Metabolism Flashcards
Define metabolism
A series of activities that provide cells with the molecules and energy they need to function and grow/divide
What are the molecules from metabolism used for?
Structure and reactions
What is the energy from metabolism used for?
Cell function
What is a multi-enzyme complex?
A stable assembly of enzymes usually involved in sequential catalytic reactions
What does rate of amino acid synthesis depend on?
Amount of amino acids and their individual biochemical activities
What is allosteric inhibition?
When molecules are binding to different sites which are not the active site
What is the role of enzyme multiplicity?
Prevents one product from shutting down the pathway completely
Which 3 precursors is histidine derived from?
PRPP, ATP, and glutamine
What does PRPP contribute to histidine?
5 carbons
What does ATP contribute histidine?
A nitrogen and a carbon
What does glutamine contribute to histidine?
A carbon
How many amino acids are there?
20
How many amino acids can mammals synthesise?
11
How many amino acids can plants synthesise?
20
How many amino acids can bacteria synthesise?
20
Where are the other 9 amino acids obtained from for mammals?
The diet
Why can’t mammals synthesise the other 9 amino acids?
More complex so require more energy to synthesise
Which are the 9 amino acids that mammals can’t synthesise?
- Tryptophan
- Isoleucine
- Histidine
- Phenylalanine
- Valine
- Threonine
- Methionine
- Leucine
- Lysine
What are the 7 important intermediary pathways in humans?
- glycolysis
- gluconeogenesis
- TCA cycle
- pentose phosphate pathways
- fatty acid catabolism
- urea cycle
- oxidative phosphorylation
What are nucleosides?
Bases covalently joined to sugars
How are deoxy-nucleotides formed?
By the reduction of ribonucleotides
Which enzyme catalyses deoxy-nucleotide synthesis?
Ribonucleotide reductase
How many subunits does ribonucleotide reductase have?
2
What is the function of the first subunit (R1) in ribonucleotide reductase?
Site of reduction
What is the function of the second subunit (R2) of ribonucleotide reductase?
Contains a stable free radical on a Tyr
What do cancer cells need as precursors for RNA and DNA?
Nucleotides
What is the role of chemotherapeutic agents?
Inhibit growth of tumours
How do chemotherapeutic agents inhibit growth of tumours?
Reducing the amount of precursors available for RNA and DNA
How can chemotherapeutic agents act to inhibit metabolism?
By targeting enzymes in nucleotide biosynthetic pathways
How do the synthesis of the purine ring system and pyrimidine bases differ?
Purine ring system is built step by step, attached to sugar and phosphate whereas pyrimidine bases are synthesised separately to sugar and phosphate and then attached post-synthesis
What does synthesis of AMP require?
GTP
What does synthesis of GMP require?
ATP
