Metabolism Flashcards
Name the metabolic pathways
Catabolic
Anabolic
Amphibolic
anabolic pathway
are a series of biochemical reactions in living organisms that involve the synthesis of complex molecules from simpler ones
catabolic pathway
is a series of biochemical reactions in living organisms that involve the breakdown of complex molecules into simpler ones
amphibolic pathway
metabolic pathways that have characteristics of both catabolic and anabolic pathways
which of the metabolic pathways requires energy?
which one produces energy?
anabolic
catabolic
metabolism
set of chemical reactions that occur within living organisms to maintain life
glycolysis
forms of glycolysis?
It is defined as a sequence of reactions transforming glucose to lactate & pyruvate with the production of ATP.
aerobic and anaerobic glycolysis
aerobic glycolysis
what does it form
the breakdown of glucose in the presence of oxygen
Acetyl Co-A
anaerobic glycolysis
what does it form
the breakdown of glucose in the absence of oxygen
lactic acid, which is the final product(in mammals)
how many pyruvates will be formed per glucose molecule?
2 per glucose
purpose of glycolysis
to produce intermediates for other biosynthetic pathways
to produce energy
site of glycolysis
the cytoplasm
outline the steps of glycolysis
Hexokinase catalyzes the phosphorylation of glucose (from ATP) to form glucose 6-phosphate
Glucose 6-phosphate is converted to fructose 6-phosphate by phosphoglucose isomerase
This reaction involves the conversion of an aldose to a ketose
Fructose 6-phosphate is phosphorylated by phosphofructokinase(PFK) to form fructose 1,6-bisphosphate and ADP
Fructose 1,6-bisphosphate (a six-carbon molecule) is split by aldolase into two three-carbon molecules: glyceraldehyde 3-phosphate and dihydroxyacetone phosphate
Only glyceraldehyde 3-phosphate(G3P) is used for the remainder of glycolysis
But dihydroxyacetone can be converted back to G3P
G3P is converted to 1,3 biphosphoglycerate.
The enzyme involved is glyceraldehyde 3-phosphate dehydrogenase and uses Pi and NAD+
The high-energy phosphate bond in 1,3-bisphosphoglycerate is then used to generate ATP
1,3-bisphosphoglycerate is converted by phosphoglycerate kinase to3-phosphoglycerate
3-phosphoglycerate is converted by phosphoglycerate mutase to 2-phosphoglycerate* This step moves the phosphate group to a different carbon on the same molecule
2-phosphoglycerate is converted to phosphoenolpyruvate (PEP) by enolase
This dehydration reaction changes the low-energy phosphate ester bond of the former to the high-energy phosphate bond of PE
The final reaction involves the conversion of phosphoenolpyruvate to pyruvate via pyruvate kinase
what is the TCA cycle also known as
the Krebs cycle
via which cycle can lactate be turned back into glucose
the Cori cycle
what are the primary control steps in glycolysis catalyzed by
PFK(phosphofructokinase)
hexokinase
pyruvate kinase
how is PFK inhibited and by what?
allosterically by ATP
what inhibits hexokinase
glucose-6-phosphate
note that hexokinase levels increase after PFK inhibition
TCA cycle unabbreviated
tricarboxylic acid cycle
is the TCA cycle an aerobic or anaerobic pathway
aerobic pathway
purpose of TCA cycle
it contributes to glucose formation from the carbon skeleton of some amino acids
Oxidative Decarboxylation
Generates high-energy molecules in the form of NADH and FADH2, which participate in oxidative phosphorylation to produce ATP.
it provides building blocks for the synthesis of some amino acids
outline the steps in generating acetyl COA
pyruvate moves into the mitochondria
Pyruvate dehydrogenase(PDH) catalyzes the reaction between pyruvate and CoA to form acetyl CoA and CO2. NADH is formed during this step
is the TCA cycle a closed cycle?
no, it is a traffic cycle, because as compounds can enter and leave as required
what reaction does PDH catalyze?
in the oxidative decarboxylation of pyruvate (pyruvate decarboxylation)
how many enzymes is PDH comprised of
name some of the co-enzymes required by PDH
3
Thiamine
FAD
NAD
Co-A
lipoic acid
briefly outline the steps involved in the TCA cycle
the formation of citric acid
formation of isocitrate
isocitrate oxidative decarboxylation
α-ketoglutarate oxidative decarboxylation
succinate formation
oxidation of succinate
hydration of fumurate
oxidation of malate
two carbon atoms enter the TCA cycle and leave as?
2 CO2 molecules
how many of the following molecules does the TCA cycle form?
NADH
FADH
ATP
3
1
1
when oxidized, how many ATP molecules would the following form?
NADH
FADH
3
2
in total, how many ATP molecules are formed per acetyl-CoA molecule during the TCA cycle
12
the first five steps in glycolysis can be termed as
the preparatory phase
the last five steps of glycolysis can be termed as
the payoff phase
how many irreversible steps are involved in glycolysis, and which steps are these
3
step 1
step 3
step 10
what inhibits pyruvate kinase
allosterically inhibited by ATP
the function of the PPP
generates NADPH
provides the body with pentoses required for the biosynthesis of nucleotides
PPP unabbreviated
Pentose phosphate pathway
where does the PPP take place in the cell
the cytoplasm
what are the speed and direction of the two irreversible reactions of the PPP determined by
the availability of intermediates and how much they are needed
how many irreversible reactions is the PPP made of
2
difference in function between NADH and NADPH
NADH used in oxidative phosphorylation while NADPH is used for powering biosynthesis
in which cells is the PPP particularly important in
cells that synthesise lipids and steroids
the products of the two irreversible oxidative reactions of the PPP
ribulose-5-phosphate, CO2,2NADPH (for each oxidized glucose)
the irreversible oxidative reactions of the PPP are important in the?
cells that synthesise fatty acids(like mammary and liver cell)
Adrenal cortex, where
steroid synthesis is dependant on NADPH
Red blood cells, which needs NADPH to keep glutathione in a reduced state
briefly describe the irreversible oxidative reactions in the PPP
Glucose-6-phosphate is oxidized by NADP to form 6-phosphogluconolactone, under the action of Glucose-6-phosphate dehydrogenase
NADPH is formed
6-phosphogluconolactone is oxidized to form Ribulose-5-phosphate, under the action of 6-phosphogluconate dehydrogenase.
CO2 is formed, and NADP is reduced to form NADPH
where do the reversible non-oxidative reactions of the PPP happen
all cells that synthesise nucleotides and nucleic acids
briefly describe what happens during the reversible non-oxidative reactions of the PPP
Ribulose 5-phosphate undergoes isomerisation to ribose 5-phosphate
uses for ribulose 5-phosphate
for nucleotide biosynthesis
intermediate for glycolysis
what is G6PD deficiency
lack of the enzyme glucose-6-phosphate dehydrogenase
function of G6PD
helps red blood cells to produce NADPH
effects of G6PD deficiency
lack of NADPH, red blood cells will be susceptible to reactive oxygen species and oxidative stress. Therefore, proteins in membranes get oxidized
RBC will be lysed
gluconeogenesis
The metabolic process by which organisms produce glucose from non-carbohydrate precursors
name three sources of glucose
diet
glycogenolysis
gluconeogenesis
substrates used in gluconeogenesis
lactate
amino acids
glycerol
name the two enzymes involved in the conversion of pyruvate phosphoenolpyruvate
pyruvate carboxylase
PEP Carboxykinase
how is pyruvate converted to phosphoenolpyruvate in gluconeogenesis
First pyruvate is converted to oxaloacetate via pyruvate carboxylase.- Then, oxaloacetate is converted to PEP via PEP carboxykinase
process by which fructose-1,6-bisphosphate is converted to fructose-6-phosphate in gluconeogenesis
remove phosphate from fructose 1,6-biphosphate.- This is mediated by: fructose 1,6-biphosphatase
process by which glucose-6-phosphate is converted to glucose in gluconeogenesis
remove phosphate from
glucose-6-phosphate under the action of glucose-6- phosphatase
is the osmotic balance affected by glycogen
no
glycogenesis
a biological process that involves the formation and storage of glycogen
where does glycogenesis occur in the cell
the cytosol
is the cytosol the same as the cytoplasm
no
it is the liquid portion of the cytoplasm
what is required for glycogenesis to occur
D-glucose and energy provided by ATP
describe the process of glycogenesis
Glucose is phosphorylated to form glucose-6-phosphate. ATP is used, and ADP is formed in this step. This step is catalysed by hexokinase
Glucose-6-phosphate is converted to glucose-1-phosphate, under the action of phosphoglucomutase
G-1-P interacts with UTP to form UDP-glucose, under the action of glucose-1-phosphate uridylyl transferase. PPi is formed in this step
UDP-glucose delivers glucose to growing glycogen. this is catalysed by glycogen synthase. UDP is formed in this step
is glycogenolysis a hydrolysis reaction? what enzyme is it catalysed by
no, it is a phosphorolysis reaction.
it is catalysed by phosphorylase
what does phosphorylase do
breaks down alpha 1-4 glycosidic bonds
which hormones activate phosphorylase
epinephrine
glucagon
the preliminary effect of the hormones that activate phosphorylase
to enhance the formation of cAMP
function of cAMP
it initiates a series of reactions that lead to the activation of phosphorylase
is the TCA cycle viewed as a closed cycle?
no
all the intermediates in the TCA cycle are glucogenic. why is this?
because the TCA cycle leads to the formation of oxaloacetate which is transformed to PEP, under the action of PEP carboxykinase
functions of cholesterol
important constituent of cell membranes
serves a precursor to the synthesis of steroid hormones and bile salts
beta oxidation
Beta-oxidation is a metabolic pathway that occurs in the mitochondria of cells and is responsible for breaking down fatty acids to produce energy in the form of adenosine triphosphate (ATP)
requirements for beta oxidation to occur
activated acyl-CoA molecules, NAD+, FAD
is beta oxidation aerobic or anaerobic
it is aerobic
in beta oxidation, fatty acids are converted to an active intermediate known as
Fatty Acyl-coA
where does the activation of fatty acids occur
where does the oxidation of fatty acids occur
in the cytosol
in the mitochondria
can the Fatty Acyl-CoA pass the mitochondrial membrane
how are they transported into the mitochondria then?
no
via translocation by carnitine
the process of acyl group translocation
these steps/processes are required for beta oxidation to occur, as fatty acids cannot pass the mitchondrial membrane without it
Activation with CoA
Formation of Acylcarnitine
Transport into Mitochondria
Formation of Acyl-CoA in Mitochondria
the formation of acyl-CoA is catalysed by?
acyl-CoA synthethase
function of carnitine palmitoyltransferase I (CPT-I)
this is an enzyme of the outer mitochondrial membrane
The enzyme carnitine palmitoyltransferase I (CPT-I) catalyzes the transfer of the acyl group from acyl-CoA to carnitine, forming acylcarnitine.
free carnitine is acquired due to it
function of carnitine-acylcarnitine translocase
catalyses the transfer of Acylcarnitine into the mitochondrial matrix in exchange for free carnitine
function of Carnitine palmitoyltransferase II
this is an enzyme of the inner mitochondria membrane
catalyses the transfer of the acyl group from carnitine to CoA
in beta oxidation, the fatty acid is cleaved between the …………….. and …………… carbon
alpha and beta
describe the process of beta oxidation
Oxidation that produces FADH2 (acyl-CoA dehydrogenase)
Hydration step (enoyl-CoA hydrolase)
Second oxidation that produces NADH (dehydrogenase)
A thiolytic cleavage that releases a molecule of acetyl-CoA (β-ketothiolase)
at which end does the cleavage of the fatty acid in beta oxidation start
the carboxylic end
the products of each cycle of beta oxidation
1 NADH, 1 FADH2 and a molecule of acetyl CoA
