UW Entrepreneurship in the news…
Patients with celiac disease have lost normal
stomach cell function because of their own
immune system overreacting to gluten.
Gliadin is a component of gluten,
and removing gliadin may help...
Can you bioengineer an enzyme to degrade gliadin that will
survive in the acidic stomach environment?
UW Entrepreneurship in the news…
Patients with celiac disease have lost normal
stomach cell function because of their own
immune system overreacting to gluten.
Gliadin is a component of gluten,
and removing gliadin may help...
Can you bioengineer an enzyme to degrade gliadin that will
survive in the acidic stomach environment?
(a UW spinoff company)
!$35 Million to do just that
Peer Instruction
Purine-pyrimidine pair
JUST RIGHT
Purine-purine pair
NOT ENOUGH SPACE
Pyrimidine-pyrimidine pair
TOO MUCH SPACE
Space inside sugarphosphate backbones
1) Why do purines bind only to pyrimidines?
Sugar-phosphate backbone
5ʹ
Guanine
Cytosine
Adenine
Thymine
3ʹ
2) Why will Guanine pair only with Cytosine?
3) Base pairs in DNA helices form with antiparallel
structure. Can they form antiparallel bonds as well?
3ʹ
5ʹ
Peer Instruction
1) Describe this
polymerization
reaction. 2) What kind of
reaction is this?
3) Why is this new bond called a phosphodiester linkage?
Building DNA: Double Helix Measurements
Distance between
bases: 0.34 nm
Length of one complete
turn of helix: 3.4 nm
(__ rungs per turn)
Width of the helix: 2.0 nm
[DNA helix]
Clicker Question #3
Chargaff’s Rule:
We know that in DNA there are A-T and G-C base-pairs.
If I tell you that a DNA molecule is 30% guanine,
what is the % of thymine in that molecule?
1. 
2. 
3. 
4. 
5. 
6. 
0%
10%
20%
30%
40%
50%
Respond at PollEv.com/biology200
(or text BIOLOGY200 to 22333 once to join)
Peer Instruction
RNA: Structure and Function
The primary structure of
RNA differs from DNA in
two ways:
-
-
Loop
Stem
Single
stranded
Double
stranded
The presence of the 2’–OH
group on ribose makes RNA
much (more/less) reactive and
(more/less) stable than DNA.
Building DNA: Making a Copy
“It has not escaped our attention that the specific pairing we have postulated
immediately suggests a possible copying mechanism for the genetic material.” -Watson and Crick, 1953
Key Concepts
•  Find the structure of a nucleotide, and point out the nitrogenous base,
the phosphate group(s), the ribose ring, whether it is DNA or RNA,
what base it is, and whether this is a relatively high-energy or lowenergy molecule compared to other nucleotides.
•  What is the nickname for this nucleotide? (for example: ‘dGMP’)
•  Explain, without skipping over any parts, why adding ATP hydrolysis to
a reaction can allow an organism to drive an otherwise impossible
reaction.
•  Imagine that the genome of a new bacteria found on Mars is 35%
Guanine. What percentage of the new genome is likely to be Cytosine?
What assumptions are you making in your calculation?
•  Why is RNA more like protein than DNA?
•  Why is it more like DNA than protein?
•  What extra work must you do to complete a Bio200 exam?
•  Is this a good or bad exam system? Why?
Class 5 Learning Goals
Monday, Janary 9th, 2017
Lipids and Membranes
•  After this class, you should be able to:
– 
– 
– 
– 
Classify a molecular as one of three main classes of lipids
Describe the structure and formation of a lipid bilayer
Predict the comparative solubilities of any two molecules
Predict the solubilities of a molecule through two different bilayers
Lipid Structures
Peer Instruction
1) What are the defining features of each class of lipids?
2) Which are amphipathic, and why?
Using phospholipids
Clicker Question #1
Which of these structures do you think are likely to form
spontaneously in water?
3.
1.
2.
4.
Video: Bilayer formation
Lipids: How might cells be formed?
1) Why do lipid bilayers form?
Peer Instruction
2) In what ways can individual phospholipids
move within a bilayer?
Peer Instruction
Explain this data.
Clicker Question #2
How permeable is the lipid bilayer to methane?
1. 
2. 
3. 
4. 
Very permeable
Slightly permeable
Slightly unpermeable
Extremely unpermeable
Clicker Question #3
What about ATP; will it permeate a lipid bilayer?
1.  Yes, permeates very easily
2.  Yes, but only a little
3.  Slightly, but it could if the
membrane were slightly loosened
4.  Almost completely impermeable
Clicker Question #4
(A tougher one)
How permeable is an RNA monomer?
1. 
2. 
3. 
4. 
Very
Slightly
Unpermeable
Extremely
unpermeable
Clicker Question #5
(Tougher, but very relevant to pollution issues)
How permeable is benzene to membranes?
1. 
2. 
3. 
4. 
Very
Slightly
Slightly unpermeable
Extremely unpermeable
Peer Instruction
What compounds cross lipid bilayers most readily?
Rank these molecules from most to least likely to cross a plasma membrane:
Glucose
CO2
H 2O
O2
K+
Peer Instruction
Are membranes with straight lipid tails more or less
permeable than membranes with kinked tails?
Are membranes with long tails more or less permeable
than membranes with short tails?
Are warmer membranes more or less permeable than
colder membranes?
Membranes: Saturation of C-C bonds in lipid tails
Clicker Question #6
(An over-simplified question)
Imagine a pure membrane from only one of
these four phospholipids:
3
1
4
2
Which membrane will be the most permeable to ethanol?
Clicker Question #7
(A complicated question)
Imagine adding a dose of cholesterol to the
phospholipid membrane in one of your cells… Cholesterol: What effect will this have on the membrane?
1. 
2. 
3. 
4. 
The membrane will be MORE permeable.
The membrane will be LESS permeable.
The membrane permeability will not change.
It will depend on the specific phospholipid
composition of the membrane.
TransmembraneTransport
Get one copy of the worksheet
for each person
Either:
•  Work in a group, or
•  Work individually then check with people around you
Clicker Question #8
Is the membrane of this cell semi-permeable?
1.  Yes, because molecules can cross the membrane easily.
2.  Yes, because molecules cannot cross the membrane
easily.
3.  Yes, because some molecules cross the membrane
easily, but other molecules do not cross easily.
4.  No, it is not semi-permeable.
Clicker Question #9
What is the difference between Cell A and Cell B?
1.  Cell A actively transports molecules across the membrane.
2. 
3. 
4. 
Cell B creates a ‘door’ to allow molecules to go down their
concentration gradient and come into the cell .
Cell B uses passive diffusion to push molecules out of the cell.
Cell B actively transports molecules up a concentration gradient and
out of the cell.
Clicker Question #10
Orientation for Page 2:
What does this image show?
1.  A cross section of a transport protein taken within
the hydrophobic area of a membrane.
2.  A cross section of a lipid membrane.
3.  A hollow tube of multiple cells.
4.  A protein floating outside of the hydrophilic layer
of phospholipids.
Key Concepts
• 
• 
• 
• 
What kind of lipid is estradiol? Safflower oil?
Will a lipid bilayer form faster in pure water or muddy water? Why?
Which will go through a lipid bilayer faster:
–  Benzene or methane? Potassium ions or methane? Glucose or ATP?
Through which membrane will sodium ions move more quickly:
–  A membrane with long, straight tails or short, kinked tails?