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What is the primary function of the cell membrane?
What is the primary function of the cell membrane?
Which of the following best describes the structure of the cell membrane?
Which of the following best describes the structure of the cell membrane?
Which type of lipid is NOT found in the cell membrane?
Which type of lipid is NOT found in the cell membrane?
What characteristic of phospholipids is critical for the membrane's function?
What characteristic of phospholipids is critical for the membrane's function?
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How does cholesterol contribute to the cell membrane?
How does cholesterol contribute to the cell membrane?
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What role does the cell membrane play in transportation?
What role does the cell membrane play in transportation?
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The term 'plasma membrane' refers to which of the following?
The term 'plasma membrane' refers to which of the following?
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Which statement is NOT a characteristic of a cell membrane?
Which statement is NOT a characteristic of a cell membrane?
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What is the primary role of transport proteins in the cell membrane?
What is the primary role of transport proteins in the cell membrane?
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Which type of protein is responsible for transmitting messages to the cell's exterior?
Which type of protein is responsible for transmitting messages to the cell's exterior?
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Which model describes the cell membrane as a two-dimensional liquid where lipids and proteins can move freely?
Which model describes the cell membrane as a two-dimensional liquid where lipids and proteins can move freely?
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What are glycoproteins primarily involved in within the cell membrane?
What are glycoproteins primarily involved in within the cell membrane?
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What makes up approximately 50% of the cell membrane's composition?
What makes up approximately 50% of the cell membrane's composition?
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Which of the following is NOT a characteristic of structural proteins in the cell membrane?
Which of the following is NOT a characteristic of structural proteins in the cell membrane?
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What is the primary chemical composition of carbohydrates found in the cell membrane?
What is the primary chemical composition of carbohydrates found in the cell membrane?
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What aspect of the Davson-Danielli Model emphasizes how lipids arrange themselves?
What aspect of the Davson-Danielli Model emphasizes how lipids arrange themselves?
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Study Notes
Cell Membrane
- The cell membrane is an organelle found in all cells
- It selectively controls the entrance and exit of substances
- Functions of the cell membrane include protection, support, and transport.
Cell Membrane: Characteristics
- Also known as the plasma membrane
- A biological membrane separating the cell's interior from its environment
- A semi-permeable membrane, filtering substances into and out of the cell
- Contains bead-like structures embedded within it
- Coined by C. Nageli and C. Cramer in 1855
Cell Membrane: Functions
1. Protection and Support
- Keeps the cell intact
- Maintains the cell's shape and form
- Acts as a barrier that protects the cell from foreign substances
2. Acts as a Receptor
- A binding mechanism for the cell
- Receives chemical signals from the environment
3. Transportation of Materials
- Regulates the entrance and exit of substances (gases, sugar, amino acids, ions)
- Acts as a medium for nutrients entering and waste exiting the cell
Cell Membrane: Structure
- Composed of a phospholipid bilayer, proteins, and carbohydrates
- Phospholipids have a hydrophilic head and hydrophobic tail. This structure is important to membrane permeability.
- Cholesterol is a lipid that helps maintain membrane fluidity.
- Proteins are embedded within the phospholipid bilayer and perform various functions (structural, transport, receptor).
- Glycoproteins are carbohydrates attached to proteins on the external surface and play a part in receiving/transmitting signals.
Cell Membrane: Chemical Composition
1. Lipids
- Main components of the membrane
- Include phospholipids, glycolipids, sphingolipids, and sterols.
2. Proteins
- 50% of the membrane
- Include structural, transport, receptor, and enzyme proteins.
3. Carbohydrates
- Sugars attached to proteins (glycoproteins) or lipids (glycolipids)
- Primarily located on the outer surface of the membrane and help in cell signaling.
Cell Membrane: Models
1. Davson-Danielli Model (1935)
- Also known as the sandwich model
- Proposes a membrane structure with a lipid bilayer sandwiched between protein layers.
- The polar heads of phospholipids face outwards.
2. Fluid-Mosaic Model (1972)
- The most widely accepted model
- Proposes a fluid, dynamic membrane where lipids and proteins move laterally.
- Lipids and proteins are embedded in the phospholipid bilayer, and the polar heads of the phospholipids face outwards.
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Description
This quiz explores the essential functions and characteristics of the cell membrane, also referred to as the plasma membrane. It highlights its role in protection, support, and selective transport of substances. Test your understanding of its structure and significance in cellular biology.
