Transcript 1.1-BIO-HOM-HomeostasisIntro.CellMembrane

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 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?
• 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?
• Each molecule that makes up the cell
membrane is called a phospholipid.
• The cell membrane = phospholipid bilayer (2
layers of phospolipids. .
Cell Membrane
• Each molecule in the cell membrane is a
phospholipid.
• The cell membrane is a phospholipid bilayer.
Head
Tail
Cell 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
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 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 Recap
What 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?
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 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
•Protein
2. What does it mean that the cell membrane
is “selectively permeable?”