Metabolic Pathways Flashcards
Why is it important to become familiar with some of the essential metabolic pathways?
selecting and processing an organism that can efficiently make a given product is essential to bioengineering. It’s also possible to also remove and add genes to an organism to alter its metabolic functions in a predetermined way.
What can cause a difference in microbial metabolism?
- genetic and environmental changes
Even the same species may produce different products when grown under different nutritional and environmental conditions.
E.g. Saccharomyces cerevisae (bakers yeast) on glucose produces ethanol under anaerobic conditions and more yeast cells under aerobic conditions. Moreover, at high glucose levels some ethanol can be produced under aerobic conditions too. This indicates metabolic regulation not only by oxygen but by glucose as well.
What are the two key processes of metabolic pathways? Briefly describe what they
Catabolism – intracellular process of degrading a compound into smaller and simpler products,(e.g. Glucose to CO2 and H2O). Catabolism also produces energy for the cell.
Anabolism – involved in the synthesis of more complex (e.g. glucose to glycogen [polysaccharide of glucose] and requires energy).
What is the source of energy used to fuel cellular metabolism?
“reduced” forms of carbon (sugars,hydrocarbons, etc.)
The Sun is the ultimate source via the process of photosynthesis in plants
CO2 + H2O + hv -> CH2O + O2
What are the 3 major categories of metabolic reactions?
1.) Degradation of nutrients
2.) Biosynthesis of small molecules (amino acids, nucleotides)
3.) Biosynthesis of large molecules
Energy in biological systems is stored and transferred in which compound?
Adenosine tri-phosphate (ATP)
How is energy actually released from ATP? Write the equation for this
Hydrolysis of ATP. The standard free energy release in the hydrolysis of ATP is 7.3 kcal/mol. Biological energy is stored in ATP by reversing this reaction to form ATP from ADP and Pi, and ADP can similarly release energy.
What are the higher energy phosphate compounds that transfer their p group to ATP and what are the lower energy phosphate compounds that ATP transfers its p group to
High energy - phosphoenol pyruvate and 1,3-diphosphoglycerate
Lower energy - glucose-6-phosphate and glycerol-3-phosphate
Describe ATP formation in respiration
The electrons (or H atoms) carried by NADH are transferred to oxygen via a series of intermediate compounds (respiratory chain). The energy released from this electron transport results in the formation of up to three ATP molecules. ATP can be formed from the reducing power in NADH in the absence of oxygen if an alternative electron acceptor is available (e.g. (NO3)-.
What 3 phases can aerobic catabolism of organic compounds such as glucose be split into?
- Glycolysis (or Emben-Meyerhof-Parnas) pathway: from glucose to pyruvate
- Krebs, tricarboxylic acid (TCA), or citric acid cycle for conversion of pyruvate to NADH and CO2
- Respiratory or electron transport chain for the formation of ATP by transferring electrons from NADH to an electron acceptor.
Where does glycolysis occur?
Cytoplasm
What is the end result of glycolysis?
Glucose, which splits into 2 pyruvate molecules. Also small amount (2 moles) of ATP.
List 4 steps of glycolysis
(1) Phosphorylation of glucose to glucose-6-phosphate by hexokinase
(2) Glucose-6-phosphate converted to fructose-6-phosphate by phosphoglycose isomerase
(3) Fructose-6-phosphate is converted to fructose 1,6-diphosphate by phosphofructokinase.The first and third reactions are the only two ATP-consuming reactions in glycolysis.
(4) Breakdown of fructose 1,6-diphosphate into dihydroxyacetone phosphate DHAP) glyceraldehyde 3-phosphate (GA-3P) by aldolase (Key steps because C6 to C3). Following a number of further steps, the end product (pyruvate) is attained. The lactate you see in the figure is a product that arises if there is not sufficient oxygen(Same process as when you exercise to the limit and lactate builds up in the muscles because oxygen supply is not adequate enough under extreme exertion).
Give an overview of the Krebs cycle
The pyruvate is now fed into the Krebs cycle. Entry into the Krebs cycle is provided by the acylation of coenzyme-A by pyruvate (1). Amongst the various steps in the Krebs cycle, Succinate (2) and a-ketoglutarate (3) are also produced which are precursors for the synthesis of certain amino acids. In addition, the most important products in the overall reaction are 3 NADH (4) and 1 GTP (5)The major roles thus of the TCA cycle are (a) to provide electrons (NADH) for the electron transport chain (respiration) (b) to supply C skeletons for amino acid synthesis, and (c), to generate energy (GTP).
What is the respiration reaction sequence also called?
electron transport chain
GIve a brief overview of what happens in the respiration phase
Electrons carried by NADH + H+ and FADH2 are transferred to oxygen via a series of electron carriers, and ATPs are formed. Three ATPs are formed from each NADH + H+ and two ATPs for each FADH2 in eucaryotes. The major role of the electron transport chain is to regenerate NADs for glycolysis and ATPs for biosynthesis. The term P/O ratio is used to indicate the number of phosphate bonds made (ADP + Pi ATP), for each oxygen atom used as an electron acceptor. (e.g. ½ O2 + NADH + H+ H2O + NAD+). Takes place in the inner mitochondria.
Diagram of mitochondria with kreb and respiration cycle
What is the main goal of The hexose-monophosphate pathway (HMP)
Although this pathway produces significant reducing power, which could be used, in principle, to supply energy to the cell, its primary role is to provide carbon skeletons for biosynthetic reactions and the reducing power necessary to support anabolism.
What is a vital part of biosynthesis that consumes a large amount of cellular building blocks?
Production of Amino acids
Many amino acids are also important commercial products, and the alteration of pathways to induce overproduction is critical to commercial success. The 20 amino acids can be grouped into various families.
In the absence of oxygen, what is the pyruvate produced by glycolysis turned into?
Lactate
NAD+ is restored
The whole pathway yields much less energy overall than complete oxidation
In some organisms that can grow anaerobically, such as yeasts, pyruvate is converted via acetaldehyde into carbon dioxide and ethanol. Again this pathway regenerates NAD+ from NADH,as required to enable glycolysis to continue (b). (Fermentation)
