plasma membrane

Meaning

1. 1nouncountablebiology

   The thin flexible barrier around a cell, made mostly of fats and proteins, that decides which substances can pass in or out.

   Grammar: Countable: each cell has one plasma membrane.

   Patterns

   • across the plasma membrane
   • the plasma membrane of a cell

   Oxygen moves easily across the plasma membrane of a red blood cell.

   The plasma membrane keeps the cell's contents separate from its surroundings.

   Proteins embedded in the plasma membrane help carry sugar into the cell.

Word forms

Common combinations

across the plasma membrane

Water moves across the plasma membrane by osmosis.

selectively permeable plasma membrane

A selectively permeable plasma membrane lets only some molecules through.

plasma membrane protein

Each plasma membrane protein has a specific job.

rupture the plasma membrane

Some toxins rupture the plasma membrane and kill the cell.

fluid plasma membrane

Cholesterol keeps the fluid plasma membrane stable.

Synonyms and how they differ

cell membrane

Cell membrane is the everyday term used in schools, while plasma membrane is the more formal, precise phrase in textbooks.

cytoplasmic membrane

Cytoplasmic membrane is an older, rarer term, mostly seen with bacteria.

plasmalemma

Plasmalemma is a specialist word used mostly in plant biology and is rare outside it.

Word family

plasma noun

the fluid inside a cell or part of blood

membrane noun

a thin layer that surrounds or separates parts

membranous adjective

made of or like a thin layer

permeable adjective

allowing liquids or gases to pass through

Commonly confused: plasma membrane or cell wall? plasma membrane or blood plasma?

Practice

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