Cell Membrane and Membrane Transport Quiz

Questions and Answers

Describe the structure and components of eukaryotic membranes.

The eukaryotic plasma membrane is a phospholipid bilayer with proteins and cholesterol embedded in it.

Unlike prokaryotic cells, eukaryotic cells have:

A membrane-bound nucleus and numerous membrane-bound organelles.

Describe the general functions of the eukaryotic plasma membrane.

The plasma membrane regulates the concentration of substances that can permeate a cell.

What does hypertonic mean?

It causes a cell to shrink. Signup and view all the answers

What does hypotonic mean?

It causes a cell to swell or expand. Signup and view all the answers

What does isotonic mean?

Cell stays the same. Signup and view all the answers

Relate the 'fluid mosaic model' to membrane structure and function.

The fluid mosaic model describes the cell membrane as a tapestry of several types of molecules that are constantly moving. Signup and view all the answers

Explain how the plasma membrane structure provides selective permeability.

The membrane's lipid bilayer structure provides access control through permeability. Signup and view all the answers

How does cholesterol contribute to the membrane?

Cholesterol contributes to the fluidity of the membrane. Signup and view all the answers

What is the main function of the plasma membrane?

Regulates which materials enter and leave the cell. Signup and view all the answers

Describe how each membrane component contributes to the function of the eukaryotic membrane.

Phospholipids form the basic fabric of the membrane, proteins facilitate transport and signaling, and carbohydrates serve as cellular markers. Signup and view all the answers

What are integral membrane proteins?

Proteins integrated into the membrane with at least one hydrophobic region. Signup and view all the answers

What are peripheral membrane proteins?

Proteins found on the outside and inside surfaces of membranes. Signup and view all the answers

Describe factors affecting membrane fluidity.

The fluid mosaic model helps maintain membrane fluidity, though the membrane can become rigid and burst if penetrated. Signup and view all the answers

How do changes in temperature affect membrane fluidity?

As temperature increases, membrane fluidity increases; at lower temperatures, fluidity decreases. Signup and view all the answers

List and describe key roles/functions of membrane proteins.

Transport, signaling, cell recognition, intercellular joining, and attachment. Signup and view all the answers

Compare and contrast passive and active transport across eukaryotic membranes.

Passive transport does not require energy and moves substances along their concentration gradient, while active transport requires energy to move substances against their gradient. Signup and view all the answers

Describe exocytosis and endocytosis.

Exocytosis is the process of vesicles fusing with the plasma membrane to release substances outside the cell; endocytosis is when cells absorb substances by engulfing them. Signup and view all the answers

Study Notes

Eukaryotic Cell Membrane Structure and Components

Eukaryotic plasma membrane consists of a phospholipid bilayer with embedded proteins and cholesterol.
The membrane is pliable, composed of two adjacent sheets of phospholipids.
Cholesterol enhances membrane fluidity and stability.

Unique Features of Eukaryotic Cells

Eukaryotic cells possess a membrane-bound nucleus.
Numerous membrane-bound organelles such as endoplasmic reticulum, Golgi apparatus, mitochondria, and chloroplasts are present.
Typically contain several rod-shaped chromosomes.

Functions of the Eukaryotic Plasma Membrane

Regulates substance concentration that permeates the cell.
Maintains the internal environment through selective permeability.

Types of Solutions and Their Effects on Cells

Hypertonic: Causes cells to shrink due to water loss.
Hypotonic: Causes cells to swell or expand due to water influx.
Isotonic: Cells maintain their shape and volume.

Fluid Mosaic Model

Describes the membrane as a dynamic structure made of various molecules (phospholipids, cholesterol, and proteins).
Movement of components is crucial for maintaining cellular integrity and acting as a barrier.

Selective Permeability of the Plasma Membrane

The lipid bilayer controls access due to tightly packed phospholipids and a hydrophobic core.
Allows specific molecules to enter or exit, ensuring homeostasis.

Roles of Membrane Components

Phospholipids: Form the basic structure; possess both hydrophilic and hydrophobic properties.
Proteins: Include integral proteins (spanning the membrane) and peripheral proteins (attached to surfaces); facilitate various functions.
Carbohydrates: Located on cell surfaces, attached to proteins/lipids; serve as cellular markers for recognition and immune response.
Membrane Fluidity: Affected by the structure of fatty acid tails in phospholipids; essential for membrane function.

Integral Membrane Proteins

Integrated within the membrane with at least one hydrophobic region anchoring them to the phospholipid bilayer.
Transmembrane proteins extend across the membrane.

Peripheral Membrane Proteins

Located on the outside and inside surfaces of membranes; attached to integral proteins or phospholipids.
More loosely associated, do not penetrate the hydrophobic core.

Factors Affecting Membrane Fluidity

The fluid mosaic model ensures membrane flexibility; integral proteins and lipids allow movement.
Excessive rigidity may cause membrane rupture, particularly with increased internal pressure.

Temperature Influence on Membrane Fluidity

Increased temperature enhances phospholipid bilayer fluidity.
At lower temperatures, phospholipids cluster closely, reducing fluidity due to decreased kinetic energy.

Key Roles of Membrane Proteins

Functions include transport, signaling, cell recognition, intercellular joining, and attachment to the cytoskeleton.

Passive vs. Active Transport

Passive transport: Movement of molecules without energy input (e.g., diffusion, facilitated diffusion).
Active transport: Requires energy to move substances against their concentration gradient (e.g., sodium-potassium pump).

Exocytosis and Endocytosis

Exocytosis: Process through which substances are expelled from a cell in vesicles.
Endocytosis: Mechanism for cells to internalize substances, including nutrients and signaling molecules.

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Description

Test your knowledge on the structure and components of eukaryotic cell membranes with this quiz. Explore details about the phospholipid bilayer, embedded proteins, and the role of cholesterol. Perfect for biology students studying cell biology.