Molecule Catabolism (Lec 4)

Question 1

Lipid Classification

Answer 1

1. Lipids that contain fatty acids (complex lipids), further separated into storage lipids and membrane lipids
2. Lipids that do not contain fatty acids (choleserol, vitamins, pigments)

Question 2

Fatty Acids

Answer 2

Carboxylic acids with hydrocarbon chains containing 4 to 36 carbons

Question 3

Saturated Fatty Acids

Answer 3

No double bonds between carbons in the chain

Question 4

Monosaturated Fatty Acids

Answer 4

1 double bond between carbons in the chain

Question 5

Polysaturated Fatty Acids

Answer 5

More than 1 double bond between carbons in the chain

Question 6

Fuel Storage: Fatty Acids

Answer 6

Fatty acids carry more energy per carbon because they are more reduced and carry less water as opposed to Polysaccharides

Question 7

Glucose vs. Fats

Answer 7

Glucose and Glycogen: fullfil short-term energy requirements, quick delivery
Fats: fullfil long-term energy needs, slow delivery, good storage

Question 8

Fatty Acid Transport into Mitochondria

Answer 8

Triacylglycerides (TAGs) are degraded into Glycerol and Fatty Acids and transported into the Mitochondria for β oxidation via acyl-carnitine/carnitine transporter

Question 9

Acyl-carnitine/Carnitine Transporter

Answer 9

Fatty Acyl-CoA + Carnitine -> Fatty Acyl-Carnitine –> Carnitine + Fatty Acyl-CoA

Question 10

Fatty Acid Oxidation

Answer 10

Stage 1: oxidative conversion of 2 carbon units into Acetyl-CoA via β oxidation, generating NADH and FADH2

Stage 2: Oxidation of Acetyl-CoA in Citric Acid Cycle generating NADH and FADH2

Stage 3: Generation of ATP from NADH and FADH2 via Electron Transport Chain

Question 11

The β-Oxidation Pathway

Answer 11

Each pass removes one acetyl moiety in the fomr of Acetyl-CoA

Question 12

Fatty Acid Oxidation

Answer 12

Performed by a single multi-function, multi-subunit protein (Hetero-octamer). ATP total yield = 108ATP

Question 13

Hetero-Octamer

Answer 13

Built up of:

• 4 Alpha subunits (responsible for binding to membrane)
• 4 Beta subunits

Question 14

Oxidation of Unsaturated Fatty Acids: Isomerase

Answer 14

Converts Cis double bonds starting at Carbon 3 to trans double bonds

Question 15

Oxidation of Unsaturated Fatty Acids: Reductase

Answer 15

Reduces Cis double bonds not at Carbon 3

Question 16

Ketone Bodies

Answer 16

When oxaloacetate is depleted, Acetyl-CoA is converted into Ketone Bodies. 3 forms exit the liver: Acetone, Acetoacetate, and β-hydroxybutyrate

Question 17

Formation of Ketone Bodies: Part 1

Answer 17

3 Acetyl CoA -> HMG-CoA

Question 18

Formation of Ketone Bodies: Part 2

Answer 18

HMG-CoA -> 3 Ketones

Question 19

Catabolism/Anabolism of Fatty Acids

Answer 19

Catabolism (Beta Oxidation)

• produces Acety-CoA, reducing power (NADH, FADH2)
• takes place in the mitochondria

Anabolism

• requires Acetyl-CoA, Malonyl-CoA and reducing power (NADPH)
• takes place in Cytosol in animals

Question 20

Fatty Acid Synthesis

Answer 20

Overall goal: attach acetate unit (2-carbon) from malonyl-CoA to a growing chain (Palmitate) and then reduce it.

Question 21

Fatty Acid Synthesis Steps

Answer 21

• Condensation of the growing chain with activated acetate
• Reduction of carbonyl to hydroxyl
• Dehydration of alcohol to trans-alkene
• Reduction of alkene to alkane

Question 22

Fatty Acid Synthesis: Step 1

Answer 22

Malonyl-CoA Is Formed from Acetyl-CoA and Bicarbonate

- catalyzed by acetyl-CoA carboxylase (ACC)

Question 23

Fatty Acid Synthesis: Step 2

Answer 23

Elongation of Fatty Acyl chain by 2 Carbons per step

- catalyzed by Fatty Acid Synthase (FAS)

Question 24

Amino Acid Catabolism

Answer 24

1. Recycled into new proteins

2. Oxidized for energy (removal of amino group in Urea cycle, entry into central catabolism (TCA cycle)

Question 25

Excretory Forms of Nitrogen

Answer 25

1. Ammonium 2. Urea 3. Uric Acid

Question 26

Enzymatic Transaminations

Answer 26

Transfer of one amine to usually α-ketoglutarate results in synthesis of glutamate. Catalyzed by amino-transferases

Question 27

The Glucose-Alanine Cycle

Answer 27

Works to remove lactate in bloodstream by converting it into Pyruvate and then converted into Alanine for transport to liver

Question 28

The Urea Cycle: Initial Phase

Answer 28

1. NH4+ from excess Glutamate converted to Carbomoyl Phosphate

Question 29

The Urea Cycle: Following Phases

Answer 29

2. Carbomoyl Phosphate condensed with Ornithine to produce Citrullene 3. Citrullene combines with Aspartate (uses ATP) to form Argininosuccinate 4. Argininosuccinate is cleaved to form Arginine 5. Arginine is hydrolysed to regenerate Ornithine 6. Process begins again

Question 30

Ketogenic vs. Glucogenic AA's

Answer 30

Ketogenic: can be converted to Ketone bodies Glucogenic: can be converted to Glucose

Question 31

End Products of Amino Acid Degredation

Answer 31

Can be converted to Acetyl-CoA (7), Pyruvate (6), α-ketoglutarate (5), Succinyl-CoA (4), Fumarate (2) and Oxaloacetate (2)

Question 32

Biosynthesis of Amino Acids and Nucleotides

Answer 32

Transaminations and rearrangements using Pyridoxal Phosphate (PLP). Catalyzed by amidotransferases

Question 33

Amino Acid Origins

Answer 33

Citric Acid Cycle: α-ketoglutarate, oxaloacetate Glycolysis: pyruvate, 3-phosphoglycerate, phosphoenolpyruvate Pentose Phosphate Pathway: ribose 5-phosphate, erythrose 4-phosphate