Clinical Relevance of Cell Membranes and Transport Flashcards
What is phosphatidylserines role in cell membranes
When cells undergo apoptosis, it is displayed on the extracellular surface to tag the cell for phagocytosis
-It is usually in the inner surface of the membrane
What is Niemann-Pick disease and what does it cause
Deficiency in sphingomyelinase which causes sphingomyelin to build up in lysosomes of spleen and liver, causing hepatosplenomegaly
Also causes neurologic damage leading to mental retardation, seizures and ataxia
-Cherry red spot in patients eye is a hallmark of this disease
A-SMase (sphingomyelinase) cuts sphingomyelin into what two components
Ceramide and phosphoryl choline
Which factors effect membrane fluidity
Temperature
Lipid composition
Cholesterol
Cholesterol effect on membrane fluidity
If membrane is too fluid, cholesterol will fill in gaps and help reduce fluidity
If membrane is too rigid, cholesterol can prevent close packing of lipids and increase fluidity
Dampens large fluidity changes caused by temperature
What is spur cell anemia
Characterized by elevated levels of cholesterol in the membrane, which decreases fluidity and flexibility of membranes. Erythrocyte membranes will break as they pass through the capillaries of the spleen (where RBCs are stored)
What causes cystinuria
Defect in the transporter that takes up cystine. It will accumulate in the kidney and create cystine crystals
What is hartnup disease
Defect in transporter for nonpolar or neutral amino acids located in kidney and intestines
Tryptophan is one of the AAs effected which is significant because Tryptophan is precursor for serotonin, Niacin (NAD precursor) and others
What are cardiotonic drugs
Cardiac glycosides
They inhibit the Na+/K+ ATPase leading to increased intracellular Na+. This causes defect in secondary transporter called Sodium/Calcium transporter (NCX) leading to increased Ca2+ in sarcoplasmic reticulum
-Increases contraction if given at right dosage
What causes cystic fibrosis
Defect in CFTR gene which encodes protein that actively pumps Cl- out of airway epithelial cells and sweat cells. This causes Na+ to flow into the cell followed by water, causing thicker mucus and airway is susceptible to bacterial infection
Outer sheet lipids include
Phosphatidylcholine
Sphingomyelin
Glycolipids
Inner sheet lipids include
Phosphatidyl-inositol/serine/ethanolamine
What is the purpose of glycocalyx on membranes
It is a protective sheet of glycolipids that also aids in cell adhesion and cell identification
