Chapter 14: Introduction to Metabolism Flashcards
two types of metabolism
Catabolism
Anabolism
in which nutrients and cell constituents are broken down to
salvage their components and/or to generate energy.
Catabolism
in which biomolecules are synthesized from simpler
components.
Anabolism
another name for Anabolism
biosynthesis
another name for Catabolism
degradation
Metabolic pathway’s reactants,
intermediates, and products are referred to as
metabolites
are series of connected enzymatic reactions that produce specific product
Metabolic pathway
are the major free energy sources for biosynthetic reactions.
ATP and NADPH
acetyl unit linked to coenzyme A to form what
acetyl-coenzymeA (acetyl-CoA)
what does the citric acid cycle produce
the reduced
coenzymes NADH and FADH2,
A striking characteristic of degradative metabolism
The pathways for the catabolism of a large number of diverse substances converge on a few common intermediates
what does electron transport and
oxidative phosphorylation produce
water
Citric acid cycle, electron transport and oxidative phosphorylation, fatty acid oxidation, amino acid breakdown
mitochondrion
Glycolysis, pentose phosphate pathway, fatty acid biosynthesis, many reactions of gluconeogenesis
cytosol
Enzymatic digestion of cell components and ingested matter
Lysosome
DNA replication and transcription, RNA processing
nucleus
Posttranslational processing of membrane and secretory proteins; formation of plasma membrane and secretory vesicles
Golgi apparatus
Synthesis of membrane-bound and secretory proteins
Rough endoplasmic reticulum
Lipid and steroid biosynthesis
Smooth endoplasmic reticulum
Oxidative reactions catalyzed by amino acid oxidases and catalase; glyoxylate cycle reactions in plants
Peroxisome (glyoxysome in plants)
is largely responsible for the synthesis of glucose from noncarbohydrate precursors so as to maintain a relatively constant level of glucose in the circulation
mammalian liver
specialized for storage of triacylglycerols.
adipose tissue
rate of flow
flux
Most enzymes in a metabolic pathway operate near what
equilibrium
are Metabolic pathways reversible
no
If a metabolite is converted to another metabolite by
an exergonic process, free energy must be supplied to what
convert the second metabolite back to
the first. This energetically“uphill” process requires a different pathway for at least one of the
reaction steps
For the pathway as a whole, flux is set by what
the rate-determining step of the pathway
is the pathway’s slowest step, which is often the first committed step of
the pathway.
the rate-determining step of the pathway
Cellular mechanisms to control flux through the rate-determining steps
Allosteric control
Covalent modification
Substrate cycles
Genetic control
example of Allosteric control
negative feedback
regulation
the product of a pathway inhibits an earlier step in the pathway.
Allosteric control
example of Covalent modification
enzymatic phosphorylation and dephosphorylation of ezymes
to control by external signals such as hormones.
Covalent modification
Controlling rates of two opposing
nonequilibrium reactions by different enzymes.
Substrate cycles
Enzyme concentrations
Genetic control
The“high-energy” intermediate
adenosine triphosphate (A TP)
ATP consists of what
adenosine moiety (adenine + ribose)
Why are the phosphoryl group-transfer reactions of A TP so exergonic?
- The resonance stabilization of a phosphoanhydride bond is less than that of its hydrolysis
products. - Another factor is the destabilizing effect of the electrostatic repulsions between the charged
groups of a phosphoanhydride compared to those of its hydrolysis products. - Another destabilizing influence is the smaller solvation energy of a phosphoanhydride
compared to that of its hydrolysis products. Some estimates suggest that this factor provides
the dominant thermodynamic driving force for the hydrolysis of phosphoanhydrides.
In the absence of what even a thermodynamically favored reaction (ΔG < 0) may not occur in a living system.
an appropriate enzyme,
functions similarly to drive some of the reactions of signal transduction.
GTP hydrolysis
help maintain a relatively constant level of cellularA TP .
“High-energy” compounds other than ATP
can be regenerated by coupling its
formation to a more highly exergonic metabolic process.
ATP
The flow of energy from“high-energy” phosphate compounds to A TP are catalyzed by enzymes known as
kinases
which transfer phosphoryl
groups from ATP to other compounds or from phosphorylated compounds to AD
kinases
acts as an ATP “buffer” in cells of muscle and nerve cells that contain creatine kinase.
Phosphocreatine
functions as a carrier of acetyl
and other acyl groups
CoA
Macronutrients proteins, carbohydrates, and lipids are broken down by the digestive system
to their component
amino acids, monosaccharides, fatty acids, and glycero
requires the intake of O2 and water, as well as micronutrients composed of vitamins and minerals
The metabolic utilization of the latter
substances
is involved in nearly all reactions that involve A TP and other nucleotides, including the synthesis of DNA, RNA, and proteins.
Mg
is a cofactor in a variety of enzymatic
reactions including that catalyzed by carbonic anhydrase
Zn 2+
is a vital participant in signal transduction processes.
Ca
Metabolic reactions are catalyzed by
enzymes
