Cell Membrane
The cell membrane, also called plasma membrane, is a thin selectively permeable boundary that controls movement of substances into and out of the cell.
Practice This ConceptMain explanation
Teacher explanation
The membrane is mainly made of lipids and proteins. It allows some substances to pass more easily than others. Diffusion moves particles from higher to lower concentration, osmosis is diffusion of water through a selectively permeable membrane, and active transport uses energy to move substances against a concentration gradient.
Example
Raisins swell in water because water enters by osmosis through their outer membrane.
Simple analogy
Diffusion is for particles; osmosis is water through a membrane.
Common confusion
Students often write that osmosis is movement of any substance, but osmosis is specifically movement of water through a selectively permeable membrane.
Exam tip
In membrane transport answers, mention the direction of movement and whether energy is needed.
Study the cell membrane diagram carefully
Use the labelled diagram to keep cell membrane clear in short answers and revision.
What this diagram makes clear
This diagram keeps the labels and direction of cell membrane in the right order.
Where this helps in exams
Use this for labelled diagram work and short exam answers on cell membrane.
Revision cue
Revise cell membrane through the labels before writing the answer.
Answer writing and exam use
1-mark use
Write the exact meaning of cell membrane in one clean line.
2-mark use
Define cell membrane and add one example or condition.
3-mark use
Explain cell membrane, show the method or example, and mention the common mistake.
Practice this concept with focused MCQs
Open the concept quiz intro first, review the test details, and then start a focused MCQ set from this concept only. Instant score and answer review are live now.
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