Membrane Structure and Function Chapter 5

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Questions and Answers

What is the definition of a plasma membrane?

A biomembrane separating cell contents from the environment.

What is the structure of the phospholipid bilayer?

Two layers of phospholipids forming the membrane structure.

The term 'amphipathic' refers to molecules having both hydrophilic and hydrophobic regions.

True

What model describes the membrane structure with lipids and proteins in motion?

The fluid-mosaic model. Signup and view all the answers

What is a leaflet in the context of a phospholipid bilayer?

Half of a phospholipid bilayer facing different regions. Signup and view all the answers

What are transmembrane proteins?

Proteins spanning the entire membrane bilayer. Signup and view all the answers

How are lipid-anchored proteins attached to the membrane?

Proteins attached to the membrane via lipid covalent bonds. Signup and view all the answers

What are peripheral membrane proteins?

Proteins loosely bound to the membrane surface. Signup and view all the answers

Lipid molecules are fixed in their positions within the membrane.

False Signup and view all the answers

What is the importance of bilayer fluidity?

Fluidity is essential for cell function and division. Signup and view all the answers

What role does cholesterol play in membrane fluidity?

Cholesterol stabilizes membrane fluidity at varying temperatures. Signup and view all the answers

What is the definition of passive transport?

Movement across membranes without energy input. Signup and view all the answers

What is simple diffusion?

Molecules pass directly through the phospholipid bilayer. Signup and view all the answers

What is facilitated diffusion?

Diffusion aided by transport proteins across membranes. Signup and view all the answers

What is active transport?

Movement against concentration gradient using ATP. Signup and view all the answers

What is osmosis?

Water movement across membranes due to solute gradients. Signup and view all the answers

What is a hypertonic environment?

Causes cells to lose water and shrink. Signup and view all the answers

What is the function of transport proteins in the membrane?

Proteins facilitating movement of specific ions/molecules. Signup and view all the answers

What are channels in the context of membrane transport?

Transmembrane proteins forming passageways for solutes. Signup and view all the answers

What are transporters?

Proteins that bind solutes and change conformation. Signup and view all the answers

What is primary active transport?

Direct energy use to transport solute against gradient. Signup and view all the answers

What is secondary active transport?

Uses existing gradients to drive transport of another solute. Signup and view all the answers

Describe the Na+/K+ pump.

Exports Na+ and imports K+ using ATP. Signup and view all the answers

What is an electrogenic pump?

Generates electrical gradient by exporting positive charge. Signup and view all the answers

Study Notes

Membrane Structure and Function

Plasma membrane: A biomembrane separating a cell's interior from the surrounding environment.
Phospholipid bilayer: The fundamental structure of the membrane, composed of two layers of phospholipids.
Amphipathic: Describes molecules with both hydrophilic (water-loving) and hydrophobic (water-fearing) regions. Phospholipids are amphipathic.
Fluid-mosaic model: Describes the membrane as a dynamic structure with lipids and proteins moving within the bilayer.
Leaflet: One half of a phospholipid bilayer, facing either the interior or exterior of the cell.
Transmembrane proteins: Proteins that span the entire phospholipid bilayer.
Lipid-anchored proteins: Proteins bound to the membrane via covalent attachments to lipids.
Peripheral membrane proteins: Proteins associated with the membrane surface, not embedded within the bilayer.
Semifluid: Refers to the ability of lipid molecules to move laterally within the membrane.
Bilayer fluidity: The membrane's fluidity is crucial for cell function and processes like division.
Cholesterol: A lipid that regulates membrane fluidity within a given temperature range.
Passive transport: Movement of substances across a membrane without the input of energy.
Simple diffusion: The direct passage of small, nonpolar molecules across the phospholipid bilayer.
Facilitated diffusion: Movement of substances through a membrane protein channel, still without energy input.
Active transport: Movement of substances across a membrane against their concentration gradient, requiring energy.
Osmosis: The movement of water across a selectively permeable membrane down its concentration gradient.
Hypertonic environment: A surrounding solution with a higher solute concentration than the cell's interior, causing water to leave the cell.
Hypotonic environment: A surrounding solution with a lower solute concentration than the cell's interior, causing water to enter the cell.
Transport proteins: Proteins embedded within the membrane that facilitate the movement of ions or molecules across.
Channels: Transmembrane proteins that form a channel-like passageway, allowing specific substances to pass through.
Transporters: Proteins that bind to specific solutes and undergo conformational changes to move them across the membrane.
Uniporters: Transporters that move a single type of molecule across the membrane.
Symporters: Transporters that move two types of molecules in the same direction across the membrane.
Antiporters: Transporters that move two types of molecules in opposite directions across the membrane.
Primary active transport: Active transport that directly utilizes ATP to move a solute against its gradient.
Secondary active transport: Active transport using an existing ion gradient to move a second substance against its gradient.
Na+/K+ pump: A primary active transport protein that moves sodium ions out of and potassium ions into a cell.
Electrogenic pump: A pump that generates a voltage across a membrane by transporting ions.

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Description

Test your knowledge on the fundamental concepts of membrane structure and function. This quiz covers key topics such as the plasma membrane, phospholipid bilayer, and various types of membrane proteins. Challenge yourself and enhance your understanding of cellular membranes.