Biological Membranes Flashcards
(15 cards)
What occurs during the gel-to-liquid crystalline phase transition of a membrane?
The surface area must increase and the thickness must decrease as the membrane goes through a phase transition.
How does heat affect ordered bilayers?
Ordered bilayers become less ordered, while comparatively disordered bilayers become even more disordered.
What is the transition temperature in membranes?
The transition temperature is higher for more rigid and ordered membranes than for relatively fluid and disordered membranes.
What is differential scanning calorimetry (DSC)?
A powerful method to obtain information about phase transitions in lipid bilayers.
How does a DSC instrument work?
It has a sample cell for the bilayer and a reference cell containing a standard that will not undergo a phase transition. The temperature is increased in a controlled fashion, and the power needed to maintain the temperature is measured.
What does the graph from a DSC instrument indicate?
It provides information about both the transition temperature and the amount of energy needed for the phase transition.
What is the major difference between fats and oils?
The percentage of unsaturated fatty acids in the triglycerides and phosphoglycerides of membranes.
Why does butter melt in your mouth?
It has a high proportion of short-chain fatty acids.
How do the membranes of internal organs differ from skin tissues?
The membranes of internal organs of warm-blooded mammals have a higher percentage of saturated fats.
What happens to the fatty acid composition of bacterial membranes at different temperatures?
It reflects more unsaturated fatty acids at lower temperatures and more saturated fatty acids at higher temperatures.
What is the correlation between saturated fats and cardiovascular disease?
A diet high in saturated fats is correlated with an increased risk of heart attacks and strokes.
Why is canola oil considered a good dietary choice?
It has a high ratio of unsaturated fatty acids to saturated fatty acids.
What is the irony in the creation of butter substitutes?
They were created from polyunsaturated oils by partially hydrogenating the double bonds, making them more saturated.
What health risks are associated with trans fatty acids?
They raise the ratio of LDL cholesterol compared to HDL cholesterol, similar to the effects of saturated fatty acids.
What recent development has occurred in butter substitutes?
New butter substitutes have been marketed that advertise ‘no trans fatty acids.’
