Quick Lesson on Cell Membrane Structure

Cell

Membrane
Structure
Unit 3.2

Multiple Choice

controls entry into and out of cell

• centrioles

• cell (plasma) membrane

• cell wall

• chromosomes

Multiple Choice

where proteins are made

• centrioles

• vacuole

• ribosomes

• nucleolus

Remember the Phospholipid?

Hydrophilic Head - the
“head” is negatively
charged making it
attractive to water

Hydrophobic Tails - the
“tails” are fatty acid
chains which are NOT
attracted to water

Problem: There is water inside and outside of cells.

How are both ends of phospholipids satisfied?

How to solve the problem…

Phospholipids form a
BILAYER!
• The hydrophilic heads

point outward and
inward to face water.

• The hydrophobic tails

face toward each
other (away from
water!)

Multiple Choice

What is another term for "selectively permeable"?

• Porous
• Acts like a switch
• Permanent
• Semipermeable

Multiple Choice

Another term for equilibrium is...

• Equality
• Babycakes
• Homeostasis
• Balance

Multiple Choice

The function of the plasma membrane is....

• to regulate what enters and leaves the cell.
• fight bacteria and viruses that enter the cell.
• provide rigid support and protection to the cell.
• make sure each cell can move

Multiple Choice

What molecule is pictured?

• Integral Protein

• Carbohydrate chain

• Phospholipid

A Selectively Permeable Membrane is Formed.

This membrane regulates what gets in and out of

cells, regulating HOMEOSTASIS.

INTEGRAL PROTEIN
INTEGRAL PROTEIN

PERIPHERAL PROTEIN

Other Parts of the

Membrane

Integral Proteins
● run completely through

the bilayer

● aid in transport of

molecules and structure

Peripheral Proteins
● located on one side

(inside or outside) of the
bilayer

● aid attachment of the

cytoskeleton (inside) and
the ECM (outside

Proteins

Membrane Protein Functions

Cholesterol of the Membrane

● Keeps the membrane of all cells flexible
● Helps keep the membrane of plant cells from

freezing in frigid temperatures, like in the Tundra

INTEGRAL PROTEIN

PERIPHERAL PROTEIN

Draw

Circle all of the Cholesterol that is in the cell membrane.

Cholesterol Keeping Order

“The purple "tails" of the lipid
molecules that form the cell
membrane are far less orderly
in the absence of cholesterol
(top image) than when
cholesterol is present (bottom),
a finding made possible by
magnifying the membrane with
neutron diffraction.”
(NIST)

Glycocalyces

Glycolipids and Glycoproteins

● Cell communication, recognition
● Points of attachment

INTEGRAL PROTEIN

PERIPHERAL PROTEIN

Cell Communication

Cells need to communicate.

Can you see the green cell “hands”? Think of the Game "7 Up"

Fluid Mosaic Model

Multiple Choice

What is the "big idea" of the fluid mosaic model of plasma membranes?

• the plasma membrane creates a specialized FLUID that looks like a MOSAIC.

• the plasma membrane is a MOSAIC.

• the fluid mosaic model is NOT related to the plasma membrane.

• a plasma membrane is a MOSAIC of components that move FREELY and FLUIDLY.

Multiple Choice

Not all proteins that are embedded (part of) the cell membrane penetrate the whole membrane (go from one side to the other)

• true
• false

Multiple Choice

The 'fluid' part of the name for the cell membrane comes from the

•  embedded proteins
•  lipid tails
• phosphate heads

Multiple Choice

What is the name of the macromolecule that makes up the majority of the cell membrane?

• Lipid

• Carbohydrate

• Nucleic acid

• Protein

Multiple Choice

Small, nonpolar, hydrophobic molecules such as fatty acids

• easily pass through the membrane's bilayer

• very slowly diffuse through the bilayer

• require transport proteins

• enter through endocytosis

Multiple Choice

Membrane phospholipids

• have hydrophobic heads that face the center of the membrane and are shielded from water

• have hydrophilic tails that face outward

• remain fluid because they are tightly packed

• none of these

Multiple Choice

Describes the arrangement of the cell membrane as bendable and made of many parts.

• the fluid mosaic model

• the major mobility model

• the crazy cell model

• the cell theroy model

Multiple Choice

Where can PROTEINS be found when part of a plasma membrane?

• On the outside of the membrane

• On the inside of the membrane

• Embedded part of the way into the membrane

• Embedded the whole way through the membrane

• All of the above

Poll

How well do you understand Cell Membranes so far?

• Extremely Well!

• Pretty Well!

• Kinda well.

• Not too well.

• I am super lost.

Fundamental Concepts

• Systems of specialized cells within organisms help

them perform the essential functions of life.
(BI-LS1-1)

• Multicellular organisms have a hierarchical

structural organization, in which any one system is
made up of numerous parts and is itself a
component of the next level. (BI-LS1-2)