question

GLUT 5

answer

fructose transporter

question

GLUT 4

answer

Muscle and adipose; movement to membrane is controlled by insulin and exercise

question

GLUT 3

answer

neurons

question

GLUT 1

answer

RBC and Brain

question

HK III

answer

other extra-hepatic tissues

question

HK II

answer

muscle

question

HK I

answer

brain

question

function of hexokinase

answer

phosphorylates glucose to G6P to trap in in the cell and limit concentration of free glucose

question

HK IV

answer

aka Glucokinase, found in liver and beta cells of pancreas; not product inhibited; high Km for glucose

question

Which steps of the glycolysis pathway are irreversible? What enzymes are involved? What inhibits the enzymes?

answer

Preparation for splitting by PFK 1 (F6P --> F-1, 6P2) AND the final oxidation step by PK (PEP --> PYR);
inhibited by high ATP concentrations

question

When aldolase catalyzes the splitting of F-1, 6-P2 what are the two products?

answer

DHAP and G-3-P

question

For every ____ carbons of the initial glucose molecule, there will be a net synthesis of ____ NADH and ____ ATP?

answer

3, 1, 2

question

How many ATP are netted from the complete glycolytic pathway?

answer

2 ATPs (and 2 NADHs)

question

What are the two uses for DHAP?

answer

Can be converted to G3P by isomerase OR to accept the reducing equivalents of NADH (so that it can be used for ATP production) by alpha glycerol phosphate dehydrogenase

question

What is the major enzyme of anaerobic glycolysis, and what does it do?

answer

lactate dehydrogenase; converts pyruvate to lactate by re-oxidizing NADH

question

What is the role of carnitine and what enzymes are involved in its use?

answer

carriers the fatty acid across the inner mitochondrial membrane; transferase I moves the FA from CoA to carnitine, translocase moves the acyl-carnitine into the matrix, transferase II moves the fatty acid from carnitine back to CoA

question

Name the products and their quantities resulting from one sequence of beta oxidation?

answer

1 FADH2, 1 NADH, 1 acetyl-CoA, 1 fatty acyl CoA which is two carbons shorter than the initial reactant

question

Describe the flavoprotein involved in the beta oxidation sequence, its name and function, and why it is important?

answer

fatty acyl-CoA dehydrogenase, a large complex in the inner mitochondrial membrane; the packet energy bound to FADH2 is passed through this complex to CoQ --> III-->cytochrome c --> IV --> OXYGEN to form H2O

question

What happens to odd chain fatty acids during beta oxidation? What enzymes and coenzymes are involved?

answer

The last three carbons are liberated as propionyl Co-A, which is converted into succinyl CoA. The first enzyme is propionyl-CoA carboxylase bound to biotin; the second enzyme is MM-CoA mutase bound to Ad-B12

question

What is the difference in the Beta oxidation pathway used for very long chain fatty acids?

answer

1) takes place in the peroxisomes 2) the flavoprotein is a fatty acyl CoA oxidase which reacts directly with molecular oxygen to yield hydrogen peroxide 3) the oxidation stops at the medium chain level and transports the products back to the mitochondria

question

What is the name of the flavoprotein involved in the TCA cycle and where is it located within the cell?

answer

succinate dehydrogenase, inner mitochondrial membrane; the "missing" Complex II

question

Name the enzymes of the TCA cycle that are involved in reactions that produce energy

answer

isocitrate, a-KG, succinate, malate, thiokinase

question

what is the purpose of the alpha glycerol phosphate shuttle and what is the main enzyme involved?

answer

passes reducing equivalents of NADH to DHAP, which becomes alpha glycerol phosphate, crosses the outer mitochondrial membrane, and passes the reducing equivalents to a flavoprotein; the enzyme is alpha glycerol phosphate dehydrogenase

question

oxidative portion of the HMP shunt pathway

answer

G-6-P to carboxylic acid via 2 hydrogenases; produces NADPH; final product is ribulose phosphate

question

which pathway converts acetyl CoA into palmitate? what is the rate-limiting enzyme in this process? What is the product after catalyzation by the rate-limiting enzyme?

answer

Fatty Acid synthesis, acetyl CoA carboxylate, malonyl CoA

question

Which organs have the ability to use active transport to move glucose?

answer

The intestine and the kidney. called sodium-glucose symports, use ATP.

question

what types of substances must be transported in the blood stream via albumin?

answer

fatty acids, bilirubin, lipid soluble drugs

question

non-oxidative portion of HMP shunt

answer

takes F-6-P and G-3-P and arranges the carbon backbones to yield ribose phosphate for nucleotide synthesis; freely reversible, may be used as a salvage pathway

question

ribose phosphate

answer

used for purine and pyrimidine nucleotide synthesis

question

gluconeogenesis

answer

a backup system that allows the liver to maintain blood glucose for days; catalyzes the synthesis of glucose from lactate, glycerol, and glucogenic amino acids (major source); 2 OAA --> glucose

question

What process occurs simultaneously with gluconeogenesis?

answer

the urea cycle

question

glucagon

answer

polypeptide
alpha cells of pancreas
released in hypoglycemia
receptor in liver and adipose
phosphorylation of enzymes via protein kinase A leads to glycogenolysis, TAG hydrolysis, and gluconeogenesis
inhibited by insulin

question

insulin to glucagon ratio

answer

increased with increased glucose concentration, activation of regulatory enzymes in metabolic pathways

question

citrate shuttle system

answer

used in glycolysis; citrate, a product of OAA and acetyl CoA is transported out of the mitochondria and broken down into its components in the cytosol

question

Ketone bodies

answer

water-soluble lipid fuels that are continuously released from the liver, made only in the liver mitochondria, can be used by the brain when glucose levels are low. Can NOT be used by the liver or RBC.

question

ketogenesis

answer

acetyl CoA --> ketone bodies. The acetyl coA comes from Fatty acid oxidation and is in excess due to OAA being used for gluconeogenesis instead of the TCA cycle.

question

glucose-6-phosphatase

answer

removes the phosphate group of G-6-P in glycogenolysis, allowing the conversion of glycogen to glucose; only present in liver, kidney, and intestinal cells

question

lipogenesis

answer

excess carbohydrate is converted into triacylglycerol (TAG) in the cytosol of the cell.

question

phosphofructokinase 1

answer

used in preparation for splitting in glycolysis; phosphorylates the F-6-P at the 1 position, forming F-1, 6-P2, this is the irreversible and controlling step of the glycolysis pathway

question

G-6-P dehydrogenase

answer

used in the synthesis of the first NADPH from G-6-P in the oxidative portion of the hexose mono phosphate shunt, product is 1 NADPH and lactonase

question

pyruvate dehydrogenase

answer

a large enzymatic complex used in aerobic glycolysis for the conversion of pyruvate to acetyl CoA

question

acetyl CoA carboxylase

answer

catalyzes the carboxylation of acetyl CoA resulting in malonyl CoA

question

pyruvate carboxylase

answer

catalyzes the conversion of pyruvate to OAA, depends on biotin

question

what enzymes are involved in TAG synthesis?

answer

acyl-CoA transferase and phosphatase

question

What is the role of citrate in fatty acid synthesis? What enzymes are involved?

answer

Bringing acetyl CoA to the cytosol. Synthase turns Acetyl CoA and OAA into citrate, which crosses the mitochondrial membrane. Lyase turns citrate back into OAA and acetyl CoA

question

OAA

answer

a four carbon dicarboxylic acid that functions as a carrier molecule in the TCA cycle

question

What is the source of OAA in gluconeogenesis?

answer

The glucogenic amino acids that come from the breakdown of functional body proteins.

question

Urea cycle

answer

Removes the amino group from the amino acids of the body being used to make OAA for gluconeogenesis. Always occurs simultaneously with gluconeogenesis

question

glycogen phosphorylase

answer

the key enzyme in the glycogenolysis pathway. Uses phosphoric acid to remove glucose molecules from glycogen as G-1-P. Activated by phosphorylation by PKA.

question

G6PD deficiency

answer

a genetic deficiency that leads to normocytic, normochromic hemolytic anemia when the individual is exposed to certain drugs (i.e. antimalarial drugs). NADPH levels can not adapt to increased stress due to lack of G6P in oxidative portion of HMP shunt

question

glycation

answer

a consequence of sustained hyperglycemia; glucose is added to an amino group of protein, causing the protein to rearrange and change its function, i.e. the thickening of the basement membrane of kidney tubules

question

inositol

answer

an alcohol needed for cell signaling compounds, inhibited in hyperglycemia, causing pronounced problems with long-bodied nerve cells (i.e. in the legs)

question

aldose reductase

answer

an enzyme in the lens of the eye that reduces excess glucose to a sorbitol, which is subsequently trapped in the cells, causing an influx of water and cataracts

question

HgbA1c

answer

the product of the glycation of hemoglobin, the best lab value indicator of non-compliance with insulin-dosing in an IDDM patient

question

hormone sensitive lipase

answer

a key enzyme in hydrolysis of fat stores, present in adipose cells. Activated by phosphorylation. Fatty acids and glycerol are the products of the reaction catalyzed.

question

acetoacetic acid

answer

a ketone body that at high concentrations, turns into acetone. Accounts for the acetone smell on the breath of a diabetic in metabolic acidosis

question

1st stage of starvation

answer

glycogenolysis, gluconeogenesis (and urea cycle), lipolysis

question

2nd stage of starvation

answer

body is living off of fat stores only, length of this stage depends on amount of body fat, fatty acids are used for the muscles heart and liver, ketone bodies are used for the brain (60% brain energy from ketone bodies)

question

3rd stage of starvation

answer

kidney joins liver in gluconeogenesis; all functional body proteins are eventually broken down, leading to death

question

glycogen stores

answer

last 2 days

question

5 major classes of lipoproteins

answer

Chylomicrons (CM), Very Low Density Lipoproteins (VLDL), Intermediate Density Lipoproteins (IDL), Low Density Lipoproteins (LDL), High Density Lipoproteins (HDL)

question

Functions of lipoproteins

answer

1) FA and TG for energy storage in adipose and energy production in muscle and liver via B-hydrolysis
2) Provide cholesterol for membrane biosynthesis
3) cholesterol for steroid hormone synthesis
4) cholesterol for bile production
5) fat soluble vitamins to liver for storage
6) remove excess membrane building materials for recycling in the liver

question

lipoproteins

answer

molecular aggregates of various lipids and apoproteins

question

apoprotein functions

answer

1) solubilize lipid components for transport in blood and lymph. 2) direct the secretion of lipid components from their site of synthesis into the circulation 3) direct the clearance or removal of the lipid components from the circulation into tissues for metabolism or excretion

question

chylomicrons

answer

largest and least dense; 98/2 lipid/protein; origin in intestine; dietary delivery of TG,C, and fat-soluble vitamins

question

VLDL

answer

second largest, second most dense, 90/10 lipid/protein; origin in liver; denovo FFA and TGs to muscle and adipose

question

IDL

answer

82/18 lipid/protein; origin in circulation; VLDL--> IDL

question

LDL

answer

second smallest and second most-dense; 75/25 lipid/protein; origin in liver/circulation; cholesterol to liver and peripheral tissues

question

HDL

answer

smallest and most dense; 45/55 lipid/protein; liver/intestines; delivers cholesterol from tissues

question

apoB48

answer

used in making chylomicrons in the intestinal epithelial cells, an edited version of apoB100

question

apo C11

answer

present on the CM, VLDL, and HDL, origin in the liver, activates target tissue lipoprotein lipase in the cell membrane of the capillary bed epithelium

question

perilipin

answer

coats the lipid droplet of the adipose cell and restricts access, promoting storage

question

apoE

answer

contained in the remnant polar coat of chylomicrons, contributes to the uptake mechanism of dietary cholesterol in the liver

question

statins

answer

targets HMG-CoA reductase by acting as a competitive inhibitor at the rate-limiting step for cholesterol biosynthesis

question

SREBP

answer

steroid response element binding protein; a transcription factor fequired for HMG-CoA reductase expression; activity is decreased with increased cholesterol/cholesterol ester levels

question

HMG CoA Reductase

answer

the enzyme involved in the rate-limiting step for cholesterol synthesis from acetyl CoA; the target of statins, also inhibited by a negative feedback from the presence of cholesterol

question

apo B100

answer

found in the polar coat of VLDL and LDL; coordinates the stability of the hydrophobic core

question

effect of diabetes on LDL

answer

excess glucose can modify LDL, cause apoB100 glycation, blocking internalization and promoting artherosclerosis

question

can cells degrade cholesterol?

answer

no, that is why it is necessary for LDL delivery to the cell be strictly controlled

question

Reverse Cholesterol Transport

answer

a mechanism for transferring cholesterol from peripheral tissue back to the liver for disposal; HDL accepts cholesterol

question

Niemann Pick Type C disease

answer

a genetic disorder in which the sterol binding protein that traffics cholesterol to the plasma membrane of the cell is not functioning; cholesterol accumulates in the endosomes and degradation function of the lysosomes is decreased

question

ABCA1

answer

ATP binding cassette-apo1 activated; off loads cholesterol and some phospholipids HDL; can be found in both plasma membrane and Golgi

question

Tangier's disease

answer

a genetic mutation that causes a disorder of decreased ABCA1, leading to decreased HDL efficiency and increased cholesterol levels in cell membrane; causes orange-ish skin color and increased systemic atherosclerosis disease

question

LCAT

answer

lecithin cholesterol acyl transferase; the cholesterol esterification enzyme activated by apoA1

question

bile salts

answer

made from the cholesterol carried by HDL to the liver; join with cholesterol and phospholipase to form vesicles and are released to bile

question

artherosclerosis

answer

a chronic inflammatory disease of the intima of the major blood vessels

question

oxidation during the atherosclerosis process

answer

the step where LDL infiltrates into the intima and is modified by intimal lipoxygenases released by damaged cells

question

the scavenger pathway step of the atherosclerosis process

answer

modified apoB100 in oxidized LDL triggers it; the oxidized LDL-modified B100 is picked up by a macrophage, leading to lysosomal degradation in the macrophage and the buildup of C/CE

question

Foam cells

answer

a macrophage that has built up CE deposits and coalesced; leads to macrophage death and deposit of C/CE left behind to build up in the vessel as plaque

question

optimal cholesterol levels

answer

LDL less than 100, total cholesterol less than 200, HDL less than 40

question

Bile Acid Binding Resin drugs

answer

sequester bile salts, blocking readsorption of bile acids, fat micelles, and some dietary fats; causes loose stools and decrease 10-20% in serum cholesterol levels

question

Nicotinic Acid

answer

inhibits VLDL synthesis in the liver, leading to decrease of LDL; excessive amounts are toxic to the liver

question

plant sterols

answer

complete block of bile salt, cholesterol, and excess lipid resorption by the intestines

question

Vytorin

answer

a combined therapy that blocks intestinal cholesterol uptake and inhibits cholesterol biosynthesis in liver. Increases LDL receptors in the liver. A combination of simvastatin and plant sterol

question

advicor

answer

inhibits cholesterol and VLDL biosynthesis in liver; lovastatin + niacin

question

What is the conjugated form of bilirubin and where is it found in the body? What enzyme/coenzyme is involved in its formation?

answer

bilirubin diglucuronide, in the hepatocytes of the liver, transferase/UDP-glucuronide

question

where does hemoglobin breakdown occur in the body?

answer

in the macrophages of the spleen

question

What process is disrupted by lead poisoning? Which enzymes does it disrupt? What is excreted in the urine as an indicator of lead poisoning?

answer

Heme synthesis, 5ALA-DH and ferrochelatase, 5ALA-DH is excreted in the urine because it is not being used

question

PRPP

answer

an activated form of R-5-P, used in the denovo synthesis of purine and pyridine nucleotides

question

dihydrofolate reductase

answer

the catalyzing enzyme of the transition from folic acid to tetrahydrofolate (the coenzyme form of folate); a target of cancer drugs

question

thymidalate synthase

answer

an enzyme that converts dUMP --> dTMP; dTMP can become dTTP; folate is a key coenzyme in this pathway

question

dTTP

answer

a nucleotide necessary for DNA replication; the rate-controller of cell replication

question

anemia caused by folate deficiency and mechanism involved

answer

macrocytic anemia; lack of dTTP for DNA synthesis = RBCs "stuck" in macrocytic (immature) phase

question

anemia caused by B12 deficiency

answer

pernicious anema = a macrocytic anemia; usually due to a disorder of intrinsic factor rather than a dietary deficiency of B12

question

antioxidant

answer

prevents peroxides from forming free radicals in the cell membrane; in the RBC, includes vitamin E, glutathione, superoxide dismutase and catalase

question

ferrochelatase

answer

used to catalyze the heme synthesis reaction in which the iron is added to the porphyrin ring

question

Name some of the necessary components for Heme biosynthesis

answer

glycine, succinyl CoA, ferrochelatase, 5ALA, 5ALA-DH

question

ferritin

answer

stores Fe3+ in the cells; presence in the blood indicates cell damage

question

ceruloplasmin

answer

synthesized in the liver, oxidizes Fe2+ to Fe3+ for addition to transferrin

question

apotransferrin

answer

assists ceruloplasmin with transfer of Fe2+ to transferrin

question

transferrin

answer

binds Fe3+ and transports it into the cell, where the entire complex is enveloped by a lysosome; the pH of the lysosome allows the transferrin to release the Fe3+ to ferritin and be transported out of the cell

question

Name some of the causes of normocytic normochromic anemia

answer

hemorrhage, G6PD deficiency, PK deficiency, sickle cell hemolytic crisis, defect of methemoglobin reductase

question

what is the primary cause of microcytic hypochromic anemia?

answer

iron deficiency

question

Name three key folate reactions

answer

serine --> glycine, homocysteine --> methionine, dUMP --> thymidylate (TMP)

question

glutathione reductase

answer

an NADPH-dependent enzyme that catalyzes the reduction of oxidized glutathione to the reduced form (active form)

question

protoporphyrin IX

answer

a porphyrin ring that is the main constituent of heme; synthesized from glycine and succinyl CoA

question

Hemophilia A

answer

deficiency of factor VIII

question

the extrinsic pathway

answer

initiates the coagulation cascade, tissue factor III + Factor VII

question

tissue factor III

answer

aka thromboplastin, a transmembrane protein found in the membrane of cells of the sub-endothelium, exposed when vascular damage occurs, binds factor VII to begin extrinsic pathway

question

VII

answer

aka SPCA, a serine protease that binds to tissue factor III in the extrinsic pathway

question

intrinsic pathway

answer

HMW-kininogen, pre-kallikrein, calcium, factors VIII, IX, XI, and XII; end result is the activation of Factor IX

question

Factor XII

answer

activates pre-kallikrein to kallikrein in the intrinsic pathway, becomes activated by kallikrein, XIIa activates XI

question

IX

answer

activated by XIa in the intrinsic pathway; activates X in common pathway, the deficient factor in Hemophilia type B

question

Factor X

answer

activated by IXa, activates prothrombin (II) to thrombin (IIa); has maximal activity when co-factored with calcium, Factor Va, and phospholipid

question

warfarin

answer

inhibits vitamin K epoxide reductase, leading to a decrease in vitamin K and causes anticoagulation

question

II

answer

prothrombin; activated by Xa complex; IIa = thrombin, which hydrolyzes fibrinogen to fibrin

question

XIII

answer

activated by thrombin (IIa), catalyzes the formation of cross-links between fibrin molecules of the soft clot to the hard clot

question

Factor VIII

answer

the deficiency in Hemophilia type A, activated by thrombin, VIIIa joins the complex that activates Factor X

question

tPA

answer

tissue plasminogen activator; a serine protease found on vascular epithelial cells that breaks down plasminogen to plasmin

question

plasmin

answer

the enzyme that degrades fibrin clots

question

serpin

answer

a serine protease inhibitor, activity is enhanced by heparin

question

urokinase

answer

an endogenous anticoagulate that activates plasminogen

question

streptokinase

answer

a protein produced by B-hemolytic stretococcus taht activates plasminogen to plasmin

question

thrombomodulin

answer

an integral membrane protein of endothelial cells, binds to thrombin and activates protein C

question

protein C

answer

an anticoagulant that forms a complex with protein S to degrade Va and VIIIa

question

vitamin K dependent Factors

answer

II, VII, IX, X

question

von Willibrand factor

answer

a large molecular weight protein found in the circulation and in the platelets, binds to the sub-endothelial proteins and to a platelet receptor, GpIb

question

which factors are in the complex that activates prothrombin (II) to thrombin (IIa)

answer

Va, Xa, phospholipid of platelet membrane, and calcium

question

methemoglobin

answer

hemoglobin where the oxygen has dissociated, leaving the iron in the Fe3+ form

question

superoxide dismutase

answer

breaks down the toxic superoxide ion associated with deoxyhemoglobin and converts it to water and molecular oxygen

question

causes of increased serum bilirubin

answer

G6PD deficiency, blocked common bile duct, deficiency of UDP-glucuronide/transferase, hemolysis

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