11 topics with brief reviews: definitions, key facts, and class questions.
Biological membranes are not just a lipid barrier around the cell, but a complex integrative system. In this section, we analyze the architecture of the plasmalemma: how membrane lipids and proteins ensure its fluidity, asymmetry, and selective permeability.
You will study in detail the mechanisms of cellular exchange: from passive and active transport to large-scale processes of endocytosis and exocytosis. The second half of the section is dedicated to molecular «communication». We will analyze the function of membrane and intracellular receptors, as well as signal transduction pathways via second messengers: the adenylate cyclase and inositol phosphate systems, catalytic receptors, and the MAPK cascade.
At colloquia and exams, students are most often failed on signal transduction mechanisms—professors will certainly ask you to draw a diagram of how second messengers work. Understanding these cascades is absolutely essential: this is your future foundation for studying pharmacology, since most drugs act precisely on membrane receptors and ion channels.
Which lipids predominate in biological membranes and why?
The base consists of glycerophospholipids (most often phosphatidylcholine). Due to their pronounced amphiphilicity, they spontaneously form a stable bilayer.
What does the term "transmembrane asymmetry" mean?
This is a structural feature of the membrane where the outer and inner lipid layers differ from each other in the composition of lipids and embedded proteins.
What is the main difference between simple and facilitated diffusion?
Simple diffusion occurs spontaneously through the lipid bilayer without the participation of proteins (this is how gases, water, and alcohol pass). Facilitated diffusion strictly requires carrier proteins (for example, for glucose transport).
What is the main feature of secondary active transport?
In secondary active transport, the carrier does not cleave ATP independently. Energy is derived from the concentration gradient of another substance previously established by other pumps using ATP.
In which membrane regions does substance binding occur during endocytosis?
The binding of transported macromolecules occurs in specialized regions of the plasma membrane called coated pits.
What is the difference between the effects of intracellular and membrane receptors?
Intracellular receptors (for steroid and thyroid hormones) produce a slow but prolonged effect. Membrane receptors (for peptide hormones) provide a rapid but short-lived response.
Master the entire topic in the "Biochemistry" course
This is a summary. The course covers everything tested in classes and exams.
3,616 pages of study guides on all topics
Assignments and quizzes after every topic — just like in a colloquium