Carbs 1 and 2 Flashcards
what is the OH group’s linkage if it is below the plane of the sugar?
alpha
Do our bodies utilize D or L sugars?
D
what is the OH group’s linkage if it is above the plane of the sugar?
beta
what type of bonds link sugars?
glycosidic bond
what sort of group is found on a reducing sugar?
reactive carbonyl (Hemiacetals)
which can reduce metals hence the name
swaps H+ on the carbonyl group with an O
Anomeric carbon
reducing carbon on a sugar
Which end of a oligo or poly - saccharide has the anomeric carbon?
reducing end
A patient is found to be unable to absorb disaccharides, what could be the issue?
An enzyme in the gut called disaccharidases which are tethered to cells in the lumen and breakdown disaccharides into monosaccharides. this is could be the culprit because we can only absorb monosaccharides
what cleaves an alpha 1,6 bond?
Isomaltase
What cleaves an alpha 1,1 bond?
Trehalose
what breaks an beta 1,4 bond?
Lactase
Lactose = galactose and glucose
what pathways does G6P participate in?
Glycolysis
Pentose phosphate pathway
glycogen synthesis
what type of link bonds branches to glycogen molecules?
alpha 1,6
every polymer of glycogen is attached to _____
glycogenin
which is a protein
what enzyme is responsible for the conversion of G6P to G1P?
phosphoglucomutase
what are the building blocks of glycogen?
UDP-Glucose
What starts the seeding process for glycogen?
When glycogenin glycosylates itself by attaching the glucosyl residue of UDP-glucose to the hydroxyl chain of a Ser residue in the protein
What link connects branches to the core glycogen molecule?
alpha 1,6
glycogen degradation proceeds through a _______ rxn
phosphorolysis
use of phosphate to break the bond
Why is an ATP not required to make G6P for glycolysis ?
G1P and G6P are energetically equivalent
what is the activity of glycogen phosphorylase?
will cut down the glycogen chains to “limit dextrins”
Glycogen phosphorylase and glycogen synthase are reciprocally regulated.by…
phosphorylation with ATP
When glycogen phosphorylase B is phosphorylated then it is (active/inactive)
active
Insulin secretion in response to an increase in blood sugar levels induces …
more GLUT4 receptors to come to the cell surface to increase uptake of glucose
Glucagon signals to the liver result in …
the conversion of glycogen phosphorylase B to glycogen phosphorylase A and the inhibition of glycogen synthase
Fructose metabolism occurs in …
the liver
What does the Pentose phosphate pathway generate?
5 carbon sugars and NADPH
What intermediate links the Fructose metabolism pathway to Glycolysis?
DHAP - dihydroxyacetone phosphate
Name the three enzymes involved in Fructose metabolism
Fructokinase
Aldolase B
Triose Kinase
Hereditary Fructose intolerance is characterized by ….
insufficient Aldolase B activity causing pts to accumulate very large stores of F1P
symptoms: Jaundice, vomiting and convulsions
What does the Pentose phosphate pathway produce?
NADPH
Ribose 5-phosphate
What does the first (oxidative phase)stage of the PPP generate ?
2 moles of NADPH per 1 mole of G6P
What does the second (non oxidative phase)stage of the PPP generate ?
ribose 5 phosphate
converts unused intermediates to fructose 6-P and glyceraldehyde 3-P
What pathway do RBCs rely on to avoid oxidative damage?
HMP shunt
What can not be oxidized by the electron transport chain?
NADPH
What molecules does UDP glucose serve as a percursor for?
glycosides
lactose
glycolipids
glycoproteins
What is the ocular consequence and mechanisms of elevated sugar in diabetes?
elevated glucose leads to generation of fructose in the lens of the eye. Excess will be converted to sorbitol at a faster rate then it can be cleared.
Leads to increase in osmotic pressure
What are the functions of Glucuronides?
to aid in excertion of bilirubin and drugs
overall it supplys negatively charged group to couple with OH on the target molecule
More charges = increased solubility
describe synthesis of lactose
Galactose is produced from conversion of UDP-glucose to UDP-galactose by epimerase
then glucose and galactose are linked by an alpha bond
What residues on proteins are short carbohydrates attached?
serine
threonine
asparagine
What are the general features of glycoproteins?
highly branched
no repeating disaccharide units
what are the functions of glycoproteins?
most proteins in the blood - clotting enzyme, antibodies, hormones
structural components of ECM - collagen
Mucus secretions
What is the primary component of the glycolipid, sphingosine?
ceramide with carbohydrate pieces
What is a function of glycolipids?
cell recognition
example: ABO blood groups
Name the enzymes that metabolize ETOH
liver alcohol dehydrogenase
Microsomal ethanol oxidizing system (MEOS)
What is the side effect of the metabolism of the small alcohol, ETOH?
ADHs have preferences for different chain lengths of alcohols
at high concentrations, ETOH will be non specifically metabolized leading to large increase in amount of Acetaldehyde bi product which is toxic
leads to nausea and vomiting
Where is the liver cell is the majority of ETOH metabolized?
Mitochondrial ALDH2
an allelic variance of ALDH2 which has very low affinity for substrate confers resistance to alcoholism
In the liver, acetyl CoA will be used in ….
cholesterol and fatty acid synthesis
What is MEOS composed of?
Cytochrome P 450 reductase and cytochrome P 450
oxidizes ETOH to acetaldehyde
What enzyme shows the most activity toward ETOH?
CYP2E1
Chronic ETOH consumption leads to …
increasing the NADH/NAD+ ratio resulting in changes to fatty acid metabolism, ketoacidosis, lactic acidosis, hyperuricemia and hypoglycemia
What are the consequences of excessive drinking, with respect to fatty acid metabolism?
inhibition of oxidation of fatty acids leading to the accumulation
increases in the amount of triacylglycerols which are incorporated to VLDLs which build up in liver and enter the blood
What conditions are the result of excess ETOH? Think about what happens metabolically
Hyperlipidemia
fatty liver
What is the mechanism of Alcohol induced ketoacidosis?
High NADH leads to reversal of Acetyl CoA to the TCA cycle
instead Acetyl CoA is used to generate ketone bodies
build up in the blood is toxic
What is the consequence of Lactic acidosis?
the altered NADH/NAD+ ratio
will shift the reaction of lactate dehydrogenase towards lactate
High lactate will lead to decreased excretion of uric acid => Gout
Lactate also inhibits gluconeogenesis so fasting blood sugar levels drop
pt with mutation in CYP2E1 rendering protein non functional, what do expect to happen when pt consumes large amount of alcohol?
majority of ingested ethanol would get converted into acetaldehyde via ADH
