Biochemistry Addendum Iii

Front 1

302. What is the acyl carrier in fatty acid elongation systems?

Back 1

Co-A (not ACP)

Front 2

303. What is an important precursor for eicosanoids?

Back 2

Arachidonate

(20:4∆5,8,11,14)

Front 3

304. What are the two essential long chain FA's?

Why are they essential?

Back 3

Linoleate & Linolenate

-They are essential because we cannot make them ourselves

Front 4

305. Which omega 3 FA's correspond to linoleate and linolenate?

Back 4

Linolenate: omega 3 fatty acids

Linoleate: omega 6 fatty acids

Front 5

306. What is used to add double bonds in FA synthesis?

Back 5

Fatty acyl-CoA desaturase

Front 6

307. What is fatty acyl-CoA desaturase?

Back 6

A mixed function oxidase that makes unsaturated FA's

Front 7

308. How does the reaction of adding doubles bond work?

Three things...

Back 7

1. Reduction of dioxygen oxidizes 2 different molecules
(a fatty acyl-CoA and NADPH)

2. Two e- come from the fatty acid and two e- come from NADPH
(unusual that you use e- to oxidize)

3. O2 is e- acceptor

Front 8

309. What are the two enzymes that use oxygen as an e- acceptor?

Back 8

1. Oxidases

2. Oxygenases

Front 9

310. What do oxidases do?

Two things...

Back 9

1. Use O2 just to dump e- on

2. O2 is not incorporated into the oxidized product

Front 10

311. What is an example of an oxidase?

Back 10

cytochrome oxidase

Front 11

312. What are the two types of oxygenases?

Back 11

1. Monooxygenases

2. Dioxygenases

Front 12

313. What are monooxygenases?

Back 12

They are mixed function oxygenases that add only 1 oxygen molecule to the substrate

Front 13

314. What are dioxygenases?

Back 13

They add both oxygen molecules (O2) to the substrate

Front 14

315. What are the energetics of FA synthesis for one molecule of palmitate?

Back 14

NEED:
1 acetyl-CoA
7 malonyl-CoA
14 NADPH

YIELD:
1 palmitate
7 CO2
14 NADP+
8 CoA
6 H2O

Front 15

316. How many ATP are needed for FA synthesis?

Back 15

42 ATP!
(expensive and chunky synthesis)

Front 16

317. How is FA biosynthesis regulated?

Back 16

Through phosphorylation of acetyl-CoA carboxylase

Front 17

318. Under what conditions do you make fat?

Five things...

Back 17

1. High blood glucose (ate)
2. Increased insulin levels
3. Activate phosphatase (dephosphorylate acetyl-CoA carboxylase; ACC)
4. ACC activated
5. Acetyl-CoA is converted to malonyl-CoA

Front 18

319. Under what conditions do you burn fat?

Four things

Back 18

1. Low blood glucose (starving)

2. Increased glucagon levels

3. Activate PKA (phosphorylate ACC)

4. ACC is inactivated

Front 19

320. What two things allosterically regulate FA degradation?

Back 19

1. Carnitine acyltransferase I

2. Malonyl-CoA

*elevated levels repress

Front 20

321. What are eicosanoids and what are they derived from?

Back 20

They are potent signaling molecules

Family of short range signaling lipids

They are derived from arachidonic acid

Front 21

322. What are three types of eicosanoids?

Back 21

1. Prostaglandins

2. Thromboxanes

3. Leukotrienes

Front 22

323. What do prostaglandins do?

Back 22

Cause inflammation

Front 23

324. What do thromboxanes do?

Back 23

cause blood vessel constriction

Front 24

325. What do leukotrienes do?

Back 24

cause smooth muscle contraction

Front 25

326. What is required for synthesis of eicosanoids?

Two things...

Back 25

1. Arachidonic acid

2. Dioxygenase

Front 26

327. How is thromboxanes and other prostaglandins synthesized?

Three steps...

Back 26

1. Form arachidonate

2. Use cyclooxgenase to put on peroxide

3. Modifications

Front 27

328. What is arachidonate derived from?

Back 27

Linoleate

Front 28

329. What is cyclooxgenase (COX)?

Back 28

A key enzyme in forming eicosanoids and causes human discomfort

Front 29

330. What are most of our common medicines?

Back 29

COX inhibitors

Front 30

331. What are the two isozymes of COX?

Back 30

Cox-1: required for secreting the mucin that lines and protects your stomach

Cox-2: required for inflammation

Front 31

332. What does aspirin inhibit?

What does this result in?

Back 31

-It inhibits both isoforms of COX

-It causes stomach irritation

Front 32

333. Why have we developed specific COX-2 inhibitors (Vioxx and Celebrex)?

What's bad about them though?

Back 32

-To eliminate to unhappy side effect of stomach irritation

-They have the unpleasant side effect of increasing the risk of heart attacks

Front 33

334. What are cholesterol, steroids, and isoprenoids based on?

Back 33

Isoprene

*used to make a vast number of other products

Front 34

335. What are three important points about cholesterol?

Back 34

1. It has a four ring fused nucleus

2. It has a hydroxyl group

3. Start with acetate to synthesize it

Front 35

336. What is the order of events in steroid synthesis?

Back 35

1. Acetate to Mevalonate

2. Mevalonate to Activated Isoprene

3. Activated Isoprene to Squalene

4. Squalene to Cholesterol

Front 36

337. What happens in converting acetate to mevalonate?

Two things...

Back 36

1. Condense two acetyl-CoA which then condenses with third acetyl-CoA to form 6 C compound

2. Reduction of HMG-CoA to mevalonate is rate-limiting step

Front 37

338. What is the key enzyme in the regulation of steroid synthesis?

What does it catalyze?

Back 37

HMG-CoA reductase is key enzyme that regulates steroid synthesis

It catalyzes reduction of HMG-CoA to mevalonate through a 4 e- reduction using 2 NADPH (NADPH -> NADP+)

Front 38

339. What do drugs used to reduce cholesterol level inhibit?

Back 38

They are competitive inhibitors of HMG-CoA reductase

Front 39

340. How does squalene form?

Back 39

Through successive condensations of activated isoprene

Front 40

341. How is squalene converted into cholesterol?

Back 40

Form an epoxide using an oxidase whose cofactor is NADPH

Then, cyclize the epoxide to the steroid nucleus using the enzyme cyclase

Front 41

342. What activates and deactivates HMG-CoA reductase?

Three things...

Back 41

1. Insulin activates by promoting dephosphorylation of the reductase

2. Glucagon deactivates by promoting phosphorylation of the reductase

3. Cholesterol inhibits the reductase

Front 42

343. Can lipids move in the blood stream freely?

Why or why not?

Back 42

Lipids are too hydrophobic to move freely in the blood stream and need to be complexed to various proteins for transport

Front 43

345. What two proteins do lipids bind to for transport?

Back 43

1. Serum Albumin: bind/move FA's

2. Lipoproteins: bind/transport triacyglycerols and cholesterol

Front 44

346. What are the four major classes of human plasma lipoproteins?

Back 44

1. Chylomicrons

2. Very low density lipoprotein (VLDL)

3. Low-density lipoprotein (LDL)

4. High-density lipoprotein (HDL)

Front 45

347. Which lipoproteins mostly carry FA's?

Two...

Back 45

1. Chylomicrons

2. VLDL

Front 46

348. Which lipoproteins carry a significant amount of cholesterol?

Two

Back 46

1. LDL

2. HDL

Front 47

349. Which lipoprotein is the biggest and which is the smallest?

Back 47

The biggest is chylomicrons (lowest density)

The smallest is HDL

Front 48

350. What do chylomicrons mostly transport?

To where?

Back 48

Dietary lipids are packaged in chylomicrons

Most of their triacylglycerol content is released to adipose and muscle tissue during transport through the capillaries

Front 49

351. What is LDL termed?

Back 49

"Bad" cholesterol

*It raises level of cholesterol in the body

Front 50

352. Where does LDL travel to?

Back 50

It delivers cholesterol to peripheral tissue or returns to the liver

Front 51

353. What is HDL termed?

Back 51

"Good" cholesterol

*It reduces level of cholesterol in the body

Front 52

354. Where does HDL travel to?

Back 52

It takes excess cholesterol and goes to the liver for excretion

Front 53

355. Why is too much cholesterol bad?

Back 53

It plugs up the pumping (clogs arteries)

beefy chunkiness

Front 54

356. Is there any was to reduce the LDL and raise the HDL? How?

Two ways

Back 54

Yeah, Jimmy Jam

1. Eat monounsaturated fat (olive oil, canola oil-this is the best way)

2. Eat polyunsaturated fat (corn, soybeans)

Front 55

357. What fat will raise both LDL and HDL?

Back 55

Saturated fats (whole milk, butter, cheese)

Front 56

358. What fat is the worst for and raises only LDL?

Back 56

Trans fats (unnatural fats in fast food, chips, shortening)

Front 57

359. How can you tell the types of fats apart to know if it's good or bad for you?

Three ways?

Back 57

1. Monounsaturated and polyunsaturated fats are liquids

2. Saturated fats are solids

3. Trans fats are solid or semi-solid

Front 58

360. What is the major path for nitrogen into biomolecules?

Two parts...

Back 58

1. Nitrogen fixation (N2 -> NH4)

2. NH4 to glutamate/glutamine (glutamine synthetase)

Front 59

361. What is the minor path for nitrogen into biomolecules?

Two parts...

Back 59

1. Nitrogen fixation

2. NH4 to oxaloacetate/glutamate (glutamate dehydrogenase)

Front 60

362. Where does organic nitrogen come from?

Back 60

We are surrounded by nitrogen (80% of air is N2)

Front 61

363. Can we use any of the N2 in the air? Why or why not?

Back 61

NO, CHIPPY.

The energy to dissociate N≡N is too high (930 KJ/mol to dissociate)

Front 62

364. What is the source of nearly ALL organic nitrogen?

How is this done?

Back 62

Nitrogen fixation

Only a few species of bacteria make the enzyme nitrogenase which converts N2 to ammonia in an 8 e- reduction

Front 63

365. What is the biologically useful form of nitrogen?

Back 63

Ammonia

Front 64

366. What is the main place for NH4 to assimilate into the blood?

Back 64

Glutamine through glutamine synthetase

Front 65

367. How is NH4 assimilated into glutamine?

Back 65

1. Glutamate is converted to L-glutamine

2. Glutamine synthetase is the enzyme used

Front 66

369. What is glutamine synthetase?

Two points...

Back 66

1. A major pathway for incorporating ammonia into biomolecules

2. Critical control point regulated by feedback inhibition

Front 67

368. What does glutamine serve as?

Back 67

It is a biosynthetic precursor of many biomolecules

Front 68

370. What is feedback inhibition?

Back 68

Where the final product of the pathway allosterically inhibits the first committed step of the pathway

Front 69

371. Where is feedback inhibition common?

Two places

Back 69

1. Regulation of amino acids

2. Nucleotide biosynthesis

Front 70

372. What are three allosteric regulators for glutamine synthetase?

Back 70

1. Feedback inhibition
2. Anything that uses glutamine is an allosteric regulator to this enzyme
3. End produces of glutamine metabolism

Front 71

373. In what two ways can the nitrogen from glutamine (or glutamate) be transferred to other molecules?

Back 71

1. Amidotransferase

2. Aminotransferase

Front 72

373. What is done in amidotransferase?

Back 72

Move the amide nitrogen from glutamine to other acceptor molecules

Front 73

374. How does amidotransferase work?

Two things...

Back 73

1. The ϓ-amido nitrogen of glutamine is released as NH3

2. The NH3 travels through a channel to the second active site where it reacts with an acceptor

Front 74

375. What does aminotransferase do?

Back 74

It can indiscriminately swap the α-amino groups between amino acids and ketoacids

Front 75

376. What cofactor is used in all aminotransferases?

Back 75

Pyridoxal Phosphate (PLP)

Front 76

377. What is the common donor in aminotransferase?

Back 76

Glutamate