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Cell membraneAim: What is the anatomy and function of the cell membrane?

Vocabulary development:

- Membrane means a cover.

- Hydrophilic is"water-loving."

- Hydrophobic is "water-fearing".

- Bilayer is a double layer.

- Glycoproteins is a carbohydrate attached to a protein.

- Permeable is the ability of something to pass through a barrier.

- Anatomy is the parts of something.

-Polar means opposite side.

-Homeostasis is the maintenance of stable internal conditions in a changing environment.

Do Now: Identify and list the different parts or properties of the cell membrane by analyze, looking and using the three diagram on pages 1 & 2.

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Plasma MembraneAll living cells, prokaryotic and eukaryotic, have a plasma membrane that encloses their contents and serves as a semi-porous barrier to the outside environment. The membrane acts as a boundary, holding the cell constituents together and keeping other substances from entering.

Write and explain the main function of the cell membrane.

The arrangement of phospholipids in the lipid bilayer makes the cell membrane selectively permeable. That is, the lipid bilayer allows only certain substances to pass through. Small uncharged molecules and, to some extent water, can pass through the phospholipids bilayer. The nonpolar area in the center of the bilayer repels ions and polar molecules. Thus, such substances cannot pass easily through the membrane. The plasma membrane is permeable to specific molecules, however, and allows nutrients and other essential elements to enter the cell and waste materials to leave the cell. Small molecules, such as oxygen, carbon dioxide, and water to some extent, are able to pass freely across the membrane, but the passage of larger molecules, such as amino acids and sugars, is carefully regulated by transport proteins embedded in the membrane.

• Write and explain the differences in passage through the cell membrane according to size.

All living cells and many of the tiny organelles internal to cells are bounded by thin membranes (endocellular membrane). These membranes are composed primarily of phospholipids and proteins and are typically described as phospholipid bi-layers.

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In this sketch, the spheres represent the phosphate end, which is polar and water soluble (hydrophilic). The twin extensions represent the fatty acid components which are not water soluble (hydrophobic).

The plasma membrane is composed of a double layer (bilayer) of lipids, oily substances found in all cells. Most of the lipids in the bilayer can be more precisely described as phospholipids, that is,

lipids that feature a phosphate group at one end of each molecule. Phospholipids are characteristically hydrophilic ("water-loving") at their phosphate ends and hydrophobic ("water-fearing") along their lipid tail regions. In each layer of a plasma membrane, the hydrophobic lipid tails are oriented inwards and the hydrophilic phosphate groups are aligned so they face outwards, either toward the aqueous cytosol of the cell or the outside environment.

Write and explain the number of lipid layers are used to make a cell membrane? Also, explain

the differences between hydrophilic and hydrophobic.

Within the phospholipid bilayer of the plasma membrane, many diverse proteins are embedded, while other proteins simply adhere to the surfaces of the bilayer. Some of these proteins, primarily those that are at least partially exposed on the external side of the membrane, have carbohydrates attached

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to their outer surfaces and are, therefore, referred to as glycoproteins. The arrangement of proteins also involves the hydrophobic and hydrophilic regions found on the surfaces of the proteins: hydrophobic regions associate with the hydrophobic interior of the plasma membrane and hydrophilic regions extend past the surface of the membrane into either the inside of the cell or the outer environment.

Where are the proteins located in the cell membrane?

Plasma membrane proteins function in several different ways. Many of the proteins play a role in the selective transport of certain substances across the phospholipid bilayer, either acting as channels or active transport molecules. Others function as receptors, which bind information-providing molecules, such as hormones, and transmit corresponding signals based on the obtained information to the interior of the cell. Membrane proteins may also exhibit enzymatic activity, catalyzing various reactions related to the plasma membrane.

List the possible function of the different proteins embedded in the cell membrane.

A cell membrane is made of a double layer of phospholipid molecules. Each layer is a mirror image of the other layer. The structure is called a lipid bilayer.

Located within the lipid bilayer of the cell membrane are proteins of different types. Each type of membrane protein plays a vital role in the life of a cell. Cell-surface markers are membrane proteins that are attached to a carbohydrate on the cell’s surface. Together, the protein and carbohydrate help other cells recognize the cell type—liver cell or heart cell, for example. Receptor proteins are membrane proteins that recognize and bind to specific substances outside the cell. When this happens, the inside of the cell changes, as well. In this way, receptor proteins help cells detect and change in response to things in the environment outside the cell. Enzymes are proteins that change the rate of chemical reactions. Various enzymes in the cell membrane are involved in important biochemical reactions inside the cell. Many substances needed inside the cell cannot pass through the cell membrane on their own. Transport proteins are membrane proteins that aid the movement of these substances through the lipid bilayer of the cell membrane. In this way, transport proteins help carry a variety of substances into and out of the cell.

1. The prefix bi- means “two.” Why is the term lipid bilayer a good name for a cell membrane?

2. Why are the proteins described in the second paragraph classified together in a group referred to as membrane proteins?

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http://study.com/academy/lesson/cell-membrane-functions-role-structure.html

https://translate.google.com/translate?sl=es&tl=en&js=y&prev=_t&hl=en&ie=UTF-8&u=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DQQgXfuFyKM4&edit-text=&act=url

The Cell Membrane is a Fluid Mosaic

A cell is the basic unit of life, and all organisms are made up of one or many cells. One of the things that all cells have in common is a cell membrane. It is a barrier that separates a cell from its surrounding environment. This outer boundary of the cell is also called the plasma membrane. It is composed of four different types of molecules:

1. Phospholipids 2. Cholesterol 3. Proteins

4. Carbohydrates

The fluid mosaic model describes the structure of a cell membrane. It indicates that the cell membrane is not solid. It is flexible and has a similar consistency to vegetable oil, so all the individual molecules are just floating in a fluid medium, and they are all capable of moving sideways within the cell membrane. Mosaic refers to something that contains many different parts. The plasma membrane is a mosaic of phospholipids, cholesterol molecules, proteins and carbohydrates.

Phospholipids

Phospholipids make up the basic structure of a cell membrane. A single phospholipid molecule has two different ends: a head and a tail. The head end contains a phosphate group and is hydrophilic. This means that it likes or is attracted to water molecules.

The tail end is made up of two strings of hydrogen and carbon atoms called fatty acid chains. These chains are hydrophobic, or do not like to mingle with water molecules. This is just like what happens when you pour vegetable oil in water. The vegetable oil will not mix with the water.

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The phospholipids of a cell membrane are arranged in a double layer called the lipid bilayer. The hydrophilic phosphate heads are always arranged so that they are near water. Watery fluids are found both inside a cell (intracellular fluid) and outside a cell (extracellular fluid). The hydrophobic tails of membrane phospholipids are organized in a manner that keeps them away from water.

Cholesterol, Proteins and Carbohydrates

When you hear the word cholesterol, the first thing you probably think of is that it is bad. However, cholesterol is actually a very important component of cell membranes. Cholesterol molecules are made up of four rings of hydrogen and carbon atoms. They are hydrophobic and are found among the hydrophobic tails in the lipid bilayer.

Cholesterol molecules are important for maintaining the consistency of the cell membrane. They strengthen the membrane by preventing some small molecules from crossing it. Cholesterol molecules also keep the phospholipid tails from coming into contact and solidifying. This ensures that the cell membrane stays fluid and flexible.

Some plasma membrane proteins are located in the lipid bilayer and are called integral proteins. Other proteins, called peripheral proteins, are outside of the lipid bilayer. Peripheral proteins can be found on either side of the lipid bilayer: inside the cell or outside the cell. Membrane proteins can function as enzymes to speed up chemical reactions, act as receptors for specific molecules, or transport materials across the cell membrane.

Carbohydrates, or sugars, are sometimes found attached to proteins or lipids on the outside of a cell membrane. That is, they are only found on the extracellular side of a cell membrane. Together, these carbohydrates can act as a glue to attach cells together.

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This is the fluid mosaic model of a cell membrane.

Cell Membrane Functions

The plasma membrane of a cell has two main roles:

1. It is a physical barrier. 2. It regulates exchange of materials with its surroundings.

The cell membrane is important because it separates and protects a cell from its surroundings. This allows the intracellular conditions of a cell to be very different from the extracellular conditions. For example, nerve cells in your body will maintain a high concentration of potassium inside. Outside, in the extracellular fluid, there is very little potassium and lots of sodium. These concentration differences are absolutely necessary for the function of nerve cells, which is to send signals or nerve impulses.

SKILL: ORGANIZING INFORMATION

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The second paragraph of this passage identifies four different types of proteins found in the cell membrane. Complete the table below by listing each type of protein and its function in the spaces provided.

Type of protein Function

3. 4.

5. 6.

7. 8.

9. 10.

____11.Would you expect a skin cell to have different cell-surface markers than a muscle cell?a. No; all cells need to mark their outer surfaces.b. Yes; each different type of cell might need to signal other cells in different ways.c. No; all cells have an outer membrane formed of a lipid bilayer.d. Yes; the cell-surface markers would be different because the cells are of different types.

In the space provided, write the letter of the description that best matches each term.

______12. cell-surface marker

______13. receptor protein

______14. enzyme

______15. transport protein

16. What is homeostasis, and what is the main way that the cell membrane helps maintain homeostasis?

17. The ______________________ ______________________ is made of a double layer of phospholipids.

The double layer of phospholipids is called a(n) ______________________

______________________.

18. The lipid bilayer forms because there is ______________________ both inside and

______________________ of the cell.

19. The phosphate ______________________ of a phospholipid is polar. It is ______________________

a. helps with chemical reactions inside the cell

b. recognizes and binds to substances outside the cell, enabling the cell to sense its environment

c. helps substances move across the cell membrane

d. identifies the cell type

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______________________ water.

20. The long fatty acid ______________________ of a phospholipid are nonpolar. They are

______________________ ______________________ water.

21. The lipid bilayer forms a barrier, preventing most molecules from passing through it. Only molecules

that are ______________________ in size and ______________________ can pass through the lipid

bilayer.

22. Ions, which are ______________________ particles, and ______________________ molecules are

repelled by the nonpolar interior of the lipid bilayer.

23. The cell membrane includes various kinds of ______________________. Some face the inside of the

cell. Some face the ______________________ of the cell. Others span the entire width of the

______________________

24.

25.

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Aim: What is the anatomy and function of the cell membrane?

Standard 4

Students will understand and apply scientific concepts, principles, and theories pertaining to the physicalsetting and living environment and recognize the historical development of ideas in science.

Key Idea 1:Living things are both similar to and different from each other and from nonliving things.

Common Core Learning Standards for Literacy in History/Social Studies, Science, and Technical Subjects.RST.11-12.4, RST.11-12.7, WHST.11-12.2a, WHST.11-12d, WHST.11-12.4.

INSTRUCTIONAL MODIFICATIONS FOR ELL/SP, ED, STUDENTS (IF APPLICABLE)1-Provide dictionaries/glossaries2-Provide alternate reading/writing material to differentiate task3-Provide extra scaffolding for vocabulary attainment4-Provide extra wait time for oral response to questions5-Use of graphic organizers6-Use more visuals through technology

- Instructional objectives: In addition to being provided with the opportunity to read, write, and speak in order to increase literacy….SWBAT

Objectives:

-Identify the parts of the cell membrane.

-Explain the main function of the cell membrane.

-Explain and describe the parts of cell membrane.

-Explain key vocabulary words.

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Key Questions:-How many layers is the cell membrane made-up of?-What is glycoprotein made-up of ?-What is a lipid?-What is a protein?-How does a cell maintain homeostasis?-Explain the main function of the cell membrane.-Explain the differences in passage through the cell membrane.-Explain the differences between hydrophilic and hydrophobic.-Explain the possible different function of the proteins embedded in the cell membrane.

Assessing students’ prior knowledge, understanding, and misconceptions: (5-8 min)Do Now: Write a sentence or moreIdentify and list the different parts or properties of the cell membrane by analyzing, looking and using the three diagram on pages 1 & 2.What do you know about the cell membrane? / What questions do you have about the cell membrane?

Motivation/context: Show short Video of the fluid mosaic membrane (5-6 min)

Introduction of understanding (associate the new understanding with prior knowledge) (10-20 min)-Analyze the diagrams on page 1 & 2.-Describe the parts & organic molecules of the cell membrane.

Development of lesson (10-20 min)Use page 3: Reading comprehension of “How does a cell maintain homestasis?”Use diagrams on page 1 & 2, and key question on page 3.

Check Point(s) Have students report to each other and /or to the entire class what they have learned as a check on the progress of the teaching by writing on the smart board. Ask key questions during the check point. (5 min)

Further development of lessonReading comprehension out loud on page 4 &5, use diagrams on page 4 too.Answer key questions on pages 4 & 5.

Check Point(s) Have students report to each other and /or to the entire class what they have learned as a check on the progress of the teaching by writing on the smart board. Ask key questions during the check point. (5 min)

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