Essential Fatty Acids

Question 1

Are glycerophospholipids saturated?

Answer 1

Glycerophospholipids in membranes contain a saturated and an unsaturated fatty acid

Question 2

What is contained in a glycerophospholipid?

Answer 2

In position 1: a saturated fatty acid mostly with 16 or 18 carbons

In position 2: An unsaturated fatty acid with 16, 18, 20 or 22 carbons containing one or more double bonds

Question 3

What does MUFA mean?

Answer 3

Monounsaturated fatty acid

Question 4

What does PUFA mean?

Answer 4

Polyunsaturated fatty acid

Question 5

How does chain length and double bonds affect melting points?

Answer 5

The melting points of fatty acids increases with chain length and decreases with double bonds

Question 6

How many single carbon to double carbon ratio in stearic acid? What is the melting point?

Answer 6

18:0 melting point- 70 degrees Celsius

Question 7

What is the single carbon bind to double bond ratio of palmitic acid? What is the melting point?

Answer 7

16:0

Melting point- 63 degrees Celsius

Question 8

What is the single carbon bind to double bond ratio of oleic acid? What is the melting point?

Answer 8

18:1

13 degrees Celsius

Question 9

What is the single carbon bind to double bond ratio of palmitoleic acid ? What is the melting point?

Answer 9

16:1

1 degrees Celsius

Question 10

What is the single carbon bind to double bond ratio of linoleic acid?what is the melting point?

Answer 10

18: 2

- 5 degrees Celsius

Question 11

What is the single carbon bind to double bond ratio of a-linolenic acid? What is the me,ting point?

Answer 11

18: 3

- 11 degrees Celsius(comeback)

Question 12

Explain the desaturation of fatty acids in humans

Answer 12

Desaturation of fatty acids is restricted in animals

-Humans can introduce a double bond between carbons 9 and 10. And form 🔼9

Ex. Oleic acid (18:1) is formed in humans from stearic acid (18:0)

Question 13

Why can fatty acids be grouped into specific families?

Answer 13

Animals cannot form double bonds beyond 🔼9 toward the methyl end and that is why fatty acids can be grouped into specific families

Question 14

What determines the fatty acid family?

Answer 14

The family is determined by counting backwards from the last carbon , independent of the length of the fatty acid until the first double bond is reached. This number will determine the w-family

a-linolenic is shown which. Is of the w-3 (n-3 ) family

Question 15

How can animals form longer chain fatty acids?

Answer 15

Animals can introduce double bonds between 🔼9 and the carboxyl end and form longer fatty acids of the same family. But they cannot change the family

Question 16

What can linoleic acid be used to form?

Answer 16

Linoleic acid 18:2, w6 can be used to form arachidonic acid 20:4, w6

Food rich in w6 fatty acids- nuts, avacado and corn

Question 17

What can a-linolenic (w3) can be used to form?

Answer 17

a-linoleic acid (w3) can be used in humans to synthesize EPA and DHA which are found in biomembranes

Fish eat algae and form EPA and DHA

a-linoleic acid 18:3, w3 —> EPA(eicosapentaenoic acid 20:5, w3)- - >. DHA( docosahexaenoic acid 22:6, w3

Question 18

What is the purpose of TAG synthesis in hepatocytes?

Answer 18

Fatty acid synthesis and TAG synthesis for release into the blood inside of VLDL for fatty acid usage by other tissues

Question 19

What is the purpose of TAG. degradation in adipocytes?

Answer 19

Fatty acids generated from TAG degradation in lipoproteins are taken up and are stored in form of TAGs. This benefits the whole body during fatty acid synthesis

Question 20

Outline TAG synthesis in fat cells and hepatocytes

Answer 20

Glycolysis and glycerol (only liver) go to form glycerol 3-p

Glycerol 3-p And 2 fatty acyl CoAs form phosphatidic acid

Phosphatidic acid forms Pi and DAG

DAG uses 1 fatty acyl CoA to form TAG

Question 21

What is the MAG pathway for TAG synthesis?

Answer 21

Only in intestinal mucousal cells

MAG formed by pancreatic lipase

Fatty acid CoA along with MAG form DAG

DAG along with fatty acyl CoA form TAG

Question 22

What effect does high blood glucose and insulin have on TAG?

Answer 22

Increases TAG synthesis

Question 23

How does epinephrine effect TAG?

Answer 23

Epinephrine —> fight and flight (cAMP) lead to TAG degradation

Question 24

How does epinephrine lead to TAG degradation in fat cells?

Answer 24

Epinephrine via cAMP/protein kinase pathway leads to phosphorylation of and activation of hormone sensitive lipase (HLP) in fat cells. This leads to TAG degradation and release of glycerol and free fatty acids into the blood

Question 25

How are free fatty acids transported in the blood?

Answer 25

Free fatty acids aren’t water soluble and they are transported by albumin in hydrophobic pockets

-Albumin stays in the blood when fatty acids enter the cells

Question 26

What is the preferred fuel for heart and oxygenated muscle?

Answer 26

Fatty acids are the preferred fuel for energy generation in heart and oxygenated resting muscle

Question 27

When does liver need fatty acid oxidation?

Answer 27

The liver fatty acid oxidation during fasting for energy generation and for allosteric regulation to perform gluconeogenesis

Question 28

How does fatty acyl CoA synthetase (thiokinase) synthesize fatty acyl-CoA ?

Answer 28

The enzyme uses a free fatty acid, free CoA and ATP as substrates and forms fatty acyl CoA

The overall reaction is irreversible

• ATP is cleaved to AMP+ PPi
• PPi is immediately cleaved to 2

Totally 2 energy-rich bonds are cleaved which is counted often as 2 ATP

Question 29

What is free fatty acyl CoA used for ?

Answer 29

The free CoA pool is limited and the rapid turnover of fatty acyl CoAs is needed to generate free CoA again

Used in :
Energy (B-oxidation keto genesis )

Storage (triacylglycerols)

Membrane lipids (phospholipids, sphingolipids)

Question 30

What is the Carnitine shuttle?

Answer 30

• Fatty acids are activated to fatty acyl CoA at the outer mitochondrial membrane. They cannot pass the inner mitochondrial membrane for fatty acid degradation in mitochondria because they contain the bound CoA.
• The carnitine shuttle transfers the long-chain fatty acyl groups (16-20C) as carnitine esters into the mitochondrial matrix for degradation by B-oxidation

Question 31

Outline the carnitine shuttle

Answer 31

1. Fatty acyl CoA cannot pass the inner mitochondrial membrane therefore fatty acyl carnitine is formed by carnitine palmitoyl transferase 1 (CTP 1)
2. Fatty acyl carnitine is transferred through the inner mitochondrial membrane into the mitochondrial matrix by a translocase which transfers at the same time free carnitine out of the matrix (like a revolving door)
3. In the mitochondrial matrix, fatty acyl carnitine and free CoA are used to form again fatty acyl CoA by carnitine palmitoyl transferase II

Question 32

What is the site of synthesis, location of action and activation method of Hormone sensitive-lipase?

Answer 32

Site of synthesis: fat cells

Location of action: fat cells
Special: this lipase is only active when phosphorylated by protein kinase A

Activation method:phosphorylation following epinephrine action

Active inside of fat cells at low serum insulin and high epinephrine levels

Question 33

What is the site of synthesis, location of action, and activation method of pancreatic lipase?

Answer 33

Site of synthesis: pancreatic cells

Location of action: intestinal lumen

Special dietary TAG is only degraded to MAG and 2 fatty acids

Activation method: TAGs, bile salts, colipase

Active after a meal in the intestinal lumen and released by CCK from the pancreas