of ion concentration gradients. Signup and view all the answers

Which transport mechanism uses a carrier protein but does not directly utilize ATP?

Secondary active transport Signup and view all the answers

In the context of cardiac glycosides, what is their primary effect on ion transport?

They inhibit primary active transport of sodium-potassium ATPase. Signup and view all the answers

How does the sodium-potassium pump contribute to primary active transport?

By moving sodium ions out of and potassium ions into the cell against their gradients. Signup and view all the answers

What happens to electrochemical gradients when ATP levels are reduced?

They significantly decrease, leading to loss of ion specificity. Signup and view all the answers

What role does facilitated diffusion play in relation to active transport?

It permits passive movement of molecules across the membrane down their gradient. Signup and view all the answers

Study Notes

Membrane Transport

Transport across membranes includes passive and active transport.
Passive transport moves substances down their concentration or electrochemical gradient, without energy expenditure.
Active transport moves substances against their concentration or electrochemical gradient, requiring energy.

Types of Transport

Passive Transport:
- Substances move down their concentration gradient.
- No energy is required.
- Examples include simple diffusion, facilitated diffusion, and osmosis.
Active Transport:
- Substances move against their concentration gradient.
- Energy (ATP) is required.
- Examples include primary active transport and secondary active transport.

Passive Transport Subtypes

Simple diffusion:
- Small, uncharged molecules (e.g., oxygen, carbon dioxide) can pass directly through the lipid bilayer.
- The rate-limiting step is moving across the lipid bilayer from the aqueous environment.
- Ions and charged molecules diffuse poorly across the lipid bilayer.
Facilitated diffusion:
- Molecules that are not lipid-soluble or too large to move through the lipid bilayer (e.g., glucose, amino acids) travel through protein channels or carrier proteins.
- No energy expenditure is needed.
- Examples include glucose transporters (GLUTs) and aquaporins.
Osmosis:
- The movement of water across a selectively permeable membrane from an area of high water concentration to an area of low water concentration.

Active Transport Subtypes

Primary active transport:
- Directly uses ATP for transport.
- Example: sodium-potassium pump (Na+/K+ ATPase).
Secondary active transport:
- Uses the electrochemical gradient of one substance (e.g., Na+) to move another substance against its gradient.
- Examples include SGLT-1 and SGLT-2 for glucose transport.
- Subtypes include symport (both substances move in the same direction) and antiport (substances move in opposite directions).

Sodium-Potassium Pump (Na+/K+ ATPase)

An important primary active transport protein maintaining ion gradients necessary for cell function.
Transports 3 Na+ ions out and 2 K+ ions in per ATP molecule hydrolyzed.
Contributes to resting membrane potential and drives secondary active transport.
It's a crucial component of cell function in various tissues.
The pump itself has 4 subunits (two alpha and two beta).

ABC Transporter Protein Family

Transports diverse substrates, including drugs, and plays a major role in drug resistance.
The transporter has 2 transmembrane and 2 ATP domains (casettes).
Often found in tumor cells, resisting cytostatic drugs.

Proton Pump

Transports protons (H+) across a membrane, usually actively.
A critical component in cellular processes including respiration and stomach HCl secretion.
Uses energy from ATP hydrolysis.

Gibbs-Donnan Equilibrium

Ions, with opposite charges, distribute unequally across a membrane.
When a semipermeable membrane separates two solutions containing diffusible and non-diffusible ions, the concentration difference creates a membrane potential.
The imbalance in concentrations on both sides, of the membrane, results in an uneven distribution of ions.
Unequal ion distribution creates a membrane potential across the membrane.

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Description

This quiz covers the fundamental concepts of membrane transport, including both passive and active transport mechanisms. You will explore key examples of each type, along with detailed subtypes of passive transport such as simple diffusion and osmosis.