Cell Membrane Video Player 00:0001:54 Show Transcript The cell membrane, also known as the plasma membrane, is found in all cells. Both prokaryotes and eukaryotes have a cell membrane, and some will also have a cell wall. The purpose of the cell membrane is to help the cell maintain homeostasis by regulating what enters and leaves the cell to help keep a stable, internal environment. The cell membrane also helps to protect the cell. The cell membrane is known as selectively permeable as it only allows some things to enter and leave. The cell membrane is actually a complex assortment of proteins, lipids, and carbohydrates. It is composed of a phospholipid bilayer which consists of hydrophilic (or water-loving) heads and hydrophobic (water-hating) tails There are also many imbedded proteins which also help in the transport of larger molecules through the membrane. Small items like ions and water can pass freely from areas of higher concentration to lower concentration through the membrane by diffusion and osmosis. Larger molecules need a larger protein channels to pass, and many circumstances require energy, or ATP, to help large molecules or smaller ones pass against the concentration gradient. The cell membrane is vital all cells to help regulate and maintain conditions necessary for stability and survival. Close Question 1 The ___ ___ is responsible for maintaining homeostasis within any cell. Responses A cell wallcell wall B cell membranecell membrane C endoplasmic reticulumendoplasmic reticulum Question 2 A membrane that only "lets" certain molecules in while keeping other molecules out is ___ ___. Responses A flexibleflexible B bilipid layersbilipid layers C selectively permeableselectively permeable Question 3 Large molecules and wastes move through the membrane through ____ ______. Responses A lipid layerslipid layers B protein channelsprotein channels C carbohydrate gatescarbohydrate gates Skip to navigation

Answer 1

Question 1: B) cell membrane
Question 2: C) selectively permeable
Question 3: B) protein channels