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Questions and Answers
Which characteristic of phospholipids is most responsible for their spontaneous assembly into bilayers?
Which characteristic of phospholipids is most responsible for their spontaneous assembly into bilayers?
- The presence of glycerol backbone
- The presence of phosphate groups
- Their high molecular weight
- Their amphiphilic nature (correct)
The two leaflets of the plasma membrane always maintain a symmetrical distribution of phospholipids to ensure uniform membrane properties.
The two leaflets of the plasma membrane always maintain a symmetrical distribution of phospholipids to ensure uniform membrane properties.
False (B)
Briefly explain how the presence of cholesterol affects the fluidity of an animal cell membrane at different temperatures.
Briefly explain how the presence of cholesterol affects the fluidity of an animal cell membrane at different temperatures.
Cholesterol acts as a fluidity buffer, reducing fluidity at high temperatures and preventing rigidification at low temperatures.
In plant cells, the structural strength provided in addition to the plasma membrane is from a carbohydrate-based cell __________.
In plant cells, the structural strength provided in addition to the plasma membrane is from a carbohydrate-based cell __________.
Match the following lipids with their primary function or characteristic within cell membranes:
Match the following lipids with their primary function or characteristic within cell membranes:
Which of the following factors contributes most significantly to the formation of lipid rafts within the plasma membrane?
Which of the following factors contributes most significantly to the formation of lipid rafts within the plasma membrane?
Saturated fatty acid tails in phospholipids increase membrane fluidity due to their inability to pack tightly together.
Saturated fatty acid tails in phospholipids increase membrane fluidity due to their inability to pack tightly together.
Explain how the asymmetric distribution of phospholipids in the plasma membrane leaflets contributes to cell signaling.
Explain how the asymmetric distribution of phospholipids in the plasma membrane leaflets contributes to cell signaling.
The presence of a cis double bond in the unsaturated fatty acid tail of a phospholipid introduces a __________ in the tail, enhancing membrane fluidity.
The presence of a cis double bond in the unsaturated fatty acid tail of a phospholipid introduces a __________ in the tail, enhancing membrane fluidity.
How do plant cells compensate for the lack of cholesterol in their plasma membranes to maintain membrane integrity?
How do plant cells compensate for the lack of cholesterol in their plasma membranes to maintain membrane integrity?
Which of the following is the MOST direct consequence of amphotericin B and nystatin binding to ergosterol in fungal cells?
Which of the following is the MOST direct consequence of amphotericin B and nystatin binding to ergosterol in fungal cells?
The endoplasmic reticulum (ER) membrane is initially asymmetric, and this asymmetry is directly inherited by the plasma membrane.
The endoplasmic reticulum (ER) membrane is initially asymmetric, and this asymmetry is directly inherited by the plasma membrane.
Briefly explain how the amphiphilic nature of phospholipids drives the self-assembly of lipid bilayers in aqueous environments.
Briefly explain how the amphiphilic nature of phospholipids drives the self-assembly of lipid bilayers in aqueous environments.
In the fluid mosaic model, the 'fluid' aspect refers to the ability of membrane components to move _________ within the plane of the membrane.
In the fluid mosaic model, the 'fluid' aspect refers to the ability of membrane components to move _________ within the plane of the membrane.
Match each antifungal drug with its mechanism of action:
Match each antifungal drug with its mechanism of action:
Which of the following lipid components is predominantly found in the outer leaflet of the plasma membrane?
Which of the following lipid components is predominantly found in the outer leaflet of the plasma membrane?
The presence of cholesterol in the plasma membrane always decreases membrane fluidity, regardless of temperature.
The presence of cholesterol in the plasma membrane always decreases membrane fluidity, regardless of temperature.
Describe a specific function of membrane proteins that contributes to cell communication or interaction with the external environment.
Describe a specific function of membrane proteins that contributes to cell communication or interaction with the external environment.
The conversion of a symmetric ER membrane into an asymmetric plasma membrane involves the action of enzymes called _________ that selectively transfer specific phospholipids to different leaflets.
The conversion of a symmetric ER membrane into an asymmetric plasma membrane involves the action of enzymes called _________ that selectively transfer specific phospholipids to different leaflets.
Which of the following BEST explains why ergosterol is an effective target for antifungal drugs?
Which of the following BEST explains why ergosterol is an effective target for antifungal drugs?
Which of the following characteristics distinguishes integral membrane proteins from peripheral membrane proteins?
Which of the following characteristics distinguishes integral membrane proteins from peripheral membrane proteins?
Black membranes are spherical vesicles used to study the motion of individual lipid molecules.
Black membranes are spherical vesicles used to study the motion of individual lipid molecules.
What is the primary function of cellulose in the plant cell wall, and what property does it provide?
What is the primary function of cellulose in the plant cell wall, and what property does it provide?
The structural rigidity of the plant cell wall allows for the generation of a large internal pressure known as ______ pressure.
The structural rigidity of the plant cell wall allows for the generation of a large internal pressure known as ______ pressure.
Match the following components of the plant cell wall with their primary function:
Match the following components of the plant cell wall with their primary function:
What would happen to a plant cell without a cell wall when placed in a hypotonic solution?
What would happen to a plant cell without a cell wall when placed in a hypotonic solution?
Which of the following is NOT a component of the plant cell wall?
Which of the following is NOT a component of the plant cell wall?
Animal cells possess a cell wall that provides structural support and prevents them from bursting in hypotonic environments.
Animal cells possess a cell wall that provides structural support and prevents them from bursting in hypotonic environments.
Describe the role of turgor pressure in plant cell expansion, especially during growth.
Describe the role of turgor pressure in plant cell expansion, especially during growth.
Liposomes are ______ vesicles that form spontaneously from phospholipids in water and are useful for studying membrane properties.
Liposomes are ______ vesicles that form spontaneously from phospholipids in water and are useful for studying membrane properties.
Flashcards
Plasma Membrane
Plasma Membrane
The outer boundary of a cell, composed mainly of phospholipids and proteins.
Phospholipids
Phospholipids
Lipids with a polar head and two non-polar tails, forming the main structure of cell membranes.
Lipid Bilayer Formation
Lipid Bilayer Formation
The spontaneous assembly of phospholipids into a double-layered structure in water.
Membrane Fluidity
Membrane Fluidity
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Lipid Rafts
Lipid Rafts
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Membrane Asymmetry
Membrane Asymmetry
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Sterols
Sterols
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Amphipathic
Amphipathic
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Phosphoglycerides
Phosphoglycerides
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Sphingolipids
Sphingolipids
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Ergosterol
Ergosterol
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Amphotericin B & Nystatin
Amphotericin B & Nystatin
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Miconazole & Lamisil
Miconazole & Lamisil
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Self-Assembly of Phospholipid Membranes
Self-Assembly of Phospholipid Membranes
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Fluid Mosaic Model
Fluid Mosaic Model
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ER membrane (symmetric)
ER membrane (symmetric)
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Functions of Membrane Proteins
Functions of Membrane Proteins
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Membrane Proteins
Membrane Proteins
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Molecular transport (Membrane Proteins)
Molecular transport (Membrane Proteins)
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Peripheral Membrane Proteins
Peripheral Membrane Proteins
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Integral Membrane Proteins
Integral Membrane Proteins
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Liposomes
Liposomes
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Black Membranes
Black Membranes
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Plant Cell Wall
Plant Cell Wall
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Cellulose
Cellulose
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Pectin
Pectin
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Turgor Pressure
Turgor Pressure
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Osmosis in Plant Cells
Osmosis in Plant Cells
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Transmembrane proteins
Transmembrane proteins
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Study Notes
- Cells are enclosed by the plasma membrane, mainly made of phospholipids and sterols (like cholesterol in animal cells).
- Phospholipids form bilayers spontaneously, making up the base structure of cellular membranes.
- Lipid bilayers are two-dimensional fluids, allowing lateral movement of components; the plasma membrane includes microdomains (lipid rafts) with various compositions.
- The two leaflets of the plasma membrane differ in phospholipid distribution.
- The plasma membrane is linked to a variety of proteins that perform vital tasks.
- Plant cells have cell walls made of carbohydrates for extra structural support.
Phospholipids and Membranes
- The most common lipids are phospholipids.
- Phospholipids are amphiphilic (or amphipathic) because they contain a polar head and two non-polar hydrocarbon tails.
- One tail is saturated (no double bonds), and another is unsaturated (one cis double bond), increasing fluidity.
Sterols and Membranes
- Sterols are another important lipid that membranes contain.
- Sterols have firm ring-like structures which stiffen phospholipids and are necessary for a strong membrane.
- Cholesterol is a major sterol in animal cells. Phytosterols in plant cells, and ergosterol in fungi.
Ergosterol and Antifungal Drugs
- Ergosterol is a target for antifungal drugs since it is in fungi, but not animals.
- Amphotericin B and nystatin target ergosterol specifically, and create ion pores allowing ions to exit the cell.
- Miconazole and lamisil prevent ergosterol synthesis, stopping growth.
Self-Assembly of Phospholipid Membranes
- Phospholipids are capable of self-assembling into bilayers because they are amphiphilic.
- The outside part of the polar head grouping connect to water.
- The hydrocarbon tails attach to one another on its inside.
The Fluid Mosaic Model
- Features of the plasma membrane use the fluid mosaic model to describe it.
Membrane Asymmetry
- Phosphatidylcholine, sphingomyelin, and ganglioside are asymmetrically distributed on the extracellular space of the plasma membrane.
- Phosphatidylethanolamine and phosphatidylserine are asymmetrically distributed on the cytosolic side of the plasma membrane.
Membrane Proteins
- Plasma membranes contain both lipids and proteins.
- Proteins carry out different tasks including molecular transport, signal transduction, cytoskeleton anchoring, and interaction with other tissues or cells.
- Proteins can be peripheral (connected to the membrane surface) or integral (inserted into the membrane).
- Integral membrane proteins may transverse both leaflets via a transmembrane zone, or become fixed via connection of lipid clusters and insert it into one leaflet.
Studying Lipid Membrane Properties
- Artificial lipid bilayers may have characteristics studied by Scientist in a lab.
- Liposomes are vesicles that are spherical and form from phospholipids naturally in water. Size is determined by lipid concentration and type of phospholipids used.
- Black membranes are planar lipid bilayers created over a hole existing in a separate area between 2 aqueous areas.
- Lipid movement can be studied using black membranes.
Plant Cell Wall
- All plant cells are encased in a carbohydrate matrix known as the plant cell wall.
- The plant cell wall is external and separate from the plasma membrane.
- Cellulose, which gives tensile strength equal to steel, is the plant cell wall's primary element and is a glucose polymer.
- Interwoven with cellulose microfibrils is pectin, a polysaccharide mix that gives resistance to compression.
- Lignin (for waterproofing) and additional cross-linking polysaccharides are further constituents.
Turgor Pressure
- Turgor pressure is the substantial internal pressure produced by rigid plant walls.
- Water goes into cell through osmosis because the intracellular environment has surplus solutes.
- A cell wall prevents cell swelling and bursting, because cells lacking a cell wall will swell.
- Cell walls provide swelling resistance, even at 10+ atmospheres of hydrostatic pressure.
- Plants remain stiff and expand cells during growth because of rigidity.
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Description
Explore cell membrane structure, phospholipid assembly, and cholesterol's role in membrane fluidity. Understand lipid distributionas well as the function of lipid rafts. Learn about plant cell walls and the influence of fatty acid tails and phospholipid asymmetry in cell signaling.
