Lecture 24 Flashcards
Is glycolysis alone efficient for extracting energy?
no, only makes 2 ATP which is only 3% of the total energy in a glucose molecule
Where is most of the energy harnessed in glycolysis?
the pyruvate molecules
How to get the most energy from glucose
fully oxidize glucose with oxygen
How to get more ATP from glucose without oxygen after glycolysis
fermentation pathways
The fate of pyruvate depends on what
kind of organism
specific cell type
availability of O2
Fermentation can create what molecules
Lactate or Ethanol, discarded as waste by cells
What does fermentation do to NADH that’s formed from glycolysis
resets it, it oxidizes it back to NAD+
Lactate fermentation involves what electron transfer
involves the direct transfer of electrons from NADH to pyruvate to create lactate
Benefit of fermentation
replenishes the supply of NAD+ so glycolysis can continue
What uses the lactate fermentation pathway
Anaerobic microbes with glucose or lactose
Dairy products to make cheese and yogurt
Oxygen-deprived muscle cells
Benefits of lactate in our bodies
can be converted back to glucose for energy
Lactate fermentation in our muscles occurs when
the oxygen is used up too fast causing the hypoxic condition and making the lactate convert into more glucose to make more ATP
Cancer cells use
lactate fermentation
The warburg effect is
even in presence of O2, cancer cells rely on anaerobic pathways to get ATP called aerobic glycolysis
uses lactate pathway by up-regulation of enzymes causing glucose intake by cancer cells to be increased by the GLUT1 transporter
this allows tumors a growth advantage over normal tissue
Lactate fermentation steps
Glucose -> pyruvate + NADH + LDH -> lactate
LDH in lactate fermentation
Lactate dehydrogenase
Alcoholic fermentation steps
Glucose -> pyruvate + H + PDC ->acetaldehyde + NADH + ADH -> ethanol
ADH in ethanol fermentation is
alcohol dehydrogenase
PDC in ethanol fermentation is
Pyruvate decarboxylase
Different way to enter glycolysis without glucose
polysaccharides like starch (plants) or glycogen (animals)
Entering glycolysis by starch or glycogen skips
the first ATP-dependent step (splitting into 2 G3P molecules), but still causes 2 net ATP bc ATP is used when forming starch or glycogen
Can ezyme reactions be reversed?
If no energy is required for the reaction
Why can some enzymatic reactions not run in reverse
because if the reaction required converting ATP, reversing is unlikely without other enzymes (different from the ones used to go in the forward direction)
Why would you want to reverse glycolysis?
if glucose is running low
Gluconeogenesis is
reversed glycolysis to make glucose
Gluconeogenesis occurs by
different enzymes than glycolysis
Where does gluconeogenesis mainly occur
the liver to support body
Are most biosynthetic pathways a simple reverse of catabolism?
No
What reaction can run in reverse?
Ethanol fermentation, by oxidizing the ethanol
this happens when we drink alcohol bc too much ethanol is toxic
Where does pyruvate oxidation occur
cytoplasm into the mitochondrial matrix
Pyruvate oxidation substrate
2 pyruvate
Pyruvate oxidation products
2 acetyl CoA
2 NADH (6ATP)
2 CO2
