2.1 metabolic pathways, cellular respiration Flashcards
describe a metabolic pathway
metabolic pathways are integrated and controlled pathways of enzyme-catalased reactions within a cell.
types of steps and routes that can occur in metabolic pathways
metabolic pathways can have reversible and inversible steps and alternative routes within a cell.
anabolic and catabolic pathways
anabolic- builds up large molecules from small molecules and requires an input of energy.
catabolic - breaks down large molecules to small molecules, releases energy.
types of proteins embedded in a membrane and describe their reaction
enzymes- used to catalase many reactions within the cell.
pores- specific channel forming proteins in the membrane, structured as pores to only let certain molecules into the cell.
pumps- protein carriers that can transfer molecules through the membrane, usually from a low to high concentration.
metabolic pathways and enzymes
metabolic pathways are controlled by the presence or absence of particular enzymes and the regulation of the rate of reaction of key enzymes.
induced fit enzymes in relation to activation energy, affinity of the substrate and products for the active site
> in the presence of a substrate, the active site changes shape to better fit the substrate after it binds with active site.
the active site places reactants in the correct position for the reaction to occur.
This lowers the activation energy and promotes enzyme/substrate reaction.
After the reaction, products which have a low affinity to the active site of the enzyme, leave the active site, allowing the enzyme to have an increased affinity for the substrate molecules.
process of competitive inhibition
> competitive inhibitors bind to active site of enzyme, preventing substrate from directly binding to active site of the enzyme.
competitive inhibition can be reversed by increasing substrate concentration ( as substrate molecules increase in concentration they outnumber the competitive inhibitor molecules and more active sites are occupied by the substrate molecules.
process of non competitive inhibitors
> non competitive inhibitors bind to part of enzyme other than active site. This changes shape of the active site which prevents substrate from binding with the active site.
cannot be reversed by increasing substrate concentration
feedback inhibition
occurs when a end product in the metabolic pathway reaches critical concentration. The end product then inhibits an enzyme found earlier in the pathway, this blocks the pathway and prevents the end product from being further synthesised.
what is respiration
a series of enzyme controlled reactions which release energy from food
glycolysis (cytoplasm)
> glycolysis is the stage involving the conversion of glucose to pyruvate.
cytoplasm
process of glycolysis (cytoplasm)
> production of pyruvate from glucose in glycolysis involves the production of several intermediate molecules.
phosphorylation of some of these intermediates requires an input of ATP molecules in a energy investment stage, leading to the direct generation of more ATP molecules in an energy pay off stage.
breakdown of glucose into pyruvate therefore results in a net gain of ATP molecules.
Dehydrogenase enzymes remove hydrogen ions and electrons from these intermediates and these are transferred to the coenzyme NAD forming NADH. NADH takes these hydrogen ions & electrons to the inner membrane of the mitochondria for use in the electron transport chain.
pyruvate in aerobic conditions
if oxygen is present, pyruvate enters the mitochondria.
process of citric acid cycle (mitochondria)
> pyruvate is broken down into an acetyl group, which binds with coenzyme A to form acetyl coenzyme A. Acetyl group from coenzyme A combines with oxolacetate to form citrate.
during a series of enzyme controlled steps, citrate is gradually converted back into oxolacetate which results in the generation of some ATP and the release of carbon dioxide.
Dehydrogenase enzymes remove hydrogen ions and electrons from intermediates and these are transferred to coenzymes NAD forming NADH. These NADH take the electrons and ions to the inner mitochondrial membrane for use in the electron transport chain.
describe the role of dehydrogenase enzymes in glycolysis and the citric acid cycle
dehydrogenase enzymes remove hydrogen ions and electrons from the intermediates and these are transferred to the coenzyme NAD forming NADH. the NADH takes the electrons to the inner membrane of the mitochondria for use in the electron transport chain.
