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What is the plasma membrane composed of?
What is the plasma membrane composed of?
A phospholipid bilayer in which proteins are embedded or associated with the cytoplasmic side.
What are the components of the plasma membrane that can function as channels, carriers, receptors, and enzymes?
What are the components of the plasma membrane that can function as channels, carriers, receptors, and enzymes?
Membrane proteins
Phospholipid membranes form bilayers because their _______ heads are attracted to water, while their _______ tails face away from the water.
Phospholipid membranes form bilayers because their _______ heads are attracted to water, while their _______ tails face away from the water.
polar, nonpolar
The hydrophilic heads of phospholipids are exposed to water.
The hydrophilic heads of phospholipids are exposed to water.
The hydrophobic tails associate together and make up the interior of:
The hydrophobic tails associate together and make up the interior of:
Note the plasma membrane's asymmetry.
Note the plasma membrane's asymmetry.
Phospholipids are considered amphipathic molecules.
Phospholipids are considered amphipathic molecules.
What largely explains why phospholipids form a bilayer in water?
What largely explains why phospholipids form a bilayer in water?
Because similar substances associate with one another, what do the hydrophilic polar heads of phospholipid molecules associate with?
Because similar substances associate with one another, what do the hydrophilic polar heads of phospholipid molecules associate with?
The hydrophobic nonpolar tails associate with each other because:
The hydrophobic nonpolar tails associate with each other because:
Proteins that are embedded in the plasma membrane are called:
Proteins that are embedded in the plasma membrane are called:
Proteins that occur only on the cytoplasmic side of the membrane are called:
Proteins that occur only on the cytoplasmic side of the membrane are called:
Fluid-Mosaic Model: Membranes are not rigid but rather are:
Fluid-Mosaic Model: Membranes are not rigid but rather are:
Membranes consist of a variety of molecules, including:
Membranes consist of a variety of molecules, including:
What does the fluid mosaic model represent?
What does the fluid mosaic model represent?
The lipid content of the membrane is responsible for:
The lipid content of the membrane is responsible for:
Cells are flexible because the phospholipid bilayer is fluid.
Cells are flexible because the phospholipid bilayer is fluid.
The greater the concentration of unsaturated fatty acid residues:
The greater the concentration of unsaturated fatty acid residues:
Phospholipids and proteins that have attached carbohydrate chains are called:
Phospholipids and proteins that have attached carbohydrate chains are called:
Glycolipids are:
Glycolipids are:
What are glycoproteins?
What are glycoproteins?
Each cell within an individual has its own 'fingerprint' because:
Each cell within an individual has its own 'fingerprint' because:
Glycolipids and glycoproteins play an important role in:
Glycolipids and glycoproteins play an important role in:
What are channel proteins?
What are channel proteins?
Channel proteins are involved in:
Channel proteins are involved in:
What are carrier proteins?
What are carrier proteins?
What do carrier proteins do?
What do carrier proteins do?
A carrier protein transports sodium and potassium ions across the plasma membrane of:
A carrier protein transports sodium and potassium ions across the plasma membrane of:
Without this carrier protein, nerve impulse conduction would be impossible.
Without this carrier protein, nerve impulse conduction would be impossible.
Cell recognition proteins are:
Cell recognition proteins are:
Cell recognition proteins help the body defend itself against:
Cell recognition proteins help the body defend itself against:
What are receptor proteins?
What are receptor proteins?
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Study Notes
Plasma Membrane Composition
- The plasma membrane consists of a phospholipid bilayer with embedded integral proteins and peripheral proteins associated with the cytoplasmic side.
- Membrane proteins function as channels, carriers, receptors, and enzymes.
Phospholipid Bilayer Characteristics
- Polar heads of phospholipids are attracted to water, while nonpolar tails orient away from water, forming the bilayer structure.
- The hydrophilic heads face external and internal surfaces, while hydrophobic tails form the membrane's interior.
Membrane Asymmetry
- Carbohydrate chains are present on the outside surface, projecting into the extracellular matrix, contributing to the membrane's asymmetry.
Amphipathic Nature of Phospholipids
- Phospholipids have both hydrophilic (water-attracting) and hydrophobic (water-repelling) regions, explaining their bilayer formation in aqueous environments.
Fluid-Mosaic Model
- Membranes are flexible rather than rigid, consisting of varied molecules, including phospholipids, cholesterol, and proteins.
- The fluidity of the membrane is influenced by lipid composition; higher unsaturated fatty acid concentration increases fluidity.
Carbohydrate-Related Molecules
- Glycolipids are lipids with attached carbohydrate chains, crucial for cell identity, synthesized in the Golgi apparatus.
- Glycoproteins are integral membrane proteins featuring carbohydrate chains and also play a role in cellular recognition.
Protein Functions in Membranes
- Integral proteins are embedded in the plasma membrane; peripheral proteins are located only on the cytoplasmic side.
- Channel proteins form passages that allow specific molecules or ions to cross the membrane.
- Carrier proteins transport specific molecules by changing shape after binding the substance.
Importance of Carrier Proteins
- A carrier protein specifically transports sodium and potassium ions essential for nerve impulse conduction, critical for cell signaling and communication.
Cell Recognition Proteins
- Glycoproteins function as cell recognition proteins, identifying the cell as 'self' and aiding in immune defense against pathogens.
Receptor Proteins
- Receptor proteins in the membrane or within the cell bind to substances, initiating metabolic changes within the cell.
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