Biology 12



Biology 12 Cell Biology - Transport across Cell Membrane

Text Reference: Chapter 5 pp 72-85

Vocabulary:

active transport, carbohydrates, carrier protein, cell membrane, channel protein, cholesterol, concentration gradient, diffusion, endocytosis, exocytosis, facilitated transport, fluid-mosaic membrane model, glycolipid, glycoprotein, hydrophilic, hydrophobic, hypertonic, hypotonic, isotonic, osmosis, passive transport processes, phagocytosis, phospholipid, phospholipid bilayer, pinocytosis, pressure gradient, protein, selectively permeable, surface area-to-volume ratio, tonicity

It is expected that students will:

B9 Analyse the structure and function of the cell membrane

B9.1 apply knowledge of organic molecules – including phospholipids, proteins, glycoproteins, glycolipids, carbohydrates, and cholesterol – to explain the structure and function of the fluid-mosaic membrane model

B9.2 identify the hydrophobic and hydrophilic regions of the phospholipid bilayer

B9.3 explain why the cell membrane is described as “selectively permeable”

B9.4 describe passive transport processes including diffusion, osmosis, and facilitated transport

B9.5 explain factors that affect the rate of diffusion across a cell membrane (e.g., temperature, size of molecule, charge of molecule, concentration gradient, pressure gradient)

B9.6 predict the effects of hypertonic, isotonic, and hypotonic environments on osmosis in animal cells

B9.7 describe active transport processes including active transport, endocytosis (phagocytosis and pinocytosis), and exocytosis

B9.8 compare specific transport processes – including diffusion, osmosis, facilitated transport, active transport, endocytosis, and exocytosis – in terms of

– concentration gradient

– use of channel or carrier protein

– use of energy

– types/sizes of molecules transported

B9.9 devise an experiment using the scientific method (e.g., to investigate the tonicity of cells)

B10 Explain why cells divide when they reach a particular surface area-to-volume ratio

B10.1 differentiate between cells that have a high or low surface area-to-volume ratio

B10.2 demonstrate an understanding of the significance of surface area-to-volume ratio in cell size

The cell membrane is often described as a ‘fluid mosaic’. What could that mean? The next 3 pages will help you to understand this concept. (pg. 73-75)

Activity: Membrane Structure (5.1)

Here is what happens when phospholipids are put in water:

Here are two great websites to visualize the cell membrane:





1. Review why the phospholipid molecule is an ideal molecule to make up cell membranes.

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What characteristic of the phospholipid bilayer could be described as fluid?

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Here is a more detaileld diagram to illustrate what your cell membranes might look like:

What do we mean when we describe the cell membrane as a ‘mosaic’?

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What is the function of cholesterol in the animal cell membrane?

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2. What are some of the functions of membrane proteins?

a) __________________________________________________________________ __________________________________________________________________

b) ____________________________________________________________________________________________________________________________________

c) __________________________________________________________________

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d) __________________________________________________________________

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e) _________________________________________________________________

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f) __________________________________________________________________

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3. How do Substances Cross The Cell Membrane? (pg. 75)

Crash Course – Transport:

What do we mean when we say that molecules diffuse ‘down their concentration gradient’?

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Website activity: Activity: Diffusion (5.3)

Activity: Selective Permeability of Membranes (5.1)

Why are cell membranes described as selectively permeable?

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Activity: Osmosis and Water Balance in Cells (5.5)

Activity: Facilitated Diffusion (5.6)

3. Passive Transport across the cell membrane

One solute:

BLAST Animation: Diffusion (5.3)

What do we mean when we say that some molecules or ions cross the cell membrane by passive transport?

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More than one solute:

BLAST Animation: Passive Diffusion Across a Membrane (5.3)

What is simple diffusion across the cell membrane? _____________________________

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Give some examples of molecules that are able to move by simple diffusion across the plasma membrane.

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What determines whether or not a molecule/ion can travel across the phospholipid bilayer by simple diffusion?

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Does simple diffusion require an input of energy (ATP) by the cell? ________________

Does simple diffusion require a membrane protein? _____________________________

Explain factors that affect the rate of diffusion across a cell membrane

Try to find 5 factors to explain.

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How is facilitated transport similar to simple diffusion?

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How does facilitated transport differ from simple diffusion?

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Give some examples of biologically important molecules that must cross the membrane by facilitated transport?

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What is osmosis? (pg. 76) _________________________________________________________________________________________________________________________________

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What happens to plant and animal cells when they are placed in hypertonic, hypotonic and isotonic solutions? (pg. 76-77)

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Some molecules move across the cell membrane by active processes. What does this mean? (pg. 78) __________________________________________________________

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Activity: Active Transport (5.8)

List the three types of transport that are considered to be active methods:

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What are the distinguishing features of active transport?

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Give some examples of molecules or ions that cross the membrane by active transport:

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BLAST Animation: Active Transport (5.8)

What is exocytosis? (pg. 79)_________________________________________________

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Activity: Exocytosis and Endocytosis (5.9)

BLAST Animation: Endocytosis and Exocytosis (5.9)

Give some examples of molecules that must leave the cell by exocytosis:

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Is exocytosis an active or passive process? ______________________ Why? ________

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What is endocytosis? _____________________________________________________

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Which cells in your body do a lot of endocytosis? __________________________________________________________

What must happen after the vesicle is formed? ____________________________________________________________________________________________________________________________________________________________________________

Is endocytosis an active or passive process? _____________________ Why? ________

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There are two types of endocytosis – phagocytosis and pinocytosis. What is the difference between phagocytosis and pinocytosis? (pg. 79)

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[pic]BioFlix: Membrane Transport chapter 5

Complete this concept map to help with your understanding of how substances cross the cell membrane:

Demonstrate an understanding of the relationship and significance of surface area to volume, with reference to cell size

cool site

What is the average size range for cells? ________________________________

WHAT LIMITS CELL SIZE?

In order to grow, cells need to take in _____________________________ and get rid of __________________________________.

Which part of the cell controls the entrance and exit of these materials? _________________________________________

What determines how much material is needed by the cell, or how much waste is produced by the cell? ______________________________

Study the large cell on the left below. How does its volume compare to the total volume of the 27 small cells on the right? _______________________________

How does its surface area compare? ___________________________________

What which has a better RATIO of surface area to volume, the one large cell, or the 27 small cells? _________________________________________

Explain why cells stop growing and divide once they reach a certain size.

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