Cell Membrane Flashcards
What membrane lipids are found on the outer sheet?
Phosphatidylcholine
Sphingomyelin
Glycolipids
What membrane lipids are found on the inner sheet?
Phosphatidylinositol
Phosphatidylserine
Phosphatidylethanolamine
What are the functions of glycocalyx
- Protection: the carbohydrate shell protects membrane components from mechanical injury or premature enzymatic degradation.
- Cell Adhesion: enables cell to make more stable contacts with other cells, important during tissue formation and fertilization
- Cell identification: allows the body to differentiate its own healthy
cells from foreign or diseased cells. Very important in red blood cells
What phospholipid serves as a label in dying cells and is recognized by and removed by phagocytes
Phosphatidylserine
It is displayed on extracellular side
Describe the genetics of niemann-pick disease
A rare hereditary disorder. Autosomal recessive
What causes N-P disease?
sphingomyelinase, the enzyme that breaks down sphingomyelin
If sphingomylinase is deficient, what happens to the SM?
It accumulates in the lysosomes of liver, spleen, CNS, and bone marrow. Leads to enlargement of liver and spleen and neurologic damage. Cherry red spot in eyes of patients
Do not live past 18 months
What acts as antigens on RBCs?
Carbohydrate components of glycolipids or glycoproteins
Female 28, first born healthy. Having difficultly carrying fetus to term. Blood type checked and female has Rh- antigens. What is the diagnosis?
Erythroblastocic fetalis
Mother’s first child was Rh+. When born, mother was exposed to child’s Rh+ antigens and created antibodies. Antibodies in later pregnancies were able to cross placenta and attack the fetus
How does temperature influence membrane fluidity?
The temp at which membranes switch from fluid to rigid semi-crystalline state is called transition/melting temp (Tm)
Temps below Tm, lipids are in ordered packing and keeps in a rigid state
Temps above - fluid
How does temperature influence membrane fluidity?
The temp at which membranes switch from fluid to rigid semi-crystalline state is called transition/melting temp (Tm)
Temps below Tm, lipids are in ordered packing and keeps in a rigid state
Temps above - fluid
What lipid composition causes a decrease in membrane fluidity?
Saturated, long fatty acids due to tighter packing of these straight chain lipids which strengthens their interaction between them and hence reduces their mobility
What lipid composition causes an increase in membrane fluidity?
Unsaturated, short fatty acid chains bc kinks do not allow tight packing between lipids
How does cholesterol increase fluidity?
When there is too much saturated fatty acids or temp is below Tm, the membrane becomes too rigid, but the cholesterol prevents the close packing of the lipids
How does cholesterol stabilize fluidity?
If membrane is fluid due to unsaturated fatty acids, the cholesterol fits in gaps created by kinks in the tail lipids.
Cholesterol decreases membrane fluidity by intercalating in between and reducing mobility of fatty acid tails
