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Worksheet 16: Week 10 Wednesday/Thursday

1. Most nitrogen on Earth is in the form of ___ N2 ______ . N2 can be incorporated into

biomolecules by some bacteria: this process is called __ nitrogen fixation _ . The reaction that

fixes nitrogen is catalyzed by _____nitrogenase ____ and is very highly __endergonic _________

it uses up ___16 _ ATPs.

2. Where do plants get nitrogen from?

Nitrate (No3-) in the soil or NH3 (fixed by bacteria).

3. Where do animals get nitrogen from?

Proteins or Nucleic acids in our diet.

4. Amino acid metabolism summary: The first step in catabolism of amino acids is to transfer the

amino group from the amino acid to _____alpha ketogluterate ____ , forming______glutamate _______________ .

The majority of the glutamate is converted to ___glutamine ___, so that it can be

transported through the blood to the ___liver ______. In the liver, it goes through the urea cycle.

The urea is then transport to the __ kidneys _____, where it is excreted.

The amino groups from the rest of the glutamate are either excreted directly from the

kidneys, or used for biosynthesis of other amino acids.

5. In each round of the urea cycle, ___1 _____- molecule of urea is produced. It contains 2 amino

groups: 1 from ____ carbomyl phosphate and 1 from ____aspartate _____.

6. Which enzymes of the urea cycle are located in the mitochondria?

Orithinine transcarbamoylase

Which enzymes are located in the cytosol?

Arginino succinate synthetase

Arginonosuccinate lyase

Arginase

7. When a fat molecule is broken down, it is first broken up into ___glycerol__ and fatty

acids_____. Then the glycerol is catabolized to __glyceraldhyde 3-phosphate__________, which

can enter the ___glycolysis________ pathway. The fatty acids are catabolized to __actyl-

coA_______, which can enter the __TCA cycle____.

8. What is the net ATP production when palmitate, a 16:0 fatty acid, is completely broken down?

8 Acetyl CoA moleculeseach acetyl coA will produce 10 ATP! Each acetyl coA goes through

one round of the citric acid cycle. Every NADH is 2.5 ATP and every QH2 is 1.5 ATP.

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The citric acid cycle makes 1 ATP, 1QH2, and 3 NADH. So in addition to the 8 acetyl

coA you make 7 NADHs and 7QH2 because last round produces 2 at once. Therefore

16:0 fatty acid when it is broken down will have 10 atp/8 acetyl coA=80 ATP and 7

NADH and 7QH2 so extra 28 ATP for a total of 108. But dont forget that we used 2

ATP in the beginning. So subtract those two to get a FINAL OF 106 ATP.

9. What is the net ATP production when the fat molecule shown below is completely broken

down?

Do the glycerol and fatty acids separately!

Glycerol: uses one atp makes one NADH! But if its completely broken down It goes to

glycolysis. 2 ATP, 1 NADH ( (b/c not glucose G3PD). PyruvateAcetyl CoA (by PDH makes

1 NADH)TCA cycle (10ATP)so it is going through electron transport when you are

converting NADH/QH2 to ATPs!18.5 ATP THEREFORE TOTAL = 378.5 ATP

Fatty Acids:

1st molecule:

20C 100 9NADH 22.5 9 QH2 -2 = 134 ATP

16C 106 ATP18C 90 atp (8NADH 8QH2) 120 ATP

For every 2 carbons you add you add 14 more ATP! TREND!

10. Which hormones regulate fatty acid catabolism?

Insulin (it will inhibit), Glucagon (stimulate), Epinephrine FIGHT OR FLIGHT! SO YOU WILL

NEED ENERGY FROM FAT BREAKDOWN!(stimulate).

11. Where does fatty acid catabolism occur?

The cyle part of it (4 enzymes) are in the mitochondrial matrix but the activation step is in the

cytosol so the fatty acyl-CoA synthetase. Fatty acyl-coAs are transported into the matrix on

carnitine (transporter).