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IASM > Metabolism > Flashcards

Metabolism Flashcards

1
Q

Classes of Lipids

A
  1. Bile Salt
  2. Eicosanoids
  3. Steroid hormones
  4. Triacylglycerol
  5. Phospholipids
  6. Vitamins (fat soluble)
  7. Cholesterol

BEST PVC

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2
Q

What is cholesterol precursor of?

A
  1. Bile salt
  2. Steroid hormones
  3. Vitamin D
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3
Q

Chemical structure of fatty acid

Which end is alpha-carbon? What is the another end called?

A

CH3(CH2)nCOO-
Alpha carbon: carboxylic acid end
omega : hydrocarbon end

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4
Q

What is fatty acid transported by in blood? Why does it need a transporter?

A

Albumin

Fatty acids are insoluble in water

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5
Q

What do glycogen and lipid exist as in cells?

A

Glycogen granules

Lipid droplets

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6
Q

Name 3 types of lipid-carrying vehicle

A

Micelle: lipid enclosed by bile salt (bile salt’s hydrophillic side is facing out)
Chylomicron: a type of lipoprotein, transport dietary lipids
VLDL: a type of lipoprotein, transport endogenously synthesized lipids

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7
Q

What is the major lipid in human diet?

A

Triacylglycerol

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8
Q

Where is triacylglycerol mainly digested in? What is it broken down to?

A

Intestinal lumen

Triacylglycerol -> free fatty acids + 2-monoacylglycerol

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9
Q

Where will triacylglycerol go after being absorbed by enterocytes?

A
  1. Fatty acids + 2-monoacylglycerol get reconverted to traicylglycerol
  2. Packaged in chylomicrons
  3. Chylomicrons are secreted into the lymph
  4. Enter blood circulation
  5. Digested by LPL (lipoprotein lipase) on capillary wall
  6. Fatty acids are released and taken up by muscles & other tissues / adipose tissue
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10
Q

What are the 2 hormones secreted by intestine for hydrolysis? What are their functions?

A
  1. Cholecystokinin
    - gall bladder -> release bile acids
    - pancreas -> release digestive enzymes
  2. Secretin
    - liver, pancrease -> secrete bicarbonate -> raise pH in intestinal lumen (around 6) -> optimize actions of digestive enzymes
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11
Q

Steps of digestion & absorption for triacylglycerol

A
  1. Hydrolysis - by lipases
  2. Micelle formation - get across water layer next to enterocytes
  3. Absorption by enterocytes
  4. Formation of chylomicrons - reassembled into TGA -> incorporated in chylomicrons
  5. Exocytosis of chylomicrons into body circulation
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12
Q

What kind of fatty acids are hydrolyzed preferentially by lingual lipase & gastric lipase? How does their absorption differ from others?

A

short & medium length fatty acids (<=12 C)
1. short & medium length: directly absorbed through enterocytes -> go to portal blood while bound to albumin

  1. longer fatty acids: packaged with micelle to increase solubility -> enter enterocytes -> uptaken by chylomicrons -> enter lymphatic system -> blood circulation
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13
Q

Which part of micelle does not enter enterocyte and which part does? Where does the remaining part go?

A 
Bile salt (outside) doesn't enter enterocyte
Lipid-soluble component enter enterocyte membrane

Enterohepatic circulation: Bile salts are reabsorbed and sent back to liver

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14
Q

Where are the major and minor accumulation sites of traicylglycerol?

A

Major: Adipose tissue
Minor: liver, skeletal muscle

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15
Q

What are the 3 types of monosaccharides? 3 types of common disaccharides?

A 
Monosaccharide:
1. Glucose
2. Galactose
3. Fructose
Disaccharide
1. Sucrose: glucose &amp; fructose
2. Maltose: glucose &amp; glucose
3. Lactose: glucose &amp; galactose
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16
Q

What are the subunits in an ATP synthase? What are they driven by respectively?

A

F0 unit: proton-driven

F1 unit: ATP driven

17
Q

What are the residues of amylopectin called?

A

alpha-limit dextrins

18
Q

GI tract journey of carbohydrates

A
  1. salivary alpha-amylase cleave alpha-1,4-glycosidic linkage
  2. salivary alpha-amylase becomes inactivated in low pH stomach
  3. pancreatic alpha-amylase
  4. mucosal cell membrane-bound enzymes cleave carbohydrates into monosaccharides
  5. Absorbed by enterocytes and enter portal circulation
  6. Reach liver
  7. Distributed to peripheral circulation for metabolic needs
19
Q

List the transporters on enterocytes

A
  1. sodium-glucose linked transporter (SGLT)(brush border membrane):
    transport glucose & galactose
  2. GLUT 5 (both membranes):
    transport fructose
  3. GLUT 2 (basal lateral membrane):
    transport fructose, galactose and glucose into capillary
20
Q

3 places where SGLTs are expressed

A
  1. Epithelia of intestine
  2. Renal tubules (in kidney)
  3. Choroid plexus (in brain, produce CSF)
21
Q

Where are the various GLUTs expressed?

A

GLUT 1: blood cell, blood-brain-barrier, baby (fetus cell)
GLUT 2: Liver, Kidney, Pancreas, Intestine
GLUT 3: Neurons, Placenta
GLUT 4: Muscles, Fat cells (adipocytes)

22
Q

3 Storage Spaces of Glucose

A
  1. Liver: as glycogen, fatty acid in triacylglycerol
  2. Muscle: glycogen
  3. Adipocytes: as triacylglycerol
23
Q

2 Phases of glycolysis

A
  1. Energy-investment phase

2. Energy-generation phase

24
Q

Types of glucose tests available

A
  1. Random Plasma Glucose Test
  2. Fasting Plasma Glucose Test (FPG)
  3. Oral Glucose Tolerance Test (OGTT)
25
Q

How many oxygen molecules are required for generating energy from 1 glucose molecule during aerobic cellular respiration?

A

6O2 + 1 glucose -> 6CO2 + 6H2O + >30 ATP

26
Q

What are the possible products of biosynthesis by C atoms from glucose?

A
  1. Ribose -> form nucleic acid (DNA, RNA)
  2. Glycolytic intermediates
    - > amino acid synthesis
    - > fatty acid synthesis
  3. Glycogen synthesis
27
Q

List all the glycolytic intermediates formed during glycolysis (in order)

A

Glucose -> Glucose-6-P -> Fructose-6-P -> Fructose-1,6-P2 -> Phosphoenolpyruvate -> pyruvate

28
Q

What are the enzymes facilitating conversion between fructose-6-P and fructose-1,6-P2?
Give a common allosteric regulator of these 2 enzymes? What is it produced by?

A

PFK1: facilitate fructose-6-P to fructose-1,6-P2
fructose-1,6-bisphosphatase: fructose-1,6-P2 to fructose-6-P
Allosteric regulator: fructose-2,6-P2 (+ for PFK1)(- for fructose-1,6-bisphosphatase)
Allosteric regulator is produced by PFK2

29
Q

What domains does PFK2 have?

A

Kinase catalytic domain: form fructose-2,6-P2

Phosphatase catalytic domain: form fructose-6-P

30
Q

Does high insulin dephosphorylate or phosphorylate enzymes?

A

dephosphorylate

e.g. PFK2, PK

31
Q

Give 3 pairs of enzymes that drive opposing pathways of glucose metabolism

A

Fructose-1,6-bisphosphatase VS PFK1
PEPCK VS PK
Glycogen phosphorylase VS glycogen synthase

32
Q

What are the 3 metabolic pathways (uses) of amino acids?

A
  1. Synthesis of specific proteins
  2. Transformation into non-protein compounds
  3. Degraded for energy
33
Q

Can amino acids be stored? What do our body do with its surplus?

A 
Cannot be stored
Surplus: 
used as fuel source
ketone bodies -> acetoacetyl CoA -> TCA cycle
glucose -> pyruvate
34
Q

What is the enzyme responsible for catalyzing transamination and deamination of amino acids? What is its cofactor?

A

Enzyme: amino-transferase
Cofactor: PLP

IASM (18 decks)

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