Endocytosis

Question 1

What is the mechanism for selective uptake of specific macromolecules?

Answer 1

Clathrin-mediated endocytosis

Question 2

Where does endocytosis occur?

Answer 2

Specialized portions of the ECM called clathrin-coated pits

Question 3

What happens after clathrin-coated vesicles bud off?

Answer 3

Fuse with early endosomes

Question 4

What is the significance of the pH of early endosomes being 6-6.2?

Answer 4

Causes dissociation of ligands from receptors.

Receptors can be returned

Ligands can be degraded

Question 5

Why is recycling important?

Answer 5

About 50% of the plasma membrane is internalized by endocytosis every hour.

Most is replaced by recylcing

Question 6

What are two types of clathrin-independent endocytosis?

Answer 6

Macropinocytosis

Internalization of caveolae

Question 7

What are the three specific areas that allow endocytosis?

Answer 7

Clatherin

Caveola

Lipid rafts (via GPI anchors)

Question 8

What is required for LDL uptake?

Answer 8

Binding to specific receptors in clathrin-coated pits

Question 9

What two mutations can cause familial hypercholesterolemia?

Answer 9

Mutations that prevent binding of LDL

Mutations that prevent the receptors from concentrating in the coated pits

Question 10

What are symptoms of and LDLR mutation?

Answer 10

Accumulation of cholesterol

Plaque and inflammation

CVD

Question 11

What is alpha-1 anti protease?

Answer 11

Serpin that is synthesized in the liver, inhibits elastase

Question 12

What two diseases can result from a mutation in a1AP?

Answer 12

Emphysema and liver disease

Question 13

What is the most severe a1AP mutation?

Answer 13

Glu342Lys mutation

Called the Z allele

Question 14

What are the two reasons for symptoms of a1AP mutation?

Answer 14

Reduced inhibition of elastase in lungs

Aggregation in ER of liver cells, causing dysfuntion

Question 15

What is CEDNIK syndrome?

Answer 15

Cerebral dysgenesis, neuropathy, ichthyosis, and palmoplantar keratoderma.

Causes failure to thrive

Question 16

What mutation is responsible for CEDNIK syndrome?

Answer 16

Autosomal recessive

Mutation in SNAP29 on chromosome 22

Failed endocytosis and secretion

Question 17

What is I-cell disease?

Answer 17

Mucolipidosis, Autosomal Recessive.

Mutation in GNPTAB gene, catalyzes first step in tagging lysosomal enzymes with M6P in golgi

Failure of lysosomal function

Question 18

What are the symptoms of I-cell disease?

Answer 18

Coarse facial features

Joint limitations

Cardiomegaly

Early mortality