10 Questions
What is the primary function of the plasma membrane?
To facilitate communication and signalling between cells
What is the thickness of the plasma membrane?
5 to 8 nm
What type of proteins penetrate the phospholipid bilayer and remain permanently attached to the membrane?
Integral proteins
What is the main component of the plasma membrane?
Phospholipids
What type of proteins are temporarily associated with one side of a membrane?
Peripheral proteins
What determines the composition of a membrane protein?
The function of the protein within the cell
What is the primary function of prostaglandins and leukotrienes?
To regulate smooth muscle contractility and immune responses
What is the molecular formula of cholesterol?
C27H46O
What is the result of high levels of cholesterol in the bloodstream?
Deposits of cholesterol and other fatty substances accumulate in the interior walls of the blood vessels
What is the origin of the names of prostaglandins, thromboxanes, and leukotrienes?
The organs where they were first discovered
Study Notes
Plasma Membrane
- The plasma membrane, also known as the cell membrane, separates the interior of the cell from the outside environment.
- It is a double-membraned cell organelle, also called the phospholipid bilayer.
- The plasma membrane is composed of carbohydrates, phospholipids, proteins, and conjugated molecules, and is approximately 5-8 nm in thickness.
- It functions as a physical barrier between the external environment and the inner cell organelles, and is selectively permeable, allowing only certain molecules to move in and out of the cell.
Functions of Plasma Membrane
- Facilitates communication and signaling between cells.
- Enables the movement of molecules across the membrane.
Proteins in Plasma Membrane
Integral Proteins
- Penetrate the phospholipid bilayer to remain permanently attached to the membrane.
- Examples include glycoproteins, ion channels, carrier proteins, and protein pumps.
Peripheral Proteins
- Are temporarily associated with one side of the membrane.
- Can be removed by polar solvents.
- Examples include receptor complexes involved in cell signaling (e.g., G proteins).
Protein Composition
- Determined by its function within the cell.
- Non-polar amino acids (hydrophobic) associate with the lipid bilayer, while polar amino acids (hydrophilic) face aqueous solutions.
- The inner surface of a protein channel is lined with polar amino acids to facilitate the passage of specific polar or charged molecules.
Eicosanoids
- Derived from 20-carbon polyunsaturated fatty acids, typically arachidonic acid.
- Include prostaglandins, leukotrienes, and thromboxanes.
- Regulate many cell functions, including smooth muscle contractility, immune responses, and inflammatory functions.
Cholesterol
- A waxy substance present in blood plasma and all animal tissues.
- Chemically, an organic compound belonging to the steroid family.
- Essential to life; a primary component of the plasma membrane.
- Synthesized by the liver and other organs.
- High levels in the bloodstream contribute to atherosclerosis.
Learn about the structure and composition of the plasma membrane, also known as the cell membrane, and its role in separating the cell interior from the outside environment.
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