BIOCHEM Citric Acid Cycle, Saccharides, Glycolysis Flashcards
is the final common pathway for the oxidation of carbohydrate, lipid, and protein because glucose,
fatty acids, and most amino acids are metabolized to acetyl CoA or intermediates of the cycle.
Citric Acid Cycle
Krebs Cycle has a central role in ____________, ____________, and ______________________
Gluconeogenesis, Lipogenesis, Interconversion of amino acids.
The cycle starts with reaction between the acetyl moiety of
____________ and the four-carbon dicarboxylic acid __________, forming a six-carbon tricarboxylic acid,__________ . In the subsequent reactions, two molecules of _______ are released and oxaloacetate is regenerated
acetyl-CoA, oxaloacetate, citrate, CO2
________________ provides the main pathway for ATP
formation linked to the oxidation of metabolic fuels
The citric acid cycle
The citric acid cycle process is ________, requiring __________ as the final oxidant of the reduced coenzymes
aerobic, oxygen
The enzymes of the citric acid cycle are located in the __________________, either free or attached to the inner ______________ membrane
mitochondrial matrix, mitochondrial
Entry of Carbon
Anaplerosis
Exit of Carbon
Cataplerosis
The initial reaction between acetyl-CoA and oxaloacetate
(C4) to form citrate (C6) is catalyzed by
citrate synthase
Citrate is isomerized to isocitrate by the enzyme
aconitase
________ ATP ARE FORMED PER TURN OF THE CITRIC ACID CYCLE
TEN
Four of the B vitamins are essential in the citric acid cycle and hence energy-yielding metabolism:
riboflavin, niacin, thiamin (vitamin B1), pantothenic acid
_________, as FAD, is the cofactor for succinate dehydrogenase;
riboflavin
_________, as NAD+ , is the electron acceptor for isocitrate dehydrogenase, α-ketoglutarate dehydrogenase, and malate dehydrogenase;
niacin
________, as thiamin diphosphate, is the coenzyme for decarboxylation in the α- ketoglutarate dehydrogenase reaction; and
thiamin (vitamin B1)
__________, as part of coenzyme A, is esterified to carboxylic acids to form acetyl CoA and succinyl-CoA.
pantothenic acid
All the intermediates of the Krebs cycle are potentially ___________, since they can give rise to oxaloacetate, and hence production of glucose
glucogenic
The key enzyme that catalyzes transfer out of the cycle into gluconeogenesis is _________________________, which catalyzes the decarboxylation of oxaloacetate to phosphoenolpyruvate, with GTP acting as
the phosphate donor
phosphoenolpyruvate carboxykinase
___________________ reactions form pyruvate from alanine, oxaloacetate from aspartate, and α-ketoglutarate from glutamate
aminotransferase
Acetyl-CoA, formed from pyruvate by the action of pyruvate dehydrogenase, is the major substrate for ________________________________ synthesis in nonruminants
long-chain fatty acid
In most tissues, where the primary role of the citric acid cycle is in energy-yielding metabolism, _________________via the respiratory chain and oxidative phosphorylation regulates citric acid cycle activity
respiratory control
The citric acid cycle is _____________, since in addition to
oxidation it is important in the provision of ____________________ for gluconeogenesis, ______________ for fatty acid synthesis, and interconversion of amino acids. For these processes to be sustained they rely on a balance of anaplerosis and cataplerosis in the citric acid cycle
amphibolic, carbon skeletons, acetyl-CoA
Producers of NADH+ in Krebs Cycle
Conversion of Isocitrate to Alpha-Ketoglutarate
Conversion of Alpha-Ketoglutarate to Succinyl-CoA
Conversion of Malate to Oxaloacetate
Producers of FADH in Krebs Cycle
Conversion of Succinate to Fumarate
are extremely polar molecules that are widely
distributed in plants and animass.
Carbohydrates
is the most important carbohyrate; most ietary carbohyrate is absorbe into
the boostream as simpe sugars
Glucose
is a major metaboic fue of mammas (except ruminants)an a universa fue of the fetus
Glucose
Glucose is the precursor for synthesis of a the other carbohyrates in the boy, incuing ______________ for storage, _______ and _________ in nucleic acids, _______________ for synthesis of _____________ in mik, in glycolipids, and in combination with protein in gycoproteins
glycogen, ribose & deoxyribose, galactose, lactose
is the stuy of the roes of saccharies in heath an disease
Glycobiology
is the entire compement ofsaccharies of an organism, whether free or in more compexmoecues.
Glycome
an analogous term to genomics and proteomics, is the comprehensive study of
glycomes, including genetic, physiological, pathological, and other aspects
Glycomics
Classification of Saccharides
(1) monosaccharides
(2) disaccharides
(3) oligosaccharides
(4) polysaccharides.
Also called as simple sugars and are sugars that cannot
be further hydrolyzed to simpler saccharides.
MONOSACCHARIDES
They can be classified as trioses, tetroses, pentoses,
hexoses, or heptoses which depend on the number of
carbon atoms and location of the carbonyl (C=O)
MONOSACCHARIDES
formed when the aldehyde or
ketone has been reduced to alcohol group, and are also
synthesized by reduction of monosaccharides for use in
the manufacture of foods for weight reduction and for
diabetics.
Polyhydric Alcohol
They are the condensed products of two (2) monosaccharide units
(ex. lactose, maltose, and sucrose).
DISACCHARIDES
They are the condensed products of 3-10 monosaccharides and mostly are not digested by human enzymes.
OLIGOSACCHARIDES
They are the condensed products of more than 10
monosaccharide units (ex. starches and dextrans which
can be linear or branched polymers)
POLYSACCHARIDES
They’re sometimes classified as hexosans or pentosans
depending on the constituent monosaccharides
(hexoses, pentoses, respectively).
POLYSACCHARIDES
A wide variety of polysaccharides collectively known as
____________________________ are not digested by human
enzymes and are major component of dietary fiber (ex.
cellulose and inulin)
nonstarch polysaccharides
- account for some of the
properties of glucose - shows the linear
arrangement of the carbon
atoms and the aldehyde
group
Straight Chain
Structural Formula
(Aldohexose)
- glucose can undergo a
reaction between the
aldehyde group and a
hydroxyl group - thermodynamically
favored and accounts for
other properties of glucose
Cyclic Structure (Hemiacetal
Formation)
- a way to present the cyclic
structure of glucose in a two dimensional format - the molecule is viewed from
the side and above the plane
of the ring - the bonds nearest to the
viewer are bold and thickened,
while the hydroxyl groups are
shown above or below the
plane of the ring
Haworth Projection
OH group on the right side when drawn in
the fischer projection
D-isomer
OH group on the left side when drawn in
the fischer projection
L-isomer
When polarized light passes through a solution of an
optical isomer, it rotates the light.
If the light rotates to the right, the compound is
dextrorotatory +
When polarized light passes through a solution of an
optical isomer, If the light rotates to the left, the compound is
levorotatory -
six-membered ring
Pyranose
five-membered ring
Furanose
Over 99% of glucose in solution is in the _______________ form
pyranose
are special types of sugars that are very
similar in structure but differ in the position of just
one hydroxyl (-OH) group.
Epimers
are different forms of a sugar molecule that
arise when the sugar forms a ring structure.
Anomers
The carbon atom that was part of the carbonyl group (aldehyde or ketone) becomes the
anomeric carbon in the ring
Anomeric Carbon
The hydroxyl group on the anomeric
carbon is on the opposite side of the ring from the
CH2OH group.
Alpha (α) form
The hydroxyl group on the anomeric
carbon is on the same side of the ring as the CH2OH
group.
Beta (β) form
- Metabolic intermediates
- Important in glycolysis and pentose phosphate pathway.
Trioses, Tetroses, and Pentoses:
- Integral in nucleotides, nucleic acids, and
several coenzymes. - Example: Ribose in RNA and deoxyribose
in DNA.
Pentoses
Sugars where one hydroxyl
group (-OH) is replaced by a
halogen atom (H)
DEOXY SUGARS
a homopolymer of glucose forming an α-glucosidic chain, called a glucosan or glucan
Starch
most important dietary carbohydrate in cereals,
potatoes, legumes, and other vegetables.
Starch
is a measure
used to determine how much a
food can affect your blood
sugar levels
Glycemic Index
- a main source of energy that is
stored primarily in your liver
and muscles. - sometimes called animal starch.
Glycogen
- Regulates the amount of
glucose in the blood. - It is used clinically to assess
kidney function.
Insulin
is the chief constituent of plant cell walls which is insoluble and forms long, straight chains strengthened by cross-linking hydrogen
bonds.
Cellulose
is a structural
polysaccharide in the exoskeleton
of crustaceans and insects, also in
mushrooms.
Chitin
occurs in fruits and is a
polymer of galacturonic acid linked α1 → 4, with some galactose an/or arabinose branches, and is partially
methylated.
Pectins
are proteins containing branched or unbranched oligosaccharide chains, including fucose.
Glycoproteins
is the main
pathway through which cells metabolize glucose and other
carbohydrates.
Glycolysis
While glycolysis can occur under anaerobic conditions, this has a price. It ____________________ formed per mole of glucose oxidized, so that much more glucose must be metabolized under anaerobic than aerobic conditions to supply the same quantity of ATP to supply cellular work
limits the amount of ATP
glucose enters glycolysis by phosphorylation to glucose-6-phosphate, catalyzed by _______________
hexokinase
Isomerization of glucose-6-phosphate to fructose-6-phosphate catalyzed by _________________________
glucosephosphate isomerase
Fructose-6-phosphate is then phosphorylated again to generate fructose-1,6-bisphosphate catalyzed by ____________________________
phosphofructokinase
Fructose-1,6-bisphosphate is cleaved into two 3-carbon fragments. This reaction is catalyzed by __________________
aldolase
Dihydroxyacetone phosphate (DHAP) is converted to glyceraldehyde-3-phosphate catalyzed by _____________
triosephosphate isomerase
_____________- An intermediate product of glycolysis, which can either enter the mitochondria for ________________ (if oxygen is available) or be converted to ________________ (if oxygen is scarce)
Pyruvate, oxidation, lactate
reactions in glycolysis that are markedly exergonic and are considered to be physiologically irreversible
reactions catalyzed by:
- hexokinase(and glucokinase),
- phosphofructokinase, and
- pyruvate kinase,
