Catabolic Metabolism I and II Flashcards Preview

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Flashcards in Catabolic Metabolism I and II Deck (41):

How do cells couple ATP hydrolysis to work?

mechanical work - protein changes conformation

transport work - transfer of phosphate changes conformation for transport of molecules across membranes

biochemical work - coupling favorable to unfavorable reactions, creation of activated intermediates


cellular homeostasis

the property of a sytem that regulates its internal environment and tends to maintain a stable, constant condtion of properties


Name the three homeostatic mechanisms.

1. receptor that senses a stimulus

2. control center (integrator) that determines the response to the stimulus

3. effector that carries out instructions from the control center using positive or negative feedback mechanisms


Are most sugars in the body D or L sugars?

D sugars



opening and closing of the carbohydrate ring that allows changes in the position of the hydroxyl attached to the anomeric carbon



formed by reduction of the aldehyde in an aldose sugar, all of the carbons contain hydroxyl groups


Name the major dietary carbohydrates and their subcompnents.

Maltose - glucose 1-4 glucose

Lactose - galatose 1-4 glucose

Sucrose - glucose 1-2 fructose


Name the three types of storage sources for glucose.

amylose, amylopectin, and glycogen



branched polymer of glucose linked by 1-4 glycosidic bonds except at branches which are 1-6 bonds, highly branched, degraded by glycogen phosphorylase and debranching enzyme


How does glucose get transported into the cell?


Recite glycolysis.


What is the key regulatory step of glycolysis?

phosphorylation of Fructose-6-P to fructose-1,6-bisphosphate, catalyzed by phosphofructokinase-1, thermodynamically and kinetically irreversible


fructose metabolism

transported into cells by GLUT5

mainly metabolized in the liver


essential fructosuria

benign condition due to absence of fructokinase, fructose is excreted in the urine


hereditary fructose intolerance

due to absence of aldolase B, leading to accumulation of fructose 1-phosphate


galactose metabolism

also known as Leloir Pathway, converted to glucose to enter glycolysis


classical and non-classical galactosemia

classical - GALT deficiency, build up of galactose-1-P, can lead to neurological damage

non-classical - GALE deficiency, galactose excreted in urine


Describe the different regulatory mechanisms in glycolysis

regulation by ATP/ADP/AMP and cintrate levels

levels of product and substrate regulate PFK-1 and PFK-2

glucokinase in liver regulated byby nuclear mechanism GKRP


anaerobic glycolysis

NADH is reoxidized in the cytosol by lactate dehydrogenase by the reduction of pyruvate to lactate


hemolytic anemia

erythrocyte pyruvate kinase deficiency


Warburg Effect

high rate of glycolysis in malignant tumor cells, need for ATP and ribose-5-phosphate, many times these cells experience anaerobic conditions in tumors


metabolism of sugar alcohols

in hyperglycemic conditions, excess sorbitol can cause tissue damage due to osmotic effects


fatty acid oxidation

major source of energy between meals and during increased demand

during fasting, provides ketone bodies as fuel for many tissues

higher energy yield per mole than glucose

occurs primarily in the mitochondrial matrix


activation and transport of fatty acids

uses carnitine to transfer fatty acids into the mitochondrial matrix, several important transfer proteins are used such as carnitine palmitoyl transferase I (CPTI)


Describe the beta-oxidation process of long chain fatty acids

shortened 2 carbons at a time by a series of 4 reactions

general process - oxidation, hydration, oxidation, cleavage


regulation of beta oxidation

blocked at high levels of reduced factors

oxidation pathways turn off malonyl-CoA

oxygen and a functioning ETC is required


oxidation of odd chain fatty acids

undergo beta-oxidation until a 3 carbon propionyl CoA, which is converted to succinyl CoA for the TCA cycle


energy yield for beta-oxidation

1 mole of palmitate (C16) leads to 28 moles of ATP from the 7 FADH2 and 7NADH molecules generated, 2 moles were consumed for activation


very long chian fatty acid oxidation

usually for more than 22 carbons, undergoes alpha and beta oxidation in the peroxisome

first step produces hydrogen peroxide

acetyl-CoA molecules and short acyl-CoAs are derivatized with carnitine and diffuse from peroxisomes to be taken up by mitochondria and fully oxidized



carried out in the ER

omega methyl group is oxidized to an alcohol and then turned into a carboxylic acid

the resulting dicarboxylic acids are oxidzed by beta-oxidation to compounds that are 6-10 carbons long

released in the blood and then oxidized or excreted in urine (usually indicating failure of beta-oxidation pathways)


oxidation fo ketone bodies

oxidation of beta-hydroxybutyrate and acetoacetate, the first is more reduced and provides more energy

done in mitochondrial matrix, often used in starvation conditions


disorders of fatty acid oxidation

carnitine deficiency or defect in carnitine transferase or translocase

hyperketotic hypoglycemia - caused by medium chain fatty acyl CoA dehydrogenase deficiency

dicarboxylic aciduria - consequence of omega oxidation when beta oxidation is impaired

Zellweger syndrome - defect in peroxisome biogenesis, cannot oxidize very long chain fatty acids


pyruvate dehydrogenase complex (PDC)

lniks glycolysis to TCA cycle by oxidizing pyruvate to acetyl CoA, mitochondiral large multi-subunit enzyme complex with three functional proteins

reaction uses oxidation to liberate CO2 from pyruvate - called oxidative decarboxylation


Name the three subunits of PDC and their functions.

pyruvate dehydrogenase (E1) - uses thiamine pyrophosphate as a cofactor, catalyzes the decarboxylation step and transfers acetyl group to lipoate cofactor of E2

dihydrolipoyl transacetylase (E2) - uses lipoate and CoA to transfer acetate to CoA

dihydrolipoyl dehydrogenase (E3) - uses FAD and NAD to re-oxidize the lipoate cofactor of E2


regulation of pyruvate dehydrogenase

ATP/ADP, NADH/HAD+, and acetyl-CoA/CoA ratios are the main regulators

phosphatase and kinase activate and deactivate the complex

during starvation there is high kinase, which prevents glycolysis from preceding, turning to fat and muscle oxidation


Describe and recite the tricarboxylic acid cycle.

accounts for 2/3 of ATP production from fuel oxidation

utilizes acetyl CoA from glucose, fatty acids, amino acids, and keton bodies

occurs in the mitochondrial matrix

activity tightly cooridnated with rate of electron transport chain and oxidative phosphorylation by feedback regulation reflecting the demand for ATP


What are the steps that are largely negative in the TCA cycle?

citrate synthase, isocitrate dehydrogenase, and alpha-ketoglutarate dehydrogenase


What are the important positive free energy steps of the TCA cycle?

malate dehydrogenase and aconitase


Deficienccies of what three enzymes in the TCA are more commonly found in diseases?

fumarase, succinate dehydrogenase, and alpha-ketoglutarate dehydrogenase


alcohol metabolism



a drug that inhibits acetaldehyde dehydrogenase, makes person sick after alcohol, negative stimulus for drinking