Biochem Lec 16-17 Flashcards
what is structural formula for all monosaccharides and what is simplest monosaccharide
all monosaccharide share same chemical formula of CH2O as base and simplest monosaccharide is the triose which has structural formula of CH2O and is either aldose or ketose depending on functional group attached
how are carbons of carbohydrates numbered
using numbers like C-1 for carbon in carboxyl group and one after will be C-2, and so on
what is the configuration assigned to carbohydrates
it is either L or D which is assigned to asymmetric and chiral carbon that is furthest away from carbonyl and knowing the number of chiral carbons, you can know the possible number of different isomeres using 2^x
why do sugars take on ring structure and how do they configure to such structure
ring structures are more stable as they are lowest in energy and to go from chain to ring, aldehyde and hydroxyl groups interact
what bonds allow for carbohydrates cyclization
the aldehyde and ketone carbonyl will undergo nucleophilic attack by hydroxyl groups to form either a 5-member furan ring or 6-member pyran ring
the new bond holding the ring will be either hemiacetal if it is aldehyde derivative or hemiketal if ketone derivative
how can we detect chirality of ring strucured carbohydrates
there is anomeric carbon that is chiral as it cna be alpha or beta anomer and that cna be detected by mutorotation where there is change in optical rotation of polarized light
B-anomer are higher in existance, 63%, as they are more favorable due to positioning of hydroxyl group and alpha-anomers exist 36% of the time while linear structure exist 1% of the time and dueing that time it is interacting with other molecules or changing into ring structure.
how are carbohydrates modified
sugars can be phosphorylated, methylated, or they can have the hydroxyl and carbonyl removed
these modifications will increase in complexity of carbohydrates structure
Why are different positions important
differences in L and D cause differences in order/position of functional groups which impact the interactions
how are carbohydrates chain made
by a glycosidic bond which is through a condensation reaction, so H2O is lost
what are other types of glycosidic bonds
that would be intermolecular bonds formation between hydroxyl on amine and reactive anomeric carbon on other molecule and these glycoproteins may be O-linked or N-linked
what are the monosaccharides involved in the following complex carbohydrates:
1- amylose
2- lactose
3- amylopectin
4-sucrose
1- two glucose attached by alpha-1,4 glycosidic bond
2- galactose and glucose attached by beta-1,4 glycosidic bond
3- amylopectin being chain of glucose attached by alpha-1,6 glycosidic bond at branch points
4- glucose bonded to fructose through alpha-1,2 glycosidic bond
what are polysaccharides
they are chains of polymers important for energy storage, cellular structure, and recognition
they are also known as glycans as they can be homopolymer due to having same monosaccharide, glycogens, or a heteropolymer due to having different monosaccharide, glycoproteins
what are characteristic of carbohydrate starch
can be amylose, amylopectin, and alpha amylose
amylose consist of unbranched alpha 1-4 linkages
amylopectin has linear glucose chains joined by alpha 1-4 linkages abd also alpha 1-6 linkages at branch points every 30 glucose units
alpha amylose is secreted from salivary glands and pancreas and cleaves random locations along chain to give maltose and matotriose
what are charcteristics of cellulose taht make it unqiue
it is teh most abundant organic compound and serve structural role in plants but it haves unbranched chaisn of glucose linked by beta 1-4 linkages with many hydrogen bonds and cellobiose is disaccharide glucose linked by beta 1-4 linkages
how is glycogen important and what makes it important
it is storage for long branched chains of glucose and contains branch points every 8-12 glucose units
it also has a dimer of glycogen at center and when glucose is needed or not, it will be added or removed from nonreducing ends
can cells use any type of carbohydrate for fuel
no, cells can only use monosaccahrides as source of energy so lactase, maltase, and sucrase will help cleave associated dissacharides
why is sugar sequencing more complicated
because there are many different isomeres as polysaccharides differ in composition, connectivity, and configuration while proteins were less complicated as they are made of 4 nucleotides
glucose is important for fuel and enrgy, but how does it move and enters different parts of the body
through glucose transporters and since glucose is polar molecule, it cannot diffuse through lipid bilayer and these transporters also move glucose due to concentration gradient
what are some of the key types of different glucose transporters
sodium glucose co-transporters are secondary active transporter so they move glucose from low to high concentration
glucose trasnporters- facilitated diffusion so move glucose from high to low concnetration, known as GLUT and GLUT 4 is insulin dependant
fructose transporters- also afcilitated diffusion
why would someone who has diabetes type I and takes more insulin than needed end up with hypoglycemia
that is because GLUT 4 transporters, which are insulin dependant, will keep on moving glucose to muscle and adipose cells which will decrease glucose for other cells like RBC which causes low glucose levels in the blood and lead to hypoglycemia
what is true about glycolysis which involves glucose and ATP
glucose and ATP availibilty both regulate glycolysis
what is an overview on carbohydrate metabolism and hormone involvment
in anabolic state, insluin will increase glucose utilization as the glycolitic pathway is important for ATP production from simple monosaccahrides and the excess glucose will be stored as glycogen in muscle or liver cells by glycogen synthase when ATP is high
in catabolic state, epinephrine and glucagon are the hormones that signal for glycogen breakdown and lead to ATP production or releasing glucose from liver
overview of glycolysis
it is a pathway highly utilized by cells requiring immediate soyrce of energy such as RBC and cells in cornea for example
it is a 10 step catabolic pathway found in cytoplasm and it starts with glucose, a 6C molecule
can be divided into two stages:
1- the preperation and consist of the first 5 steps where 2 ATP are used to prepare this glucose molecule for breakdown and generate 2 GAPs, 2 of the 3C molecules
2- consist of last steps, from 6 to 10, it is where the 2 pyruvates are produced and so will 2 NADH and 4 ATP also be reduced
so end up with 2 ATP as the net from glycolysis
then the two pyrivates gets oxidized in mitochondria and generate more NADH when oxygen is available
how can galalactose and fructose, also monosaccahrides be used in glycolysis
they can be converted into intermediates of the glycolysis pathway and end up being used in same way, generate teh 2 ATP
fructose gets converted into DHAP and glyceraldehyde-3-phosphate
galactose gets converted into glucose-6-phsophate
how can glycolysis be regulated
there are three steps in the glycolysis pathway that will allwo for regulating the process, that will be step 1+3+10
these three steps are irreversible
overview on how glycolysis is regulated
it si regulated using teh enzymes that cleave those reactions by active site, allosteric site, or by covalent modifications
step 1= hexokinase gets inhibited by build up of its product known as glucose-6-phosphate as it binds the allosteric site and cause confomrtaional change
step 3= phosphofructokinase 1 (PFK-1) gets inhibited by amount of ATP or citrate and will be activated by AMP, ADP ir fructose-3,6-bisphosphate
step 10= where pyruvate kinase gets inhibited by phosphorylation and other allosteric regulators
how does hexokinase end up binding and giving glucose-6-phosphate from first step of glycolysis
glucose gets phosphorylated using ATP by hexokinase where the ATP and gamnesium ions bind the enzyme’s lobe away from glucose’s binding site and these moelcules, ATP and magnesium, cause conformtaional change once the subtrate, glucose, bind by closing in the enzyme around glucose and then a C6 hydroxyl attack will produce glucose-6-phosphate
this step ends up trapping glucose in cell as GLUT transporters cannot bind glucose-6-phosphate and only liver cells have ability to reverse this step
by doing thise, the cell ensure that glucose gets used to generate energy by glycolysis, get stored as glycogen if in liver or muscle cell, or to end up used to make new molecules
how is PFK-1 regulated and how does this affect glycolysis
PKF-1 is the enzyme ctaalyzing the third step in glycolysis and that is also teh second ATP requiring step as the PFK-1 will take phosphate group from ATP and give it to C1 hydroxyl of F-6-P
but this enzyme can also be allosterically regulated as it has two sites, the active site for F-6-P and the allosteric site which if bound by ATP/citrate will inhibit enzyme, but if bound by AMP/ADP then it activate enzyme
significance of pyruvate kinase and its importance for last step of glycolysis
pyruvate kinase is last enzyme for last step of glycolysis and it is inhibited by phosphorylation as phosphorylated pyruvate enzyme can be due to having alanine/acetyl CoA/and high level of ATP, but active pyruvate kinase is one that is dephosphorylated as that means there is low ATP and high AMP and high fructose-1,6-bisphosphate
how is glycogen synthesized
when ATP is high and glycolysis slows down, excess glucose gets stored as glycogen by glycogen synthase
the enzyme can only add UDP-glucose as it create new alpha 1-4 bond on the nonreducing ends of glycogen
so glucose will still get phosphorylated by hexokinase, but glucose-6-phosphate wull be isomerized by phosphoglucomutase to form glucose-1-phosphate and then another enzyme, UDP-glucose pyerophorphorylase will use ATP and activate glucose-1-phosphate and make that UDP-glucose
this pathway is activated by insulin signaling which activate glycogen synthase using dephosphorylation
how does phosphoglucomutase reaction occur and how does metabolic state affect it
it will make glucose-6-phosphate from glucose , but will form an inetrmediate glucose-1,6-bisphosphate and then turn it to glucose-1-phosphate ]
this is nonenergy reaction and will go either way depending on metabolic state
will inhibit glycolyssi adn take glucose and phosphorylate it when there is insulin signallying due to being in anabolic phase
what is the overall reaction for glycogen synthase and the free energy change of reaction
the process consist of two steps:
1- G1P+UTP–> UDP+PPi G= 0
2- PPi–>2Pi G= -19 UDP+Glycogen(n) –>Glycogen(n+1)+UDP
this shows how the resulting diphsosphate are two unstable so they end up breaking into 2 seperate phosphates
what is glycogenolysis and when does it occur
this is during epinephrine and glucagon signalling= catabolic phase
this lead to phosphorylation and activating glycogen phosphorylase and inactivation glycogen synthase by phosphorylation as well
the pathway is glycogenolysis one where there is phosphorolysis reaction by using phosphate to release the glucose-1-phosphate from nonreducing ends and theb convert it to glucose-6-phosphate by phosphoglucomutase since glucose-1-phosphate cannot be used directly
