Lecture6 Flashcards
What are membranes for prokaryotic & eukaryotic cells?
They are one of the things prokaryotic and eukaryotic cells have in common.
What is the function of cell membranes?
The plasma membrane separates the inside and the outside of the cells. They create compartments within the cell->cell membrane, organelles, vacuoles and vesicles.
What is the structure of cell membranes?
Lipids, proteins & carbohydrates (glycolipids & glycoproteins). Membranes are composed of phospholipids.
Explain cell membranes.
Cell membranes are fluid, which means they can move. Keeping in mind that phospholipids form cell membranes. These phospholipids turn on their axis, move laterally in any direction over the surface of the membrane. Flipping across the membrane occurs very rarely (insideout)
What 2 things influence the fluidity of the cell membrane?
- The type of fatty acid chains in the phospholipid
2. The presence of cholesterol.
Explain how the type of fatty acid chains in the phospholipids influences the fluidity of the cell membrane.
If you increase the # of saturated fatty acids, the membrane fluidity will decrease. If you increase the # of unsaturated fatty acids, the membrane fluidity will increase.
Explain how the presence of cholesterol influences the fluidity of the cell membrane.
Cholesterol is amphipathic. It helps maintain the integrity of membranes-> especially the plasma membrane. The effect of membrane fluidity is temperature dependent.
How does high temperature affect the membrane fluidity?
> =37 oC
This decreases the membrane fluidity as the gaps between phospholipids fill and there is therefore less movement for the phospholipids as they are prevented from moving apart too much.
How does low temperature affect the membrane fluidity?
<37oC
This increases the membrane fluidity by preventing clumping of phospholipids.
Cell membrane: What are integral membrane proteins?
These proteins go from the outside to the inside of the membrane. They’re composed of 3 regions: 2 hydrophilic and one hydrophobic region. They’re permanently associated with the cell membrane.
Cell membrane: Explain what role integral membrane proteins have.
They play an important role in moving molecules across cell membranes. The molecules that are moved are solutes and solvents. So for this process, an example would be solute transport proteins.
Cell membrane: What are peripheral membrane proteins?
They’re temporarily associated with integral membrane proteins through weak non-covalent interactions (H-bonds). They’re easily separated from the membrane. They are a component of the transmission of information from external signals.
What are cell membrane carbohydrates?
Carbohydrates that are membrane bound are involved in cell to cell recognition. On the extracellular surface of the plasma membrane, cells can recognize other cells by binding to molecules which usually contain carbohydrates.
Cell membrane carbohydrates: what are glycolipids?
They’re carbohydrates that are covalently bonded to lipids.
Cell membrane carbohydrates: what are glycoproteins?
They’re carbohydrates that are covalently bonded to proteins.