Lecture 5 - Carbohydrates Part 2

Question 1

Which tissue requires a lot of energy and therefore has high glucose consumption?

Answer 1

neural retina (highest aerobic glucose consumption of any tissue)

Question 2

What outcome has an impaired glucose metabolism in rods?

Answer 2

retinal degeneration

Question 3

What is neuroprotection?

Answer 3

upregulation of glycolysis in photoreceptors

Question 4

What process is essential for normal rod function and prevents cone degeneration in retinitis pigmentosa?

Answer 4

aerobic glycolyiss

Question 5

What do photoreceptors deliver lactate to?

Answer 5

RPE and Muller cells (MG)

Question 6

What are the 4 processes in glucose metabolism (cellular respiration)?

Answer 6

1. glycolysis (glucose –> pyruvate)
2. pyruvate oxiation (pyruvate –> acetyl CoA)
3. citric acid cycle
4. oxidative phosphorylation

Question 7

Which of the processes in glucose metabolism produce ATP?

Answer 7

glycolysis, TCA, oxidative phosphoyrlation

Question 8

What is glycolysis and where does it take place in a cell?

Answer 8

breakdown of glucose
produces net 2 ATP and 2 pyruvate
occurs in cytosol

Question 9

Does glycolysis require oxygen?

Answer 9

no

Question 10

What is the input and output of glycolysis?

Answer 10

input: 1 glucose, 2 ATP, 2 NAD+
output: 2 pyruvate, 4 ATP (net 2), 2 NADH

Question 11

Which organ’s cells regulate glycolysis?

Answer 11

liver and skeletal lmuscle

Question 12

What are the start substrates and end products of the investment phase of glycolysis? Which additional molecules are used/gained?

Answer 12

Start: 1 glucose
End: 2 G3P
Used: 2 ATP
Gained: nothing

Question 13

What are the start substrate and end product of the payoff phase of glycolysis? Which additional molecules are used or gained?

Answer 13

Start: 2 G3P
End: 2 pyruvates
Gained: 4 ATP, 2 NADH

Question 14

In which 4 molecules can pyruvate be converted under aerobic and anaerobic conditions?

Answer 14

acetyl CoA, lactate, ethanol, or back to glucose

Question 15

What is gluconeogenesis (definition) and what is a synonym for its name?

Answer 15

synthesis of new glucose from non-carbohydrate sources
other name: endogenous glucose production (EGP)

Question 16

In which organ does gluconeogenesis mainly happen and when does it happen?

Answer 16

provides glucose when dietary intake is not enough
mainly in liver

Question 17

Which product is generated in gluconeogenesis but not produced in glycolysis?

Answer 17

oxaloacetate

Question 18

Which substrates can be utilized in gluconeogenesis?

Answer 18

pyruvate

Question 19

What concentration of acetyl CoA and ATP is needed for gluconeogenesis to proceed?

Answer 19

low [acetyl CoA]
high [ATP]

Question 20

Under which oxygen condition does lactate fermentation occur?

Answer 20

no oxygen

Question 21

What kind of process is gluconeogenesis?

Answer 21

ubitquitous process

Question 22

What is gluconeogenesis present in?

Answer 22

plants, animals, fungi, bacteria

Question 23

Which molecules are converted in which moleculels in the Cori cycle (lactic acid cycle) and in which organs does it happen in?

Answer 23

in skeletal muscles
pyruvate reduced to form lactate
NADH oxidized to form NAD+

Question 24

How can the body use lactate?

Answer 24

convert lactate back into pyruvate through gluconeogenesis in liver

Question 25

What is the second step in glucose metabolism?

Answer 25

pyruvate oxidation (pyruvate --> acetyl CoA)

Question 26

What is required and what is generated during pyruvate oxidation?

Answer 26

requires transport of pyruvate from cytosol to mitochondrion IN: pyruvate, NAD+, coenzyme A OUT: CO2, NADH, acetyl CoA

Question 27

Acetyl CoA can be obtained from which biomolecule components?

Answer 27

pyruvate, long chain fatty acids, degeneration of fatty acids

Question 28

Where in a cell does pyruvate oxidation take place?

Answer 28

mitochondrial matrix

Question 29

What is the 3rd event in glucose metabolism, where does it take place in a cell, and what is its major purpose?

Answer 29

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

Question 30

What are the 2 start substrates in TCA cycle and what do they form?

Answer 30

Start: acetate (acetyl CoA) and H2O NAD+ --> NADH release CO2

Question 31

Glutamate can be converted into which compound that's part of the TCA cycle?

Answer 31

alpha ketoglutarate (signals amino acids to feed in)

Question 32

What is the 4th event in glucose metabolism, which 2 parts does it contain, and where in a cell does it take place?

Answer 32

oxidative phosphorylation - use enzymes to oxidize nutrients and produce ATP 1. electron transport 2. chemiosmosis in mitochondria

Question 33

What is generated in the last event of glucose metabolism and by which enzyme?

Answer 33

24-28 ATP from 1 glucose molecule

Question 34

What is used to make ATP in TCA cycle?

Answer 34

3 NADH 1 FADH2 1 GTP

Question 35

What is an alternative pathway to glycolysis and does it require or produce any energy?

Answer 35

pentose phosphate pathway (PPP) no ATP needed or made parallel to glycolysis takes place in cytosol important in RBCs (erythrocytes) - don't have mitochondria

Question 36

Which moleculels does the PPP generate?

Answer 36

produces sugars that make up DNA and RNA

Question 37

What happens in glycogenesis (definition)?

Answer 37

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

Question 38

Which enzyme functions as an anchor for the initial molecule?

Answer 38

glycogenin

Question 39

What is the name of the units that are added to the enzyme anchor?

Answer 39

UDP glucose molecules

Question 40

What is the Warburg effect?

Answer 40

increase in rate of glucose intake and preferential production of lactate, even in presence of oxygen seen in photoreceptors and rapidly dividing cancer cells