Tag Archives: membrane

Cell membranes and organelles


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Key knowledge:

  • Understand the extent of the plasma membrane in forming a series of membraneous channels for the packaging and transport of biomolecules throughout eukaryotic cells.
  • Enhance knowledge and understanding of the structure and function of cell organelles.
  • Distinguish the different ways in which biomolecules enter or leave cells.
  • Develop knowledge and understanding of connections between cells.
  • Extend understanding of apoptosis.

Digital resources:

Possible Tasks:

  1. Create a “Thinglink” interactive image, labelling the different parts of a eukaryotic cell.  
  2. Create a database of terms and definitions on Quizlet. 
  3. Decorate a cake to show the different organelles of a plant or animal cell. Label with toothpick flags.
  4. Create a video describing the different forms of active transport using “common craft” style or 3D animation.
  5. Create a labelled model of the “phospholipid bilayer with integral and peripheral proteins”.

Transport of materials through Cell Membranes


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All living organisms consist of cells and all cells are surrounded by a membrane. One of the major functions of the membrane is to regulate the passage of materials into and out of the cell. These materials include dissolved gases, sugars, salts and water. Cell membranes are partially-permeable which means that some substances can easily pass through them whereas others can not. Most materials move by simple diffusion from high concentration on one side of the membrane to a lower concentration on the other. Substances which will not move by passive diffusion require energy and are actively transported.

Water is the most abundant and one of the most important substances in cells. The diffusion of water across a partially-permeable membrane is called osmosis. An egg is a large cell containing mainly water, proteins and salts for the possible benefit of the growing embryo. It is surrounded by a shell, and inside that, a membrane. It provides an excellent model to assist the understanding of the structure and function of membranes. Our experiment will use hen’s eggs, with the shell removed by dissolving the calcium carbonate in acetis acid (vinegar). We will then record the mass of each egg and place them in different concentrations of saline soution (distilled water, 1%, 5%, 10% and 20%). After several hours we will remove the eggs and weigh each to record the mass gained or lost in the solution.Download the practical investigation here: investigating-osmosis-in-chickens-eggs-ss-28 

Graph your results to show which eggs gained and lost mass due to the movement of water through the membrane. Did you get any unexpected results? What may have caused any irregularities?

Create a table listing the different forms of transport through cell membranes (passive diffusion, facilitated diffusion, active transport) and describe how each of these methods worked and what materials may be transported using each of these methods.

Concepts in Biochemistry – Cellular Transport

Teacher’s Domain – Transport of substances through the cell membrane

Cell membrane animation on You Tube

Beetroot and cell membranes

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What’s beetroot got to do with cell biology? Well, today we did a practical experiment to investigate the effect of temperature on the plasma membrane of beetroot tissue. Why beetroot? Because it is relatively easy to identify the amount of damage to cell membranes by observing the pigment leakage from the tissue. We used four 5mm x 15mm cylinders of beetroot and four different treatments – room temperature (control), freezing overnight, 50 degrees Celcius and 70 degrees Celcius for 2 minutes each. Then each sample was placed in a test tube with 5 ml of water. What did our results show?

One of the questions in this practical asks why some people put hessian bags over their garden plants in winter and how some plants can survive freezing temperatures. Hessian bags can help to insulate plants against the effects of freezing – some wineries use large fans to keep air circulating over their crops for the same reason. Some plants are genetically more tolerant of frost. This article, from the CSIRO, describes how some plants can empty water out of the cell into the extracellular spaces, where the water can form ice without damaging the cell membrane. Another method is increasing solute concentration, for example by storing monosacharides in place of disacharides, which effectively lowers the freezing point of the cell contents. This is a bit like using anti-freeze in the car radiator during winter.

Revision questions (with answers!) for cell membranes at Biology-Questions-and-Answers.