Download Lecture 4 Basics: Plasma Membrane Membrane Structure Lipids

Lecture 4 Basics: Plasma Membrane
Membrane Structure
Lipids:
Definition:
Examples:
Characteristics:
Proteins:
Definition of a protein:
Protein structure:
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Why do proteins end up looking different from each other?
Polar R groups in a membrane protein:
Different membrane proteins:
Definitions:
Integral protein:
Peripheral protein:
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Carbohydrates:
Definition:
Examples:
Glycolipids and glycoproteins
Extracellular Matrix
Functions:
Important molecules
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Figures to label:
Extracellular matrix:
Plasma membrane:
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Membranes are fluid:
Why does “membrane fluidity” matter?
Factor 1: Saturation of phospholipids
Definition of saturation:
Facture 2: Temperature
Factor 3: Cholesterol
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Lecture 4 Class Notes:
If cells that normally grow at 37oC are cooled to 32oC, what change would allow the cell to maintain the
same membrane fluidity in the new environment? (MTOMBC)
A. Add more unsaturated phospholipids
B. Add more cholesterol
C. Add more phospholipids with carbon-carbon single bonds in the tail
D. Add more phospholipids that look like this:
Option
True or false
Explain why
A
B
C
D
The following paper came out in 2012:
Tavolari S, Munarini A, Storci G, Laufer S, Chieco P, Guarnieri T. 2012. The decrease of cell membrane
fluidity by the non-steroidal anti-inflammatory drug Licofelone inhibits epidermal growth factor receptor
signaling and triggers apoptosis in HCA-7 colon cancer cells. Cancer Letters: 187-94.
And had the following abstract (summary):
“Here, we provide evidence that, in HCA-7 cells, the pro-apoptotic effect of this drug relies, at least in
part, on its ability to inhibit epidermal growth factor receptor (EGFR) signalling by a decrease of cell
membrane fluidity. Indeed, Licofelone induced a relevant change in the relative proportions of some
saturated, monounsaturated and polyunsaturated fatty acids constituting HCA-7 phospholipid fraction
and significantly increased the levels of cholesterol in HCA-7 cell membrane. All of these changes
resulted in a remarkable decrease of membrane fluidity.“
1. What is HCA-7? Use your phone to look it up.
2. According to the abstract, what is the hypothesis?
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Here is a figure from the paper:
Fig. 1. Licofelone decreases HCA-7 cell membrane fluidity. (A) Fatty acid methyl esters (FAMEs) analysis of membrane phospholipids
fraction in HCA-7 cells treated for the indicated times with Licofelone 150 μM. (B) Evaluation of membrane saturation index in HCA-7
cells treated for the indicated times with Licofelone 150 μM. (C) Membrane cholesterol estimation in HCA-7 cells treated for the
indicated times with Licofelone 150 μM. (D) Pyrene labeling of HCA-7 membrane phospholipids after 0–180 min of treatment with
Licofelone 150 μM. Scale bar: 10 μm. A representative picture of cells with high (white arrow) and low (black arrow) excimer
fluorescence is also reported. *p < 0.05 and #p < 0.001.
3. Look at the level of arachidonic acid in Fig 1A. Would you predict this is a saturated or unsaturated
fatty acid?
4. According to these results, how has the level of membrane cholesterol changed?
5. Draw a before/after of the plasma membrane, showing the EFGR receptors and the membrane
components.
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