More Biochem Review – Flashcards
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Unlock answers| What do kinases do and what are their cofactors? |
| they add phosphate groups and require an ATP cofactor |
| What are carboxylases and what is their cofactor? |
| They ad carboxyl groups and require biotin cofactors |
| what are synthases and what is their cofactor? |
| they link 2 molecules together and don't have a cofactor |
| What are Methylases and what is their cofactor? |
| methylases adds a methyl group and it's cofactor is "" |
| What breaks down proteins in the stomach, and into what? |
| HCl and pepsin break down proteins into polypeptides |
| What are the pancreatic enzymes? |
| Trypsin and Chymotrypsin |
| What is the transport mechanism to absorb amino acids? |
| Facilitated Diffusion by carrier proteins |
| What happens to proteins in the cells, and why? |
| They are turned over as a way of storing nitregonous compounds, as a way of eliminating abnormal or dysfunctional proteins, and as a way of regulating enzyme function. |
| What does protein degradation occur? |
| In lysosomes and proteasomes |
| What do lysosomes do in starved cells? |
| They selectively degrade proteins containing the sequence KFERQ (lysine, fenyl alanine, glutamic acid, argenine, glutemine), only if nutrients are limited |
| How are proteasomes different from lysosomes? |
| They are large multiple protein complexes |
| What is the function of 19S? |
| it determines what proteins are to be degraded and allows them to the 20S complex. |
| How is a protein marked for degredation? |
| Attaching Ubiquitin, when the protein contains segments rich in PEST (proline, Glutamic Acid, Syrine, Threomine), or when proteins have destabilizing N-Terminal residues |
| What N terminal residues destabilize proteins and what does this do? |
| asp, arg, leu, lys, and phe all make the proteosome degrade the protein faster |
| What residues stabilize proteins? |
| Ala, Gly, Met, Ser, Thr, and Val |
| What 2 reactions remove amino groups, and what is removed as? What removes this product? |
| Transamination and Oxidative deamination and is removed as ammonia which is removed by the Liver and kidneys |
| What uses do the carbon skeletons of deaminated amino acids serve? |
| they are oxidized completely to create CO2 and H2O, they create glucose, Acetyl-CoA, and Ketone Bodies. |
| Explain 1-Transamination reaction |
| Amino group is transfered from an amino acid to another molecule by transaminase (cofactor PLP) |
| What are the 3 pairs of transaminase reactions? |
Glutamate/a-ketoglutarate Aspartate/oxaloacetate Alanine/pyruvate |
| What is the cofactor of transaminase reactions? |
| PLP, pyridoxal phosphate (a form of vitamin B6) |
| What are the markers for tissue damage? |
Syrum Glutamate Oxaloacetate Transanimase (SGOT(AST)) Syrum Glutamate Pyruvate Transanimase (SGPT(ALT) |
| Where are SGOT and SGPT produced? How do they indicate tissue damage? |
| The liver, kidneys and heart. When the cells die they release their components into the blood, including these enzymes. |
| Glucogenic amino acids produce |
| any precursos to oxaloacetate, which leaves to the cytoplasm to be turned into glucose |
| The only non-glucogenic amino acids produce... |
| acetyl-CoA or acetoacetate which are used to make ketone bodies (Ketogenic) |
| What AA's produce pyruvate? What enzyme converts them to pyruvate, and what is it's cofactor? |
Ala, Ser, Gly, Thr, and Cys Alanine Transaminase converts to Pyruvate Serine dehydratase cofactor is PLP for both of the above Glycine turns into serine by Serine-hydroxymethyltransferase (cofactor THF) or in mitochondria is turned into CH2=THF by Mitochondrial glycine cleavage complex (GCC) Threonine aldolase makes acetaldehyde (ketogenic) and glycine (glucogenic) Cys needs to have a sulfur removed |
| Which AA's produce oxaloacetate and what enzymes are used? |
Asparagine to aspartate by L-asparaginase Aspartate to oxaloacetate by transaminase (SGOT) PLP cofactor |
| What AA's can be turned into a-ketoglutarate and by what enzymes? |
Arg Pro and His are converted to Glu, Gln is converted to glu by glutaminase. Glu is converted to a-ketoglutarate by transaminase or gly dehydrogenase |
| Hydrophobic AA's are metabolized by what enzymes into what products? |
| Val, Ile, Leu are converted into a-keto acids by transamination, then into propionyl CoA, Propionyl CoA and Acetyl CoA, and Acetyl CoA and acetoacetyl CoA by branched0chain a-Keto Acid dehydrogenase complex (respectively) |
| Propionyl CoA is... |
| glucogenic |
| Acetyl CoA and acetoacetyl CoA are... |
| ketogenic and a ketone body (respectively) |
| explain the catabolism of methionine? |
| met is converted to S-adenosylmethionine (SAM), then to homocysteine, then to cystathionine, then to cystieine (glucogenic) and a-ketobutyrate to propionyl CoA (glucogenic) |
| Explain Lys Catabolism |
| Lys's side chain is transaminated, and produces acetoacetyl CoA |
| Lys and Leu are both strictly |
| ketogenic |
| explain Trp Catabolism |
| Trp is converted to 3-hydroxyathranilic acid and alanine (glucogenic), 3-hydroxyanthranilic acid is used to create either acetoacetyl CoA or NAD (converted to NADP) |
| Explain catabolism of Phe and Tyr |
Phe is converted to Tyr by phenylalanine hydroxylase. Tyr is converted to p-hydroxyphenylpyruvate by transaminase, which is then converted to fumarate (glucogenic) and acetoacetate (ketogenic) |
| What is phenylketonuria (PKU)? |
| a genetic disorder results in a deficiency in phenylalanine hydroxylase, which causes high levels of Phe in blood, which is converted to phenylpyruvate, and can cause mental retardation if not treated in a few months. (treated by limiting phenylalanine in diet, and increasing tyrosine) disappears after 10 years of age. |
| What are the biological roles of nucleotides? |
They are energy sources (like ATP Cofactors like NAD FAD and ATP Signaling like cAMP and cGMP Creation of DNA and RNA |
| What are the 3 components of nucleotides? |
Phosphate group Pentose sugar Aromatic base |
| What are the 2 bases that can be attached to nucleotides? |
| Purine (in adenine and guanine) and pyrimidine bases (cytosine, thymine (DNA) and uracil (RNA)) |
| nucleosides are... |
| nucleotides without the phosphate |
| are there any essential nucleotides? |
| no |
| Name the types and purposes of biosynthesis pathways for nucleotides. |
Salvage pathways: invlocve use of dietary nucleotides or re-use of nucleic acids degredation products De novo: biosynthesis with new materials: amino acids and pentoses |
| Explain the salvage pathways of nucleotide biosynthesis |
Nucleic acids from diet: NA's are broken down into nucleotides in GI, pancreatic nucleotidases convert into nucleosides, then nucleosides are absorbed from intestines. Tissue nucleic acids: NA's from dead cells are broken down into nucleosides by lysosomal nucleotidases |
| Explain the De novo synthesis of purine bases |
Synthesised on PRPP in 3 steps: 1. Synthesis of PRPP 2. Formation of inosine monophosphate (IMP) 3. Conversion of IMP to AMP and GMP *ATP, dATP, GTP, and dGTP can be synthesized from AMP or GMP |
| What are the products and reactants in synthesis of ATP and GTP, and what enzymes drive the reactions? |
GMP+ATP --> GDP +ADP by guanylate kinase GDP+ATP--> GTP +ADP by NDP kinase AMP+ATP--> 2 ADP by adenylate kinase ADP goes to oxidative phosphorylation pathway to become ATP. |
| Explain purine nucleotide degredation |
| AMP is turned into hypoxanthine, and GMP into xanthine. Xanthine oxidase turns hypoxanthine into xanthine, and xanthines are turned into uric acid by xanthine oxidase. |
| What problems are associated with heightened levels of uric acid? |
| Kidney stones, and uric acid crystal precipitation in joints (known as gout). Gout leads to deformities. |
| What can cause Gout? |
Excessive synthesis of purine nucleotides due to elevated levels of PRPP synthetase or mutations leading to loss of feedback inhibition of PRPP synthetase. Impared excretion of uric acid (kidney malfunctioning). |
| How is gout treated? |
| Allopurinol inhibits xanthine oxidase |
| Explain de novo synthesis of pyrimidine bases |
Bases are made and then linked to PRPP 4 steps: 1. synthesis of orotate 2. linking of orotate to PRPP and synthesis of UMP 3. Synthesis of CTP 4. Synthesis of deoxythymidine |
| What enzymes are used to make orotate? |
carbamoyl phosphate synthetase 2 (activated by ATP and PRPP, inhibited by UTP) , and aspartate transcarbamoylase (ATCase) |
| what enzymes are used in linking of PRPP and synthesis of UMP |
| orotate phorphoribosyl transferase and OMP carboxylase |
| What is the path of synthesis of CTP (note enzymes)? |
| UMP-->UDP-->UTP- (CTP synthetase, inhibited by CTP and activated by GTP)->CTP |
| dTMP is synthesized.... |
| from dUMP by thymidylate synthase |
| Detail the path of pyrimidine nucleotide degredation |
CMP-->cytidine-->uridine-->uracil-->dihydrouracil--> B-alanine |
| What enzyme synthesizes deoxyriobnucleotides? |
| Ribonucleotide diphosphate (rNDP) reductase, by removal of 2' OH |
| Tymidylate synthase.... |
| turns dUMP to TMP |
| talk about the enzymes used in dTMP biosynthesis |
Tymidylate synthase (inhibited by uracil analogs) Dihydrofolate reductase (inhibited by methotrexate, aminopterin, and trimethoprim) ;Serine transyhdroxymethylase |
