Skildum: Nutrition, Proteins, Carbohydrates Flashcards
What are the main dietary carbohydrates?
fructose lactose (Gal + Glu) sucrose (Fru + Glu) amylose (a1,6 bonds) amylopectin (a1,6 & a1,4 branches)
What are the dietary disaccharides and their linkages?
lactose (Gal + Glu); b-1,4
sucrose (Fru + Glu); a-1,2
trehalose (Glu + Glu); a-1,1 (mushrooms)
How are starches that enter the mouth broken down?
Starch is broken down by salivary amylase to maltose, maltotriose, and alpha dextrin. Pancreatic amlase breaks these products down further to maltose maltriose and limit dextrans. They are then transported into intestinal epithelial cells by brush border enzymes.
Where is amylase activity highest?
Duodenum
What type of enzyme is amylase? What does it do?
Endoglycosidase
Cuts alpha 1-4 bonds in polysaccharides
What are the 4 disaccharidases of the brush border?
Glucoamylase
Sucrase/isolmaltase complex
trehalase
b-glycosidase complex
What does glycoamylase/maltase do?
Exoglycosidase that cuts glucose off the NON-REDUCING ends of starch
Cleaves alpha 1-,4 bonds of MALTOSE to form two molecules of GLUCOSE.
What is isomaltose?
Disaccharide w/ alpha 1-6 bond
Where is glucoamylase activity the highest?
ileum
What is the sucrase?
ISOMALTASE COMPLEX w/ TWO extracellular domains w/ diff substrate specificities.
What is the difference between the sucrase and isomaltose ends of the sucrase?
Sucrase cuts sucrose into glucose and fructose
Isomaltose cuts the a-1,6 bond in isomaltose
Where is sucrase isomaltase activity the highest?
jejunem
Trehalase has ONE catalytic site. What is it’s ONE substrate?
Trehalose
What is trehalose and where is it found?
Two glucose units bonded through the number 1 carbons.
Found in insects, algae, mushrooms and other fungi.
What is a beta glycosidase complex?
A glycophosphatidylinositol (GPI) glycan anchored protein with two catalytic domains.
What are the two catalytic domains of a beta glycosidase complex?
- Glucosyl ceramide domain: A glycophosphatidylinositol (GPI) glycan anchored protein with two catalytic domains.
- Lactase domain: Splits the 1,4 bond in lactose to make galactose and glucose.
How are carbs absorbed when then conc in the lumen exceeds that of the blood?
facilitated diffusion
How are carbs absorbed when the conc in the lumen is LOWER than that of the blood?
cell must expend ENERGY get the monosaccharides inside
What is fructose?
Naturally occurring monosaccharide found in honey
or….
product of SUCRASE acting on SUCROSE–> glucose and FRUCTOSE
What is high fructose corn syrup?
mix of fructose and glucose
What are substrates for fermentation by gut bacteria?
amylose and amylopectin
Short chain fatty acids (acetate, propionate and butyrate) are produced by bacteria and used as fuel by…
colonocytes
What causes lactose intolerance?
No lactose>
bacteria ferment lactose to LACTIC ACID>
water enters gut to balance diff in H conc>
DIARRHEA
glycolysis
all tissues
glycogenogenesis
all tissues
fatty acid synthesis
liver
cholesterol synthesis
liver
AA synthesis
mainly liver, but most tissues
glycosylation of proteins/lipids
all tissues
Describe how protein is broken down.
Mechanically chewed>
Low pH DENATURES proteins; activates PEPSINOGEN>
LUMENAL PROTEASES digest to tripeptides, dipeptides, and amino acids>
Tripeptides, dipeptides and amino acids are transported into the intestinal epithelial cell>
INTRACELLULAR PEPTIDASES digest tri- and dipeptides to amino acids>
AMINO ACIDS are transported into the blood
PEPSINOGEN + H
PEPSIN
TRYPSINOGEN + ENTEROPEPTIDASE
TRYPSIN
CHYMOTRYPSINOGEN + TRYPSIN
CHYMOTRYPSIN
PROELASTASE + TRYPSIN
ELASTASE
PROCARBOXYPEPTIDASES + TRYPSIN
CARBOXYPEPTIDASES
What do endopeptidases do and what determines their specificity?
cleave peptide bonds w/in a chain
side chain of the carbonyl containing acid
What does trypsin do?
cuts peptide bonds in which carbonyl is provided by arginine or lysine
What do exopeptidases do?
cut SINGLE AA from ends of peptide chains
What protein transporters are Na dependent?
all but L
What are sources of the intracellular AA pool?
Extracellular amino acids
Protein degradation
de novo synthesis from glycolysis or TCA cycle intermediates
What are the three key cofactors for enzymes in AA metabolism?
PLP
FH4
BH4
PLP is a cofactor for…
transaminations
deaminations
carbon chain transfers
PLP deficiency
seizures
diarrhea
anemia
EEG abnormalities
FH4 is a cofactor for
one carbon transfers
FH4 def
megaloblastic anemia
BH4 is a cofactor for
ring hydroxylations (Phe> Tyr)
BH4 def
seizures
developmental delays
What controls protein synthesis and degradation?
the metabolic state in the cell
What is the role of the mTORC1 complex in protein synthesis?
It ACTIVATES protein synthesis and INHIBITS autophagy
What inhibits protein synthesis and PROMOTES autophagy?
activation of AMPK
What does AMPK block?
TSC2 autophagy / protein synthesis
p53 cell cycle, DNA repair
p27 cell cycle
ACC acetyl CoA carboxylase; fatty acid synthesis
HMGCR cholesterol synthesis
PFKBF3 key subunit of PFK-2; regulation of glycolysis
What are the dietary protein requirements for an infant?
?
What is the most important circulating carbohydrate?
glucose
Does our diet contain glucose?
Almost none!
We eat other carbs (polysaccharides, disaccharides, fructose) that are converted to glucose by our body
What dietary carbohydrate’s structure most resembles glycogen?
Amylopectin (linear glucose chain w/ 1,4 linkage and 1,6 branch points)
What happens to ingested fructose and disaccharides?
They go straight to the small intestines and are broken down by brush border enzymes there.
Protein malnutrition is called…
kwashiorkor
