8.1 Flashcards
ribose
is glucose without the third finger
“the RIB is missing the third bone”
hydrolysis of polysaccharides is/is not thermodynamically favorable?
YES, MONOSACCHARIDES are lower energy than polysaccharides. we GET ENERGY from breaking down polysaccharides
Glycolysis
produces ATP and NADH (2 each, net) occurs CYTOPLASM (how does NADH get into the mitochondria - glycerol phosphate shuttle / malate-acetate shuttle) does NOT require oxygen
Pyruvate dehydrogenase (PDH)
pyruvate is decarboxylated to form an acetyl group
which is attached to coenzyme A with a Sulfur
2 NADH is produced per glucose
Mg2+
required for ALL reactions involving ATP
stabilizes the negatives
NADH is produced during glycolysis when
an glyceraldehyde (GAD3P) is oxidized to COOH (-ate) in the 5th step of glycolysis
mediated by GAP-DH (glyceraldehyde dehydrogenase)
glycolysis ATP is made
when a phosphate comes OFF a substrate
is consumed when a phosphate is ADDED to a substrate
PFK
Phosphofructokinase (3rd step, phosphorylates F-6-P)
irreversible, a “COMMITTED STEP”
Note: it is allosterically down-regulated by ATP, even though a reactant is ATP
coenzyme A (CoA)
attached to acetyl unit, used to pass acetyl around (useful in fatty acid and cholesterol synthesis)
pyruvate is oxidized/reduced to form acetyl-CoA
decarboxylated = oxidized
PDH
glycerol phosphate shuttle
transports NADH from cytoplasm to the mitochondria, delivers directly to Ubiquinone (like FADH2) which generates 1.5 ATP per NADH
Flavoprotein
FAD - useful in redox
PGK and PK
In the second half of glycolysis, these KINASES take phosphates FROM the substrate and create 1 molecule of ATP
PK - 10
PGK - 7 (reversible)
pk = pyruvate kinase (think point to the right) pgk = phosphoglycerate kinase
HK, PFK
“Hong Kong is first”
they are kinases that phosphorylate in steps 1 and 3 of glycolysis - they PLACE phosphate on the substrate = LOSS OF ATP
Gluconeogenesis
We’re out of GLUCOSE AND GLYCOGEN
occurs in LIVER (and kidneys)
NONCARB precursors -> glucose
precursors include LACTATE, PYRUVATE, Krebs cycle intermediates (less Krebs = more energy), carbon skeleton of amino acids
REQUIRES NADH and ATP
Regulatory control of glycolysis
Steps 1, 3, and 10 are most IRREVERSIBLE
HK, PFK, PK
glycerol enters (in gluconeogensis)
at DHAP
phosphorylated glucose
CANNOT CROSS THE CELL MEMBRANE
dephosphorylation must occur before glucose can leave the liver
ATP and GTP are
HYDROLYZED = release energy
pyruvate carboxylase
CARBOXYLASE = ADD CARBOXYL GROUP (COOH)
1st step of gluconeogenesis
PHOSPHATASE
two useful at the END of gluconeogenesis
- Fructose-1,6-bisphosphatase
- Gluce-6-phosphatase
- TASE = REMOVE PHOSPHATES
“TASER removes criminals”
Steps of glycolysis that gain and lose ATP
Step 1: LOSE ATP Step 3: LOSE ATP Step 6: GAIN 2 NADH Step 7: GAIN 2 ATP Step 10: GAIN 2 ATP
gluconeogenesis (steps in reverse order)
Step 1: LOSE 2 ATP
Step 2: LOSE 2 GDP
Step 5 (same as step 7): LOSE 2 ATP
Step 6: LOSE 2 NADH
GNG: needs 4 ATP, 2 GTP, and 2 NADH
what intermediates can take part in GNG?
most intermediate of cellular respiration
EXCEPT ACETYL-COA
Free fatty acids CANNOT be converted to glucose
Glycerol backbone CAN
GNG is highly
ENDERGONIC
starvation mode induces…
glycogenolysis, gluconeogenesis, lipolysis, and ketogenesis
REDUCE insulin, INCREASE glucagon and epi and norepi
ELEVATED cellular AMP which ACTIVATE PFK and inhibit F-1,6-BPase
glucagon
associated with Gluconeogenesis
insulin stimulates
F-2,6-BP, which stimulates PFK, which stimulates glycolysis, inhibits F1,6-bPase and therefore reduces gluconeogenesis
what regulates?
- Enzymes that are irreversible
- Intermediates inhibit (citrate decrease PFK)
- Energy supplies
Respiration is stimulated by high ADP:ATP NAD+/NADH
inhibited by the opposite
memorize the glycolysis/gluconeogenesis table (p. 157)
Glycolysis is downregulated by ATP (“Think, the purpose of glycolysis is to MAKE ATP”)
Glycogenesis and glycogenolysis occur in
LIVER and SKELETAL MUSCLES
skeletal muscle LACKS glucose-6-phosphatase; the glucose stays phosphorylated and cannot leave the muscle cell
insulin stimulates
GLYCOLYSIS AND GLYCOGENESIS (“we have lots of sugar, let’s create more glycogen”)
decreases GNG (“we have enough glucose”
glucagon stimulates
GLYCOGENOLYSIS, when blood sugar is low, release glucose from the liver into the blood
“Break down glycogen, we need more glucose”
and GNG.
NADPH
reducing agent in ANABOLIC processes = Fatty Acid synthesis
NEUTRALIZES ROS!!
PPP primary enzyme
the first step is Glucose-6-phosphate dehydrogenase (G6PDH) = PRIMARY POINT OF REGULATION = inhibited by NADPH
G-6-P -> 6-phosphogluconate
pyruvate decarboxylase
First step in alcohol fermentation; REMOVE a CO2 from pyruvate
create Acetylaldehyde (2 carbon)
ETC is… versus substrate level phosphorylation
OXIDATIVE PHOSPHORYLATION!! NADH, FADH2
Substrate-level phosphorylation occurs with production of ATP or GTP from ADP and GDP (2 per krebs cycle)
fatty acid catabolism
an ALTERNATIVE to glycolysis/cellular respiration
fermentation products
Lactate, ethanol
DRAW the steps (ethanol is two carbon, meaning pyruvate had to be decarboxylated via PDC)
Lactate keeps the carboxylic acid, reduces the carbonyl group
Hexose monophosphate shunt
PPP
produces NADPH and Ribose-5-phosphate, and intermediates of glycolysis
Ribose-5-phosphate
5 carbon: produces nucleotides
glycogen metabolism (glycogenolysis): phosphoglucomutase (reversible), glycogen phosphorylase (adds P to glucose)
glycogen phosphoryLASE = 1 glucose is REMOVED from glycogen and phosphorylated to form Glucose-1-P
Glucose-1-P and Glucose-6-P is reversible, enzyme is phosphoglucomutase
G-6-phosphaTASE = REMOVES phosphate (phosphotase = REMOVE!)
Phosphorylase versus kinase
Phosphorylase and kinase are very similar
Phosphorylase takes from INORGANIC phosphate sources
glutamATE versus glutamic acid
ATE is the ANIONIC FORM
“acid has the H”
3PG
phosphoglyceric acid (anionic form) - this is a carboxylic acid
PGK = kinase that takes phosphate from ATP and adds it to 3PG
ENOlase
cleaves C-O bonds
Step 9 of glycolysis
removes H2O
PEP carboxykinase (PEPCK)
the 2nd step of GNG
2 GTP -> GDP
two CO2 leave
form PEP
hormonal control of Glycolysis and GNG
F-2,6-bP
up-regulates PFK, inhibits fructose-1,6-bisphosphatase
reciprocal control
insulin + (lots of glucose, low ADP), glycolysis
glucagon - (little glucose, high ATP), GNG
ATP downregulates
Glycolysis
CAC is regulated by…
ATP and NADH
step 3) isocitrate dehydrogenase (D->S)
step 4) α-ketoglutarate dehydrogenase
