Nitrogen Metabolism Flashcards Preview

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Flashcards in Nitrogen Metabolism Deck (36):
1

General concepts in this section?

-Urea cycle
-Breaking down amino acids for energy

2

How can we store carbohydrates?

Glycogen in our liver

3

How do we store fat?

Adipose tissue

4

How do we store amino acids?

We can't!

5

What two ways do we get protein?

1. Diet

2. Protein turnover (breakdown pre-existing proteins)

6

What is the average half-life of a protein?

1-2 days

7

What are enzymes that break down proteins in our digestive system called?

Proteases / peptide protease / proteases

8

What's an example of a protease that we talked about?

Chymotrypsin

9

How does protein in our cells get broken down (what's the process called)?

Ubiquitination

10

Where do proteins tagged by ubiquitin go?

The proteosome
Peptide bonds broken inside proteosome

11

What two major things are amino acids used for?

1. Build new proteins
2. Broken down for energy

12

What are essential amino acids?

Can't be synthesized by precursors (so need them in our diet)

13

How will proteins eventually be stored if needed?

Stored as fat - go into citric acid cycle, turned into adipose tissue

14

Why does nitrogen need to be removed in amino acid catabolism?

It's toxic

15

What is transamination?

Move NH3 to a-ketoacids to make amino acids

How you make nonessential amino acids from essential

16

How many metabolic intermediates are there when you remove the amino group of an amino acid?

7 intermediates: all 7 can turn into different stuff

>pyruvate, acetyl-CoA, and intermediates in the citric acid cycle

17

What is the precursor to purines?

Glutamine

18

What is the precursor to pyrimidines?

Carbanoyl phosphate (also involved in urea cycle)

19

What is the basic structure of the proteosome?

Two regulatory subunits on the top/bottom

Catalytic subunit in the middle

20

What do the regulatory subunits of the proteosome do?

Only allow polyubiquitinated proteins through
Denature protein

21

What does the catalytic subunit of the proteosome do?

Cleaves protein into 7-9 amino acid polypeptides

Spits out all the chains + ubiquitin

22

What happens to amino acid chains after they're spit out by the proteosome?

Split up into individual amino acids by cytosolic proteases

23

What is ubiquitin?

It's a protein that marks other proteins for degredation

Inactive by itself until activated

24

What first activates ubiquitin?

E1 - ubiquitin activating enzyme- (phosphorylation)

Prepare ubiquitin to get attached to a protein

25

What happens after ubiquitin is phosphorylated by E1?

Transferred to E2 (ubiquitin-conjugating enzyme)

26

What is E2 complexed with?

E3 (ubiquitin protein ligase)

27

What does the E2-E3 complex do to ubiquitin?

Attach ubiquitin to a protein ready to be degraded

28

How does a protein 'know' when it's ready to be degraded?

There are markers on the hydrophobic core of the protein; when a protein starts to unfold due to age, those markers get exposed and the E2-E3 complex can bind

29

What amino acid is ubiquitin added at?

A lysine residue, ALWAYS

30

When does polyubiquitination happen?
How many ubiquitins are necessary?

Added one at a time after the first ubiquitin is added

Need at least 4 ubiquitins to get into the proteosome

31

What happens once an amino group is removed from amino acid?

Left with a carbon skeleton
R group removed by an enzyme specific to that amino acid
Goes into citric acid cycle as a metabolic intermediate

32

What are glucogenic amino acids?

Amino acids that can eventually be turned into glucose

33

What are ketogenic amino acids?

Get turned into ketone bodies / Acetyl-CoA

34

What happens to excess ammonia after amino acid breakdown?

Transported to liver

After liver, excretion as urea from urea cycle

35

What's the general idea of the urea cycle?

Remove ammonia from amino acids, get urine out. Carbanoyl phosphate involved in the beginning step

36

How do you synthesize amino acids (anabolism)?

Synthesized from intermediates in glycolysis, pentose phosphate pathway, citric acid cycle