What is metabolism
The enzyme-catalyzed chemical reactions that occur in a cell to either breakdown biomolecules to obtain energy in ATP form, or reactions that synthesize biomolecules that our bodies need.
catabolism
chemical reactions that breakdown biomolecules (gives off energy)
anabolism
chemical reactions that lead to the synthesis of biomolecules (requires energy)
primary functions of metabolism
- to generate ATP
- to convert molecules that we ingest into the building blacks of what we need
- to assemble proteins, nucleic acids, lipids, and polysaccharides
- to synthesize and degrade biomolecules (hormones) that have specialized function in cells
different forms of metabolic pathways
- linear - straight sequence of reactions
- branched - where intermediates can follow multiple routes
- circular - looped sequence where the end product regenerates the starting molecule (like the citric acid cycle)
which parts of a pathway are usually regulated
the irreversible reaction. its frequently rate limiting, which means it proceeds slowly and can be modulated to control the overall pathway flow
amphibolic
functioning as both anabolic and catabolic depending on the cell’s energy state
What is the input of free energy required for
- Mechanical work
- Active transport
- Biosynthesis
what do enzymes do
speed up the rate of chemical reactions but do not change the equilibrium constant or make a thermodynamically unfavorable reaction proceed
what are the two thermodynamic properties
- The free energy difference (∆G) between products and reactants, which explains if the reaction is possible; spontaneous or not
- The activation energy is needed to start the reaction which determines how fast it proceeds, and is influenced by enzymes
what is the free energy value of ATP hydrolysis
-30.5 kJ/mol
what is large standard free energy charge due to
large difference in stability of the products compared to the reactants
what are the four reasons for large difference in stability of products and reactants
- electrostatic repulsion: At pH 7, ATP has four negative charges that repel each other. Hydrolysis reduces this repulsion.
- resonance stabilization: Pi, one of the hydrolysis products, is more resonance-stabilized than the phosphates in ATP
- entropy increase: Hydrolysis increases entropy by converting one molecule (ATP) into two (ADP and Pi).
- stabilization by hydration: Water molecules bind more favorably to ADP and Pi, making the reverse reaction less favorable.
How much ATP do we consume
80 kg per day, 500 g per minute
when will a carbon atom release more energy when oxidized
when it is more reduced
key step in glycolysis
- Glyceraldehyde-3-phosphate (G3P) is oxidized.
- Electrons are transferred to NAD⁺, forming NADH.
- The product, 1,3-bisphosphoglycerate, has high energy and donates a phosphate to ADP, forming ATP.
motifs
A motif is a small, recurring pattern in metabolism that has a function.
activated carriers
carry energy or chemical groups from one reaction to another, helping enzymes do their jobs. many are small organic molecules that act as coenzymes which help enzymes catalyze a reaction, but does not catalyze on its own
what are the three major types of activated carriers
- carriers for fuel oxidation
NAD+ : accepts 2 electrons and 1 proton to become NADH
FAD: accepts 2 electrons and 2 protons to become FADH2
- biosynthesis
NADPH: used in anabolic reactions. supplies electrons. oxidized to NADP+ - two carbon fragments
CoA: carrier of 2 carbon units contains acetyl groups. important in both catabolism and anabolism. acetyl groups attach through sulfhydryl group to for acetyl CoA. hydrolysis of acetyl CoA has a very large negative free energy change.
why are vitamins important
most activated carriers that act as coenzymes are derived from vitamins (typically B vitamins)
