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biochemistry exam 4

Terms in this set (154)

fatty acid oxidation is inhibited by ___ ___
malonyl coA
acetyl coA carboxylase can be made more active allosterically with ___
citrate and INSULIN(dephosphorylates the carboxylase after it has been phosphorylated by AMPK)
acetyl coA carboxylase contains the cofactor ____
biotin
ketone bodies are made by combining ____ molecules
acetyl coA
B oxidation of fatty acids occurs in the ?
mitochondrial matrix
what is the smallest plasma lipoprotein?
chilomicrons
the rate-determining step of cholesterol biosynthesis is catalyzed by ___ ___ ___
HMG coA REDUCTASE
the rate-determining step of cholesterol biosynthesis requires ____
NADPH
the urea cycle produces? 2 things
fumarate and urea
where does the urea cycle occur?
the liver
_____________ reactions are an important first step in the breakdown of most amino acids
transamination reactions (move amino group)
THF is essential for the conversion of __ to ___
serine to glycine
THF is essential for the construction of ___ bases
purine
THF can carry __ around in a variety of oxidation states
carbon
glutamine can be converted TO glutamate by _____
glutaminase
glutamine can be a donor of __ atoms for purine biosynthesis
purine
glutamine can be synthesized FROM glutamate by ___ ____, with the input of ATP and ammonia
glutamine synthetase
____ _____ is an important precursor for pyrimidine base biosynthesis
carbamoyl phoshate
ribonucleotide reductase is ?
under a lot of allosteric control
the melting point of fatty acids ____ as the carbon chain length increases
increases
the melting point of fatty acids ____ as the number of double bonds INCREASES
decreases
sphingolipids are an important class of ___ ___
membrane lipids
discuss different ways glutamate is involved in amino acid metabolism
do it
discuss fatty acid breakdown: start with the activation of the fatty acid once it gets into the target cell. outline the steps all the way to the production of acetyl coA. mention organelles, key enzymes, and cofactors when necessary. also mention regulation.
1) the fatty acid is linked to coA and activated by acyl coA synthetase.
2) it is then transferred to carnitine by carnitine acyltransferase I.
[1 and 2 occur in cytoplasm]
3) a translocase then transports the acyl carnitine into the mitochondria
4) in the mitochondria, carnitine acyltransferase II transfers the coA to the molecules
5) fatty acyl coA is now ready to be degraded

activation of the fatty acid is regulated by: epinephrine and glucagon steroid hormones (they start g-protein phosphorylate cascades)
discuss fatty acid synthesis: start with citrate in the mitochondria and end with the production of butyryl ACP (reduced 4 carbon chain attached to acyl carrier protein. mention transport mechanisms and cofactors involved
do it!
draw the urea cycle: including all enzymes, reactants, and products, and parts of the cell where it occurs
do it!!
draw the gluocse-alanine cycle: show enzymes active at each step, especially the first few steps. mention the purpose of the cycle
do it!!
discuss the construction of LDLs and a discussion of their function and cellular uptake
low-density lipoproteins:
structure: proteins component and various lipids (HIGH proportion of lipids because it is less dense)
function: major carrier of cholesterol in the blood (ex)chilomicrons)
discuss the importance of PRPP in the production of nucleotides
do it
discuss the atom origins or purines and pyrimidines
do it
draw the structure of cholesterol
do it
draw the structure of a triacylglycerol
do it
how are fatty acids transported into the mitochondrion?
fatty acids are transferred to CARNITINE by carnitine acyltransferase I, and a translocase transports the acyl carnitine into the mitochondria
how does odd chain length fatty acid breakdwon differ from even chain length?
even:
requires both isomerase AND reductase
odd:
requires only isomerase
what amino acid donates most of the atoms for the production of the ____ ring
purine
what is the purpose of ketone bodies, which organ are they produced in, and what is the target organ?
?
describe the metabolism of diabetic ketosis
do it
what is the rate-determining step of fatty acid synthesis and mention one method of controlling the activity of the enzyme
ACC: acetyl coA carboxylase [epinephrine and glucagon ACTIVATE AMPK, making phosphorylation of ACC]= inhibition of fatty acid synthesis.
ACC is activated by citrate
what are the reactants and products for the enzyme arginase?
arginine--> urea + ornithine
what is the rate-determining step of pyrimidine biosynthesis?
aspartate transcarbamoylase
what organelle in the cell is carbamoryl phosphate synthetase I (CPS I) active in?
MITOCHONDRIA OF LIVER CELLS
name 2 purely ketogenic amino acids
lysine and leucine
biotin is the cofactor found in __ __ ____
propionyl coA carboxylase
name a disease that can result from defects in the breakdown of purines
gout
name a least one way aspartate can be synthesized (2)
1) asparaginase
2) aspartate aminotransferase
can glycine be produced from serine? yes/no
yes
what reaction is catalyzed by PRPP synthetase?
ribose 5 phosphate ----> PRPP
true/false: in purine biosynthesis, the base is built on the ribose sugar, starting with an amidation of carbon number ONE of the ribose
TRUE
briefly describe the difference between DNA and RNA structures
2' carbon is reduced???
true/false: aspartate transcarbamoylase catalyzes the main regulatory step of PYRIMIDINE biosynthesis
TRUE
true/false: GTP is required for the production of AMP
true
what causes Lesch-Nyhan syndrome?
deficiency of HGP RT
true/false: GMP inhibits its own biosynthesis
true
what enzyme converts ribonucleotides into deoxyribonuceotides?
ribonucleotide REDUCTASE
what are the 5 major classes of lipids?
1) free fatty acids
2) triacylglycerols
3) phospholipids
4) glycolipids
5) steroids
what is the basic structure of a fatty acid, and what are 2 examples?
carboxylic acid-[hydrogen-bearing carbon chains]-methyl group
ex) palmitate and oleate
draw the structure of palmitate
do it (15 chinas then c-o-o -
where is the major site for TAG storage in mammals?
adipose tissue
what kind of fatty acids are essential to our diet, because we can't sythesize them?
cis polyunsaturated fatty acids
what molecules are the storage forms of fatty acids?
triacylglycerols (TAGs)
what is the structure of TAGs composed of?
3 fatty acids esterified to one molecule of glycerol
____ assist in the solubilization of greasy substances by forming micelles. they are the direct result of treating fatty acids with a STRONG BASE
salts
TAGS are ___ (hydrophobic/hydrophillic) and ___ (reduced/oxidized)
TAGs are hydroPHOBIC and REDUCED
what are the 3 common types of membrane lipids?
phospholipids, glycolipids, and cholesterol
what are the 4 components of a phospholipid?
fatty acids (@+), a platform (glycerol or sphingosine), a phosphate, and an alcohol
draw the basic structure of a phospholipid
do it
what disease can result from the lack of an enzyme that degrades sphingomyelin?
Niemann-Pick disease
glycolipids are ____ -containing lipids
carbohydrate
___ are located on the extracellular surface of the cell membrane and play a role in cell-to-cell recognition
glycoplipids
what kind of platform are steroids built on, and what are they composed of?
> built on a tetracyclic platform
>conposed of 3 cyclohexane rings and a cyclopentane ring fused together
what is the most common steroid?
cholesterol
what does cholesterol play a role in?
maintaining membrane fluidity.
>also is a precursor to steroid hormones
membrane lipids are ___ molecules
amphipathic -have both hydrophillic and hydrophobic properties
what are the HYDROPHOBIC properties of membrane lipids provided by?
fatty acid components
what are the HYDROPHILLIC properties of membrane lipids provided by?
alcohol and phosphate components
why are proteins sometimes covalently bound to lipids?
to localize the protein to the cell membrane
_____ can be modified with lipids
proteins
are membranes asymmetric or symmetric?
asymmetric
what 2 molecules from bimolecular sheets (lipid bilayers in aqueous solutons)?
phospholipids and glycolipids
what is the definition of the MELTING TEMPERATURE of a membrane?
the temperature at which a membrane transitions from being HIGHLY ordered to VERY FLUID
what is the melting temperature of a membrane dependent on? 2 things
1) length of fatty acids in the membrane lipid
2) degree of CIS UNSATURATION
(saturated/unsaturated) _____ fatty acids pack together better in the membrane
saturated
what is the difference between membrane proteins and membrane lipids?
membrane PROTEINS:
allow transport of molecules and information across the membrane
membrane LIPIDS:
establish a permeability barrier
where are integral membrane proteins located?
embedded in the hydrocarbon core of the membrane
where are peripheral membrane proteins located?
bound to the POLAR head groups of membrane LIPIDS or to the exposed surfaces of integral membrane proteins
what is the composition of integral membrane proteins? and how many amino acids long are they, typically?
>membrane-spanning alpha-helices
?usually 19-20 amino acids long
what 2 conditions MUST be met in order for a small molecule to cross a membrane by diffusion?
1) the concentration of the molecule must be higher on one side of the membrane than another
2) the molecule must be lipophilic or soluble in nonpolar solutions
a polar molecule can only pass through a membrane down their concentration gradient through the help of a ___ ____. this is called facilitated/passive transport
channel protein
active transport requires a source of energy to allow a molecule to travel...?
AGAINST their concentration gradient
____ proteins function as pumps or channels to facilitate the flowof small molecules across the cell membrane
transport
the sodium potassium pump uses the energy of ___ ____
ATP hydrolysis
the sodium potassium pump simultaneously pumps ___ Na+ ions OUT of the cell and ___ K ions INTO the cell against their gradient
pumps 3 Na out and 2 K in against their gradient
[3NO 2KI]
how are fatty acids linked to glycerol?
by ester linkages
what are the 2 kinds of adipose tissue, and where are they located?
1) subcutaneous- below the skin
2) visceral- around intestinal organs
what are the 3 ways fatty acids are processed/made accessible?
1) degradation of TAGs to release fatty acids and GLYCEROL into the blood for transport to energy-requiring tissue
2) activation of the fatty acids and transport into the mitochondria for oxidation
3) degradation of the fatty acids to acetyl coA for processing in the citric acid cycle
what do lipases do?
chop up TAGs into fatty acids and glycerol
TAGs are stored in adipocytes as a __ __
lipid droplet
ATGL (in TAG breakdown) is activated by the ?
phosphorylation of perilipin by PKA
transport of the products of TAG breakdown occurs through the bloodstream in __ or ___ complexes
albumin or lipoprotein
how many fatty acids can 1 molecule of albumin carry?
~7
fatty acids are linked to ____ before they are oxidized for breakdown.
coenzyme A
what enzyme attaches coenzyme A to fatty acids in fatty acid breakdown?
acyl coA synthetase
how does coenzyme A help fatty acids in fatty acid degredation?
it solubizes the fat
what enzyme renders the reaction of the attachment of coA to a fatty acid irreversible?
pyrophosphatase
in fatty acid degredation, the fatty acid must be transferred to ____ after being linked to coA, since coA can't move across the membrane
carnitine
what 3 organ use fatty acids as fuel?
heart, kidney, and muscle
what happens to fatty acids as soon as they get into the muscle cell?
they are activated with coenzyme A by acyl coA SYNTHETASE
what are the 3 products of fatty acid breakdown?
acetyl coA, NADH, and FADH2
what process produces products that feed right into the citric acid cycle? [products are: acetyl coA, NADH, and FADH2]
fatty acid degredation
in the fatty acid pamitate breakdown, it needs to proceed through fatty acid oxidation/breakdown ___ times to be broken down into 8 MOLECULES OF ACETYL COA
7 times
the complete oxidation of palmitate yields ___ molecules of ATP
106
after acetyl coA is produced in fatty acid degradation, ___ and ___-chain length fatty acids require additional steps
UNsaturated and odd-chain length fatty acids
for odd-chain length fatty acid breakdown, what are the extra final steps required?
propionyl coA---[propionyl coA carboxylase]--> methylmalonyl coA-[methylmalonyl coA mutase]->succinyl coA
what are the 3 kinds of ketone bodies?
acetoacetate, 3-hydroxybutryate, and acetone
what 2 organs prefer ketones are a fuel source instead of glucose?
muscle and renal cortex of the kidney
true/false: the liver doesnt USE ketone bodies for fuel, it just makes them
true
animals cant convert fatty acids to glucose, so fats are converted to ___ ___
acetyl coA
ketone bodies are strong ___ and can lead to acidosis
strong acids
an overproduction of ketone bodies can occur when ___ is left untreated=diabetic ketosis
diabetes
what happens in diabetic ketosis?
if insulin is absent/not functioning properly, glucose CANNOT enter cells. therefore, all energy must be derived from fats, which leads to an overproduction of acetyl coA.
acetyl coA builds up because oxaloacetate isnt available to replenish the citric acid cycle.
this leads to fatty acid release from adipose tissue on account of the lack of insulin function
what is the predominate fuel for the brain?
glucose
where does fatty acid synthesis occur?
cytosol
where does fatty acid degradation occur?
mitochondrial matrix
what are the 3 basic stages of fatty acid synthesis?
1) acetyl coA is transferred OUT of the mitochondria and INTO the cytoplasm. citrate is also transported into the cytoplasm and cleaved into oxaloacetate and acetyl coA
2) acetyl coA is activated to form malonyl coA
3) repetitive addition/reduction of 2 carbon units to synthesize c16 fatty acid. this occurs on an acyl carrier protein, ACP.
what enzyme transports citrate into the cytoplasm from the mitochondria in order to generate acetyl coA for fatty cid synthesis?
ATP-citrate lyase (activated by insulin)
fatty acid synthesis requires ____ power in the form of NADPH
reducing
some of the NADPH required for fatty acid synthesis can come from..? 2 ways
>oxaloacetate oxidation, generated by ATP-citrate lyase-combined action of MALATE fOGENASE and MALIC ENZYME
or
>NADPH synthesized from the pentose phosphate pathway
for fatty acid synthesis, you need NADPH from the ____ and acetyl coA from the ___
need NADPH from the cytosol and acetyl coA from the mitochondrial matrix
the commited step of fatty acid synthesis, catalyzed by acetyl coA carboxylase, forms ___ ___
malonyl coA
what protein does fatty acid synthesis occur on?
acyl carrier protein (ACP)
what 2 enzymes attach substrates to the acyl carrier protein (ACP) in fatty acid synthesis?
1) acetyl transacylase
2) malonyl transacylase
what are the 4 rxns that occur in fatty acid synthesis? in order
condensation, reduction, dehydration, and reduction
what 3 things does the synthesis of palmitate require?
1) 8 acetyl coA
2) 14 NADPH
3) 7 ATP
how does ACC (acetyl coA carboxylase from fatty acid synthesis) inhibit fatty acid degredation?
ACC's product, malonyl coA, prevents the entry of the fatty acyl coA into the mitochondria by INHIBITING carnitine acyltransferase I
what is the committed step of cholesterol synthesis?
formation of mevalonate by HMG coA REDUCTASE
what cofactor is required for making cholesterol?
NADPH
what is the major site of cholesterol biosynthesis?
liver
what 2 molecules do lipoproteins transport throughout an organism?
cholesterol and TAGs
what are the 2 purposes of the protein component of a lipoprotein?
1) solubilize the lipid
2) direct the particles to specific targets
lipoproteins are classified according to ___
density
the ____ the proportion of lipid, the LESS DENSE the lipoprotein
GREATER
what is the major carrier of cholesterol in the blood?
LDLs
what carries cholesterol released into the blood BACK to the liver in a process called reverse cholesterol transport?
HDLs
chylomicrons are the LEAST dense lipoprotein, so they have the highest level of ____
lipids
cholesterol is the precursor of ___ hormones
steroid
(and vitamin D/bile salts)
vitamin D plays a key role in regulation of ___and ___ metabolism
calcium and phosphate
what is the active form of vitamin D called?
calcitrol
amino acids are obtained from the diet. when proteins are digested, ____ [stomach], ____, and _____ [small intestine] act together to release oligiopeptides and amino acids eventually
pepsin [stomach]
trypsin [small intestine]
chymotrypsin [small intestine]
what is the primary use for amino acids?
precursors for proteins or other biomolecules
are leftover amino acids stored or degraded?
degraded
what are the 2 most common aminotransferases in the process of amino acid degredation?
alanine and aspartate aminotransferase [use alpha ketoglutarate]
what happens in the urea cycle?
excess NH4+ (ammonia) is converted into urea
SAM (S-adenosylmethionine) is a ____ agent
methylating
PKU results if ?
phenylalanine hydroxylase activity is missing or deficient
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