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48 Cards in this Set
- Front
- Back
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What does a glycerophospholipid look like? |
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What are the polar head groups found in phospholipids? |
1. Ethanolamine (amino alcohol) 2. Choline (amino alcohol) 3. Serine 4. Inositol |
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Which polar head group is this? |
Serine |
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Which polar head group is this? |
Choline |
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Which polar head group is this? |
Inositol |
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Which polar head group is this? |
Ethanolamine |
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What is the phosphatidyl part of a phospholipid? |
The glycerol backbone, 2 fatty acids chains and the phosphate group. N.B Even with different fatty acid chains, it's still a phosphatidyl |
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Other membrane lipids are based on sphingosine rather than glycerol. What is the difference between sphingosine and glycerol? |
Sphingosine has a backbone quite like glycerol, except that it has a permanent hydrocarbon chain (C15) |
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What is this important membrane phospholipid bases on sphingosine? |
Sphingomyelin (sphingosine with an added fatty acid, phosphate and polar head group-choline) |
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Where is sphingomyelins found? |
In the myelin sheath of neurones |
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In summary, what are the two kinds of phospholipid? |
1. Glycerol based- glycerophospholipid 2. Sphingosine based- sphingomyelin |
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Another type of membrane lipid is a glycolipid/glycosphingolipd. What is this? |
Sphingosine based Add a fatty acid chain and a carbohydrate polar head group No phosphate group |
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What is a glycolipid based on sphingosine? |
A cerebroside which has no phosphate but has a single sugar head group ( glucose or galactose) |
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Where are cerebrosides important? |
In brain cell membranes |
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What is a ganglioside? |
A glycolipid based on sphingosine. Has an oligosaccharide head group. |
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What is an example of a ganglioside? |
ABO blood group determinants |
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What are two saturated fatty acids that you would find in cell membranes? |
Palmitic acid Stearic acid |
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How many carbons are in palmitic acid? |
16 |
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How many carbons are in stearic acid? |
18 |
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What is an example of a mono-unsaturated acid in a membrane? |
Oleic acid |
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How many carbons are their in oleic acid? |
18 |
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What configuration are naturally occurring mono unsaturated fatty acids found in? |
The cis configuration |
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What are polyunsaturated fatty acids and what are three examples of them? |
Fatty acids with two or more C=C bonds Linoleic acid Linolenic acid Arachidonic acid |
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How many carbons does linoleic acid have? How many double bonds does it have? |
18 carbons 2 double bonds |
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How many carbons does linolenic acid have? How many double bonds does it have? |
18 carbons 3 double bonds |
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How many carbons dos arachidonic acid have? How many double bonds does it have? |
20 4 |
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What is this? |
Arachidonic acid |
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Is the bilayer formation energetically favourable? |
Yes |
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In the cell, where is new membrane formed? |
in ER |
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What is the minimum vesicle size? |
25 nm |
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How does new membrane get from the ER to where it is needed? |
Vesicles carry it |
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What are some important membrane properties? |
It is flexible ( so can form vesicles) It is fluid |
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How much does a lipid float within the layer per second? |
2μm |
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Why is the flip flop movement between the two layers rare and how can it be helped? |
Difficult to achieve as polar head groups would have to move through the hydrophobic region. Special 'flippase' enzymes can help with this |
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What two forms can the cell membrane transition between? |
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How do longer chain fatty acids affect the transition temperature and why? |
They increase the transition temperature because they increase VdW interactions. |
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How do longer chain fatty acids affect membrane fluidity? |
They decrease it it |
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How do unsaturated fatty acids affect the transition temperature? |
They reduce it |
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How do unsaturated fatty acids affect membrane fluidity? |
They increase it because they make the membrane less company |
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How do bacteria respond to a changing environment? |
By varying the proportion of unsaturated fatty acids in their plasma membrane |
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Cell membranes in a reindeers leg have an increased number of un-saturated fatty acids. What is a possible explanation for this? |
Unsaturated fatty acids increase membrane fluidity because the cis double bond between carbons introduces a kink in the fatty acid chain, so the phospholipids cannot pack so tightly in the membrane, reducing VdW forces between them. Thus, the unsaturated fatty acids reduce the Tm of the membrane so it will stay in a liquid rather than a gel form at low temperatures. A liquid membrane is necessary for proper biological function. |
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What is the Tm? |
The T m (melting temperature) is the temperature at which the membrane undergoes the transition from the gel to the liquid crystal state. |
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What does cholesterol do at low temperatures? |
Increases membrane fluidity by preventing fatty acids packing too tightly |
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What does cholesterol do at high temperatures? |
It stiffens the membrane by filling the space between unsaturated fatty acids |
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How does cholesterol act as a 'fluidity buffer' ? |
It blurs the membrane transition temperature. Cholesterol mean the membrane won't go so suddenly from liquid form to the stiff gel form. Cholesterol makes it a more gradual transition. |
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The permeability of the lipid bilayer is higher for molecules that are.... |
small, uncharged, non-polar. |
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What are four important roles that proteins play in membrane function? |
Transporters Anchors Receptors Enzymes |
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Why is cholesterol important in animals but not in bacteria? |
Bacteria ( which do not contain cholesterol), vary the proportion of unsaturated fatty acids in their membranes in response to changes in temperature but animals don't do this. |
