9.3 - Cell Membrane

Multiple Choice

In which type of cell can you find ribosomes?

• Prokaryotic cells
• Unicellular Cells

• All of types of cells

• Eukaryotic cells

Multiple Choice

How many sub units does a ribosome have?

• 1
• 4
• 2
• 3

Multiple Choice

What are the two things that ribosomes are composed of?

• Carbohydrates and nucleotides
• Deoxyribonucleic acid (DNA) and lipids
• Ribosomal RNA (rRNA) and proteins
• Lipids and amino acids

Multiple Choice

What is the main role of ribosomes?

• Protein synthesis
• Waste removal
• Cell division
• Energy production

Open Ended

Why is protein in our bodies important?

Labeling

Label the parts of the ribosome

Drag labels to their correct position on the image

Small Subunit

Large Subunit

9.3 - Cell
Membrane

Genova

Lesson Objectives

●Describe the roles of each of the component of the cell membrane in
maintaining the internal environment of the cell.

●Describe the Fluid Mosaic Model of cell membranes

Vocabulary Terms

●Cell Membrane

●Semipermeable membrane

●Fluid Mosaic Model

●Phospholipid

●Phospholipid bilayer

●Hydrophilic

●Amphipathic

●Hydrophobic

Cell Membrane

Open Ended

What do you know about the cell membrane?

What is the role of the cell membrane?

●Cell membrane of plasma membrane is define the border of a cell

○What is inside vs. outside of the cell.

●Cell membrane --> Specialized structure that surrounds the cell and
its internal environment; controls movement of substances into/out
of cell.

●Function:

○Allows the cell to interact with the environment.

○Exclude, take in, excrete various substances

○Protect the cell from outside substances.

What is the cell membrane made out of?

●Cell membrane are composed of lipids which makes them have a
semi-permeable membrane

●Semi-permeable membrane --> Membrane that allows certain
substances to pass through

●Other building block of membranes:

○Proteins --> Involved in cross-membrane transport and cell communication

○Carbohydrates --> Decorates both proteins and lipids and help cells recognize each
other.

Open Ended

What are the three main things that makes up the cell membrane?

Fluid Mosaic Model

What is the Fluid Mosaic Model?

●Fluid Mosaic Model --> A model that describes what the cell
membrane looks and functions like.

○Proposed by S.J Singer and Garth L. Nicolson in 1972

○Evolved overtime and it still provides a good basic description of the structure and
behavior of membranes in many cells.

Open Ended

Why use the term "mosaic"?

Why “Mosaic”?

●According to the fluid mosaic
model, the plasma membrane is a
mosaic of components:

○Phospholipids

○Cholesterol

○Proteins

●Diagram basically shows a snapshot
of the dynamic process in which
phospholipids and proteins are
continually sliding past each other.

Multiple Choice

What do you think will happen to the cell
membrane when poked with a fine needle?

• The cell membrane will simply part around the needle

• The cell membrane will turn into a liquid.
• The cell membrane will disappear completely.
• The cell membrane will become stronger and more resilient.

Composition of the Plasma Membrane

●Principal components:

○Lipids (phospholipids and cholesterol)

○Proteins

○Carbohydrates groups are attached to some proteins and lipids.

Lipids

●Phospholipids --> a lipid made of glycerol, two
fatty acid tails, and a phosphate-linked head
group.

○Biological membranes are usually made up of two
phospholipids known as the phospholipid bilayer.

○Phospholipid bilayer --> biological membrane involving two
layers of phospholipids with their tails pointing inward

●Cholesterol are composed of four carbon rings.

○Found alongside phospholipids in the core of the membrane.

Labeling

Label the parts of the phospholipid

Drag labels to their correct position on the image

Phosphate-liked head

Fatty Acid Tail 2

Fatty Acid Tail 1

Open Ended

What does the term "bilayer" mean?

Where are the proteins and carbohydrates located?

●Proteins can be found partway
into the plasma membrane,
cross the membrane entirely,
or be loosely attached to its
inside or outside face

●Carbohydrates groups are only
found on the outer surface and
attached to proteins
(glycoproteins) or lipids
(glycolipids)

How much lipid, proteins, or carbohydrates make up the membrane?

●Depends on the cell

●For example: Human cells

○50% protein

○40% Lipids

○10% Carbohydrates

Assignment

Cell Membrane Simulation

Click this link to get to the assignment, it will also be in Google Classroom!

https://phet.colorado.edu/sims/cheerpj/membrane-channels/latest/membrane-channels.html?simulation=membrane-channels

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Phospholipids

Phospholipids

●Basic fabric of the cell
membrane

●Phospholipids are amphipathic

●Amphiphathic --> Molecule that
contains both a hydrophobic
and a hydrophilic end

Hydrophilic

●Hydrophilic --> Molecule that is attracted
to water

○“water-loving”

●The head portion of the phospholipid

○Slightly charged negative or positive

○Interacts well with water

○Faces outwards in the membrane

Hydrophobic

●Hydrophobic --> Molecule that repels water

○“Water-fearing”

●Tail portion of the phospholipid

○Nonpolar fatty acid tail

○Interact better with nonpolar molecules

○Interacts poorly with water

○Faces inwards in the membrane

Dropdown

The head portion of the phospholipid is

Select answer

​ ​

Dropdown

The tail portion of the phospholipid is ​

Select answer

Dropdown

The whole structure of a phospholipid is

Select answer

Multiple Choice

With these barriers, can water enter the membrane?

• Yes

• No

• Sometimes

What is a liposome and a micelle?

●Phospholipid behavior in certain
conditions:

○If small tails → form a micelle (a small, single-layered sphere)

○If bulkier tails → form liposome (a hollow droplet of bilayer membrane)

Multiple Choice

What phospholipid structure is this?

• Liposome

• Micelle

• Inverted micelle

• Phospholipid Trilayer

Proteins

Proteins

●Second major components of the membrane:

●Two categories:

○Integral

○Peripheral

Integral Proteins

●Integral membrane proteins --> proteins integrated into the
membrane

●Characteristics:

○Contain at least one hydrophobic
region that anchors them into the
membrane

○Some stick partway into the membrane

○Protein that sticks out are usually
hydrophilic

○Others stretch from one membrane
to another → transmembrane
protein

Peripheral Protein

●Peripheral membrane proteins --> found on the outside and inside
surfaces of membranes, attached
either to integral proteins or to
phospholipids

●Characteristics:

○Do not stick to the hydrophobic core

○More loosely attached

Carbohydrates

Carbohydrates

●Third major component of the
membrane

●Found outside of the membrane and
bound:

○Glycoprotein - carbohydrates + protein

○Glycolipid - carbohydrates + lipids

●Characteristics:

○Form distinctive cellular markers (ID Badges)

■Allows other cells to recognize them

■Immune system don’t attack them!

The components of the plasma membrane

Component

Location

Phospholipids

Main fabric of the membrane

Cholesterol

Tucked between the hydrophobic tails of the membrane phospholipids

Integral proteins

Embedded in the phospholipid bilayer; may or may not extend through both layers

Peripheral proteins

On the inner or outer surface of the phospholipid bilayer, but not embedded in its hydrophobic core

Carbohydrates

Attached to proteins or lipids on the extracellular side of the membrane (forming glycoproteins and glycolipids)

Have we achieve our objectives?

Vocab Recap

●Cell Membrane - Specialized structure that surrounds the cell and its internal environment; controls movement of substances into/out of cell

●Semipermeable membrane - Membrane that allows certain substances to pass through

●Fluid Mosaic Model - A model that describes what the cell membrane looks and
functions like

●Phospholipid - Amphipathic lipid made of glycerol, two fatty acid tails, and phosphate group

●Phospholipid bilayer - A biological membrane involving two layers of phospholipids with their tails pointing inward

●Amphiphathic - Molecule that contains both a hydrophobic and a hydrophilic end

●Hydrophilic - Molecule that is attracted to water (“water-loving”)

●Hydrophobic - Molecule that repels water (“water-fearing”)

Word Bank #6 - 10

●Semi-permeable

●Alongside

●Lipid

●Cholesterol

●Carbohydrates

●Peripheral

●Hydrophobic

●Hydrophilic

●Amphipathic

●Micelle