Lecture 5 - Carbohydrates Part 2 Flashcards
Which tissue requires a lot of energy and therefore has high glucose consumption?
neural retina (highest aerobic glucose consumption of any tissue)
What outcome has an impaired glucose metabolism in rods?
retinal degeneration
What is neuroprotection?
upregulation of glycolysis in photoreceptors
What process is essential for normal rod function and prevents cone degeneration in retinitis pigmentosa?
aerobic glycolyiss
What do photoreceptors deliver lactate to?
RPE and Muller cells (MG)
What are the 4 processes in glucose metabolism (cellular respiration)?
- glycolysis (glucose –> pyruvate)
- pyruvate oxiation (pyruvate –> acetyl CoA)
- citric acid cycle
- oxidative phosphorylation
Which of the processes in glucose metabolism produce ATP?
glycolysis, TCA, oxidative phosphoyrlation
What is glycolysis and where does it take place in a cell?
breakdown of glucose
produces net 2 ATP and 2 pyruvate
occurs in cytosol
Does glycolysis require oxygen?
no
What is the input and output of glycolysis?
input: 1 glucose, 2 ATP, 2 NAD+
output: 2 pyruvate, 4 ATP (net 2), 2 NADH
Which organ’s cells regulate glycolysis?
liver and skeletal lmuscle
What are the start substrates and end products of the investment phase of glycolysis? Which additional molecules are used/gained?
Start: 1 glucose
End: 2 G3P
Used: 2 ATP
Gained: nothing
What are the start substrate and end product of the payoff phase of glycolysis? Which additional molecules are used or gained?
Start: 2 G3P
End: 2 pyruvates
Gained: 4 ATP, 2 NADH
In which 4 molecules can pyruvate be converted under aerobic and anaerobic conditions?
acetyl CoA, lactate, ethanol, or back to glucose
What is gluconeogenesis (definition) and what is a synonym for its name?
synthesis of new glucose from non-carbohydrate sources
other name: endogenous glucose production (EGP)
In which organ does gluconeogenesis mainly happen and when does it happen?
provides glucose when dietary intake is not enough
mainly in liver
Which product is generated in gluconeogenesis but not produced in glycolysis?
oxaloacetate
Which substrates can be utilized in gluconeogenesis?
pyruvate
What concentration of acetyl CoA and ATP is needed for gluconeogenesis to proceed?
low [acetyl CoA]
high [ATP]
Under which oxygen condition does lactate fermentation occur?
no oxygen
What kind of process is gluconeogenesis?
ubitquitous process
What is gluconeogenesis present in?
plants, animals, fungi, bacteria
Which molecules are converted in which moleculels in the Cori cycle (lactic acid cycle) and in which organs does it happen in?
in skeletal muscles
pyruvate reduced to form lactate
NADH oxidized to form NAD+
How can the body use lactate?
convert lactate back into pyruvate through gluconeogenesis in liver
What is the second step in glucose metabolism?
pyruvate oxidation (pyruvate –> acetyl CoA)
What is required and what is generated during pyruvate oxidation?
requires transport of pyruvate from cytosol to mitochondrion
IN: pyruvate, NAD+, coenzyme A
OUT: CO2, NADH, acetyl CoA
Acetyl CoA can be obtained from which biomolecule components?
pyruvate, long chain fatty acids, degeneration of fatty acids
Where in a cell does pyruvate oxidation take place?
mitochondrial matrix
What is the 3rd event in glucose metabolism, where does it take place in a cell, and what is its major purpose?
citric acid cycle/TCA/Krebs
major energy producing pathway, series of chemical reactions to release stored energy
in mitochondria (eukaryotes)
electrons transferred from NAD+ to make NADH –> used to make ATP
What are the 2 start substrates in TCA cycle and what do they form?
Start: acetate (acetyl CoA) and H2O
NAD+ –> NADH
release CO2
Glutamate can be converted into which compound that’s part of the TCA cycle?
alpha ketoglutarate (signals amino acids to feed in)
What is the 4th event in glucose metabolism, which 2 parts does it contain, and where in a cell does it take place?
oxidative phosphorylation - use enzymes to oxidize nutrients and produce ATP
1. electron transport
2. chemiosmosis
in mitochondria
What is generated in the last event of glucose metabolism and by which enzyme?
24-28 ATP from 1 glucose molecule
What is used to make ATP in TCA cycle?
3 NADH
1 FADH2
1 GTP
What is an alternative pathway to glycolysis and does it require or produce any energy?
pentose phosphate pathway (PPP)
no ATP needed or made
parallel to glycolysis
takes place in cytosol
important in RBCs (erythrocytes) - don’t have mitochondria
Which moleculels does the PPP generate?
produces sugars that make up DNA and RNA
What happens in glycogenesis (definition)?
glycogen synthesis
glucose moleculels added to chains of glycogen for storage
activated during rest periods following Cori cycle in liver
also activated by insulin in response to high glucose levels
Which enzyme functions as an anchor for the initial molecule?
glycogenin
What is the name of the units that are added to the enzyme anchor?
UDP glucose molecules
What is the Warburg effect?
increase in rate of glucose intake and preferential production of lactate, even in presence of oxygen
seen in photoreceptors and rapidly dividing cancer cells
