Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Biochem 2 > 1. Nitrogen balance. Digestion of proteins. Function of proteases, their regulation. Absorption of amino acids, amino acid transporters > Flashcards

1. Nitrogen balance. Digestion of proteins. Function of proteases, their regulation. Absorption of amino acids, amino acid transporters Flashcards

1
Q

What is the role of nitrogenase complex?

A

Convert nitrogen to amonia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Give the whole equation representing the role of nitrogenase complex

A

(In lect)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Give the percentages of biological nitrogen fixation on earth and oceans

A

60% on earth
40% oceans

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Definition of nitrification

A

the oxidation (as by bacteria) of ammonium salts to nitrites and the further oxidation of nitrites to nitrates.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Definition of denitrification

A

the microbial process of reducing nitrate and nitrite to gaseous forms of nitrogen, principally nitrous oxide (N2O) and nitrogen (N2)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the normal protein intake?

A

45 - 60g protein/day

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the normal protein intake in case of pregnancy, breastfeeding?

A

45 - 60g/ day + 50%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is nitrogen balance?

A

total daily intake equals total daily excretion 0.8 g/bw.kg/day

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is positive nitrogen balance?

A

Positive nitrogen balance: 1.0-1.1 g/bw.kg/day: childhood, pregnancy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are the symptoms of Kwashiorkor?

A
  1. Decreased body weight
  2. Oedema (decreased albumin)
  3. Diarrhoea (decreased intestinal epithelial cells)
  4. Steatorrhoea (decreased pancreas enzyme)
  5. Skin atrophy
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Some special aspects of the vegetarian diet
-> What is the energy content (in comparison to mixed diet)

A

30 - 50 cal./100g (vs. 150 - 300 cal/100 g for mixed diet)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Some special aspects of the vegetarian diet
-> What is the protein content (in comparison to mixed diet)?

A

Protein content: 1 - 2 g/100 g (vs 15 - 20g/100 g for mixed diet)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Some special aspects of the vegetarian diet
-> Is the protein nutritional value of vegetarian diet low or high?

A

Low

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Some special aspects of the vegetarian diet
-> Is the digestibility of the protein low or high?

A

Low

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Is the vegetarian diet suitable for adults? How?

A

Yes, it is generally enough, if the limitations are considered (legumes are low in methionine while cereals are low in lysine)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Is the vegetarian diet suitable for children and pregnancy? Why?

A

No, it is problematic
-> Cause low birth weight, slower growth in the first 5 years of life

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What are the 9 essential AAs? (definition based on N-balance)

A
  1. Histidine (His)
  2. Isoleucine (Ile)
  3. Leucine (Leu)
  4. Valine (Val)
  5. Lysine (Lys)
  6. Methionine (Met)
  7. Threonine (Thr)
  8. Tryptophan (Trp)
  9. Phenylalanine (Phe)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What are the 3 semi-essential amino acids?

A
  1. Arginine (Arg)
  2. Tyrosine (Tyr)
  3. Cysteine (Cys)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Protein Digestion
-> Are whole proteins absorbed? Why?

A

No, whole proteins are not absorbed
-> Why? - Too large to pass through intact membranes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Whole proteins cannot be absorbed
-> How do our body absorb them? Is there any additional digestion?

A

The proteins must be digested into di- and tri- peptide or individual amino acids priot to absorption
-> Additional digestion occur in the cytosol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Are structures of protein more diverse than carbohydrates?
-> What is the consequence?

A

Yes, proteins structures are more diverse than carbohydrate structures
-> Proteins require broad spectrum peptidases and transporters

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Protein digestion - stomach
-> What is the first step?

A

Chief cells secrete pepsinogen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Protein digestion - stomach
1st step: chief cells secrete pepsinogen
-> This process is stimulated by ____

A

Cephalic vagal input

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Protein digestion stomach

1st step: chief cells secrete pepsinogen
-> What are the 3 substances that enhance this secretion?

A
  1. Acetylcholine
  2. cholecystokinin (CCK)
  3. Gastrin
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Protein digestion stomach Pepsinogen is auto-activated to pepsin at which pH?
< 4
26
Pepsinogen is auto-activated to which substance? (at pH < 4)
Pepsin
26
Protein digestion stomach the Pepsinogen is auto-activated to which substance? (at pH < 4)
Pepsin
27
Protein digestion - stomach What is the role of pepsin?
It cleaves proteins at large aliphatic or aromatic side groups (~ complete 10 - 20% of digestion)
28
Protein digestion stomach At which pH that pepsin is inactivated? Why?
> 4.5; protects intestinal tissues
29
Protein digestion stomach -> Protein leaves stomach as __
Mix of insoluble protein, soluble protein, peptides and amino acids
30
What are the 2 major enzymes that participate in digestion of proteins in intestine?
- Proteases - Enteropeptidases
31
Protein digestion in the intestine -> How are proteases produced?
They are produced as zymogens in the pancreas
32
Protein digestion in the intestine -> How is the secretion of zymogens occur?
Into the intestine for secretin and cholecystokinin stimuli
33
Protein digestion in the intestine -> What is the role of enteropeptidases?
It converts trypsinogen to trypsin by limited proteolysis, which in turn activates other enzymes (chymotrypsinogen, prelastase, procarboxypeptidase)
34
Protein digestion in the intestine -> Enteropeptidase converts trypsinogen to trypsin by limited proteolysis, which in turn activates other enzymes which are ___ (3)
1. Chymotrysinogen 2. Proelastase 3. Procarboxypeptidase
35
Where are pancreatic proteases stored?
In acinar cells as pro-enzymes (zymogens)
36
The role of pancreatic proteases
1. Trypsinogen -> Trypsin 2. Chymotrypsinogen -> chymotrypsin 3. Procarboxypeptidase A & B -> Carboxypeptidase A & B 4. Proelastase -> Elastase
37
What are the 3 amino acids that are a part of serin-proteases?
1. Aspartic acid (active center) 2. Histidine 3. Serine (reactive)
38
Locations of Asp, His, Ser during activation of serin-proteases
These 3 AAs are located at very distant locations in the polypeptide chain, but are just spatially juxtaposed during activation
39
What are the 3 major members of the serine-proteases family?
Trypsin, chymotrypsin, elastase
40
What is SERPIN-s?
a broadly distributed family of protease inhibitors that use a conformational change to inhibit target enzymes. -> another possibility to regulate protease activity
41
What is the role of SERPIN-s?
An ester bond is formed between COO group of the inhibitor and the Ser OH
42
Give a major example of an inhibitor of elastase
α1-protease inhibitor –also an inhibitor of elastase
43
Why is Met358 important?
It is essential for enzyme binding
44
How is methionine affected in smokers?
In smokers, this methionine is oxidized to methionine sulfoxide and inactivated. => As a result, elastases function uncontrollably, consequence: lung emphysema
45
How is protein digestion occur in cytosol?
1. The vast majority of di- and tri- peptides are digestied into AAs by cytoplasmic peptidases 2. Peptidases -> cleave N-terminal amino acids
46
What is the role of peptidases?
Cleaving N-terminal AAs
47
Protein Absorption — Amino acids -> How many transporters of free amino acids are there in the brush border?
7
48
Protein Absorption — Amino acids There are 7 transporters of free amino acids in the brush border -> What are their mechanisms?
1. Na+ - independent carriers (2) - Proton-co transport - Facilitated diffusion 2. Na+ dependent (5) - Carriers are coupled to Na+ concentration gradient
49
How is protein transport occurred in basolateral membrane of the enterocyte?
The basolateral membrane of the enterocyte contains transporters which export AAs from the cell into the blood - Diffusion - Both Na+ depedent and indepedent carriers
50
Type(s) of AAs that can be absorbed into blood
Only free AAs
51
Protein Absorption Overview -> Where does most protein absorption take place?
In the duodenum and jejunum
52
Protein Absorption Overview -> Most AAs are absorbed into the bloodstream, but why do some AAs still remain in the enterocytes?
They are used to support the cells
53
Protein Absorption Overview -> more than 99% of protein enters the bloodstream as ___
AAs
54
What is ubiquitinilation?
A signal for degrading denatured unfolded proteins
55
The ubiquitin ligases recognize different degradation signals which are ___
1. Denatured, unfolded proteins 2. Oxidated AA 3. Modified or non-functional AA
56
What is an example for unbiquitinilation?
Transcriptional regulation of erithropoietin gen (EPO) by hypoxia induced factor
57
What are the 3 types of intracellular proteolysis? (tissue proteases)
1. Lysosomal 2. Proteasomal 3. Autophagosomal
58
Tissue proteases -> What are the 2 enzymes participating in extracellular proteases?
1. Matrix metalloproteases 2. Elastase
59
What are tissue proteases?
proteases degrading endogen proteases
60
What is the role of metalloproteases and cysteine Cathepsin?
Shaping dentin
61
What are the enzymes degrading ECM components? (teeth)
1. Kollagenases 2. Gelatinases 3. Stromeolysine 4. Enamelysine 5. Cathepsin-K
62
Enzymes degrading ECM (teeth) derive from __
1. Pulp odontoblasts 2. Saliva enzymes
63
The organic material of dentin is 90% __
collagen
64
Give a major example of Zn-proteases
Matrix metalloproteinases (MMPs)
65
What is the role of matrix metalloproteinases?
Degrade ECM components
66
Matrix metalloproteinase (MMP) is synthesized as ___
an inactive proenzyme
67
Matrix metalloproteinases (MMPs) are activated by __
conformational change/limited proteolysis)
68
What are the inhibitors for matrix metalloproteinases (MMPs)?
TIMP (tissue inhibitors of metalloproteinases)
69
Degradation of dentin ECM by host matrix metalloproteases (MMP) -> What will cariogenic bacteria do if they are present in the caries cavity?
They will release lactic acid and reduce the local pH
70
Degradation of dentin ECM by host matrix metalloproteases (MMP) -> Degradation of dentin ECM by host matrix metalloproteases (MMP) -> What is the consequence?
Acidic environment demineralizes the dentin matrix and induces the activation of host MMPs derived from dentin or saliva
71
3 steps of degradation of dentin collagen with Cathepsin - K
1. Binding of catK monomers to glycosaminoglycans (GAGs) to collagen fibrils 2. Dimerization of catK at the edges of gap regions 3. Disintegration of collagen fibers by liberation of alpha-chain sized fragments
72
What is the fate of amino group in degradation of amino acids?
1. Transamination 2. Deamination 3. Incorpration of free ammonia (Ornithine cycle)
73
Degradation of amino acids - Fate of amino-group -> What happen during transamination?
Reversible exchange of the amino- and oxogroup
74
Degradation of amino acids - Fate of amino-group -> What are the 2 enzymes with corresponding locations participate in the exchange of amino group?
1. ALAT: Ala aminotransferase (liver) 2. ASTA: Asp aminotransferase (heart and muscle)
75
Degradation of amino acids - Fate of amino-group -> Characteristics of prosthetic group of the transaminases
The prosthetic group binds to Lys side chain of the enzyme
76
Degradation of amino acids - Fate of amino-group -> What happen during oxidative deamination?
1. Glutamate-dehydrogenase reaction 2. Production of free ammonia
77
Degradation of amino acids - Fate of amino-group -> What are the enzymes involving in deamination?
1. a-aminogroup–oxidativedeamination – Glu Dehydrogenase 2. a-amino group – Ser(Thr) dehydratase – His és Gly (Glycine cleavage enzyme 3. a-amino group oxidation with flavoproteins – L- aminoacid oxidases (FMN, H2O, O2) 4. b or g amid group (deamination) – glutaminase – asparaginase
78
What happen if there is a mutation in glycine cleavage enzyme?
Glycine encephalopaty
79
Deamination -> What is the enzyme involving in oxidative deamination of alpha-amino group?
Glu dehydrogenase
80
Deamination of alpha amino group -> What are the enzymes involving?
– Ser(Thr) dehydratase – His és Gly (Glycine cleavage enzyme
81
What is the enzyme involving in alpha-amino group oxidation with flavoproteins?
1. L-amino acid oxidases (FMN, H2O, O2) 2. D-amino acid oxidases (FAD, H2O, O2) (bacterial AA degradation)
82
What are the 2 enzymes involving in deamination of beta or gamma amid group?
1. Glutaminase 2. Asparaginase
83
Free ammonia is incorporated into which cycle?
Ornithine cycle

Biochem 2 (38 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions