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Why do phospholipids spontaneously form lipid bilayers?

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Wize University Biology Textbook > The Plasma Membrane

Components and Structure

5 Activities

Why do phospholipids spontaneously form lipid bilayers?
More Components and Structure Questions:
Practice: Membrane Proteins
Which part of the integral membrane protein shown below would be composed of hydrophobic amino acids?
Write a point form essay outline for the following prompt:
Describe three ways in which proteins can associate with a membrane, and give an example of a specific type of protein for each category. What does that protein do? How is the function of the protein related to its association with the membrane?
Thesis statement:
Transmembrane proteins have domains which span across a lipid membrane. These domains typically consist of multiple α\alpha-helices, or β\beta-sheets arranged in a barrel shape. These secondary structures are formed via hydrogen bonding. The interior of the membrane is composed of hydrophobic lipid tails which do not normally associate with the polar molecules involved in hydrogen bonds. Explain how this apparent paradox is resolved.
model
What is the name of the model that... "places membrane proteins as being embedded within the membrane and on the surface of the membrane?"
Which of the following will decrease the membrane fluidity of a cell?
Practice: Membrane Proteins
Which part of the integral membrane protein shown below would be composed of hydrophobic amino acids?
Phospholipids are _________________ molecules, with a _________________ head group and ______________ tails.
The bilayer formation of phospholipids is stabilized primarily by:
Water molecules:
i. Are large ionic molecules
ii. Are small polar molecules
Choose the correct statements regarding the cell membrane
i. They allow certain molecules to enter and exit the cells
ii. They allow all molecules to enter and exit the cell
Membrane Proteins
Which statement is FALSE about membrane proteins?
Classification of lipids
A term meaning the compound contains both hydrophobic and hydrophilic elements
model
What is the name of the model that... "places membrane proteins as being embedded within the membrane and on the surface of the membrane?"
Membrane Fluidity
Which statement BEST describes what happens to phospholipids in the bilayer at higher temperatures?
Membrane Characteristics
Which statement best describes the fluid mosaic model?
Which part of the integral membrane protein shown below would be composed of hydrophobic amino acids?
If a cell was mutated so that it was suddenly only able to produce saturated fatty acids, how would you expect the fluidity of the cell membrane to change?
A certain ligand is known to be able to bind to multiple cell surface receptors. However, once it binds to any one of its receptors, it requires a lot of energy to dissociate the ligand from the receptor. What can you say about this ligand?
Which of the following would result in a highly impermeable membrane?
Consider the following structure of a typical steroid hormone:
Why do steroids have fast acting activities in cells? (ie. treating cells with steroids results in relatively fast responses)
Why does increasing temperature increase the spontaneous transport of molecules through the membrane?
Consider the following molecules:
1. CO2 gas
2. Benzene (6 Carbon ring)
Practice: Permeability
Rank from most permeable to least permeable:
1. Membrane made of all saturated fatty acids
2. Membrane made of 1/2 saturated and 1/2 unsaturated fatty acids
Practice: Membrane Transport 4
Predict the permeability for the following molecules to cross the plasma membrane from highest to lowest.
Membrane Permeability
Place the following compounds under the appropriate category on their ability to cross a phospholipid bilayer: Fast, Slow, Can't Cross.
A mesophile with a mutation in the promoter of the desaturase gene is grown at low temperatures. What would be the phenotype of this membrane?
Which of the following is true of unicellular organisms at high temperatures?
You are a scientist studying the lipid bilayer of mammalian cancer cells. You find that certain melanoma (skin cancer) cells have a higher expression level of an enzyme that is responsible for adding C=C (carbon-carbon double bonds) to the tails of fatty acid chains. How is this likely to change the membrane of melanoma cells as compared to healthy, non-cancerous cells?
Which of the following lipids is NOT a major component of cell membranes?
Practice: Membrane Fluidity
Which of the following will decrease the membrane fluidity of a cell?
Which of the following would act to increase membrane fluidity at high temperatures?
What is the effect of cholesterol on a lipid bilayer?
Which type of phospholipid movement uses an enzyme?
On a lipid membrane, what fatty acid chains would most favor high fluidity?
Which of the following statements are false?
Which of the following would span the entire plasma membrane?
What is the effect of cholesterol on a lipid bilayer?
Which of the following would successfully pass through a phospholipid bilayer (with no transport proteins) at the slowest rate?
Fill in the blank: A phospholipid molecule with much longer acyl chains is considered ___________ compared to a phospholipid with shorter acyl chains.
How would the passage of small uncharged polar molecules across a phospholipid bilayer be described?
What is the role of cholesterol in the plasma membrane?
Why is the plasma membrane (PM) structure referred to as the "fluid mosaic model"?
In your own words, explain how cholesterol modulates membrane fluidity.
Membrane Proteins
Determine whether the following lipids will spontaneously form a lipid bilayer or micelle (Enter bilayer or micelle as your answer)
when placed in an aqueous solution. Explain your answers.
Make a domain map of each protein shown in the figure below, and predict how each would look in a hydropathy plot. Label the N terminus and C terminus, as well as the relative location of any signal sequences.
Make a protein domain map/diagram based on the following hydropathy plot. Label any start/stop transfer sequences, and indicate the localization of each domain (membrane, cytosol, or ER lumen).
Transmembrane proteins have domains which span across a lipid membrane. These domains typically consist of multiple α\alpha-helices, or β\beta-sheets arranged in a barrel shape. These secondary structures are formed via hydrogen bonding. The interior of the membrane is composed of hydrophobic lipid tails which do not normally associate with the polar molecules involved in hydrogen bonds. Explain how this apparent paradox is resolved.
Write a point form essay outline for the following prompt:
Describe three ways in which proteins can associate with a membrane, and give an example of a specific type of protein for each category. What does that protein do? How is the function of the protein related to its association with the membrane?
Thesis statement:
Membrane Proteins
Explain the purpose of flippase and scramblase. Why are these enzymes necessary (i.e. why can’t the process that they control be passive)?
Membrane Proteins
Explain why membrane sterols (e.g. cholesterol) have different effects on membrane fluidity at different temperatures.
Membrane Proteins
List 3 functions of the plasma membrane. Explain how different components of the plasma membrane contribute to each function.
Membrane Proteins
Explain why the plasma membrane is referred to as a “fluid mosaic”.