- Summary list for 1.4 Membrane transport
- Mindmaps
- Exam style question about osmosis in plant tissues
- Model answer
- Model answer
- Model answer
- Multiple choice questions
- 1.4 Membrane transport 1/1
The membrane controls what enters and leaves the cell. This includes using diffusion and osmosis. Sometimes the membrane uses integral proteins as channels and pumps, sometimes the membrane surrounds something which needs moving into or out of the cell.Learn and test your biological vocabulary for 1.4 membrane transport using these flashcards.
Summary list for 1.4 Membrane transport
- Particles move across membranes by simple diffusion, facilitated diffusion, osmosis and active transport.
- The fluidity of membranes allows materials to be taken into cells by endocytosis or released by exocytosis. Vesicles move materials within cells.
- Know how the structure helps the function of sodium–potassium pumps for active transport and potassium channels for facilitated diffusion in axons.
- Understand why tissues (or organs) waiting to be used in medical procedures must be bathed in a solution with the same osmolarity as the cytoplasm to prevent osmosis.
- Skill: Estimation of osmolarity in tissues by bathing samples in hypotonic and hypertonic solutions. (Practical 2)
Mindmaps
These diagram summaries cover the main sections of topic 1.4 about membrane transport.
Study them and draw your own list or concept map from memory.
Exam style question about osmosis in plant tissues
Explaining osmosis is an important skill from this topic.
Answer the question below, on a piece of paper, then check your answer against the model answer below.
The images show two views of some red onion cells under the microscope during osmosis.
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Describe how osmosis changes the cells in this experiment [4]
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Click the + icon to see a model answer.
Multiple choice questions
This quiz contains a set of multiple choice questions covering the topic. Explanations of each answer are displayed after you click to check the answer(s).
START QUIZ!
Which of the following best describes exocytosis?
The fluidity of membranes allows materials to be released by exocytosis.
Vesicles move materials within cells to the membrane, e.g. enzymes in cells of a gland.
Sodium channels are made from a protein.
Where in the cell are sodium channel proteins found.
Sodium channel proteins are found spanning the plasma membrane. Their structure helps the function for facilitated diffusion in cells because they allow ions to pass cross the membrane.
If the protein was not a trans-membrane protein then it would not be able to transport ions across the membrane.
This box contains a lung waiting for a transplant operation.
What is special about the solution inside the box which surrounds the tissue?
Tissues and organs must be kept in a solution with the same osmolarity as the cytoplasm of the cells to prevent osmosis. If they were kept in pure water, osmosis would carry water into the cells and they would burst, causing damage to the cells.
The four cells shown below have each been surrounded by a solution for 1 hour.
Which cells have been in a hypertonic solution ?
Cell A is swollen turgid, it is in a hypotonic solution or an isotonic solution.
The cells B, C and D show increasing signs of plasmolysis, and so they must be in hypertonic solutions.
Skill: Estimation of osmolarity in tissues by bathing samples in hypotonic and hypertonic solutions. (Practical 2)
The graph below shows the % change in mass at different concentrations of sucrose.
Which of the following is the best estimate of the molarity of the cytoplasm of these cells?
When a sample of cells show no change in mass, then the net movement of water by osmosis must be zero. This shows the concentration of the cytoplasm of the cells. In this graph it would be about 0.3 mol
Which of the following are methods by which molecules can move across membranes?
I. Simple diffusion
II. Facilitated diffusion
III. Cytokinesis
IV. Active transport
There are actually four types of membrane transport which are required in DP Biology, Simple diffusion, facilitated diffusion, osmosis and active transport.
Which of the structures listed below are involved in membrane transport?
- Ribosomes
- Flagella
- Integral proteins
- Protein channels
Many transmembrane proteins are involved in transport of molecules across membranes. These can either provide a sort of molecular pore through which ions or molecules can pass (facilitated diffusion), or they can use ATP to actively move molecules, even against the concentration gradient (active transport).These are just two examples, transport can also occur by simple diffusion through the phospholipid bilayer, or by endocytosis.
Cells are often stored in isotonic conditions because they can be damaged in other concentrations, hypertonic, or hypotonic. Which of the descriptions of hypertonic is the most accurate?
Hypertonic solutions have a higher concentration of solutes, and lower water potentials than cells.
The diagram shows the transport of sodium ions across a membrane.
Which explanation gives the best description of the type of membrane transport shown?.
Facilitated diffusion does not require energy from ATP so this process is active transport. It can move sodium ions against the concentration gradient, but this is not always the case.
Which label in the image below shows the process of endocytosis?
Endocytosis is the process where a substance is surrounded by the plasma membrane which forms a vesicle inside the cell that then moves into the cytoplasm, separating from the plasma membrane.
Drag and drop activities
Test your ability to construct biological explanations using the drag and drop questions below.
Test your construction of biological explanations using the drag and drop questions below.
Passive transport across the cell membrane.
Drag and drop the correct term into the gap to describe passive transport.
Osmosis muscle cells down against (ATP) Diffusion hypotonic shape oxygen diffusion gradient into the cell hypertonic channel protein
In passive transport, substances can pass across the plasma membrane their without energy expenditure by diffusion or facilitated transport.
occurs across the membrane through the bilayer, for example into muscle cells.
is a form of diffusion where water passess across the plasma membrane from a to a solution.
Facilitated transport uses a . This protein combines with a certain substance, changes (conformation) taking the molecule without using energy, for example glucose into .
Explanation/Examiner hint. Use correct terminology.
Just for fun
Have some fun while revising. try this educational Revision arcade game about membrane transport.
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