Passive and Active Transport

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Questions and Answers

Which of the following scenarios accurately describes secondary active transport?

The engulfment of large particles or cells by a cell, forming a vesicle that brings the particle inside.
The passive movement of water across a semipermeable membrane from an area of low solute concentration to an area of high solute concentration.
The movement of a substance against its concentration gradient, directly powered by ATP hydrolysis.
The movement of a substance down its concentration gradient, coupled with the movement of another substance against its concentration gradient, using the energy derived from the first substance's movement. (correct)

A cell is placed in a solution, and water begins to move out of the cell, causing it to shrink. Which of the following best describes the solution?

Hypertonic (correct)
Hypotonic
Isotonic
Equimolar

In primary active transport, what is the direct source of energy used to move substances across the cell membrane?

The resting membrane potential.
The concentration gradient of the transported substance.
The movement of another ion down its electrochemical gradient.
Hydrolysis of ATP. (correct)

A researcher observes a cell engulfing a large, nonspecific solid particle. Which process is the cell utilizing?

Phagocytosis (A) Signup and view all the answers

Selective serotonin reuptake inhibitors (SSRIs) are used to treat clinical depression by:

Inhibiting the reuptake of serotonin, increasing its availability in the synaptic cleft. (D) Signup and view all the answers

What happens when a ligand crosses a membrane?

A change in gene expression or protein synthesis. (A) Signup and view all the answers

What is the most widely accepted model of the cell membrane?

The Fluid Mosaic Model (B) Signup and view all the answers

Why do phospholipids make ideal membranes?

Phospholipids make ideal membranes because there is water inside and outside the cell. (D) Signup and view all the answers

Size plays a big role in substances crossing the plasma membrane.

True (A) Signup and view all the answers

What is passive transport?

Things moving from high concentration to low concentration happen without energy (B) Signup and view all the answers

What is active transport?

Movement from low concentration to high concentration requires energy. (A) Signup and view all the answers

Membrane potential is the difference in charge between the inside and outside of the cell.

True (A) Signup and view all the answers

What are the three types of driving force that molecules are subjected to?

Chemical, Electrical, and Electrochemical (A) Signup and view all the answers

The chemical force for ions changes often.

False (B) Signup and view all the answers

Electrical driving force is dependent on _________

membrane potential Signup and view all the answers

What is the membrane potential at rest for most cells?

-70 mV. (C) Signup and view all the answers

Flashcards

Passive Transport

Movement across a membrane without requiring energy input from the cell.

Active Transport

Movement of a substance across a membrane from an area of low concentration to high concentration, requiring energy.

Osmosis

The diffusion of water across a semipermeable membrane from an area of low solute concentration to an area of high solute concentration.

Hypertonic

A solution with a higher solute concentration compared to another solution.

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Endocytosis

The process where cells engulf material from outside by packaging it into vesicles that bud inward from the plasma membrane.

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Study Notes

Passive processes in physiology don't require energy.

Diffusion

Simple diffusion involves direct movement through a membrane.
Facilitated diffusion requires a carrier protein to aid movement across a membrane.
The rate of simple diffusion is determined by the driving force, which is the concentration difference, and the membrane surface area.
Diffusion occurs over short distances.

Active Transport

Active transport moves substances against their concentration gradient, from low to high concentration.
Primary active transport uses ATP directly for energy.
Secondary active transport uses energy derived from the movement of another substance.
Cotransport involves the movement of two substances in the same direction.
Countertransport involves the movement of two substances in opposite directions.
Primary active transport maintains a constant chemical force for sodium and potassium.
There is always more sodium outside the cell and more potassium inside the cell.
Pumps are a form of active transport.
The resting membrane potential for most cells is -7, and active transport makes it negative.

Osmosis

Osmosis is the movement of water from an area of high concentration to low concentration passively.
Water moves to equalize concentration on both sides of a membrane.
Water moves toward the more concentrated side to dilute it.
Isotonic solutions have the same solute concentration.
Hypertonic solutions have a higher solute concentration.
Hypotonic solutions have a lower solute concentration.
Water always moves towards hypertonic areas.

Endocytosis

Endocytosis involves packaging substances into a vesicle to bring them into the cell.
Phagocytosis is "cell eating," where nonspecific solids enter the cell.
Pinocytosis is "cell drinking," where nonspecific liquids enter the cell.
Substances bind to a receptor for endocytosis.
Selective serotonin reuptake inhibitors (SSRIs) used to treat clinically depressed people, work by stopping receptor mediation, forcing serotonin to bind to the receptor.

Exocytosis

Exocytosis is the reverse of endocytosis.
Large molecules are packaged in vesicles for transport out of the cell.
Like dissolves like.

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Description

Passive processes in physiology do not require energy. Active transport moves substances against their concentration gradient, from low to high concentration. Primary active transport uses ATP directly for energy. Secondary active transport uses energy derived from the movement of another substance.