Cell Biology Chapter 2: Cell Membrane Structure and Functions
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Cell Biology Chapter 2: Cell Membrane Structure and Functions

Explore the properties and functions of the cell membrane, including its flexibility and fluidity, and how it changes shape during cell growth and division. Learn about the structure of the cell membrane and its role in cellular processes.

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Questions and Answers

What property of the cell membrane allows it to change shape during cell division?

Fluidity

What is the primary function of the cell membrane's differential permeability?

To control the movement of substances into and out of cells

What is the main reason why the cell membrane is fluid and flexible?

The movement of phospholipid and protein molecules

What type of substances can freely move across the cell membrane?

<p>Small, non-polar molecules</p> Signup and view all the answers

What is the term used to describe the cell membrane's ability to allow certain substances to pass through while restricting others?

<p>Differential permeability</p> Signup and view all the answers

What is the result of the cell membrane's ability to fuse and break during cell division?

<p>The formation of two identical cells</p> Signup and view all the answers

What is the primary mechanism by which the cell membrane regulates the exchange of materials with its environment?

<p>Passive diffusion of solutes across the phospholipid bilayer</p> Signup and view all the answers

In a hypertonic environment, what would be the net movement of water molecules?

<p>From the cell to the surrounding environment</p> Signup and view all the answers

What is the primary role of cholesterol molecules in the cell membrane?

<p>To regulate the fluidity of the phospholipid bilayer</p> Signup and view all the answers

What is the term used to describe the movement of water molecules from an area of high concentration to an area of low concentration?

<p>Osmosis</p> Signup and view all the answers

What is the arrangement of phospholipids in the cell membrane?

<p>A fluid mosaic model</p> Signup and view all the answers

What is the primary function of the phospholipid bilayer in the cell membrane?

<p>To regulate the exchange of materials between the cell and its environment</p> Signup and view all the answers

What is the main effect of a hypotonic solution on a cell?

<p>Water enters the cell, causing it to swell</p> Signup and view all the answers

What is the purpose of facilitated diffusion?

<p>To allow cells to regulate the movement of specific molecules</p> Signup and view all the answers

What is the characteristic of transport proteins that ensures they only transport specific molecules?

<p>Specificity</p> Signup and view all the answers

What is the result of a cell being placed in an isotonic solution?

<p>There is no net movement of water</p> Signup and view all the answers

What is the role of channel proteins in facilitated diffusion?

<p>They form a channel for molecules to pass through</p> Signup and view all the answers

What is the result of a cell being placed in a hypertonic solution?

<p>Water leaves the cell, causing it to shrink</p> Signup and view all the answers

What is the primary reason why a plant cell in a hypotonic solution would experience an increase in turgor pressure?

<p>Water enters the cell through osmosis, causing the cell to swell.</p> Signup and view all the answers

In which type of solution would a plant cell maintain its shape and size due to no net movement of water into or out of the cell?

<p>Isotonic solution</p> Signup and view all the answers

What would happen to a plant cell if it were placed in a hypertonic solution and the cell wall were not strong enough to withstand the osmotic pressure?

<p>The cell would swell and lyse.</p> Signup and view all the answers

What is the primary mechanism by which water molecules move from an area of high concentration to an area of low concentration through a selectively permeable membrane?

<p>Osmosis</p> Signup and view all the answers

What would be the effect on a plant cell if it were placed in a hypotonic solution and the cell wall were strong enough to withstand the osmotic pressure?

<p>The cell would swell and lyse.</p> Signup and view all the answers

Study Notes

Cell Membrane

  • The cell membrane is selectively permeable, allowing certain substances to pass through while keeping others out.
  • Selective permeability is crucial for maintaining cellular homeostasis and regulating the exchange of materials between the cell and its environment.
  • This is achieved through a combination of lipid and protein components.

Osmosis

  • Osmosis is the movement of water molecules from an area of high concentration to an area of low concentration through a selectively permeable membrane.
  • There are three types of osmotic environments:
    • Isotonic: equal concentration of solutes inside and outside the cell
    • Hypotonic: lower concentration of solutes outside the cell
    • Hypertonic: higher concentration of solutes outside the cell
  • Osmosis plays a crucial role in maintaining cellular structure and function, as well as regulating the balance of fluids within the body.

Membrane Structure

  • The cell membrane is composed of a phospholipid bilayer, with hydrophilic heads and hydrophobic tails.
  • Phospholipids are arranged in a fluid mosaic model, with proteins and cholesterol molecules embedded within the bilayer.
  • The cell membrane is semi-fluid, allowing for lateral movement of phospholipids and proteins.
  • The structure of the cell membrane allows for the regulation of what enters and leaves the cell, as well as providing mechanical support and protection.

Osmosis

  • Definition: Movement of water molecules from high to low concentration through a selectively permeable membrane
  • Types:
    • Isotonic: Equal solute concentration inside and outside the cell
    • Hypotonic: Higher solute concentration inside the cell
    • Hypertonic: Lower solute concentration inside the cell
  • Effects on cells:
    • Isotonic: No net water movement, cell maintains shape
    • Hypotonic: Water enters cell, causing it to swell
    • Hypertonic: Water leaves cell, causing it to shrink
  • Importance: Maintains cellular balance and regulates cellular activities

Facilitated Diffusion

  • Definition: Passive transport with transport proteins, molecules move down concentration gradient
  • Types of transport proteins:
    • Channel proteins: Form a channel for molecules to pass through
    • Carrier proteins: Bind to molecules and change shape to transport them
  • Characteristics:
    • Specificity: Transport proteins are specific to certain molecules
    • Saturation: Can be saturated if molecule concentration is too high
    • Competition: Multiple molecules compete for the same transport protein
  • Importance: Regulates movement of specific molecules, such as glucose and amino acids, into and out of the cell

Solution in Plant Cells

Osmosis

  • Osmosis is the movement of water molecules from high to low concentration through a selectively permeable membrane
  • Crucial for plant cell growth, development, and survival

Types of Solutions

Hypotonic Solution

  • Lower solute concentration than cell sap
  • Water enters cell through osmosis, causing cell to swell
  • Can cause cell lysis if cell wall is not strong enough

Isotonic Solution

  • Same solute concentration as cell sap
  • No net water movement into or out of cell
  • Cell maintains shape and size

Hypertonic Solution

  • Higher solute concentration than cell sap
  • Water leaves cell through osmosis, causing cell to shrink
  • Can cause cell to shrivel and become flaccid

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