The plasma membrane is more than a border around a cell: it controls exchange with the environment and helps cells communicate and identify one another. This lesson explores how membrane functions support cells and how specific recognition sites can also be exploited by viruses.
The plasma membrane defines the boundary of a cell and regulates its contact with the environment. Cells exclude some substances, take in others, and release waste or other materials in controlled quantities. This selective exchange helps the cell maintain conditions needed for its activities.
All flashcards
What does the plasma membrane do as a selective boundary?
It defines the cell’s boundary and regulates which substances enter, leave, or are excluded, helping the cell manage its interactions with the environment.
What are cell-surface markers used for?
They help cells recognize one another. This supports the formation of tissues and organs and contributes to immune recognition of self versus non-self.
What is a membrane receptor?
A receptor is a specific attachment site that binds a particular substance, such as a hormone or neurotransmitter, and may trigger a response inside the cell.
How can viruses enter specific kinds of cells?
Some viruses have surface molecules that mimic the normal binding partners of host-cell receptors. Binding to compatible sites can enable the virus to enter particular cells.
How can HIV variation affect antibody recognition?
HIV mutates rapidly, changing some surface recognition sites. Antibodies that recognize earlier viral forms may not recognize new variants as effectively.
Quiz questions
According to the fluid mosaic model, how can membrane components move while the membrane remains intact?Answer: They diffuse laterally within the membrane while its overall integrity is maintained.
Which statement distinguishes integral proteins from peripheral proteins?Answer: Integral proteins are embedded in the membrane; peripheral proteins attach to its surface.
What is one role of cholesterol in an animal plasma membrane?Answer: It helps regulate membrane fluidity, and its abundance can vary with temperature.
What distinguishes a glycoprotein from a glycolipid?Answer: A glycoprotein has carbohydrate attached to protein; a glycolipid has carbohydrate attached to lipid.
What is the typical thickness of a plasma membrane?Answer: About 5–10 nm.
Based on Concepts of Biology by Samantha Fowler, Rebecca Roush, James Wise (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.