Exam 2 Flashcards
most abundant biological molecules
carbohydrates
Monosaccharides
the building blocks (monomers) of carbohydrates
Polysaccharides
polymers of monosaccharides
General formula for monosaccharides
CnH2nOn
n varies from 3 to 8
Monosaccharides are classified by their
number of carbon atoms
The letters ose designate a
sugar
two classifications of monosaccharides
aldose
ketose
Aldose
a monosaccharide containing an aldehyde group
ketose
a monosaccharide containing a ketone group
carbons in an aldose are numbered using the carbonyl carbon as
carbon 1
carbons in a ketose are numbered using the carbonyl carbon as
carbon 2
Chiral carbon
a carbon that has four different groups attached to it
Chirality is used to assign monosaccharides into the
D-configuration or L-configuration
mammalian amino acids are
L-configuration
Dextrorotary
d-configuration
right or clockwise
Levorotary
L- configuration
left or counter clockwise
D-monosaccharide
a monosaccharide that has the -OH on its penultimate carbon on the right
L-monosaccharide
a monosaccharide that has the -OH on its penultimate carbon on the left
Dextrose
old name for D-glucose
D and L configurations are
enantiomers
mirror images
Diastereomers
monosaccharides that have the same number of carbons, and have a different stereoisomeric configurations but that are NOT mirror images of each other
Epimers
differ in configuration at one asymmetric chiral carbon
subset of diastereomers
Triose
sugar with 3 carbons
Tetroses
sugar with 4 carbons
pentoses
sugar with 5 carbons
hexoses
sugar with 6 carbons
aldohexose
glucose
fructose
ketohexose
galactose
aldohexose
ribose
aldopentose
The alcohol on carbon 5 can react with the aldehyde on carbon one or the ketone on carbon two to form a
hemiacetal or hemiketal respectively
ring structure of a monosaccharide
Haworth projection
In the cyclization of glucose the carbonyl carbon becomes
the anomeric carbon
the C attached to two O atoms by single bond
In a Haworth projection the hydroxyl on the anomeric carbon can exist pointing
upwards (beta conformation)
or down (alpha conformation)
Mutarotation
the spontaneous interconversion between alpha and beta conformations of a monosaccharide
Replacement of the hydrogen on the hydroxyl of an anomeric carbon by any other atom creates a
glycoside
glycosidic bond
the bond between the other atom and the hydroxyl of a glycoside
Multiple monosaccharides can be joined together via glycosidic bonds to form a
bio-polymer
Once a glycosidic bond is formed
it is locked and cannot mutarotation
Lactose
galactose and glucose
Sucrose
glucose and fructose
starches
amylose and amylopectin
amylose has what kind of linkage
alpha 1-4 linkages
cellulose has what kind of linkage
beta 1-4 cannot be digested by humans
glycogen and amylopectin have what type of structure
main chain bonds with 1-4 linkages, branches with 1-6 linkages
Amino sugars
one or more -OH are replaced by an amino group, -NH2
peptidoglycan
polysaccharides that crosslinks
found in bacterial c
How penicillin works
looks the part of the peptidoglycan and is an irreversible inhibitor of an enzyme involved in making the cell wall
Glycoproteins
carbohydrate units covalently bonded to a polypeptide chain
A and B blood have
different sugars attached to glycoproteins on the surface of red blood cells
Two pieces of metabolism
catabolism
anabolism
catabolism
oxidative process, releases energy
Anabolism
reductive process, requires reducing agents and other sources of energy, especially ATP
Starchy foods are hydrolyzed by
amylases
spontaneous reactions
energetically favorable
not requiring energy to occur
Nonspontaneous reactions
those which require energy input to occur
How do we know which direction a reaction will occur
the standard free energy change for reaction
G degree
G indicates the
spontaneity of a reaction
G<0
reaction is Exergonic
energy-releasing and spontaneous
G>0
Endergonic, which means it required energy input and is nonspontaneous
G=0
reaction is at equilibrium
does not mean equal amounts
In order to be cells they must perform lots of ___ reactions
endergonic
How does the cell come up with the energy to do all of the endergonic reactions it needs to
coupled reactions
important features of metabolism
- metabolic pathways are all connected
- pathway activity is regulated
- not every cell carries out every pathway
- each cell has a unique metabolic repertoire
- organisms may be metabolically interdependent
Glucose units are freed by glycogen breakdown via
phosphorolysis
glucose that does not become glycogen can be catabolized to two-carbon acetyl units and converted into fatty acids for storage as triaclyglyerols
What two tissues would you expect to find lots of glycogen
liver and muscle
Pyruvate, Glyceraldehyde-3-phosphate, and acetyl-CoA are major
intermediates for several pathways
oxidation
the loss of electrons
donates them
reduction
gain of electrons
recieves them
You cannot have oxidation without
reduction
Redox states of carbon ranked from highest to lowest
lipids
carbs and proteins
CO2- waste
oxidation of glucose
overall- electrons are lost from glucose and oxygen gains electrons
but this is not a direct transfer of electrons
there are intermediate electron carriers involved
NADH and FADH2
Nicotinamide adenine dinucleotide (NAD+) is a
two electron acceptor and is reduced to NADH
these electrons can then be donated to pathways that produce ATP
ATP is commonly called
the energy currency of the cell
Why does ATP hydrolysis release so much energy
ATP hydrolysis products are more stable than reactants- highly exergonic
Molecules that can serve as energy currency in the cell
ATP
Phosphocreatine
1,3-biphosphoglycerate
phosphoenolpyruvate
glucose-1-phosphate
glucose-6-phosphate
activation
the formation of a more reactive substance, a higher energy substance
causes the next reaction to be exergonic
Other ways for the cell to harvest energy
cofactors
electrochemical gradient
light-excited molecules
Regulation occurs at
steps with the largest free energy changes
Goals of glycolysis
- formation of high-energy molecules (ATP and NADH) as cellular energy sources
- the production of pyruvate for many additional ATP and NADH produced by the citric acid cycle and oxidative phosphorylation
- production of six and three carbon intermediate compounds that can be used for other cellular purposes
Each step in glucose metabolism is catalyzed by
a distinct enzyme
the rate of pathway can be controlled by
altering the activity of individual enzymes