82814
Description
Flashcards by sophiakostich, updated more than 1 year ago
|
Created by sophiakostich
almost 11 years ago
|
|
| Question | Answer |
| When does lysosomal storage disease occur? | When lysosomal hydrolysis of particular macromolecules is defective so they accumulate. This results in enlarged lysosomes and impairement/destruction of cells. |
| True or false: most lysosomal storage diseases are autosomal dominant. | FALSE - they are single gene disorders and mostly autosomal recessive. |
| Define heterophagy and state three ways in which it may occur. | Heterophagy: digestion of material of extracellular origin. Can occur via phagocytosis, receptor-mediated endocytosis and pinocytosis/fluid-phase endocytosis. |
| Define autophagy. | Digestion of material of intracellular origin. |
| What is the structure of a lysosome? What do they contain and what is their pH? | Single membrane organelle found in cells. They have an acidic pH of 4.6 and contain enzymes that digest macromolecules. |
| What are the enzymes found in lysosomes? | Acid hydrolases including nucleases, proteases, glycosidases, lipases, phophatases and sulphatases. |
| Where are the enzymes sythesised and activated? | Synthesised in rER and activated in lysosome. |
| How is the lysosome protected from degradation? | Glycosylation of membrane proteins. |
| What is I cell disease? | Deficiency in N-acetylglucosamine phosphotransferase deficiency. Normally functions to phosphorylate mannose tags in cis golgi. Means that lysosome enzymes are secreted rather than directed to lysosome. Lysosome is engorged with undigested material. |
| What is the function of phagocytosis? Name three occasions it is used by cells. | internalise large particles. Used for nutrition, defence (macrophages and neutrophils) and removal of cellular debris and damaged cells. |
| Explain the 5 steps of phagocytosis. | 1. Actin polymerisation and contraction when receptor binds. 2. Pseudopodia engulfs target. 3. Phagolysosome formed. 4. Sugars, aa, nucleotides (useful) enter cytosol. 5. Indigestible remnants expelled. |
| Name a pathogen that inhibits phagosome from fusing with lysosome. | Mycobacterium tuberculosis. |
| Name a pathogen where bacteria are resistant to lysosomal enzymes and acid. | Coxiella burnetii |
| Name a pathogen where the pathogen damages the lysosome membrane and escapes back into cytosol. | Meningitis - listeria monocytogenes. |
| What is the function of receptor-mediated endocytosis? | Internalise solutes bound to a specific high affinity cell surface receptor. |
| What are the four things involved in receptor mediated endocytosis? | Adaptin, clathrin, dynamin and chaperones. |
| how is a ligand-receptor complex internalised in receptor mediated endocytosis? | Via a clathrin coated pit in the plasma membrane. |
| True or false: a clathrin lattice covers the cytosolic face of the coated pit. | TRUE. |
| What is the function of Adaptin in receptor mediated endocytosis? | Binds the cytosolic domain of the receptor and binds clathrin to ensure receptors are packaged and other integral proteins are not. |
| What is the main function of clathrin in receptor mediated endocytosis? | Assembly provides driving force for membrane curvature. |
| What is the function of dynamin in Receptor mediated endocytosis? | Uses energy from GTP to sever coated vesicle from membrane. |
| What is the function of chaperones in receptor mediated endocytosis? | Uncoat the vesicle. |
| Give two examples of receptor mediated endocytosis. | Transport of cholesterol in LDLs and transport or iron as transferrin. |
| What is an early endosome? | Endosome is what is made from receptor mediated endocytosis. Therefore an early endosome is the first thing that is made ish. |
| What is the function of the early endosome? | Site for sorting and recycling. It recycles receptors to the plasma membrane and the ligand goes to lysosomes e.g. LDL. |
| What difference is there in the action of endosomes in iron transport? | The ligand remains bound to the receptors in the form of apotransferrin therefore it doesnt go to the lysosome it goes back to the cell surface with the receptor. |
| True or false: viruses exploit receptor mediated endocytosis. | True - low pH causes conformational change in viral glycoprotein leading to exposure of hydrophobic region and the endosome membrane and viral envelope fuse. |
| What is taken in during pinocytosis? | Internalises extracellular fluid and dissolved particles. |
| What is cell rejuvination? | Removal of old or damaged organelles. |
| When is autophagy upregulated? | During starvation. |
| Steps in autophagy. Go. | 1. target wrapped in double membrane from ER 2. Autophagosome produced 3. fuses with lysosome 4. indigestible remnants retained as granules that accumulate with age. |
| What is autolysis? | Release of lysosomal enzymes into the cytosol. Aids disposal of dead cells. |
| How does extracellular digestion occur? Give an example. | When the lysosome discharges its enzyme via exocytosis resulting in extracellular digestion. E.g. fertilisation - acrosome is a modified lysosome. |
| What is Tay-Sachs disease a deficiency in? | beta-N-acetylhexosaminidase. |
| What is the normal function of B-N-acetylhexosaminidase? What is the result of this? | Degradation of ganglioside GM2, a major component of brain cell membranes. Results in undigested ganglioside GM2 in lysosomes of nervous tissue causing mental retardation, blindness, paralysis and death within 3 years. |
Want to create your own Flashcards for free with GoConqr? Learn more.