Lipids

Question 1

Storage form of a fatty acid.

Answer 1

Triacylglycerol

Question 2

What is the structure of a triacylglycerol?

Answer 2

Glycerol molecule esterified to three fatty acid chains.

Question 3

Triacylglycerol molcules amphipathic. What does this mean?

Answer 3

It contains hydrophobic and hydrophillic regions

Question 4

A chemical reaction between an acid and a base to form a salt. This is how soap is made using a triacylglycerol molecule as well as a base (NaOH).

Answer 4

Saponification

Question 5

enzymes that hydrolyze fats.

Answer 5

lipases

Question 6

Why are fats a better energy storage than carbohydrates?

Answer 6

1. Packing
   
   1. Able to pack closer together due to their amphapathic nature
   2. results in a unit weight that is much larger in a fat droplet than dissolved sugar
2. Energy Content
   
   1. Fat is much more reduced (remember that metabolism begins with oxidation of “foodstuff” to release energy)
   2. Thus, since carbohydrates are more oxidized, oxidizing them releases less energy.

Question 7

Describe the structure of a phospholipid. What does it make-up?

Answer 7

Diglycerol molecule with a phosphate group. This makes up the lipid bilayer membrane.

Question 8

What are the three things that increase fluidity within the lipid bilayer?

Answer 8

1. Unsaturated fatty acids (decreases tightly packing)
2. Shorter fatty acid tails
3. Cholesterol (maintains optimal fluidity)

Question 9

What is the structure of a terpene? What is it built from? What is its formula?

Answer 9

Terpenes are repeating units of isoprone. The basic formula is (C₅H₈)_n. See structure of a general isoprene below.

Question 10

Describe the structure of squalene.

Answer 10

Six isoprene units. (Triterpene). Is a compound in earwax.

Question 11

What is an example of a functionalized terpene (terpenoid)?

Answer 11

Vitamin A

Question 12

Has cholesterol backbone, is tetracyclic, amd amphapathic. This type of molecule is also synthesized in the liver and obtained via diet. It is packeged with other lipids and proteins when traveling through the blood (lipoproteins)

Answer 12

Steroids

Question 13

What are two examples of steroid hormones.Describe their nature.

Answer 13

Estrodial and Testosterone (female and male androgens, respectively)

• Can easily diffuse through lipid bilayer because they are highly hydrophobic
• Receptors are within the cell rather than on the cell membrane

Question 14

Answer 14

This is a sphingosine It is the backbone of spingolipids. A common sphingolipid in the human body is myelin sheath. Below is the structure of Myelin sheath.

Question 15

Answer 15

This the structure of wax. It is a combination of long chain fatty acids esterified to long chain alcohols. It is highly hydrophobic and used as a barrier.

Question 16

What are fat soluble vitamins?

Answer 16

A-DEK

Question 17

This vitamin is essential for growth, epithelial maintence, and immune function.

Answer 17

Vit A

Question 18

Vitamin that is erived from cholsterol and is important for regulating blood levels of calcium and phosphate.

Answer 18

Vitamin D

Question 19

Vitamin important as antioxidants.

Answer 19

Vit E

Question 20

Important coenzyme in the actvation of clotting proteins.

Answer 20

Vit K

Question 21

Answer 21

This is a prostaglandin. It is derived from a 20-carbon fatty acid. These have a vast number of roles including regulation of smooth muscle and maintaing gastric integrity

Question 22

What are the three major steps of Beta-Oxidation of fatty acids?

Answer 22

1. Activation for transport
   
   • Fatty acid + Coenzyme A form a bond in the cytoplasm of the cell to create acyl-CoA
   • This reaction is coupled with the hydrolysis of ATP
     
     • ATP ► AMP + PP_i
     • Hydrolysis of PP_I with H2O drives this reaction
   • Catalyzed by acyl synthetase (located on outer mitochondrial membrane)
2. Transport
   
   1. Carnitine hydroxyl group “attacks” acyl-CoA
      
      1. Causing CoA to take back its electrons
      2. catalyzed by carnitine acyl transferase 1 (CAT I)
   2. Acyl Carnitine diffuses into intermembrane space via porin pores
   3. Acyl carnitine translocase transports acyl carnitine from intermembrane space to matrix
   4. Coenzyme A takes acyl group away from acyl carnitine
      
      1. catalyzed by by CAT II
   5. ​Acyl-CoA is reformed
   6. Also remember that for every acyl carnitine molecule pumped into matrix, a subsequent carnitine molecule is pumped out
3. Oxidation
   
   1. During oxidation, acetyl CoA is produced, leaving an acyl CoA 2 chains shorter
      
      1. Oxidation occurs at B-Carbon (2 carbons away from carbonyl carbon)
      2. Each round of Beta oxidation cleaves a two carbon acetyl-CoA from the original molecule (last round cleaves 4 carbon fatty acyl-CoA two two acetyl-CoA molecules)

Ultimately, Acetyl CoA will get shuttled to the Kreb’s Cycle

Question 23

How doe you determine how many acetyl Co-A are produced during Beta Oxidation?

Answer 23

Divide the number of carbons in the original fatty acid molecule by 2

Question 24

How do you determine the number of cycles a fatty acid chain has to go through Beta Oxidation? How does this help determine the amount of FADH₂ and NADH are produced?

Answer 24

(n/2)-1

Number of cycles equals number of electron carriers (each one) are produced (i.e. 5 cycles will equal 5 NADH and 5 FADH₂)

Question 25

How do you calculate the Net ATP (including the 2 ATP used at the beginning of fatty acid oxidation) produced from B-oxidation

Answer 25

(number of acety CoA produced multiplied by 10) + (Number of cycles multplied by 4) - 2

(However, if the questions states that 3 ATP are produced per NADH and 2 are produced per FADH₂ - increase the 10 multiplier to 12 and 4 to 5)

Question 26

The production of ketone bodies in the liver as a result of glycogen and glucose shortage to supply energy to the CNS. This occurs in the mitochondria and from acetyl CoA: _______, _________, _________ are produces. The molecules can cross the blood brain barrier and are converted back to acetyl CoA when they reach their target tissues and enter the Kreb’s Cycle.

Answer 26

Ketone Bodies:

1. Acetone
2. Acetoacetate
3. B-Hydroxybutyrate

Question 27

List the steps of Fatty Acid Oxidation.

Answer 27

1. Citrate (contains OAA and Acetyl CoA) is “shuttled” out to cytoplasm
2. Citrate then breaks down back to OAA and Acetyl CoA
3. Acetyl CoA is carboxylated by acetyl CoA carboxylase, generating Malonyl CoA
   
   1. This reaction is coupled with ATP Hydrolysis (producing ADP + P_i)
4. Fatty Acid Synthase binds Acetyl CoA in Acyl Carrier Protein (ACP)
5. Acetyl CoA is then shifted to the next catalytic domain (a cystein residue)
   
   1. At this time, Fatty Acid synthase binds Malonyl CoA to its ACP catalytic domain
6. Acyl Group in the cystein residue condenses with malonyl CoA as the malonyl is decarboxylated
7. The four carbon unit, now in the ACP carrier, undergoes two separate reductions by NADPH
8. Four carbon acyl unit is now shifted to the cysteine residue as the ACP binds another malonyl CoA molecule
9. The first 8 steps are repeated unit the entire fatty acid chain has been synthesized (Palmitate Acid in humans)
   
   1. two carbons are added during each cycle
10. Additional enzymes come in to modify as needed.

Question 28

Fatty Acid Synthesis is described as a non-template synthesis. Why?

Answer 28

There is no template. Nothing is read to generate products. (as in the central dogma)

Question 29

List three ways in which AA are catabolized.

Answer 29

1. Protein Synthesis
2. Amino group can be taken and used to make nitrogenous compounds
   
   1. Or it can be converted to produce urea
3. Carbon skeleton can be
   
   1. Broken down into H2O and CO₂
   2. Used to make glucose
   3. Used to make acetyl-CoA

Question 30

Nucleic Acids