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BIOCHEMISTRY LECTURES

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BIOCHEMISTRY LECTURES. Figure 10-2 2. Stages in the extraction of energy from foodstuffs. Enzyme is inhibited by malonyl CoA! Why?. heart muscle kidney brain. 1. Synthesis takes place in the cytosol, in contrast with degradation, which occurs in the mitochondrial matrix.

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slide19

heart

muscle

kidney

brain

slide20

1. Synthesis takes place in the cytosol, in contrast with degradation, which occurs in the mitochondrial matrix.

2. Intermediates in fattv acid synthesis are covalently linked to the sulf-hydryl groups of an acyl carrier protein (ACP), whereas intermediates in fatty acid breakdown are bonded to coenzyme A.

3. The enzymes of fatty acid synthesis in higher organisms are joined in a single polypeptide chain called fatty acid synthase. In contrast, the degradative enzymes do not seem to be associated.

4. The growing fatty acid chain is elongated by the sequential addition of two-carbon units derived from acetyl CoA. The activated donor of two-carbon units in the elongation step is malonyl-ACP. The elongation reaction is driven by the release of CO2.

5. The reductant in fatty acid synthesis is NADPH, whereas the oxidants in fatty acid degradation are NAD+ and FAD.

6. Elongation by the fatty acid synthase complex stops upon formation of palmitate (C16). Further elongation and the insertion of double bonds are carried out by enzyme systems of the endoplasmic reticulum with the fatty acyl groups as CoA derivatives.

slide21

Schematic diagram showing the proposed movement of the biotin prosthetic group from the site where it acquires a carboxyl group from HCO3- to the site where it donates this group to acetyl CoA.

slide22

Acetyl CoA carboxylase, which catalyzes the committed step in fatty acid synthesis, is a key control site.

slide29

Citrate transport system. The system achieves net transport of acetyl CoA from the mitochondrion to the cytosol and net conversion of cytosolic NADH to NADPH. Up to two molecules of ATP are expended for each round of the cyclic pathway.

slide38

To make prostaglandins and leucotrienes, animals use

C20 fatty acids with 3,4 or 5 cis

s in key positions.

We must get fatty acids with

s in

positions w 6,9 or w 3,6,9 from plants.

slide39

18

17

16

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

D

CH3

w

slide41

Animals and plants can place a subsequent

Only plants can place a subsequent

, separated

, separated

by –CH2– from an existing

, towards the –COO- group,

regardless of the length (C16, C18, C20) of the fatty acid.

6

new

by –CH2– from an existing

, towards the CH3– group.

D

12

9

new

existing

D

9

existing

slide42

D

C18:1

w

C18:2

w

C18:3

w

C18:0

In plants

9

9

6

9

3

6

9

slide43

C18:2

w

C18:3

w

C20:3

w

PGs1

C20:4

w

PGs2

In animals or plants

6

9

6

9

12

6

9

12

6

9

12

15

slide44

C18:3 w3,6,9

C18:4 w3,6,9,12

C20:5 w3,6,9,12,15

w

3

6

9

12

15

PGs3

important eicosanoids
Important eicosanoids

Vascular endothelial cells:

vasdilatory

inhibits platelet aggregation

Platelets:

aggregates platelets

White blood cells,

mast cells

inflammatory,

allergic

cyclooxygenases
Cyclooxygenases

COX 1: constitutive

- in plateletts

- in gastrointestinal epithelial cells

COX 2: induced in inflammatory process

Selective inhibitors – non steroidal (NSAIDs) ?

How do steroids reduce inflammation?

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