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Questions and Answers
Which scientist proposed the lipid bilayer model that includes proteins adhering to lipid-aqueous interfaces?
What is the main role of liposomes in biological studies?
In the unit membrane model proposed by Robertson, what comprises the central layer of plasma membranes?
What does the fluid mosaic model recognize about the arrangement of lipids and proteins?
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Which of the following is NOT a major function of lipids?
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What type of molecules can form channels for ions in membranes?
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Which component is NOT part of glycerophospholipids?
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Which statement is true regarding the nonpolar/hydrophobic regions of integral proteins?
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What is the primary function of the nucleolus?
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Which structure surrounds the nucleolus and is formed of newly transcribed ribosomal RNA?
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What significant change occurs in the Rdna intergenic region during the evolution from anamniotes to amniotes?
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How can the Nucleolus Organizer Region (NOR) be identified in a cell?
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Which of the following is NOT a function of the nucleolus?
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What property of membranes makes them highly selective barriers?
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What is the role of liposomes in biological research?
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Which of the following accurately describes the function of channels and pumps in membranes?
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What effect do cis double bonds have on membrane fluidity?
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How does the length and saturation of hydrocarbon chains affect membrane fluidity?
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What is electrical polarization of a plasma membrane typically at rest?
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What happens to the lipid bilayer above the transition temperature?
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What is one of the key functions of membranes in terms of energy conversion?
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What is the primary mechanism for the bulk ingestion of solid materials by cells?
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Which type of endocytosis is induced by proteins, amino acids, and certain ions?
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What role does ATP play in the process of endocytosis?
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Which cells primarily perform phagocytosis as a defense mechanism?
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What is the structure that separates the two membranes of the nuclear envelope?
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What is the diameter of the nuclear pore complex (NPC)?
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What is the function of the fibrous lamina associated with the inner membrane of the nuclear envelope?
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Which types of molecules can freely pass through the nuclear pore complex?
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What is the approximate maximum mass of macromolecules that can passively diffuse across the nuclear pore complex (NPC)?
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What are the nuclear localization sequences (NLSs) necessary for?
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Which of the following is considered a cargo for export from the nucleus?
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What do the filaments of the nuclear basket help to extend into?
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Which of the following describes the primary function of the nucleolus?
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What is a characteristic component of the nucleolus that stains lightly?
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Which transport factor is also known as CRM1?
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What role does turgor pressure play in plants?
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Which component of the nucleolus is not primarily responsible for rRNA synthesis?
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Which correctly describes water potential in plants?
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How does active transport differ from passive transport?
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What is the main source of energy for active transport in cells?
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Which example illustrates passive transport?
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Facilitated diffusion requires which of the following?
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What conditions apply to water movement based on water potential?
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Which of the following correctly defines pressure potential?
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Study Notes
Theories on Membrane Structures
- 1902, membranes were thought to consist only of lipids (Overton)
- 1926, Gorter and Grendell proposed that lipids form a double layer
- 1935, Danielli and Davson proposed a lipid bilayer model including proteins adhering to both lipid-aqueous interfaces
- Artificial model systems (liposomes) supported the Danielli-Davson model
- Droplets of lipid in organic solvent can be spread over a small hole to study biophysical properties of a bilayer (e.g. permeability and electrical resistance)
- Channels for ions can be formed by adding proteins or polypeptides
- Liposomes are effective carriers for molecules like chemotherapy drugs, insulin, and antibodies
Unit Membrane Model
- Robertson (1959) proposed the unit membrane model
- This model suggests the central layer of plasma membranes is made up of lipid hydrocarbon chains, with proteins forming dense surrounding layers
- A simplified model, as it cannot account for the number of proteins across membranes
Fluid Mosaic Model
- Singer and Nicolson (1972) proposed the fluid mosaic model
- The model describes lipids and proteins in a mosaic arrangement
- Lipids and proteins can move laterally within the lipid bilayer
- Non-covalent interactions create a fluid-like state for membranes
Key Concepts
- Major functions of lipids: energy storage, membrane components
- Other functions of lipids: signals, electron carriers, emulsifying agents
- Membrane lipids (amphipathic): responsible for the spontaneous formation of lipid bilayers
- Glycerophospholipids: glycerol backbone + 2 fatty acyl tails + polar head group
- Sphingolipids: sphingosine backbone + fatty acid chain + carbohydrate or phosphate ester
- Cholesterol: affects membrane fluidity
- Membrane fluidity depends on lipid composition (chain length, double bonds, cholesterol content)
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Description
Explore the evolution of theories regarding membrane structures from the early 1900s to modern models. This quiz covers significant contributions by scientists such as Overton, Gorter, Grendell, Danielli, Davson, and Robertson. Test your knowledge on lipid bilayers and their applications in biophysics and medicine.