Cell Biology: Plasma Membrane Functionality

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Questions and Answers

What term describes a plasma membrane's characteristic of allowing certain substances to pass while restricting others?

Selectively permeable (correct)

Completely permeable

Homogeneous

Semi-permeable

Which part of the phospholipid bilayer faces the watery environment of a cell?

Glycoproteins

Cholesterol

Polar phosphate head (correct)

Nonpolar fatty acid tails

What type of transport involves movement from an area of high concentration to an area of low concentration without the need for energy?

Passive transport (correct)

Active transport

Facilitated diffusion

Endocytosis

What is the outcome when a cell is placed in a hypertonic solution?

The cell loses water and shrinks Signup and view all the answers

What drives the flow of substances across the plasma membrane?

Concentration gradient Signup and view all the answers

Which solution has a higher concentration of dissolved solutes outside the cell compared to the inside?

Hypertonic Signup and view all the answers

What type of diffusion specifically refers to the movement of water across a membrane?

Osmosis Signup and view all the answers

What happens to the concentration of solute when equilibrium is reached?

It becomes evenly spaced throughout the solution. Signup and view all the answers

What type of transport requires energy to move substances against their concentration gradient?

Active transport Signup and view all the answers

Which method of transport involves the engulfing of large particles by the cell?

Phagocytosis Signup and view all the answers

What initiates the conformational change in the sodium-potassium pump?

Phosphorylation by ATP Signup and view all the answers

What is the primary role of transport proteins in facilitated diffusion?

To facilitate the movement of ions and small molecules Signup and view all the answers

Which of the following statements best describes exocytosis?

It releases substances from within the cell to the extracellular space Signup and view all the answers

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

To maintain electrochemical gradients across the plasma membrane Signup and view all the answers

Which type of transport is characterized by the absorption of liquids by a cell?

Pinocytosis Signup and view all the answers

What occurs when the sodium-potassium pump expels sodium ions?

The protein undergoes a conformational change Signup and view all the answers

Study Notes

Plasma Membrane Functionality

Plasma membranes are selectively permeable, controlling what enters and exits the cell.
Essential for maintaining homeostasis by regulating internal conditions.

Structure of Plasma Membrane

Composed mainly of phospholipids with a hydrophilic phosphate head and two hydrophobic fatty acid tails.
The phosphate head is polar and interacts well with water, while fatty acid tails are nonpolar and repel water.

Transport Mechanisms

Movement of substances is influenced by concentration gradient, polarity, and molecular size.

Passive Transport

Occurs from high to low concentration without energy expenditure.
Simple Diffusion: Solutes move down the concentration gradient until equilibrium is achieved.
Osmosis: Special case of diffusion involving water, moving across the membrane from areas of high water concentration to low.

Tonicity of Solutions

Isotonic: Equal concentration inside and outside the cell, maintaining cell size.
Hypertonic: Higher solute concentration outside the cell, causing cell to lose water and shrink.
Hypotonic: Lower solute concentration outside the cell, leading to water influx and cell swelling.

Facilitated Diffusion

Involves transport proteins aiding the movement of specific molecules, such as ions and sugars, across the plasma membrane.

Active Transport

Transports substances from low to high concentration, requiring energy (ATP).
Utilizes carrier proteins, such as the sodium-potassium pump, to move ions against their concentration gradients.

Bulk Transport

Endocytosis: Process of enfolding the plasma membrane to take in large solutes, forming a vacuole.
- Phagocytosis: Engulfs solid particles like bacteria and dead cells.
- Pinocytosis: Involves the uptake of liquids and solutes, common in absorbing cells.
Exocytosis: Mechanism for expelling large solutes from the cell by merging vesicles with the plasma membrane.

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Description

Explore the essential functions and structure of the plasma membrane in this quiz. Understand how selective permeability and transport mechanisms play a critical role in cellular homeostasis. Delve into passive transport phenomena such as diffusion and osmosis, as well as the concept of tonicity.