Lipid metabolism US Medical PG Flashcards - Medical Study Cards
Master Lipid metabolism with OnCourse flashcards. These spaced repetition flashcards are designed for medical students preparing for NEET PG, USMLE Step 1, USMLE Step 2, MBBS exams, and other medical licensing examinations.
Lipid metabolism Flashcard Deck - 10 Cards
Flashcard 261: 3 y/o patient presents with cherry-red spots and loss of motor skills.
- Physical exam: No splenomegaly
- What is the most likely enzyme deficiency that causes this disease?
Answer: Hexosaminidase A deficiency
due to Tay-Sachs disease.
Flashcard 262: 72 y/o woman found lying on the floor in her home for the past 2 days.
- She fell and injured her right hip, was unable to get up and call for help.
- She did not drink anything during that time.
- Physical exam: dehydration, right hip tenderness.
- Labs: serum glucose 72 mg/dL & positive urine ketones.
- Radiographs: right femoral neck fracture.
- Increased activity of what enzyme is most likely contributing to both the serum & urine lab findings?
Answer: Hormone-sensitive lipase
In starvation, HSL breaks down adipose triglycerides into glycerol and fatty acids.
- Glycerol: Substrate for gluconeogenesis (maintaining serum glucose).
- Fatty acids: Substrate for ketogenesis (producing urine ketones).
Flashcard 263: Which organelle is the primary site for the initial $\beta$-oxidation of **Very Long Chain Fatty Acids (VLCFAs)**?
Answer: Peroxisomes
Extra: Very Long Chain Fatty Acids (VLCFAs, >22 carbons) cannot enter the mitochondria directly. They undergo initial $\beta$-oxidation in **peroxisomes** until they are shortened to medium or long-chain fatty acids, which are then transported to the **mitochondria** for complete oxidation.
Defects in peroxisomal VLCFA oxidation lead to conditions like **Zellweger syndrome** and **X-linked adrenoleukodystrophy**.
Flashcard 264: What is the status of the following in **Carnitine deficiency**?
- Acetoacetate
- Arachidonic acid
- Glutathione
- Homocysteine
- Lactate
- Palmitate (oxidation)
Answer: - **Acetoacetate:** Decreased (impaired ketogenesis)
- **Arachidonic acid:** Unaffected
- **Glutathione:** Unaffected
- **Homocysteine:** Unaffected
- **Lactate:** Unaffected
- **Palmitate (oxidation):** Decreased (long-chain fatty acids require the carnitine shuttle)
Extra: In **carnitine deficiency**, the transport of long-chain fatty acids (LCFAs) like **palmitate** (C16) into the mitochondria is impaired.
**Consequences:**
1. **Impaired β-oxidation**: LCFAs cannot enter the mitochondrial matrix.
2. **Hypoketotic hypoglycemia**: Since β-oxidation is the primary source of acetyl-CoA for ketogenesis and ATP for gluconeogenesis during fasting, levels of ketone bodies (like **acetoacetate**) and glucose fall.
3. **Other metabolites**: Arachidonic acid (membrane phospholipid component), glutathione (antioxidant), homocysteine (methionine cycle), and lactate (glycolysis) are not directly involved in the carnitine shuttle pathway and remain largely unaffected.
Flashcard 265: What are the followings defects in relation to hyperlipoproteinemias
-ApoC-2 production
-Cholesterol esterification in the blood
-Chylomicron remnant uptake by liver cells
-LDL particle uptake by hepatocytes
-Lipoprotein lipase activity
Answer: ApoC-2 Production: Familial chylomicronemia syndrome. Present with acute pancreatitis & eruptive xanthomas.
-Cholesterol esterification in the blood: LCAT (Lecithin-cholesterol acyltransferase). will present with low HDL & high free cholesterol in blood.
-Chylomicron remnant uptake by liver cells: Familial dysbetalipoproteinemia. Premature atherosclerosis & palmar xanthomas. Defect in ApoE protein.
-LDL particle uptake by hepatocytes: Familial hypercholesterolemia. Premature atherosclerosis with tendon xanthelasma. Defect in LDL receptor.
- Lipoprotein lipase activity: Familial chylomicronemia syndrome. High chylomicrons.
Present with acute pancreatitis with eruptive xanthomas. Defect in lipoprotein lipase & ApoC-2.
Flashcard 266: 35 y/o man comes with skin lesions on his palms.
-Patient has yellowish skin nodules over palmar creases.
-It has been increasing in size and number over the past several years.
-He has small clusters of yellow papules on his elbows, knees, and buttocks.
-Biopsy of skin lesion:accumulation of lipd-laden macrophages.
-Lack of ApoE3 & ApoE4 in his circulation lipoproteins.
-What is the most likely impaired in this patient?
Answer: Chylomicron remnant uptake by the liver cells. or VLDL remants
which means he has high accumulation of the two.
due to Familial dysbetalipoproteinemia (type 3). (palmar xanthomas)
Flashcard 267: An 18-month-old boy presents with neurologic regression.
- He developed a gradual regression of developmental milestones such as inability to sit with support.
- Poor head control, loss of social smile.
- Physical exam: enlarged liver and spleen, hypotonia, lack of deep tendon reflexes in all limbs.
- Cherry-red spot on fundoscopic exam.
The patient most likely has an accumulation of which substrate?
Answer: Sphingomyelin
(Due to Niemann-Pick disease, caused by deficiency of sphingomyelinase)
Note: Hepatosplenomegaly is present in Niemann-Pick disease but absent in Tay-Sachs disease (which involves GM2 ganglioside accumulation).
Flashcard 268: What protein is responsible for the rate limiting step in steroidogenesis?_____
Answer: StAR (Steroidogenic acute regulatory protein)
Flashcard 269: Which classes of steroid hormones (2) are decreased in 17-hydroxylase deficiency?_____
Answer: glucocorticoids and androgens
Flashcard 270: What is the mode of inheritance of Niemann Pick disease?_____
Answer: Autosomal recessive
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