5.1 plasma membrane

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Unit 1: The Cell
Chapter 5:

Membrane Structure and

Function

Lesson 5.1:

Plasma Membrane Structure and Function

Text

Learning Outcome

Most

I can describe the nature of the fluid-mosaic model as it relates to membrane structure

Learning Outcome

Some...I can ….

Distinguish Between the different structural components of membranes.

.

Learning Outcome

All...

List and describe the components of the plasma membrane

HS-LS1-1: Develop and use a model to explain how cell structures, including the plasma membrane, perform specific functions.

HS-LS1-3: Plan and conduct an investigation to show how the plasma membrane helps maintain homeostasis through transport of materials.

HS-LS1-6: Explain how molecules move and interact within cells through membrane transport processes.

HS-LS1-7: Use a model to illustrate how cellular processes, including membrane transport, support cell function and survival

What information do you have about the Plasma Membrane?

glycoproteins

glycolipids

Plasma Membrane

• The plasma membrane is common to all cells.

Separates:

• Internal cytoplasm from the external environment of the cell

  • Allows sometimes incompatible chemical reactions to occur simultaneously

  • Fluid mosaic model accounts for the structure

What does the plasma membrane separate?

A

Nucleus and mitochondria

B

Internal cytoplasm and external environment

C

Only internal organelles

D

Ribosomes and endoplasmic reticulum

What model explains the plasma membrane structure?

A

Fluid mosaic model

B

Static structure model

C

Solid lipid model

D

Layered membrane model

WE DO…Activity Group work

What are the components of the plasma membrane? And predict their functions

Phospholipid bilayer:

(amphipathic substance)

• External surface lined with hydrophilic polar heads

  • Cytoplasmic surface lined with hydrophilic polar heads

  • Nonpolar, hydrophobic, fatty-acid tails sandwiched in between

What type of substance is a phospholipid?

A

Neutral substance

B

Hydrophobic only

C

Amphipathic substance

D

Hydrophilic only

What lines the external surface of the bilayer?

A

Hydrophobic fatty tails

B

Proteins only

C

Hydrophilic polar heads

D

Lipids only

Components of the Plasma Membrane

Three components:

1. Lipid component referred to as phospholipid bilayer

2. Protein molecules

• Float around like icebergs on a sea

  • Membrane proteins may be peripheral or integral.

    • Peripheral proteins are found on the inner membrane surface.

      • Integral proteins are partially or wholly embedded (transmembrane) in the membrane.

3. Cholesterol affects the fluidity of the membrane.

What is the lipid component of the plasma membrane?

A

Protein layer

B

Phospholipid bilayer

C

Cholesterol layer

D

Carbohydrate layer

Where are peripheral proteins located?

A

Floating freely in cytoplasm

B

Inner membrane surface

C

Embedded in membrane

D

Outer membrane surface

What does cholesterol affect in the membrane?

A

Thickness of the membrane

B

Fluidity of the membrane

C

Protein synthesis

D

Carbohydrate composition

Fluid-Mosaic Model of the Plasma Membrane

The membrane is composed of a phospholipid bilayer in which proteins are embedded (integral proteins) or associated with the cytoplasmic side (peripheral proteins). The hydrophilic heads of phospholipids are exposed to water on the outside and inside surfaces of the membrane. The hydrophobic tails associate together and make up the interior of the membrane. Note the plasma membrane's asymmetry-carbohydrate chains are attached to the outside surface and project into the extracellular matrix. Cytoskeleton filaments are attached to the inside surface by membrane proteins.

What forms the interior of the plasma membrane?

A

Carbohydrate chains

B

Hydrophilic heads of phospholipids

C

Hydrophobic tails of phospholipids

D

Integral proteins

Where are peripheral proteins located?

A

In the extracellular matrix

B

Attached to hydrophobic tails

C

Associated with the cytoplasmic side

D

Embedded in the phospholipid bilayer

Phospholipids in the Plasma Membrane

The hydrophilic heads of the phospholipids are at the surfaces of the membrane the hydrophobic tails make up the interior of the membrane. Proteins embedded in the membrane serve a variety of functions.

Glycoproteins and Glycolipids

Carbohydrate chains:

Contribute to cell’s “fingerprint”

The two “Gs” play a role in cellular identification.

Important in tissue transplantation and blood transfusions

Glycoproteins

Proteins with attached carbohydrate chains

Glycolipids

Lipids with attached carbohydrate chains

These carbohydrate chains exist only on the outside of the membrane.

Makes the membrane asymmetrical

What role do glycoproteins and glycolipids play?

A

Cellular identification

B

Energy production

C

Tissue transplantation

D

Blood transfusions

Where are carbohydrate chains located?

A

Outside of the membrane

B

Inside the nucleus

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Critical Thinking Questions

Explain why phospholipids play such an important role in the structure of the cell membrane.

how can you express your feelings about this part of the lesson?