Label the parts of the below lipid molecule. Is this a saturated or unsaturated lipid? (3 pts) H H H H H H H H H H— С . I C-C-C-C-C 1 1 H H H H H C-C-C-C-H I 1 1 1 H H H H 4. Draw a lipid structure. Properly label the polar and non-polar ends of the representation of a lipid below: (3 pts) 5. Arrange the following fatty acids in order from lowest melting point to highest: myristic acid, arachidonic acid, linolenic acid, stearic acid, oleic acid. You can find the structures in our libre text or in-class homework activity. What do the highest have in common? What do the lowest have in common? (3 pts)
The Correct Answer and Explanation is :
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Question 3: Label the parts of the lipid molecule
In the lipid structure you provided, based on the notation and chemical groups involved:
- Hydrogen atoms (H) – These are attached to the carbon chain, which is typical in fatty acids.
- Carbon atoms (C) – These form the backbone of the molecule. Each carbon (except for the ones at the ends) is attached to two hydrogens, making the carbon chain.
- The notation “C-C-C-C-C” refers to a chain of carbon atoms bound together, with hydrogens filling the rest of the bonds.
- Functional Group – If the structure you are referencing is a fatty acid, the functional group at the end (COOH) will define whether the lipid is saturated or unsaturated.
Saturated vs Unsaturated:
- If all the carbon atoms in the fatty acid chain are bonded to the maximum number of hydrogen atoms (no double bonds between carbons), it is a saturated fatty acid.
- If there are double bonds between the carbon atoms (causing “kinks” in the chain), the fatty acid is unsaturated.
Given this description, the molecule in question would likely be saturated if it does not have any double bonds.
Question 4: Draw a lipid structure and label the polar and non-polar ends
In a lipid molecule, like a phospholipid:
- Polar head: The head contains a hydrophilic (water-loving) group, usually a phosphate group.
- Non-polar tail: The tails are made of fatty acid chains that are hydrophobic (water-fearing).
- Polar head: This is the part of the molecule that interacts with water (hydrophilic).
- Non-polar tail: These are the fatty acid chains, which are hydrophobic and avoid water.
Question 5: Arrange fatty acids by melting point
Here’s the order of fatty acids from lowest melting point to highest:
- Arachidonic acid (most unsaturated, lowest melting point)
- Linolenic acid (unsaturated)
- Oleic acid (monounsaturated)
- Myristic acid (saturated)
- Stearic acid (most saturated, highest melting point)
What do the highest melting point fatty acids have in common?
The highest melting point fatty acids are saturated. Saturated fatty acids have no double bonds, allowing them to pack tightly together, which results in higher melting points.
What do the lowest melting point fatty acids have in common?
The lowest melting point fatty acids are unsaturated. Double bonds in these fatty acids create kinks in the carbon chain, preventing tight packing and lowering the melting point.
Would you like more detailed explanations or clarifications on any of the points?