Biochem Flashcards
1
Q
Carbohydrates classification:
A
Monosaccharides (1)
Oligosaccharides (2-10)
Polysaccharides (>10)
2
Q
- Same molecular formula, different structures
2. (1) with only one slight structural difference
A
Isomers
Epimers
3
Q
Based on the functional group present in the sugar, they can be classified as :
A
Aldolase or Ketose
4
Q
L-glucose isomers have a ___ group on the left. But only the __ configuration is found in the human body
A
Penultimate C-OH
D
*L is in bacteria
5
Q
Aldoses
A
Mannose (hexose)
Galactose (hexose)
Glucose (hexose)
Ribose (pentose)
6
Q
Ketohexoses
A
Fructose
7
Q
Alpha vs Beta anomers
A
Beta-OH group of a sugar is above the plane of the ring
Alpha-Below
8
Q
Glycosidic linkage is indicated by the orientation of the ____ followed by __
A
Anomeric carbon
Numbers of the two carbon atoms involved in the linkage
9
Q
Two alpha-D-glucose molecules
alpha 1,4 glycosidic link
A
Maltose
*derived from starch
10
Q
Alpha-D-glucose + beta-D-fructose
1,2 glycosidic linkage
A
Sucrose
11
Q
Beta-D-galactose + alpha-D-glucose
Beta 1,4 glycosidic linkage
A
Lactose
12
Q
2 types of starch
A
- Amylose: alpha 1,4 links
- helix w/6 glucose per turns - Amylopectin: alpha 1,4 and 1,6 links
- branched
13
Q
Which is more highly branched:
Glycogen or Amylopectin
A
Glycogen
14
Q
Homopolysaccharide composed of
Beta-D-glucose units
Beta 1,4 linkage
(Humans lack the enzyme necessary to hydrolyze these links)
A
Cellulose
15
Q
Long unbranched polysaccharides containing a repeating disaccharide unit
-they contain either of two modified sugars ____ or ___
A
Hereropolysaccharide
- N-acetylglucosamine (GlcNAc)
- N-acetylgalactosamine (GalNAc)
16
Q
The most abundant heteropolysaccharides in the body are ___
A
Glycosaminoglycans (GAGs)
*Highly negatively charged molecules
17
Q
Proteoglycans vs. Glycoproteins
A
P: 10% protein, 90% carbs
G: 90% protein, 10% carbs
-ex: antibodies, blood group antigens, hormones FSH, LH, and TSH
18
Q
Glycolipids are present where?
A
Nerve tissues
Cell membrane
19
Q
Dietary sources of carbs in order of most to least prevalent
A
- Starches
- Disaccharides
- Monosaccharides
20
Q
Monosaccharides are absorbed by ___
A
Intestinal lining by facilitated diffusion
21
Q
- Digestion of amylase requires ___
2. Digestion of oligosaccharides requires ___
A
- Salivary glands and pancreas
2. Mucosal brush border enzymes (maltase, sucrase, isomaltase, lactase, trehalase)
22
Q
Maltase
- Activity
- Substrate
- Products
A
- Exoglucosidase, only alpha 1,4
- Malto-oligosaccharides
- Glucose
23
Q
Sucrase
- Activity
- Substrate
- Products
A
- Hydrolyzes sucrose and maltase activity
- Sucrose Malto-oligosaccharides
- Glucose and fructose
24
Q
Isomaltase
- Activity
- Substrate
- Products
A
- Alpha 1,6 bonds
- Alpha dextrins
- Glucose
25
Lactase
1. Activity
2. Substrate
3. Products
1. Beta glycosidase
2. Lactose
3. Glucose and galactose
26
Trehalase
1. Activity
2. Substrate
3. Products
1. Trehalose
2. Trehalose
3. Glucose
27
SGLT and GLUT
SGLT: Na+ couples glucose transporters
GLUT: Glucose transporter facilitators
28
GLUT
Skeletal muscle, heart, fat
Insulin responsive transport
GLUT 4
29
GLUT
| neurons
GLUT 3
30
GLUT
| small intestine, sperm, testes
GLUT 5
31
Digestion of proteins starts in the __
Stomach
* due to pepsin and acid condition
* continues in small intestine
32
pH of gastric juice is approximately __
| Function?
2
Denatures protein
Kills bacteria
Activates pepsinogen
33
H+ secretion to stomach?
| Cl-?
H+: CO2 and H2O
| Cl-: through two membranes from the outside through parietal cells
34
What are the two ways to activate pepsinogen?
1. Auto-activation at pH<5
2. Pepsin activated
3. HCl?
35
___ and ___ can both activate ___ cells to release Histamine
ACh
Gastrin
ECL
36
___ and ___ stimulate secretion of pancreatic digestive pro-enzymes and enteropeptidase from mucosal cells
CCK
| Secretin
37
What does enteropeptidase do?
Activates trypsinogen to trypsin
38
What does trypsin do?
Activates other pro-enzymes to active form
39
Peptide bonds susceptible for chymotrypsin?
```
Trp
Tyr
Phe
Met
Leu
```
40
Peptide bonds susceptible for trypsin?
Arg
| Lys
41
Peptide bonds susceptible for elastase?
Ala
Gly
Ser
42
Intestinal epithelial brush border peptidases:
| These produce what?
1. Endopeptidases
2. Aminopeptidases
3. Dipeptidases
-these produce free AAs and di- and tripeptides
43
In the small intestine
1. I cells secrete:
2. S cells secrete:
3. Duodenum secretes:
4. Pancreas secretes:
What are the last two activated by?
1. CCK
2. Secretin
3. Enteropeptidase (activated by CCK)
4. Trypsinogen (activated by CCK and secretin)
44
Pepsin
1. Location
2. Substrate
3. Product
4. Activated by
1. Stomach
2. Protein
3. Peptides
4. H+ or Pepsin
45
Trypsin
1. Location
2. Substrate
3. Product
4. Activated by
1. Small intestine
2. Protein
3. Peptides
4. Enteropeptidase, trypsin
46
Chymotrypsin, Elastase, and Carboxypeptidasea
1. Location
2. Substrate
3. Product
4. Activated by
1. Small intestine
2. Protein
3. Peptide/aa
4. Trypsin
47
Endopeptidase, aminopeptidase, and dipeptidase
1. Location
2. Substrate
3. Product
4. Activated by
1. Brush border
2. Peptides
3. aa, di- and tripeptides
4. N/A
48
Required protein intake
0.8g/kg body weight/day
49
Essential amino acids
PVT TIM HALL
1. Phe
2. Val
3. Thr
4. Trp
5. Ile
6. Met
7. His
8. Arg (children)
9. Leu
10. Lys
50
Amino acid metabolism
Either eliminated as urea or re-utilized to form another amino acid
51
___ require contributions from lipids, carbs, and amino acids for metabolism.
___ require contributions from carbs and amino acids
Phospholipids
| Nucleotides
52
Positive vs. Negative nitrogen balance
+ intake>output (growth, convalescence)
- output>intake (starvation, disease, burns)
53
Lingual lipase, gastric lipase, pancreatic lipase activity
Fatty acids from positions 1 and 3 are removed, this leaves 2 FFA and one 2-monoacylglycerol
54
Locations:
Lingual lipase
Gastric lipase
Pancreatic lipase
Mounts and stomach
Stomach
Small intestine
*absorption occurs in the jejunum
55
___ is only active at the surface of the lipid droplet, so activity is slow
Lingual lipase
| Gastric lipase
56
___ is secreted along with pancreatic lipase. Lipase alone is inhibited by ___, so ___ binds lipase and prevents inhibition
Procolipase (converted to colipase by trypsin)
Bile salts
Colipase
57
___ is secreted as a zymogen
Conversion of ___ to ___ is by trypsin.
Activity requires ___
Removed one FA molecule from the 2 position of phospholipids to yield ___ and ____
Phospholipase A2
Pro-- to phospholipase A2
Bile salts
One FFA and one lysophospholipid
58
Cholesterol esters are hydrolyzed to ___ and ___
Cholesterol and FFA
59
Bile salts are produced in the ___ and derived from ___.
| Example?
Liver
Cholesterol
Taurocholic acid
60
These 3 compounds in bile can form micelles
Bile salts
Cholesterol
Phospholipid (mostly phosphatidylcholine)
61
Mixed micelles contain:
```
Bile salts
PC
Cholesterol
Products of lipid digestion
Fat soluble vitamins from the diet
```
62
____ and ___ fatty acids may be absorbed by the intestine without the help of bile salts
Short and medium chain
63
3 proteins that play a role in sterol absorption
NPC1L1
SCARB1
CD36
64
Intestinal epithelial cells contain ___ which pump sterols out of the cell. Examples?
ABC transporter proteins
| ABCG5 and ABCG8
65
Absorption of FFA and MAG vs dietary cholesterol
Virtually all of FFA and MAG are absorbed
| -only 30-40% of dietary cholesterol is
66
Bile salts are absorbed in the ___, where the lipids are repackaged as ___
Ileum
| Chylomicron
67
Long chain fatty acids bind to ___ or ___, then are transported to the ___ where they're converted to ___
Intestinal FAB or FAB2
ER
Triacylglycerols
68
Long chain FFAs are first converted to ___ by ___. Most triacylgylcerol is countryside by the ____ pathway. The remainder is synthesized by the ___ pathway
Fatty acyl CoA
Acyl CoA synthase
Monoacylglycerol
Phosphatidic acid
69
Short and medium chain fatty acids enter the ___ as ____ then are transported to the the ___ bound to ___
Hepatic portal v.
FFA
Liver
Albumin
70
Cholesterol is converted to cholesteryl ester by ___
Acyl CoA cholesterol acyltransferase
71
The major apo-protein added to form chylomicrons is ___, which is produced in the ____. This is a splice variant of a gene also expressed in the ___, where the "full length" variant is produced. In the intestine it is ___ percent of that of the liver (hence the name)
B-48
ER
Liver
48
72
Newly formed lipids and apo-proteins are assembled in the ___ to form the chylomicrons, which are then secreted into ___
Golgi
| Lymph
73
Composition of chylomicrons (in order of most to least amount)
```
Triacylglycerol
Phospholipid
Cholesterol ester
Protein
Cholesterol
```
74
Signs of lack of bile pigments
Clay colored stools
75
___ is an inhibitor of gastric and pancreatic lipase. It reduced fat absorption by preventing ___ digestion. Side effects may be similar to ___
Orlistat
| Triacylglycerol
76
___ is octa-acyl sucrose (which is ___).
It is resistant to ___. It has the taste and consistency of fat, but is non-digestible.
If taking this, you should also take ___
Olestra
Lipase
Fat soluble vitamin supplements
77
Ezetimibe inhibits ___ thus diminishes cholesterol absorption
NPC1L1
78
Regulated step in bile acid synthesis
*It requires what?
7 alpha hydroxylase ---> 7 alpha hydroxycholesterol
*NADPH, O2, CYP7A, Vit C (ascorbate)
79
Formation of ___ requires 12 alpha hydroxylase.
The ___ is saturated.
___ is obtained from the carbons (C25-27) removed to form this
*these steps require __
Cholic acid
B ring
Propionyl-CoA
*NADPH, O2, CoA
80
Both cholic acid and chenodeoxycholic acid are conjugated with ___ or ___
- this years rods the four primary bile acids
* this process requires formation of ___ and ___
Glycine
Taurine
1. Taurocholic acid
2. Glycocholic acid
3. Taurochenodeoxycholic acid
4. Glycochenodeoxycholic acid
*cholyl-CoA and chenodeoxycholyl-CoA
81
Secondary bile acids are produced when ____
| What are they?
Bile acids are metabolized by intestinal bacteria
1. Deoxycholic acid
2. Lithocholic acid
82
Heme is converted to ____ by ___
This is the only known endogenous source of what?
Biliverdin
Heme oxygenase
CO
83
Biliverdin is converted to ___ by ___
Bilirubin
| Biliverdin reductase
84
Bilirubin is transported through the blood to the ___ bound to ___
Liver
| Albumin
85
Bilirubin is conjugated to form a ___ in the liver, which is then excreted through ___. It is water soluble but poorly absorbed by intestinal mucosa. In the colon, it is converted to ___ by ____
Diglucuronide
Bile
Urobilinogen (colorless)
Bacteria
86
What gives feces its color?
Urobilinogen is metabolized to stercobilinogen. Oxidation of stercobilinogen yields stercobilin, which is red-orange
87
Jaundice is due to and increase in ____
Bilirubin
88
1. Prehepatic jaundice
2. Hepatic jaundice
3. Posthepatic jaundice
1. Too much bilirubin produced, liver can't conjugate all of it
2. Liver can't conjugate any bilirubin
3. Regurgitation of conjugated bilirubin into blood (commonly an effect of gall bladder problems)
89
Prehepatic jaundice
1. Serum
2. Stools
3. Urine
1. Increased total bili, increased unconjugated bili (indirect)
2. Increased stercobilin excretion - normal color
3. Increased urobilin excretion
90
Hepatic jaundice
1. Serum
2. Stools
3. Urine
1. Increased total bili, increased unconjugated bili (indirect)
2. Decreased stercobilin excretion - light color
3. Decreased urobilin excretion
91
Posthepatic jaundice
1. Serum
2. Stools
3. Urine
1. Increased total bili, increased conjugated bili (direct)
2. Decreased stercobilin excretion - light color
3. Decreased urobilin excretion - dark brown urine
