Podcast
Questions and Answers
What is the effect of cholesterol on membrane fluidity at body temperature?
What is the effect of cholesterol on membrane fluidity at body temperature?
- It alters the permeability of the membrane.
- It decreases fluidity by restraining the movement of phospholipids. (correct)
- It has no effect on the fluidity of the membrane.
- It increases fluidity by allowing phospholipids to pack closely together.
What are lipid rafts primarily enriched with?
What are lipid rafts primarily enriched with?
- Cholesterol and sphingolipids. (correct)
- Phospholipids and proteins.
- Fatty acids and nucleic acids.
- Glycoproteins and glycolipids.
What portion of the proteins in living organisms do integral membrane proteins represent?
What portion of the proteins in living organisms do integral membrane proteins represent?
- 20-30% (correct)
- 40-50%
- 30-40%
- 10-20%
What is a characteristic of integral membrane proteins?
What is a characteristic of integral membrane proteins?
Which type of protein is permanently anchored within the membrane?
Which type of protein is permanently anchored within the membrane?
What technique is used to visualize the surface of a specimen after preparing it with a carbon and platinum coating?
What technique is used to visualize the surface of a specimen after preparing it with a carbon and platinum coating?
How can integral membrane proteins normally be removed from the membrane?
How can integral membrane proteins normally be removed from the membrane?
What is a characteristic of integral polytopic proteins?
What is a characteristic of integral polytopic proteins?
What role do membrane rafts play in cellular processes?
What role do membrane rafts play in cellular processes?
Which interaction allows integral monotopic membrane proteins to associate with membranes?
Which interaction allows integral monotopic membrane proteins to associate with membranes?
Which statement is true regarding the orientation of membrane proteins?
Which statement is true regarding the orientation of membrane proteins?
What are helix bundle proteins primarily associated with?
What are helix bundle proteins primarily associated with?
Which type of integral membrane protein can only attach to one side of the membrane?
Which type of integral membrane protein can only attach to one side of the membrane?
Which of the following is NOT a type of interaction between integral monotopic proteins and cell membranes?
Which of the following is NOT a type of interaction between integral monotopic proteins and cell membranes?
What is the role of Triton X-100 in relation to proteins?
What is the role of Triton X-100 in relation to proteins?
What do transmembrane topology differences refer to?
What do transmembrane topology differences refer to?
How do lipid bilayers with high proportions of unsaturated fatty acid tails compare to those with lower proportions?
How do lipid bilayers with high proportions of unsaturated fatty acid tails compare to those with lower proportions?
What role does cholesterol play in animal cell membranes?
What role does cholesterol play in animal cell membranes?
What factor can bacteria and yeast cells adjust to maintain membrane fluidity?
What factor can bacteria and yeast cells adjust to maintain membrane fluidity?
What does the FRAP technique specifically measure in a cell membrane?
What does the FRAP technique specifically measure in a cell membrane?
What is likely to happen to the diffusion of a membrane protein if it is anchored to the cytoskeleton?
What is likely to happen to the diffusion of a membrane protein if it is anchored to the cytoskeleton?
What distinguishes peripheral membrane proteins from integral membrane proteins?
What distinguishes peripheral membrane proteins from integral membrane proteins?
What treatment can cause peripheral membrane proteins to dissociate from the membrane?
What treatment can cause peripheral membrane proteins to dissociate from the membrane?
Which type of integral membrane protein transports ions across the membrane?
Which type of integral membrane protein transports ions across the membrane?
How does the presence of double bonds in the hydrocarbon tails affect the fluidity of a lipid bilayer?
How does the presence of double bonds in the hydrocarbon tails affect the fluidity of a lipid bilayer?
Which of the following is NOT a function of integral membrane proteins?
Which of the following is NOT a function of integral membrane proteins?
What primarily determines the fluidity of a lipid bilayer at a given temperature?
What primarily determines the fluidity of a lipid bilayer at a given temperature?
What is the role of structural proteins in the context of membrane proteins?
What is the role of structural proteins in the context of membrane proteins?
Which factor contributes to a more viscous and less fluid lipid bilayer?
Which factor contributes to a more viscous and less fluid lipid bilayer?
Where does the assembly of new membrane phospholipids begin?
Where does the assembly of new membrane phospholipids begin?
What is the primary function of flippases in membrane asymmetry?
What is the primary function of flippases in membrane asymmetry?
Why is membrane asymmetry important for the function of membrane proteins like the Na+-K+ pump?
Why is membrane asymmetry important for the function of membrane proteins like the Na+-K+ pump?
Which phospholipids are predominantly transported by flippases?
Which phospholipids are predominantly transported by flippases?
How does asymmetry arise in membranes after new membranes emerge from the ER?
How does asymmetry arise in membranes after new membranes emerge from the ER?
What is the role of floppases in membrane transport?
What is the role of floppases in membrane transport?
What characterizes the composition of biological membranes?
What characterizes the composition of biological membranes?
What happens to membrane proteins during their synthesis and insertion into the membrane?
What happens to membrane proteins during their synthesis and insertion into the membrane?
Flashcards are hidden until you start studying
Study Notes
Cholesterol and Membrane Fluidity
- Cholesterol reduces fluidity at body temperature by stabilizing phospholipid movement.
- At lower temperatures, it increases fluidity by preventing tight packing of phospholipids.
Membrane Heterogeneity
- Cellular membranes exhibit lateral heterogeneity with dynamic domains, including lipid rafts enriched in cholesterol and sphingolipids.
- These lipid rafts play crucial roles in signal transduction, membrane trafficking, cytoskeletal organization, and pathogen entry.
- Membrane domains are conserved across various life forms, indicating their functional significance.
Types of Membrane Proteins
- Integral membrane proteins represent about one-third of proteins in living organisms, permanently anchored within the membrane.
- Peripheral membrane proteins attach temporarily to the lipid bilayer or integral proteins through non-covalent interactions.
- Lipid-anchored proteins are also present as a specialized class of membrane proteins.
Integral Membrane Proteins
- Integral proteins penetrate the lipid bilayer; transmembrane proteins cross entirely, with extracellular and cytoplasmic domains.
- Integral proteins comprise 20-30% of encoded proteins; difficult to isolate due to hydrophobic domains.
- Removal typically requires detergents like SDS (ionic) or Triton X-100 (non-ionic).
Types of Integral Membrane Proteins
- Integral monotopic proteins attach to one side of the membrane; interactions with the bilayer include α-helices, hydrophobic loops, or covalently bound lipids.
- Varieties include bitopic and polytopic transmembrane proteins with unique orientations or structural arrangements.
Membrane Fluidity
- Fluidity is defined by the ease of lipid movement within the bilayer; dependent on hydrocarbon tail composition.
- Shorter fatty acid chains and higher unsaturation increase fluidity; longer chains and fewer double bonds decrease fluidity.
- Cholesterol maintains membrane fluidity in animal cells by stiffening the bilayer while balancing permeability.
Studying Membrane Fluidity
- Fluorescence Recovery After Photobleaching (FRAP) method assesses membrane fluidity by tagging and bleaching fluorescent molecules, tracking their recovery.
- Membrane proteins are generally less mobile than phospholipids; anchoring to the cytoskeleton restricts protein movement.
Membrane Assembly and Asymmetry
- New phospholipids are created in the endoplasmic reticulum (ER) and are initially deposited on the cytosolic side of the membrane.
- Membrane asymmetry originates in the Golgi apparatus through specific enzymes (flippases and floppases) that redistribute phospholipids between leaflets.
- Phosphatidylserine is primarily moved inward, whereas floppases transport choline-derived phospholipids and cholesterol outward.
Functional Importance of Membrane Asymmetry
- Membranes display structural and functional asymmetry; outer and inner surfaces have distinct compositions and functions.
- This asymmetry is vital for electrochemical gradients relevant to processes like the Na+-K+ pump, which maintains cell ion concentrations.
- The orientation of membrane proteins is crucial for their function, as seen in energy-dependent processes involving ATP and ion transport.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
