biology

Transmembrane channels

Transmembrane channels is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Transmembrane channels rather than just read about it. In short: Transmembrane channels, also called membrane channels, are pores within a lipid bilayer. The channels can be formed by protein complexes that run across the membrane or by peptides.

Key takeaways

Transmembrane channels belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Transmembrane channels to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Transmembrane channels from memory before moving on to harder problems.

Reference excerpt

Transmembrane channels, also called membrane channels, are pores within a lipid bilayer. The channels can be formed by protein complexes that run across the membrane or by peptides. They may cross the cell membrane, connecting the cytosol, or cytoplasm, to the extracellular matrix. Transmembrane channels are also found in the membranes of organelles including the nucleus, the endoplasmic reticulum, the Golgi apparatus, mitochondria, chloroplasts, and lysosomes. Transmembrane channels differ from transporters and pumps in several ways. Some channels are less selective than typical transporters and pumps, differentiating solutes primarily by size and ionic charge. Channels perform passive transport of materials also known as facilitated diffusion. Transporters can carry out either passive or active transfer of materials while pumps require energy to act. There are several modes by which membrane channels operate. The most common is the gated channel which requires a trigger, such as a change in membrane potential in voltage-gated channels, to unlock or lock the pore opening. Voltage-gated channels are critical to the production of an action potential in neurons resulting in a nerve impulse. A ligand-gated channel requires a chemical, such as a neurotransmitter, to activate the channel. Stress-gated channels require a mechanical force applied to the channel for opening. Aquaporins are dedicated channels for the movement of water across the hydrophobic interior of the cell membrane. Ion channels are a type of transmembrane channel responsible for the passive transport of positively charged ions (sodium, potassium, calcium, hydrogen and magnesium) and negatively charged ions (chloride) and, can be either gated or ligand-gated channels. One of the best studied ion channels is the potassium ion channel. The potassium ion channel can allow rapid movement of potassium ions while being selective against sodium. Using X-ray diffraction data and atomic model computations a likely structure of the channel consists of a number of protein alpha-helixes forming an hourglass shaped pore with the narrowest point halfway through the membrane's lipid bilayer. To move through the channel the potassium ions must shed their aqueous matrix and enter a selectivity filter composed of carbonyl oxygens. The potassium ions pass through one atom at a time along five different cation (positively charged ion) binding sites. Diseases caused by ion channel malfunctions include cystic fibrosis where the channel for the chloride ion will not open or is missing in the cells of the lungs, intestine, pancreas, liver and skin. The cells can no longer regulate salt and water concentrations resulting in the symptoms typical of the disease. Additional disorders resulting from malfunctions in ion channels include forms of epilepsy, cardiac arrhythmia, certain types of periodic paralysis and ataxia.

References

Worked examples

Example 1 — a first encounter with Transmembrane channels

Start with the simplest possible case. Write down what Transmembrane channels claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Transmembrane channels before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Transmembrane channels ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Transmembrane channels

In research: Transmembrane channels appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Transmembrane channels in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Transmembrane channels is common in secondary-school and first-year university syllabi. It links to neighbouring topics Membrane biology, Transmembrane proteins, so understanding it makes those chapters shorter.
In everyday life: Look for Transmembrane channels outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Transmembrane channels in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Transmembrane channels means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Transmembrane channels out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Transmembrane channels in simple terms?

Transmembrane channels, also called membrane channels, are pores within a lipid bilayer. The channels can be formed by protein complexes that run across the membrane or by peptides.

Why does Transmembrane channels matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Transmembrane channels?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Transmembrane channels.