Metabolic Pathways Flashcards
1 g of carbohydrate is equal to what kcal
1 kcal
increases the chemical reaction significantly
catalyst
are the biochemicals that come together and interact at the beginning of the
process such that they are converted into one or more different biochemicals
reactants
temporary state wherein they become or processed futher
intermediates
reactants can become ___ if the next step is a branching point
common intermediates
refer to a chemical that participates as one of the starting chemicals in a
chemical reaction that produces other substance(s).
precursor
” is used more specifically to refer to a
chemical compound preceding another in a metabolic pathway.
precursor
e types of proteins that play an important role in metabolism by catalyzing the
individual reactions in metabolic pathways.
enzymes
Enzymes that catalyze the first reaction in a metabolic pathway are sometimes subject to
___ control by the concentration of the end product of the metabolic pathwa
allosteric
” is a word used in chemistry generally (not just biochemistry) to refer to chemicals
that affect the rate (speed) of chemical reactions by participating in the reaction(s) but in
such a way that itis not consumed by the reaction itself.
catalyst
, the presence of a
___ may be necessary for a reaction to occur to any meaningful extent under certain
conditions
catalyst
are compounds that are neither the initial (starting) chemicals in a pathway or
“process”, nor the end-products used directly or secreted by the cell, nor catalysts (that
participate in but are not used-up by the reactions)
intermediates
are compounds
that are formed as temporary “steps” in the overall chemical process
intermediates
are compounds that occur at branching points in metabolic
pathways.
common intermediates
are compounds that are produced by metabolic
reactions that do not go on to participate in a subsequent reaction in the metabolic pathway.
end products
The concentration of the end products of a metabolic pathway often regulates the rate of the
reaction that produces them, i.e. effectively a ___ that prevents over-production
feedback loop
inhibition or activation of an enzyme by a small regulatory molecule that interacts at a site other than the active site
allosteric control
is a form of negative feedback by which metabolic pathways can be controlled.
end product inhibition
Some branching points in metabolic pathways are sometimes called
cross-over points
s refer to a stage in a metabolic pathway at which an intermediate
(usually a molecule or part of a molecule), could proceed to change in more than one
possible way, i.e. it could follow two or more possible “(metabolic) pathways”.
branching points
The “pathway” followed (next change undergone) by the intermediate is usually the one of
most immediate benefit to the cell, that “decision” being determined by the activity of
____ present around the intermediate.
enzyme
is a position at which at least two “paths” intersect
junction
implies that the intersection is particularly important, i.e.
one at which decisions taken about which on-going paths to follow from that point onwards
may change depending on circumstances and have important consequences.
key junction
are substances (usually compounds) that participate in metabolism processes
and are either produced during metabolism reactions or are “constituents of” i.e. parts that
make-up, foods taken into the body - then broken-down via the digestive
processes
metabolites
are therefore among the chemicals included in metabolic pathways.
They are often intermediates between reactants and end-products.
metabolites
metabolites that are molecules that are essential for an organism’s growth, development, and reproduction:
primary metabolites
metabolites that are organic compounds produced by organisms that are not essential for the organism’s growth, development, or reproduction.
secondary metabolites
is the descriptive term used to refer to some metabolic pathways or parts
of metabolic pathways that take the form of repeated ‘cycles’ in which product(s) of the
individual metabolic reactions in the sequence become the reactants, i.e. the “starting
chemicals”, for the next metabolic reaction in the sequence.
metabolic cycles
metabolic cycles include
Krebs TCA Cycle
Calvin cycle
Urea cycle
” is a point at which many “pathways” meet. These could be routes, wires,
lines of communication or similar e.g. as used in the context of air-travel or information
technology
hub
can therefore be thought of as a location at which many metabolic
processes occur, enabling substances such as molecules, e.g. reaction intermediates, to
transfer between reaction processes on an as-needed basis.
metabolic hub
example of metabolic hubs in the body
krebs TCA cycle
liver
generally modify biochemicals via a series of small steps (stages in the process) rather
than a single chemical reaction
metabolic pathways
Minor adjustments can be made to the structure of the molecules.
Energy is released / used in manageable quantities.
what characteristic of metabolic pathway
metabolic pathways generally modify biochemicals via a series of small steps
Many balances - i.e. requirements for specific enzymes - keep the rate of metabolic processes in
check.
what characteristic of metabolic pathways
each step in a metabolic pathway is a chemical rxn that can catalyze a specific enzyme
Benefit: The biochemical reactions at each stage of a metabolic pathway are more likely to proceed (that is,
continue to happen) because the products of that particular reaction do not accumulate because they go on
to participate in the next step in the metabolic pathway … which changes them into other biochemical(s).
what characteristic of metabolic pathways
chemical equilibrium may never be reached because the products of reactions do not continue to exist in that form due to participation of nexts step
one that is not part of a metabolic pathway but is
considered entirely on its own - the meaning of “isolated”. In that case only a certain proportion of the
reactants may be converted into the products of the reaction due to a natural “equilibrium” situation at which
a certain proportion of the total matter concerned is in the form of the reactants and a certain
(other) proportion in the form of the products of the reaction
isolated chemical rxn
Benefit: Accumulation of concentrations of biomolecules that are the reactants of a step in a metabolic
pathway can help to increase the rate (i.e. the “speed”) of the process. This is related to the above
considerations of “equilibrium”.
what metabolic pathway characteristic
Steps in a metabolic pathway tend to be arranged in physical space such that the product of one reaction is
in the right place to become a reactant (or “precursor”) in the next step in the sequence.
is the metabolic pathway that converts glucose C6H12O6, into pyruvic acid, CH3COCOOH
glycolysis
does glycolysis require oxygen?
no
an ancient metabolic pathway
glycolysis
parallel pathway of glycolysis
pentose phosphate pathway
what metabolic pathway, occur in the oxygen-free conditions of the Archean oceans, also in the absence of enzymes, catalyzed by
metals
glycolysis
pentose phosphate pathway
two phases of glycolysis
investment phase
yield phase
The first step is phosphorylation of glucose by a family of enzymes called ___ to form glucose 6-phosphate (G6P).
hexokinase
This reaction consumes ATP, but it acts to keep the glucose concentration low, promoting continuous transport of glucose into
the cell through the plasma membrane transporters.
conversion of glucose to glucose 6-phosphate
In addition, the conversion of glucose to glucose-6 phosphate blocks the glucose from leaking out because ___
the cell lacks
transporters for G6P, and free diffusion out of the cell is prevented due to the charged nature of G6P