40 Questions
Which two main classes can lipids be broken down into structurally?
Fatty acids and isoprenoids
What are the three components of a phospholipid?
Hydrocarbon chain, backbone glycerol, and phosphate-alcohol head group
Which phospholipid has both fatty acids linked to the glycerol backbone with an ester link?
Phosphatidate
Which phospholipid has one fatty acid linked to the glycerol backbone with an ether link while the other has an ester link?
Phosphatidylcholine
Which phosphoglyceride is the most common in the cell membrane?
Phosphatidylcholine
Which phospholipid contains a ceramide backbone?
Sphingomyelin
Which class of lipids can sphingomyelin also be classified as?
Sphingolipids
What is the role of the transfer molecule CDP in phospholipid synthesis?
It transfers the phosphate-alcohol head group to the glycerol backbone
How do phospholipids synthesized in the smooth ER reach the plasma membrane?
Through active transport
What is the basic structure of a phospholipid?
Phosphatidic acid
What is the composition of a phospholipid?
2 Hydrocarbon chains, glycerol, phosphate-alcohol head group
Where does phospholipid synthesis primarily occur?
On the luminal surface of the smooth ER and the inner mitochondrial membrane
Which steps are involved in the synthesis of glycerophospholipids?
Synthesis of glycerol shared with backbone and attachment of fatty acids to backbone via ester linkage
How is the head group added to phosphatidic acid?
One of the hydroxyl is first activated by attachment of a nucleotide, cytosine diphosphate (CDP)
What can phosphatidylserine be converted to in a reversible headgroup exchange reaction?
Phosphatidylethanolamine
What is the role of phosphatidylinositol in the cell membrane?
It plays an important role in cell signalling
How do newly made phospholipids reach the other side of the smooth ER membrane and the cell membrane?
They require a special enzyme called flippase to translocate them across the ER membrane to the cytosolic side
What nucleotide is used to help with the addition of a head group to phosphatidic acid?
Cytosine
Where does the synthesis of glycerol-3-phosphate occur?
In the liver
How is phosphatidylcholine formed from phosphatidylethanolamine?
By addition of 3 methyl groups donated by S-adenosylmethionine (SAM)
Which step in cholesterol synthesis is catalyzed by HMG CoA reductase?
Step 1
What is the main regulatory enzyme in the cholesterol synthesis pathway?
HMG CoA reductase
How many acetyl CoA molecules are needed to make squalene?
6
Which step in cholesterol synthesis involves the conversion of mevalonate into activated isoprenes?
Step 2
How many acetyl CoA molecules are needed to make Mevalonate?
3
What is the main regulatory step of cholesterol synthesis?
Condensation of 3 acetyl CoA into Mevalonate
How is HMG CoA reductase regulated in cholesterol synthesis?
Reversible covalent modification
What promotes de-phosphorylation of HMG CoA reductase, activating the enzyme?
Insulin
What promotes phosphorylation of HMG CoA reductase, inhibiting the enzyme?
Glucagon
What happens to the transcription of HMG CoA reductase gene when intracellular cholesterol levels are high?
Decreases
Which structural group does cholesterol belong to?
Isoprenoid
Which organs of the body contribute most significantly to cholesterol synthesis?
Liver and kidney
Where does cholesterol synthesis occur inside the cell?
Endoplasmic reticulum
What are the basic steps of cholesterol synthesis?
Condensation of 3 acetyl CoA into mevalonate, Formation of isopentenyl pyrophosphate, Creation of squalene
What is the role of the key regulatory enzyme HMG CoA reductase in cholesterol synthesis?
Condensation of 3 acetyl CoA into mevalonate
What influences the activity of HMG CoA reductase in cholesterol synthesis?
Insulin and glucagon
What inhibits HMG CoA reductase in cholesterol synthesis?
High intracellular levels of cholesterol
What are the main components of cholesterol?
Fused rings with various substituents
What are sterols?
Complex molecules made from 6 isoprene units
What is the function of cholesterol in the cell membrane?
To provide structural support
Test your knowledge on cell membrane and cytoskeleton by taking this quiz! Learn about phospholipids, their classification, components, and synthesis in the cell membrane. Can you name the three most common phosphoglycerides found in the cell membrane? Find out now!
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