Structure and Function of Cells:Don’t Burst My Bubble

All About YouTeacher Education Course

2016-17

Don’t Burst My BubbleNGSS 3D Learning GoalStudents carry out an investigation using a soap

film model of a cell membrane to explain how the structure of the membrane causes it to function as the boundary that controls what enters and leaves the cell.

ObjectivesDescribe how a cell membrane’s structure relates to

how the membrane functions and the cell functions Evaluate the limitations of the models used to

represent a cell membrane.

How are these organisms similar to each other?

White and Black Variations on Lichen- Free Trees

Cells are the Basic Unit of Life

All Cells Have Certain Characteristics

All cells are surrounded by a cell membrane.

Small Group Self-Managing RolesFacilitator makes sure every voice is heard

Reporter shares group’s ideas in the time given

Recorder writes official team worksheet

Timekeeper keeps group aware of time remaining

Functions of the Cell Membrane

1. Forms the flexible outer boundary of the cell and holds it together.

2. It controls what is allowed to enter and leave the cell and what is not allowed to enter and leave the cell

Don’t Burst My BubbleWork as a table group to sketch the potential

structure of A Cell Membrane given the functions listed on the worksheet.• Timekeepers: 5 minutes

Next, complete the observations and inferences listed in questions 1-3 as you explore the soap film as a Cell Membrane Model.• Timekeepers: 5 minutes

Don’t Burst My BubbleNow explore the What Passes Through? section.

• Investigate with different objects (Question 4)• Complete the table

• Create a rule or rules for what passes through (Question 5)• Consider possible structural changes that provides new

function (Question 6)• Timekeepers: 15 minutes

Next in Changing the Model use the new structure discussed to pass objects through the film.• Revise the scientific drawing (Question 7)• Timekeepers: 5 minutes

Don’t Burst My BubbleAnything unexpected or interesting?

Don’t Burst My Bubble

Graphic Organizer

selectively permeable

phospholipid bilayer

transport (in & out)

structures

cell membrane

proteins

functions

barrier, support, protection, identity

Don’t Burst My BubbleWhat is the function of a cell membrane?

• A cell’s outer boundary which is flexible and fluid, and separates the cells interior from the exterior environment

• Regulates what comes in and goes out of the cell and is its first line of defense

Don’t Burst My BubblePhospholipids

• Cell membranes are composed of molecules with two distinct sides• Hydrophilic head

• Water “loving” phosphate• Hydrophobic tails

• Water “fearing” fatty acidsForms bilayer due to interaction with water inside & outside of cell

Don’t Burst My BubbleSelectively Permeable

• Structure of cell membrane allows certain substances to pass through, while making other substances require help, or not allowing them to pass.

• https://www.pbslearningmedia.org/asset/tdc02_int_membraneweb/

Don’t Burst My BubbleFluid Mosaic Model

• Mosaic = proteins & other structures placed within lipid bilayer

• Fluid = proteins & other structures can move across lipid bilayer

Don’t Burst My BubbleAll models have limitations

prot

ein

Cel

l Mem

bran

eSo

ap B

ubbl

e

water

water

~ nm (10-9 m)

~ µm (10-6 m)~1,000x thicker

Bacteria, viruses and toxic chemicals sometimes have the ability to get into a cell despite the cell membrane’s defensive structures.

What ideas do you have about what cells can do to further protect themselves from an especially harmful environment?

Further Cell Defense Mechanisms

Increasing the cholesterol in the cell membrane makes it much more rigid and difficult for invading molecules to get through.

Cells insert a structure (amino acid) into the protein channels, protecting it against harmful invading molecules.