Cell Membrane and Cytoskeleton: Post learning - cholesterol and phospholipids

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Which two main classes can lipids be broken down into structurally?

Fatty acids and isoprenoids (correct)

Phospholipids and fatty acids

Phospholipids and sphingolipids

Sphingolipids and isoprenoids

What are the three components of a phospholipid?

Hydrocarbon chain, backbone phosphatidic acid, and phosphate-alcohol head group

Hydrocarbon chain, backbone sphingomyelin, and phosphate-alcohol head group

Hydrocarbon chain, backbone glycerol, and phosphate-alcohol head group (correct)

Hydrocarbon chain, backbone ceramide, and phosphate-alcohol head group

Which phospholipid has both fatty acids linked to the glycerol backbone with an ester link?

Phosphatidate (correct)

Phosphatidylcholine

Phosphatidylethanolamine

Phosphatidylserine

Which phospholipid has one fatty acid linked to the glycerol backbone with an ether link while the other has an ester link?

Phosphatidylcholine Signup and view all the answers

Which phosphoglyceride is the most common in the cell membrane?

Phosphatidylcholine Signup and view all the answers

Which phospholipid contains a ceramide backbone?

Sphingomyelin Signup and view all the answers

Which class of lipids can sphingomyelin also be classified as?

Sphingolipids Signup and view all the answers

What is the role of the transfer molecule CDP in phospholipid synthesis?

It transfers the phosphate-alcohol head group to the glycerol backbone Signup and view all the answers

How do phospholipids synthesized in the smooth ER reach the plasma membrane?

Through active transport Signup and view all the answers

What is the basic structure of a phospholipid?

Phosphatidic acid Signup and view all the answers

What is the composition of a phospholipid?

2 Hydrocarbon chains, glycerol, phosphate-alcohol head group Signup and view all the answers

Where does phospholipid synthesis primarily occur?

On the luminal surface of the smooth ER and the inner mitochondrial membrane Signup and view all the answers

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 Signup and view all the answers

How is the head group added to phosphatidic acid?

One of the hydroxyl is first activated by attachment of a nucleotide, cytosine diphosphate (CDP) Signup and view all the answers

What can phosphatidylserine be converted to in a reversible headgroup exchange reaction?

Phosphatidylethanolamine Signup and view all the answers

What is the role of phosphatidylinositol in the cell membrane?

It plays an important role in cell signalling Signup and view all the answers

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 Signup and view all the answers

What nucleotide is used to help with the addition of a head group to phosphatidic acid?

Cytosine Signup and view all the answers

Where does the synthesis of glycerol-3-phosphate occur?

In the liver Signup and view all the answers

How is phosphatidylcholine formed from phosphatidylethanolamine?

By addition of 3 methyl groups donated by S-adenosylmethionine (SAM) Signup and view all the answers

Which step in cholesterol synthesis is catalyzed by HMG CoA reductase?

Step 1 Signup and view all the answers

What is the main regulatory enzyme in the cholesterol synthesis pathway?

HMG CoA reductase Signup and view all the answers

How many acetyl CoA molecules are needed to make squalene?

6 Signup and view all the answers

Which step in cholesterol synthesis involves the conversion of mevalonate into activated isoprenes?

Step 2 Signup and view all the answers

How many acetyl CoA molecules are needed to make Mevalonate?

3 Signup and view all the answers

What is the main regulatory step of cholesterol synthesis?

Condensation of 3 acetyl CoA into Mevalonate Signup and view all the answers

How is HMG CoA reductase regulated in cholesterol synthesis?

Reversible covalent modification Signup and view all the answers

What promotes de-phosphorylation of HMG CoA reductase, activating the enzyme?

Insulin Signup and view all the answers

What promotes phosphorylation of HMG CoA reductase, inhibiting the enzyme?

Glucagon Signup and view all the answers

What happens to the transcription of HMG CoA reductase gene when intracellular cholesterol levels are high?

Decreases Signup and view all the answers

Which structural group does cholesterol belong to?

Isoprenoid Signup and view all the answers

Which organs of the body contribute most significantly to cholesterol synthesis?

Liver and kidney Signup and view all the answers

Where does cholesterol synthesis occur inside the cell?

Endoplasmic reticulum Signup and view all the answers

What are the basic steps of cholesterol synthesis?

Condensation of 3 acetyl CoA into mevalonate, Formation of isopentenyl pyrophosphate, Creation of squalene Signup and view all the answers

What is the role of the key regulatory enzyme HMG CoA reductase in cholesterol synthesis?

Condensation of 3 acetyl CoA into mevalonate Signup and view all the answers

What influences the activity of HMG CoA reductase in cholesterol synthesis?

Insulin and glucagon Signup and view all the answers

What inhibits HMG CoA reductase in cholesterol synthesis?

High intracellular levels of cholesterol Signup and view all the answers

What are the main components of cholesterol?

Fused rings with various substituents Signup and view all the answers

What are sterols?

Complex molecules made from 6 isoprene units Signup and view all the answers

What is the function of cholesterol in the cell membrane?

To provide structural support Signup and view all the answers