homeostasis and cell membrane notes. how do we balance external stresses such as heat and cold? our...

Homeostasis and Cell Membrane Notes

How do we balance external stresses such as heat and cold?

Our bodies will respond to our environments whenever they are stressed!

What are some examples of our body responding?

What are all of these things related to?

Homeostasis!

What is homeostasis?

• Homeostasis = the ability of an organism to maintain a stable internal environment, even when the external environment changes!

What are some examples of maintaining homeostasis?

• Sweating to keep the body at 98 degrees.• Shivering or Goosebumps to keep the body at 98

degrees.• Feeling thirsty when your cells need water.• Feeling hungry when your cells need food/sugar

(for cellular respiration!)• Blood sugar levels• Sleep• Etc……………..

What part of the cell is MOST important for maintaining

homeostasis?• Cell membrane!• The flexible part that goes around the outside of a

plant or animal cell.

What are the properties of the cell membrane?

• The cell membrane is “selectively permeable”.

What is “selectively permeable?”

• It lets SPECIFIC things inside / outside of the cell, or it keeps SPECIFIC things inside / outside of the cell.

Video Clip

• Watch the following video….• What is able to pass through easily?• What cannot pass through?• (Chapter 7 AP Disc – Selectively Permeable)

What is the cell membrane made of?

• Think back to the chemistry unit…• Mostly lipids with SOME proteins.

Think of real life situations that are “selectively permeable.”

• Movie theatre• Concert• High school dance• Bar/club (21 and up)

Selectively PermeableSelectively Permeable• Example: The movie theater!– Technically, people can be standing both inside or

outside, but you need a movie ticket in order to get inside.

– If you buy a movie ticket, you can go inside.– If you don’t have a ticket, you are denied entrance.

What does the cell membrane look like?What does the cell membrane look like?• It is made of a phospholipid bilayer• There are 2 layers to the cell membrane:Draw with me to put a picture in your notes

What is a phospholipid?What is a phospholipid?• Each molecule that makes up the cell

membrane is called a phospholipid.• The cell membrane = phospholipid bilayer (2

layers of phospolipids. .

Cell MembraneCell Membrane• Each molecule in the cell membrane is a

phospholipid.• The cell membrane is a phospholipid bilayer.

Head

Tail

Cell MembraneCell Membrane• Each molecule in the cell membrane is a

phospholipid.• The cell membrane is a phospholipid bilayer.

Head = HYDROPHILIC(LOVES WATER)

Tail = HYDROPHOBIC(HATES WATER)

Where are proteins found in the Where are proteins found in the membrane?membrane?

• Within the two layers, proteins are found.

• These proteins help molecules to cross through the membrane, and it’s also a way that the cell can communicate with its environment

Cell MembraneCell Membrane

• So…where will water like to be?

• Where is water present…inside the cell, outside the cell, or both?

• Water will be inside and outside of the cell like in an egg.

Cell Membrane RecapCell Membrane RecapWhat is the cell membrane mostly made of?• LIPIDS!What other molecule is found in the membrane?• PROTEIN!Hydrophilic vs. Hydrophobic:What part is hydrophilic? • The head!What part is hydrophobic?• The tail!What part lets stuff enter the cell?• The protein!

What does this look like? What does this look like? Can you point out the proteins and lipids?Can you point out the proteins and lipids?

Cell Membrane Animation

• You will create an animation to show the structure and function of the cell membrane.

• You must include the following parts (1 point each) and animate the parts to symbolize their role in the cell (1 point each).– Phospholipid bilayer– Hydrophilic head– Hydrophobic tail– Protein– Water location

Animation ExampleAnimation Example

I’m the hydrophilic head and I

love water! Take me

swimming!

I’m the hydrophobic tail. I hate

being around water!

I’m a protein! I am like a

“bouncer” for the cell.

Exit Quiz

1. Describe the structure and function of the cell membrane using these words:• Phospholipids•Hydrophilic head•Hydrophobic tail•Protein2. What does it mean that the cell membrane is “selectively permeable?”