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Metabolism
Proteins
| Question | Answer |
|---|---|
| What % of body mass is made of proteins | 17% |
| 7 functions of proteins | -maintain body structure (collagen) -facilitate mobility (actin/myosin) -transport(hemoglobin/membrane transport) -metabolism (enzymes) -regulation (hormones and growth factors) -immune function (immunoglobins/cytokines -energy |
| 3 types of RNA | -mRNA -tRNA -rRNA |
| what is the function/purpose of mRNA? | - Messenger RNA -genetic coding template -determines order of amino acids |
| what is the function/purpose of tRNA? | -Transfer RNA -transfer individual AA to the mRNA template |
| what is the function/purpose of rRNA? | -Ribosomal RNA -form ribosome w/ribosomal proteins |
| 4 phases of protein synthesis | 1. Amino Acid activation 2. Initiation 3. Elongation 4. Termination |
| What is Transcription? | DNA is transcribed into 3 types of RNA in the nucleus |
| Where does transcription occur? | nucleus |
| What is Translation? | mRNA is translated into protein w/ help of tRNA and rRNA in cytoplasm |
| Where does Translation occur? | cytoplasm |
| what determines the concentration of proteins in cells? | determined by a balance between the rates of protein synthesis and degradation |
| What is the result of positive protein balance? | hypertrophy (increase in protein content in cell) |
| What is the result of negative protein balance? | atrophy (loss of proteins from cells) |
| What is the 1/2 life of an average protein? | varies between 24-72 hours |
| What is the 1/2 life of regulatory enzymes/proteins? | ranges between 5-120 minutes |
| What is the Lysosomal Proteolytic Pathway responsible for? | degrades extracellular and cell-surface proteins -also intracellular proteins |
| What is the Proteasomal Proteolytic Pathway responsible for? | degrades proteins from cytoplasm, nucleus, and ER (in cells) |
| What are the Cytosolic Proteases responsible for? | -calpains -caspases -endoproteases -exoproteases |
| What is a lysosome? | membrane-enclosed vesicles that form the Golgi complex |
| How does Vesicle Fusion of Lysosomal Proteolysis work? | -endocytosis of extracellular proteins/substrates and part of the plasma membrane -membrane receptors (like LDL-R) may be degraded in lysosomes, or recycled to the cell membrane -degradation of cell-surface proteins |
| Describe Macroautophagy of Lysosomal Proteolysis. | -responsible for degradation of organelles -portion of cytosol including entire organelles is surrounded by intracellular membrane to form autophagic vacuole -vacuole fuses w/ lysosomes and its contents are completely degraded |
| why is the Macroautophagy Pathway of Lysosomal Proteolysis important? | important for the 1st stages of nutrient deprivation. -provides energy and essential AA to cells for continued protein synthesis |
| Describe Microautographagy of Lysosomal Proteolysis. | -responsible for continuous slow degradation of cytosolic proteins -invaginations in lysosome surface result in internalization of small soluble regions of cytosolic proteins -once inside lysosomal matrix, cytosolic components degraded |
| Describe Direct Transport via chaperones of Lysosomal Proteolysis | -recognition of KFERQ sequence on protein substrate by Hsc73 -binding to cytosolic tail of Igp96 -uptake of substrate protein -degradation by lysosomal proteases -responsible for 30% of cytosolic proteins |
| how many cytosolic proteins are degraded by direct transport via chaperones? | 30% of cytosolic proteins -glycolytic enzymes -proteasomes -transcription factors |
| hsc73 | -Heat Shock Cognate protein of 73kD -a molecular chaperone localized to different cellular compartments |
| KFERQ | peptide sequence that can be recognized by hsc73 |
| Proteasomal Pathway | degrades proteins from cytoplasm, nucleus, and ER (in cells) |
| Cytosolic Proteases | -Calpains -Caspases -Endoproteases -exoproteases |
| what amount of intracellular protein degradation is the Proteasomal Pathway responsible for? | responsible for 80-90% of intracellular protein degradation |
| What do Proteasomes do? | responsible for the regulated degradation of critical proteins that control cell growth, proliferation, cell differentiation, apoptosis, and immune and inflammatory responses |
| What signals in proteins are recognized by proteasomes and initiate degradation? | -specific amino acid sequence (motif) -altered structure (oxidative modification, exposure of hydophobic amino acids) -covalent attachment of ubiquitin (major pathway) |
| Ubiquitin | -small protein, highly-conserved, and present universally in eukaryotic cells -occurs in cytosol of cells -used to target proteins for destruction |
| Ubiquitin-dependent proteolysis is involved in degradation of proteins that... | -are unassembled -are damaged or misfolded -have short half-lives |
| What stimulates Proteasome Activity (degradation)? | -phosphorylation of certain domains in target protein -Glucagon -Cortisol -Disease/Injury |
| What inhibits Proteasome Activity? | -Glycosylation of certain domains in target proteins -Insulin |
| Calpains | -cytosolic protease -calcium-dependent -partially degrade membrane and cytoskeletal proteins and several membrane-associated enzymes (PKC) -activated by Calcium -Inhibited by Calpastatin -In muscle: partial proteolysis of myosin |
Created by:
kemplea
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