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BMB516 Exam 1 Lectures 4-6 + glycolysis + entry of sugars into glycolysis
Terms in this set (93)
the process of energy generation and use
what 3 things does catabolism generate?
-building blocks for anabolic reactions
3 principle end products that may be excreted
carbon dioxide, water, and ammonia
why is a constant supply of glucose important?
the brain primarily utilizes glucose
primary organ of metabolsim
-acts as major producer and storage compartment for cellular energy stores (in the form of glycogen)
-glucagon and epinephrine stimulate glycogen breakdown
-insulin stimulates the glycogen synthesis and other synthetic pathways
-insulin increases cellular glucose uptake and inhibits GNG and glycogen breakdown
carbohydrate activated precursor and building block
UDP-glucose and monosaccharide
lipids activated precursor and building block
fatty acyl-CoA and fatty acids
protein activated precursor and building block
tRNA-amino acid and amino acids
nucleic acids activated precursor and building block
dNTPs and NTPs, Ribo (and deoxyribo) nucleic acids
broken down by amylase in the mouth
non-digestible due to beta 1-4 linkages
glucose + galactose beta 1-4
glucose + fructose alpha 1-2
specific cleavage of alpha-glycosidic bonds
-result is dextrin and disaccharides
no carbohydrate digestion
-HCl stops amylase
pancreatic alpha amylase
-result is continued digestion of detains to produce more disaccccharides
-isomaltose: double glucose alpha 1-6
-maltose: double glucose alpha 1-4
mucosal cells (enterocytes)
-enzymes at luminal surface
-trehalase cleaves trehalose which is a disaccharide of glucose linked by an alpha 1-1 bond found in fungi
-yields monosaccharides which can be absorbed then released into portal circulation to liver
glucose, fructose, galactose
Na+ dependent monosaccharies
glucose and galactose
-GLUT transporter driven by Na+ co-transport
-inward movement of glucose against gradient, inward moment of Na+ is down gradient
-Na+/K+ ATPase pumps maintains low Na+ concentration inside
-CARRIER MEDIATED FACILITATED TRANSPORT/SECONDARY ACTIVE TRANSPORT
Na+ independent monosaccharide
-driven by fructose gradient
-loss of electrons
-often is loss of hydrogens
-gain of electrons
-often gain of hydrogens
gain of a water molecule
loss of a water molecule
loss of a proton
gain of a proton
-1 proton and 1 electron
aka hydrogen ion
1 proton and no electrons
1 proton and 2 electrons
any carbon attached directly to a carbonyl carbon
A carbon adjacent to an alpha carbon.
last carbon in the fatty acid chain
acid anion suffix
relationship between alpha amino acid and alpha keto acid
alpha carbon switches from ketone to amino group
COO- on end because ACID
enzyme that carries out conversion between alpha-keto acid and alpha-amino acid
FAD oxidizes what?
alkane to alkene
What is the most reduced functional group?
Alkene is the same oxidation state as what two other functional groups?
primary and secondary alcohols
primary alcohol gets directly oxidized to what?
secondary alcohol gets directly oxidized to what?
aldehyde gets oxidized to what?
fully oxidized molecule
ketone gets oxidized to what?
nothing, ketones cannot be further oxidized
tertiary alcohol get oxidized to what?
nothing, tertiary alcohol cannot be further oxidized
An enzyme that catalyzes a chemical reaction during which one or more hydrogen atoms are removed from a molecule.
-named for the more reduced molecule
An enzyme that catalyzes a reaction in which hydrogen atoms are added to a molecule
-named for the more oxidized molecule
transfer of a phosphate group to or from ATP
starts off with the name of the product
-no ATP used
followed by the name of the product
fructose dietary sources
though sucrose aka table sugar
(glucose + fructose)
or as fructose through fruits
fructose is phosphorylated by
fructokinase, which puts the phosphate group on carbon 1 not carbon 6
active in the liver, but is not regulated by its product
-fructose 1-P builds up, trapping much of the ATP in the liver without getting quick return of ATP yield by feeding product into glycolytic pathway
-thus, diets high in fructose can lead to liver damage due to loss in ATP
deficiency of fructokinase
-fructose just gets backed up and excreted in urine
usually fructose 1-P aldolase is defective (aka aldolase B)
depletion of ATP since fructose 1-P cannot b turned over
-hypoglycemia, vomiting, and liver failure
Fructose 1-P Aldolase
Splitting of fructose 1-P into glyceraldehyde and DHAP
dietary source of galactose
lactose from milk and milk products
lactose is glucose+galactose
enzyme that cleaves the beta-glycosidic linkage of lactose
Galactose -> galactose-1-phosphate.
UDP glucose + galactose 1 - phosphate --> UDP galactose + glucose 1-phosphate
glucose ⇌ glucose 6-P
glucose 6-P ⇌ fructose 6-P
Fructose-6-phosphate to fructose-1,6-bisphosphate
fructose 1,6-bisphosphate to dihydroxyacetone phosphate and glyceraldehyde 3-phosphate
triode phosphate isomerase
dihydroxyacetone phosphate and glyceraldehyde 3-phosphate
G3P to 1,3-bisphosphoglycerate
1,3-bisphosphoglycerate to 3-phosphoglycerate
3-phosphoglycerate to 2-phosphoglycerate
2-phosphoglycerate to phosphoenolpyruvate
phosphoenolpyruvate to pyruvate
Lactate dehydrogenase (LDH)
pyruvate + NADH ↔ lactate + NAD+
Net yield of aerobic glycolysis
1 glucose + 2 ADP + 2 Pi --> 2 pyruvate + 2 ATP + 2 H20 + 2 NADH + 2 H+
net yield of anaerobic glycolysis
2 lactate + 2 ATP + 2 H20
which reactions of glycolysis use ATP?
1 and 3
1: glucose -> glucose 6-P
3: fructose 6-P --> fructose 1,6 biphosphate
Which reactions of glycolysis make ATP?
7 and 10
7: 1,3BPG ---[phosphoglycerate kinase]-->3PG
10: PEP---[pyruvate kinase]---> pyruvate
Two isozymes that carry out first reaction of glycolysis
hexokinase and glucokinase
-hexokinase in all tissues
-glucokinase in liver and islet cells of pancrease
-hexokinase has a higher affinity for glucose
-liver ensures other tissues have glucose first
What is the purpose of the first rxn of glycolysis?
The investment of some energy to start the pathway ensures the cell needs to do the pathway.
purpose of the last 3 steps of glycolysis (8,9, and 10)
At this point, 2 of the 6 original carbons of glucose are now at level of carboy acid (2 molecules of 3-phosphoglycerate). It is not a good LG, however, and so the rxns purpose are to make it better bya adding a keto group to carbon 2, creating alpha keto acid. Another goal is to make the phosphate group on 3-phosphoglycerate a good enough LG so that it can be used to make ATP.
To elevate the leaving potential of the phosphate group and create a keto group on carbon 2
Which reactions of glycolysis involve substrate-level phosphorylation?
7 and 10
7: 1,3 BPG --> 3 phosphoglycerate using phosphoglycerate kinase
10: PEP ---> pyruvate using pyruvate kinase
The enzyme-catalyzed formation of ATP by direct transfer of a phosphate group to ADP from an intermediate substrate in catabolism.
3 irreversible steps of glycolysis
rxns using the enzymes hexokinase, phosphofructokinase 1 (PFK1), pyruvate kinase
Glycolysis regulation through hexokinase
-GLucose 6-P is an allosteric inhibitor of hexokinase.
-Helps control glucose uptake into cell
-Glucokinase in liver not inhibited by glucose 6-P
committed step of glycolysis and primary control point
rxn catalyzed by PFK1 aka rxn 3
-allosteric ACTIVATORS of PFK1 include fructose 2,6 biphosphate and AMP (fructose 2,6 biphosphate activates PFK1 and inhibits FBP1 ensuring gluconeogenesis is not simultaneously occurring)
-Allosteric INHIBITORS of PFK1 are ATP and citrate. (Citrate is a TCA cycle intermediate)
pyruvate kinase glycolysis regulation
-fructose 1,6 biphosphat is an allosteric activator of pyruvate kinase (FEED FORWARD ACTIVATION)
-important that pyruvate kinase is already active (from fructose 1,6 biphosphate) in order to ensure that ATP is formed
-high ATP concentrations inhibit pyruvate kinase
How is NAD+ regenerated for G3P dehydrogenase under aerobic conditions?
Though the malate-aspartate shuttle and glycerol-phosphate shuttle.
How is NAD+ regenerated for G3P dehydrogenase under anaerobic conditions?
The keto group of pyruvate is reduced to from lactate. This rxn uses NADH + H+ and oxidizes it NAD+. termed dehydrogenase
-named for more reduced molecule
Why do we need to use shuttles?
Because if we send all of NADH it will not come back since the mitochondria can use it for other processes.
GALT defciency-in rare cases, galatokinase deficiency
symptoms of galactosemia
lethargy, vomiting, diarrhea, failure to thrive, and jaundice.
GALT enzyme reaction
UDP glucose + galactose 1-phsophate --> UDP galactose + glucose 1-phosphate
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