LB145
Sec 001-004
Today’s Outline
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HAND IN StudyNotes – front of classroom.
Homework Assignment due on Tuesday.
Create a Classroom Code of Conduct.
Protein review.
Lipids + Membranes
A human experiment
Membrane transport
What is a protein?
What do proteins do?
Where do you get proteins from?
• Discuss with your neighbor:
– What are some foods that are high in protein
content?
– What are some foods that contain no protein?
What is a protein?
• A protein is a chain of amino acids.
• ALL foods contain proteins – because all living
cells contain proteins.
• When we eat proteins, our body breaks them
down into their composite amino acids. We
use these amino acids to make our own
proteins.
A Chain of Amino Acids
Lipids
Clicker Question: What is a lipid?
a) Is a group of molecules that includes: fats,
steroids and phospholipids.
b) Molecules that have fatty-acid side chains.
c) Carbon-containing compounds that are nonpolar and hydrophobic.
d) A molecule with a hydrophilic head and a
hydrophobic tail that is a major component
in cell membranes.
Lipids
• A lipid is an organic compound, found in
organisms, that is primarily non-polar and
hydrophobic.
• Three types to know
– Fats (triacylglycerol)
– Phospholipids
– Steroids
Campbell 8e, Fig. 5.15
Campbell 8e, Fig. 5.13b
Fatty acids form ester bonds with glycerol
Fats consist of glycerol linked to three fatty acids
Biological Membranes are Composed of
Phospholipids
Biological Membranes are Composed of
Phospholipids
Campbell 8e, Fig. 5.13
What is a Membrane?
• A phospholipid bilayer (a fluid mosaic).
Membrane Fluidity
The individual phospholipid molecules in lipid bilayer membranes are in constant motion
Membranes are dynamic structures
Membrane Fluidity
The Role of Steroids
Steroids
Which is true?
(a) Cholesterol reduces fluidity and reduces
permeability of membranes.
(b) Cholesterol increases fluidity and increases
permeability of membranes.
(c) Cholesterol increases fluidity and decreases
permeability of membranes.
(d) Cholesterol decreases fluidity and increases
permeability of membranes.
Role of Cholesterol
Back to talking about things that have fatty acid
side chains…
Saturated vs. Unsaturated
(a fat question)
Which of the following statements about
unsaturated fat is true?
a) They are more common in animals than plants.
b) They have double bonds in the carbon chains
of their fatty acids.
c) They generally solidify at room temperature.
d) They contain more hydrogen that saturated
fats having the same number of carbon atoms.
e) They have fewer fatty acid molecules per fat
molecule.
The Shape of Phospholipids…
• Why is one leg of the phospholipid bent?
Saturated vs. Unsaturated
Membrane Permeability
A human experiment…
Tonicity
Osmosis can cause the shrinking or
swelling of cells
Building Mental Models
• Think about a cell
membrane – how
would you draw
one?
Membrane?
Membrane?
Proteins
Cell exterior
Phospholipid
bilayer
Cell interior
Transmembrane Proteins and Transport
• Transmembrane proteins are imperative for
cellular transport.
Passive facilitated
processes
Active facilitated
process
• Channels
• Carrier proteins or transporters
• Pumps
Hydrophilic interior
Outside cell
Hydrophobic exterior
H2O
Inside cell
Gated Channels
Potassium ions enter
the channel
Outside cell
Inside cell
Closed
Positive charge
triggers channel
to open.
Electrochemical
gradient.
Open
Active Transport by Pumps
• Molecules can be transported against an
electrochemical concentration gradient.
• This requires energy.
Summary of Membrane Transport
1. Diffusion
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Small, non-polar, uncharged
2. Facilitated diffusion
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Channel Protein
Carrier Protein
3. Active transport
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Requires Energy
Your HOMEWORK
This homework is worth 5 points. Once you hand it in, you will be asked to evaluate someone else’s homework
– the quality of your evaluation will be worth an additional 2 points. All point-determinations will be made by
the teaching team.
Instructions:
- Use a word-processor (12 pt. font) for your responses.
- You MUST upload a copy of your homework to the Angel TurnItIn Dropbox folder.
- DO NOT INCLUDE YOUR NAME ON THIS ASSIGNMENT.
- When you upload your assignment to the Angel TurnItIn Dropbox folder it should have no identifying
marks.
- When you bring a copy to hand in at class on January 15th (12:40pm), you should identify yourself using
ONLY the last four digits of your PID #. If your name is on the assignment it will not be accepted.
The Question:
Compare and contrast simple diffusion, facilitated diffusion, and active transport across a biological lipid
bilayer membrane.
- Define each process as applied to a biological lipid bilayer membrane.
- Provide a specific example of each process as applied to a biological lipid bilayer membrane.
- Describe each example (what’s going on? how does it work?).
REMEMBER – It’s OK to discuss ideas with friends, but YOU MUST TURN IN YOUR OWN UNIQUE WORK!!!
For Tuesday:
• Homework #1 is due
– Available on the website.
– Be sure to follow instructions!!
– TurnItIn + Paper Copy.
• Register your clicker.
• StudyNotes #2 is due on
Thursday. It’s a big one!
7.0, 7.1, 7.2, 7.5