Metabolism — Flashcards

Flashcard 841: Briefly describe the composition or source of the following carbohydrates: - Amylose - Cellulose - Galactose - Lactose - Maltose - Sucrose

Answer: - **Amylose**: Linear glucose polymer (α-1,4 linkages) found in starch. - **Cellulose**: Glucose polymer (β-1,4 linkages) found in plant cell walls. - **Galactose**: Monosaccharide; component of lactose. - **Lactose**: Disaccharide (Glucose + Galactose); primary sugar found in milk. - **Maltose**: Disaccharide (Glucose + Glucose); product of starch breakdown. - **Sucrose**: Disaccharide (Glucose + Fructose); table sugar.

Extra: - **Fructose Metabolism**: In fructokinase deficiency, some fructose can be metabolized by **hexokinase** to fructose-6-phosphate. In **Aldolase B deficiency** (Hereditary Fructose Intolerance), toxic accumulation of fructose-1-phosphate occurs. - **Galactosemia**: Deficiency in enzymes (most commonly GALT) preventing galactose metabolism. - **Digestion**: Lactose is broken down by lactase; Sucrose by sucrase; Maltose by maltase.

Flashcard 842: Which signaling mechanisms or pathways cause an intracellular increase in the following substances? - Ca2+ - cAMP - cGMP - Cl- - mRNA - NO

Answer: • **Ca2+**: Phospholipase C (PLC) pathway (Gq protein) → IP3-mediated release from ER. • **cAMP**: Adenylate cyclase activation (Gs protein). • **cGMP**: Guanylate cyclase activation (e.g., via NO or ANP). • **Cl-**: Activation of GABA-A or glycine receptors (ligand-gated Cl- channels). • **mRNA**: Increased gene transcription (e.g., via steroid hormones or cell division). • **NO**: Synthesis from L-arginine by Nitric Oxide Synthase (NOS).

Flashcard 843: A 54-year-old man presents with anemia. Evaluation shows the cause is EPO deficiency. In this patient, mature erythrocytes are found that are unable to synthesize heme even though they contain detectable levels of cytoplasmic enzymes involved in heme synthesis. Lack of which cellular organelle best explains this phenomenon?

Answer: Mitochondria (Mitochondria play a vital role in heme synthesis; mature erythrocytes lack mitochondria.)

Flashcard 844: what are the followings in association with 2,6 bisphosphate? -Acetyl COA ---> Fatty acids -Alanine ---> Glucose -Fructose-6-phophate ---> fructose-1,6-bisphosphate -Glucose----> glycogen -NAD ---> NADH

Answer: acetyl coa  ---> fatty acids: It will stimulate this reaction. Also occurs when you have insulin, which causes glucose to enter in cells in order to start glycolysis. glycolysis --> acetyl coa --> fatty acids. -Alanine ---> Glucose: occurs when you have 2,6 bisphosphate. It will inhibit this reaction because it doesn't want glucose present in blood. -Fructose-6-phosphate  ---> fructose-1,6-bisphosphate: It will stimulate this reaction to break down glucose in glycolysis. -Glucose ---> Glycogen: It will stimulate this reaction (similar to insulin) -NAD ---> NADH: It will stimulate this reaction, because of glycolysis.

Flashcard 845: 52 y/o woman comes with skin rash that worsens with sun exposure. -Her family says: she has become irritable, hostile, and has had episodes of disorientation. -Further questionning revelas poor nutritional intake and intermittent diarrhea. -Physical Exam: well-demarcated, hyperpigmented, scaly rash on hands, forarms, & upper chest. -Cause of symptoms is due to lack of precursor vitamin for synthesis of NAD+ coenzyme. -This pathway will most likely use which compound as a precursor?

Answer: Tryptophan due to Niacin deficiency ( Diarrhea, dermatitis, dementia)

Flashcard 846: Which enzyme is targeted for inhibition in the treatment of Acute Intermittent Porphyria (AIP)? a) ALA synthase b) PBG deaminase

Answer: ALA synthase Acute Intermittent Porphyria (AIP) is caused by a deficiency of **PBG deaminase**, which leads to the accumulation of ALA and PBG. Treatment (such as hemin or high-dose glucose) works by inhibiting **ALA synthase** (the rate-limiting enzyme of heme synthesis) to prevent the further production of these neurotoxic intermediates.

Extra: Hemin provides feedback inhibition of ALA synthase, while glucose/carbohydrates suppress the induction of ALA synthase.

Flashcard 847: A healthy 34-year-old worker is trapped underground following the partial collapse of an access shaft. It takes 2 days to reach him. He has not eaten for over 30 hours. Fingerstick blood glucose concentration is 78 mg/dL. Which biochemical reactions are most likely responsible for maintaining this patient's current blood glucose levels?

Answer: Pyruvate → Oxaloacetate → Phosphoenolpyruvate (Gluconeogenesis)

Flashcard 848: 23 y/o apparently healthy man who immigrated to the US comes to a clinic for regular check up. -History: no significant medical problems but his mother told him he was born with a problem metabolizing sugar. -Patient maintains no dietary restrictions and regularly eats vegetables, fruits, and meats. -Urine samples: Repeatedly positive copper reduction test. -Glucose oxidase dipstick test: negative -Which enzyme is most likely to be deficient in this patient?

Answer: Fructokinase (Essential fructosuria is a benign, asymptomatic condition where fructose is not metabolized by fructokinase but is instead excreted in the urine, giving a positive copper reduction test but a negative glucose oxidase test.)

Flashcard 849: Describe the clinical significance or deficiency symptoms associated with the following enzymes: A) Lactase B) Aldose reductase (in the context of galactose metabolism) C) Galactokinase D) Galactose-1-phosphate uridyltransferase (GALT) E) Phosphoglucoisomerase

Answer: A.) **Lactase**: Deficiency leads to **lactose intolerance** (bloating, cramps, osmotic diarrhea). Primarily occurs in adults; congenital form is very rare. B.) **Aldose reductase**: Converts galactose to **galactitol**. In GALK or GALT deficiency, galactose levels rise and are shunted to this pathway, causing galactitol accumulation in the lens and **cataracts**. C.) **Galactokinase (GALK)**: Deficiency leads to high galactose and galactitol, resulting in **infantile cataracts**, galactosemia, and galactosuria. D.) **Galactose-1-phosphate uridyltransferase (GALT)**: Deficiency causes **classic galactosemia**. Presents in neonates with vomiting, jaundice, hepatomegaly, cataracts, intellectual disability, and **E. coli sepsis**. E.) **Phosphoglucoisomerase**: Deficiency causes **hereditary non-spherocytic hemolytic anemia** due to a block in glycolysis.

Flashcard 850: 61 y/o man found unresponsive on a sidewalk. -He presents with breath smelling of alcohol. -He has agonal respirations and a pulseless EKG; he's pronounced dead on arrival. -Autopsy: necrosis is seen in the mammillary bodies and gray matter surrounding the 3rd & 4th ventricles. -This patient's brain findings are most likely associated with a decrease in what?

Answer: Erythrocyte transketolase activity Due to Wernicke-Korsakoff syndrome caused by thiamine (B1) deficiency. Thiamine serves as a cofactor for: - Pyruvate dehydrogenase - Alpha-ketoglutarate dehydrogenase - Branched-chain alpha-ketoacid dehydrogenase - Transketolase