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Questions and Answers
Some lipid molecules are said to be amphipathic, meaning that they:
Some lipid molecules are said to be amphipathic, meaning that they:
- Carry a positive charge on one end and a negative charge on the other end
- Have asymmetric carbons and can exist in left- and right‑handed forms
- Are capable of moving rapidly from one side of a lipid bilayer to the other
- Have a dual nature with part of the molecule being hydrophobic and the other part being hydrophilic (correct)
Unsaturated fatty acids have double bonds that are in the cis configuration. One of the consequences of this configuration is:
Unsaturated fatty acids have double bonds that are in the cis configuration. One of the consequences of this configuration is:
- An alteration in the number of carbons in the molecule
- An alteration in the charge of the molecule
- Enhanced flexibility of the molecule
- A bend in the molecule (correct)
In phosphoglycerides, fatty acids are esterified at:
In phosphoglycerides, fatty acids are esterified at:
- A glycerol carbon and the phosphate group
- C‑1 and C‑2 of glycerol (correct)
- C‑1 and C‑3 of glycerol
- Any two of the three glycerol carbons
Which statement does NOT describe a difference between archaeal membrane lipids and those of bacteria and eukaryotes?
Which statement does NOT describe a difference between archaeal membrane lipids and those of bacteria and eukaryotes?
Of the three major types of membrane lipids, which is NOT found in prokaryotes?
Of the three major types of membrane lipids, which is NOT found in prokaryotes?
The fatty acid oleate contains 18 carbons and a cis double bond after C‑9. Which designation describes the composition and structure of oleate?
The fatty acid oleate contains 18 carbons and a cis double bond after C‑9. Which designation describes the composition and structure of oleate?
In biological systems, fatty acids usually contain an even number of carbon atoms. Which fatty acids are MOST common in biological systems?
In biological systems, fatty acids usually contain an even number of carbon atoms. Which fatty acids are MOST common in biological systems?
A triacylglycerol consists of fatty acids attached to:
A triacylglycerol consists of fatty acids attached to:
Fill in the blank for the fatty acid composition: $C_{18}H_{34}O_2$ is commonly known as _____
Fill in the blank for the fatty acid composition: $C_{18}H_{34}O_2$ is commonly known as _____
Which of the designations are accurate for the fatty acid?
Which of the designations are accurate for the fatty acid?
Fatty acids are carboxylic acids with a long, unbranched hydrocarbon chain. Classify the fatty acids as _____, _____, or _____
Fatty acids are carboxylic acids with a long, unbranched hydrocarbon chain. Classify the fatty acids as _____, _____, or _____
Match each fatty acid with its melting point:
Match each fatty acid with its melting point:
Which of the statements are true?
Which of the statements are true?
Select the statements about fatty acid melting points that are true.
Select the statements about fatty acid melting points that are true.
Which lipid or lipids must be obtained in the diet?
Which lipid or lipids must be obtained in the diet?
Which of the statements are true?
Which of the statements are true?
A glycerol molecule and three butyric acid molecules are shown. Delete atoms and add bonds as necessary to form a triacylglycerol (triglyceride). Draw only the triacylglycerol product.
A glycerol molecule and three butyric acid molecules are shown. Delete atoms and add bonds as necessary to form a triacylglycerol (triglyceride). Draw only the triacylglycerol product.
Classify the characteristics of triacylglycerols and phosphoglycerides:
Classify the characteristics of triacylglycerols and phosphoglycerides:
Classify each structural feature as characteristic of a sphingolipid or a phosphoglyceride:
Classify each structural feature as characteristic of a sphingolipid or a phosphoglyceride:
Select the molecules that can form the polar head group of phospholipids.
Select the molecules that can form the polar head group of phospholipids.
Which properties are true of this lipid?
Which properties are true of this lipid?
Glycerophospholipids (phosphoglycerides) are components of cell membranes. They are composed of a glycerol molecule with two fatty acids attached to the first and second carbon atoms, and a polar (hydrophilic) group attached through a phosphodiester linkage to the third carbon atom. Match each structure with the correct name.
Glycerophospholipids (phosphoglycerides) are components of cell membranes. They are composed of a glycerol molecule with two fatty acids attached to the first and second carbon atoms, and a polar (hydrophilic) group attached through a phosphodiester linkage to the third carbon atom. Match each structure with the correct name.
Sort the descriptions into properties that describe either saturated phospholipids or unsaturated phospholipids.
Sort the descriptions into properties that describe either saturated phospholipids or unsaturated phospholipids.
Select the molecules that contain sphingosine.
Select the molecules that contain sphingosine.
Block diagrams representing the general structures of three lipid types are shown. Classify each block diagram as a triacylglycerol (triglyceride), glycerophospholipid (phosphoacylglycerol), or sphingophospholipid (sphingomyelin).
Block diagrams representing the general structures of three lipid types are shown. Classify each block diagram as a triacylglycerol (triglyceride), glycerophospholipid (phosphoacylglycerol), or sphingophospholipid (sphingomyelin).
A glycolipid is:
A glycolipid is:
What basic ring structure is common to all steroids?
What basic ring structure is common to all steroids?
Is the molecule shown hydrophilic, hydrophobic, or amphipathic (amphiphilic)?
Is the molecule shown hydrophilic, hydrophobic, or amphipathic (amphiphilic)?
What is the difference between docosahexaenoate (DHA) and 19,20-dihydroxydocosapentaenoate (19,20-DHDP)?
What is the difference between docosahexaenoate (DHA) and 19,20-dihydroxydocosapentaenoate (19,20-DHDP)?
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Study Notes
Lipid Characteristics
- Amphipathic lipids have both hydrophobic and hydrophilic regions, allowing them to form structures like lipid bilayers.
- Unsaturated fatty acids feature cis double bonds, which create bends in their structure, affecting their fluidity and flexibility.
Phosphoglycerides
- In phosphoglycerides, fatty acids are esterified specifically at the C-1 and C-2 positions of the glycerol backbone.
- Phosphoglycerides are integral components of cellular membranes, providing structural integrity and functionality.
Archaeal Membrane Lipids
- Archaeal lipids differ from bacterial and eukaryotic lipids by using ether linkages instead of ester linkages, contributing to their stability in extreme environments.
- Archaeal membranes may also contain branched hydrophobic tails and alternative backbones, enhancing resilience under harsh conditions.
Types of Fatty Acids
- Cholesterol is not found in prokaryotes; instead, they contain phospholipids, phosphoglycerides, and glycolipids.
- The fatty acid oleate, which has 18 carbons and a cis double bond, is designated as 18:1.
- Fatty acids with 16 and 18 carbons are the most common in biological systems.
- A triacylglycerol is formed by the attachment of three fatty acids to a single glycerol molecule, serving primarily as an energy storage form.
Melting Points and Fatty Acids
- The melting point is affected by the saturation level of fatty acids; saturated fatty acids generally have higher melting points than their unsaturated counterparts.
- A saturated fatty acid of greater molar mass has a higher melting point, indicating that longer-chain saturated fatty acids remain solid at room temperature more often than unsaturated ones.
Essential Fatty Acids
- Essential fatty acids must be obtained through diet, contributing to various physiological functions.
- Saturated fats are predominantly solid at room temperature, while unsaturated fats tend to be liquid.
Triacylglycerols vs. Phosphoglycerides
- Triacylglycerols consist of three fatty acid chains, while phosphoglycerides contain only two fatty acids with a third carbon linked to a polar head group, often involved in membrane formation.
- Migratory birds utilize triacylglycerols as a major energy source for long-distance flight.
Structural Features
- Glycerophospholipids are recognized by their glycerol backbone linked to two fatty acids and a polar group via a phosphodiester bond.
- Sphingolipids differ from phosphoglycerides in that they contain sphingosine, not glycerol.
Glycolipids
- Glycolipids are lipids that include at least one carbohydrate unit, playing important roles in cell recognition and signaling.
Steroid Structure
- All steroids share a common basic ring structure derived from a sterol precursor, contributing to their diverse biological roles.
Polar and Nonpolar Groups
- Molecules with polar head groups and nonpolar tails are crucial for forming cell membranes, distinguishing between hydrophobic and hydrophilic regions for membrane integrity and function.
- Certain lipids, like sphingomyelins, incorporate sphingosine and play vital roles in cellular activities and membrane dynamics.
DHA vs. 19,20-DHDP
- 19,20-DHDP is more polar than docosahexaenoate (DHA), indicating a difference in their solubility and interaction in biological systems.
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