Carbohydrate structure and glycolysis Flashcards
which organs / tissues need a constant supply of glucose (need glucose at both high and low blood glucose levels)?
brain (neurons) & RBCs (erythrocytes)
stereoisomers have …
same chemical formula, different 3D structure
of isomers for a molecule =
2^ (# C atoms - 2)
enantiomers are …
mirror images of each other
anomers are specific to …
ring structures of monosaccharides
L-enantiomer has the OH group …
on the left
D-enantiomer has the OH group …
on the right
epimers have …
same chemical formula AND same 3D structure, BUT asymmetric around one carbon
the 4 most important disaccharides
lactose
sucrose
maltose
isomaltose
glycosidic bond is between …
OH group on anomeric carbon (on monosaccharide 1)
free OH group (on monosaccharide 2)
lactose
galactose beta(1 - 4) glucose
sucrose
glucose alpha(1 - 2) fructose
maltose
glucose alpha(1 - 4) glucose
isomaltose
glucose alpha(1 - 6) glucose
GLUT transporters are …
monosaccharide transporters
3 sources of glucose for glycolysis
glycogenolysis (during exercise in muscle)
dietary intake (during FED state)
glycogenolysis gluconeogenesis (during fasting / starvation)
what are 3 polysaccharides of glucose?
glycogen
starch
cellulose
glycogen structure
highly branched
starch structure (contains 2 components) and what does it supply humans?
amylose
amylopectin
dietary fuel from plants
cellulose (another name, origin, structure, behavior in humans)
aka fiber
from plants
UNbranched
not digestible, but has health benefits
draw GLUT transporter concept map out
draw glycolysis overview on whiteboard
what is the first irreversible step in glycolysis? what else is true about it?
glucose –(hexo-/glucokinase)–>
glucose-6P
committed, regulated step
NOT key step bc it’s not unique
what kind of rxn is glucose-6P –> fructose-6P?
reversible,
not regulated
what is the second irreversible step in glycolysis? what else is true about it?
fructose-6P –(PFK-1)–>
fructose-1,6-BP
- 1 ATP
KEY and regulated step
what is the last rxn in glycolysis?
PEP –(pyruvate kinase)–> pyruvate
+ 2 ATP / per glucose
regulated step
irreversible rxn =
regulated
reversible rxn =
NOT regulated
what are the 3 phases of glycolysis?
investment
splitting
energy generation
where does pyruvate go after glycolysis?
to mitochondria for TCA cycle
where does 2 NADH produced go after glycolysis?
to mitochondria for ETC
net production of glycolysis / per glucose
+ 2 pyruvate
- 2 ATP
+ 2 NADH
+ 4 ATP
what is the first step of glycolysis in fasting / starvation?
what tissue(s) does this occur?
glucose / fructose / galactose
|
{through GLUT 1 or GLUT 3}
|
(hexokinase)
|
V
glucose-6P
[- 1 ATP]
all tissues
what is the first step of glycolysis in fed state?
what tissue(s) does this occur?
glucose
|
{through GLUT 2}
|
(glucokinase)
|
V
glucose-6P
[- 1 ATP]
only liver and pancreas
draw hexokinase vs glucokinase comparison list
what does Vmax mean for an enzyme?
capacity / amount of binding that the enzyme can handle
what does Km mean for an enzyme?
the concentration of substrate required for enzyme to reach half of its Vmax
what does a low Km indicate about binding affinity?
HIGH affinity for its substrate, bc it gets saturated quickly
what does a high Km indicate about binding affinity?
LOW affinity for its substrate, bc it does not get saturated quickly
what are the 3 stages of metabolism?
- digestion & absorption in GI tract
- glycolysis
- oxidation of Acetyl-CoA in TCA
what are the products of anaerobic glycolysis? when does anaerobic glycolysis occur?
+ 2 lactate / per glucose
+2 ATP
absence of oxygen; in cells without mitochondria
how does NADH get to the ETC in the liver / heart?
malate-aspartate shuttle takes e- from cyto. NADH, takes it into mito., converts it to NADH
recycles cyto. NAD+ into cytoplasmic pool
cyto. NADH -> mito. NADH
how does NADH get to the ETC in the brain / muscle?
glycerol-3P shuttle takes e- from cyto. NADH, takes it into mito., converts it to FADH2
recycles cyto. NAD+ into cytoplasmic pool
cyto. NADH -> mito. FADH2
arsenate can cause poisoning by inhibiting what rxn in glycolysis?
first rxn in energy production phase
glyceraldehyde-3P <–> 1,3-BP
what can inhibit the rxn that produces PEP in glycolysis?
fluoride ions (ex. toothpaste)
what 3 enzymes are alloesterically regulated in glycolysis?
hexokinase
PFK-1
pyruvate kinase
what is hexokinase allosterically inhibited by?
glucose-6P
what is PFK-1 allosterically stimulated by during FED state?
AMP
fructose-2,6-BP (only in liver)
what is PFK-1 allosterically inhibited by during fasting / starvation state?
ATP
citrate
fructose-2,6-BPase (only in liver)
what is pyruvate kinase allosterically stimulated by?
fructose-1,6-BP
what is pyruvate kinase allosterically inhibited by?
ATP
where does hormonal regulation of glycolysis occur?
only in the liver
what is pyruvate kinase hormonally inactivated by? what does this prevent? where does PEP go now? in what state does this occur?
glucagon signaling
PK inhibition prevents PEP from being converted to pyruvate
PEP goes to gluconeogenesis instead
in fasting / starvation state
why is glycolysis only on during fed state?
bc in fed state, liver is a glucose consumer
+
liver wants to store glucose
why is glycolysis off during fasting / starvation states?
bc in fasting / starvation, liver is a glucose producer for all other cells in body via glycogenolysis / gluconeogenesis
if glycolysis is off then all glucose generated would just be wasted
what is pyruvate kinase deficiency? what happens in glycolysis if it is severe?
mutation in enzyme encoding pyruvate kinase
0 PK activity = ATP produced during glycolysis is half of normal amount
why can pyruvate kinase deficiency by catastrophic for RBCs?
RBCs only get ATP from glycolysis
RBCs use ATP to maintain membrane shape
without enough ATP -> become echinocytes (spikey cells)
echinocytes are digested by body = causes HEMOLYTIC ANEMIA
