Questions and Answers
What type of molecules are hydrophobic?
Hydrophobic molecules can form bonds with water.
False
What term describes molecules that have both hydrophilic and hydrophobic parts?
Amphipathic
Which of the following are the main components of biological membranes?
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Phospholipids are formed from ______ chains of fatty acids and a phosphate group.
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What is the structural characteristic of steroids in biological membranes?
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Integral proteins do not cross the lipid bilayer.
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What type of protein interacts indirectly with the membrane?
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What is the role of glycolipids in membranes?
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The two faces of a cellular membrane are the ______ face and the exoplasmic face.
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Study Notes
Chemical Foundations
- Hydrophobic (non-polar) molecules aggregate due to weak interactions, like Van der Waals forces.
- Non-polar molecules do not bond with water, leading to their insolubility in water.
- Polar molecules can dissolve in water and non-polar solvents like hexane.
Phospholipids
- Phospholipids are amphipathic, containing both hydrophobic (fatty acid chains) and hydrophilic (polar head) regions.
- Form structures in aqueous environments, such as micelles, bilayers, and liposomes.
- Fatty acids can be saturated (no double bonds) or unsaturated (one or more double bonds), affecting the rigidity and flexibility of membranes.
Structure of Membranes
- Phospholipids create organized structures, leading to formations like the lipid bilayer.
- Phosphoglycerols and sphingolipids represent classes of phospholipids, each with distinctive linkages.
- Cholesterol is a sterol that contributes to membrane fluidity and stability, characterized by a hydrocarbon formation of four rings.
Lipid Composition
- Membrane properties depend on specific lipid and protein compositions, including glycoproteins and glycolipids that enhance hydrophilicity and protein stability.
- Relative lipid and protein proportions vary across different membrane types.
Membrane Proteins
- Classifications: Peripheral (loose interaction with membrane) and Integral (span across bilayer).
- Transmembrane proteins have domains that traverse the membrane, often composed of α-helices or multi-stranded β-sheets.
- Peripheral proteins interact indirectly, attaching to the membrane through the lipid polar heads.
Functions of Membrane Proteins
- Integral proteins serve as channels or receptors in cellular signaling and transport.
- Peripheral proteins can play roles in anchoring the cytoskeleton and intracellular signal transduction.
- Membrane proteins define cell boundaries and act as barriers for permeability.
Membrane Structure
- The plasma membrane separates internal cellular environments from external ones.
- Phospholipid bilayer provides a foundational permeability barrier, essential for maintaining homeostasis.
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Description
This quiz covers the chemical foundations of membrane structures, including the behavior of hydrophobic and polar molecules, the unique properties of phospholipids, and the organization of membranes. Learn about micelles, bilayers, and the role of cholesterol in membrane fluidity.
