Metabolism Flashcards
What is metabolism
A linked series of chemical reactions that begins with a particular molecule and converts it into some other molecule in a carefully defined fashion
The pathways of metabolism are _______, and their activity is coordinated by sensitive means of communication in which _______ are predominant
interdependent, allosteric enzymes
Reactions that convert energy form fuels into biologically useful forms
Catabolic
Reactions that require inputs of energy to proceed
Anabolic
Reactions that form complex molecules
Anabolic
what is the universal currency of free energy in biological systems
ATP
The release of more phosphate groups allows for a
greater free energy release
What are three compounds that have a higher phosphoryl-transfer potential than ATP (to ADP) (list them in order form highest lowest)
Phosphoenolpyruvate (PEP) (-61.9), Creatine phosphate (-49.4) , 1.3- Biphosphoglycerate (1,3-BPG) (-43.1)
What is the free energy when ATP is hydrolyzed to ADP
-30.5 kJ mol^-1
What is the free energy when ATP is hydrolyzed to AMP
-45.6 kJ mol^-1
ATP consists of
adenine, a ribose, and a triphosphate unit
The active form of ATP is usually a complex of ATP with
Mg^2+ or Mn^2+
Groups with higher phosphoryl-transfer potential can
transfer phosphates to groups with a lower potential
Why is it important that ATP has a phosphoryl-transfer potential that is intermediate among the biologically important phosphorylated molecules
This intermediate position enables ATP to function efficiently as a carrier of phosphoryl groups
The amount of ATP in the muscle suffices to sustain contractile activity for
less than a second
what serves as a reservoir of high-potential phosphoryl groups that can be readily transferred to ADP
Creatine phosphate
The reaction of creatine phosphate + ADP —-> ATP + creatine is catalyzed by
creatine phosphate
What is the principal immediate donor of free energy
ATP
ATP is consumed within a _____ of its formation
minute
The _____ of carbon fuels is an important source of cellular engery
oxidation
The total quantity of ATP in the body is limited to approximately
100 grams
The turnover of the small quantity of ATP is
very high
A resting human being consumes about ____ of ATP in 24 hours
40kg
During strenuous exertion, the rate of utilization of ATP may be as high as
0.5 kg/minute
Motion, Active transport, signal amplification, and biosynthesis can take place only if
ATP is continually regenerated from ADP
Generation of ____ is one of the primary roles of catabolism
ATP
carbon in fuel molecules— such as glucose and fats—- is oxidized to _____. The resulting electrons are captured and used to regenerate ATP from ___ and __-
CO2, ADP, phosphate
In aerobic organisms, the ultimate electron acceptor in oxidation of carbon is _____-
Oxygen
What is the oxidation product of carbon fuels in aerobic organisms
Carbon Dioxide
in terms of oxidation- The more reduced a carbon is to begin with, the
more free energy is released by its oxidation
Which would release more free energy methane or methanol
methane
When a fuel is oxidized the oxidation takes place ____ carbon at a time
one
For a 2 hour run about how much ATP is utilized
about 60kg (132 pounds)
Which is more likely to be stored saturated or polyunsaturate fatty acids
Saturated
The carbon-oxidation energy is used in some cases to create a ______________ and in other cases to creat an ______. In either case, the end point is the formation of ____
Compound with high phosphoryl-transfer potential, ion gradient. ATP
what are some reasons that phosphates came to play a prominent role in biology
phosphate esters are thermodynamically unstable while being kinetically stable. thus energy release cn be manipulated by enzymes.
Their kinetic stability makes them ideal regulatory molecules, added to proteins by kinases and removed only by phosphatases
What is the stability of phosphate esters due to
the negative charges that make them resistant to hydrolysis in the absence of enzymes
What account for the presence of phosphates in the backbone of DNA
Their negative charge makes them resistant to hydrolysis in the absence of enzymes
What do phosphatases do
they remove phosphates from proteins
What do kinases do
They add phosphates to proteins
The binding of phosphates to metabolites can have what effect in terms of the cell membrane
it causes them to no longer diffuse through the membrane
what are the three stages of extracting energy from foodstuffs
digestion (no energy captured)- protein are hydrolyzed to their 20 different amino acids, polysaccharides are hydrolyzed to simple sugars such as glucose, and lipids are hydrolyzed to glycerol and fatty acids.
stage 2- numerous small molecules are degraded to a few simple units that play a central role in metabolism. most are converted to acetyl unit of acetyl CoA. (some ATP generation)
Stage 3- ATP is produced form the complete oxidation of the acetyl unit of acetyl CoA. ( krebs/TAC cycle/citric acid cycle
For each acetyl group that is oxidized in the citric acid cycle how many pairs of electrons are transferred
4 pairs (three to NAD+ and one to FAD)
in aerobic organisms what is used to transfer electrons to oxygen and why
electrons are not directly transferred to oxygen and special electron carriers must be used, which are either pyridine nucleotides or flavins. The reduced forms of these carriers then transfer their high-potential electrons to oxygen
What is the reactive part of NAD+
its nicotinamide ring, a pyridine derivative synthesized form the vitamin niacin.
NAD+ accepts
a hydrogen ion and two electrons, which is the equivalent to a hydride ion
In NAD+ has a positive charge at the
Nitrogen
NAD+ is the ___ form
oxidized form
many activated carriers function as
coenzymes
FAD is the ___ form
oxidized form
The reactive pare of FAD is its
isoalloxazine ring, a derivative of the vitamin riboflavin
FAD accepts
two electrons and two protons
How is FMN (flavin monnucleotide) different form FAD
it lacks adenine
High-potential electrons are required in most biosyntheses because
the precursors are more oxidized than the products. So, reducing power is needed in addition to ATP
What is the electron donor in most reductive biosyntheses
NADPH
NADPH is the ____ form of NADP+
reduced form
NADPH differs from NADH in that the
2’- hydroxyl group of its adenosine moiety is esterified with phosphate.
NADH is primarily used for the generation of
ATP
The extra phosphoryl group on NADPH is a tag that enables enzymes
to distinguish between high-potential electrons to be used in anabolism and those to be used in catabolism
Coenzyme A is derived from
Vitamin pantothenate
Acyl groups are important in both
anabolism and catabolism
Acyl groups function in the oxidation of
fatty acids
Acyl groups function in anabolism
synthesis of membrane lipids
What is the reactive site of CoA
Terminal sulfhydryl group
Acyl groups are linked to CoA by
thioester bonds
what is the free energy for the hydrolysis of acetyl CoA
-31.4 kJ mol^-1
Why is a thioster bond more thermodynamically unsable than an oxygen ester
because the electrons of the C=O bond cannot form resonance structures with the C-S bond that are stable as those they can form with the C-O bond.
Acetyl CoA carries an ____ acyl group
Activated
The kinetic stability of activated carriers in the absence of specific catalysts is essential for their biological function because
it enables enzymes to control the flow of free energy and reducing power
most interchanges of activated groups in metabolism are accomplished by a rather
small set of carriers
almost all the activated carriers that act as coenzymes are derived from
vitamins
Vitamins are
organic molecules that are needed in small amounts in the diets of some higher animals
Is it biologically more efficient to ingest vitamins than to synthesize the enzymes required to construct them form simple molecules
Yes
Vitamin A (retinol) is a precursor of
retinal, the light-sensitive group in rhodopsin and other visual pigments, and retinoic acid, an important signaling molecules.
Function of Vitamin A
roles in vision, growth, and reproduction
Function of Vitamin C (Ascorbic acid)
Antioxidant
Functions of Vitamin D
Regulation of calcium and phosphate metabolism
Functions of Vitamin E
Antioxidant
Functions of Vitamin K
Blood Coagulation
Metabolism is regulated through what 3 ways
- ) the amounts of enzymes
- ) their catalytic activities
- ) The accessibility of substrates
How are enzymes controlled for
The rate of transcription for genes coding them.
they depend on the rate of synthesis and rate of degradation
How do we control catalytic activity
Allosteric control
- feedback inhibition
hormones coordinate metabolic relations
How do we control the accessibility of substrates
Compartmentalization segregates opposed reactions
