Membranes & transport - membrane fluidity Flashcards
What are the main components of phospholipids?
Glycerol, a phosphate group, and two fatty acid chains
Phospholipids are essential for forming cell membranes.
How can fatty acids vary?
Length of the hydrocarbon chain and saturation level
Saturation refers to the presence of double bonds between carbon atoms.
What characterizes saturated fatty acids?
Every carbon atom is bonded to 4 other atoms, and they are straight chains
Saturated fatty acids have higher melting points.
What does it mean for a fatty acid to be ‘saturated’?
It contains as many hydrogen atoms as it possibly can
This means each carbon in the chain is linked to 2 hydrogen atoms.
Why do saturated fatty acids have higher melting points?
They can pack together tightly
This tight packing helps maintain membrane stability at higher temperatures.
What are unsaturated fatty acids characterized by?
One or more double bonds between carbon atoms
They can be mono-unsaturated (one double bond) or polyunsaturated (more than one double bond).
What is the effect of double bonds on the structure of unsaturated fatty acids?
They create bends or kinks in the chain
This prevents them from packing tightly, resulting in lower melting points.
How do unsaturated fatty acids affect membrane fluidity?
They allow membranes to be fluid and flexible
This is crucial for maintaining function at varying temperatures.
How do bacteria cope with temperature fluctuations affecting their membranes?
They produce enzymes called fatty acid desaturases
These enzymes increase the number of double bonds in fatty acids to maintain fluidity.
What adaptations do deep-sea marine organisms have regarding their membranes?
Correlations between sea temperature and membrane-fluidising lipid components
This includes the presence of polyunsaturated fatty acids.
What role do fatty acid unsaturation pathways play in plants like Arabidopsis thaliana?
They are key in the acclimatisation of membranes to high temperature
This helps plants adapt to changing environmental conditions.
What is cholesterol’s role in cell membranes?
It affects fluidity and permeability
Cholesterol maintains membrane structure and function across temperature changes.
What allows cholesterol to exist within the bilayer of the membrane?
Its hydrophobic and hydrophilic regions
This dual nature is essential for its function in membranes.
How does cholesterol maintain membrane fluidity at different temperatures?
It disrupts close-packing of phospholipids and holds fatty acid tails together
This increases flexibility at low temperatures and stability at high temperatures.
What barrier function does cholesterol serve in membranes?
It prevents water-soluble substances from diffusing across the membrane
Cholesterol fits in spaces between phospholipids to enhance membrane integrity.
