Chapter 14 Flashcards
Many organisms use glucose to generate what things?
- amino acids (by breaking glucose down into pyruvate then use pyruvate)
- membrane lipids
- nucleotides in DNA and RNA
- cofactors necessary for metabolism
Gluconeogenesis is the synthesis of glucose from simpler precursors like ______ and ______
pyruvate and lactate
What pathway is an alternative pathway for glucose oxidation?
the pentose phosphate pathway
Glucose can be efficiently stored in what form?
Polymeric (starch, glycogen)
What two things can happen to pyruvate after glycolysis?
- pyruvate can be further aerobically oxidized
- pyruvate can be used as a precursor in biosynthesis
How many ATP molecules are consumed in the preparatory phase of Glycolysis (steps 1-5)
2 molecules of ATP
In the payoff phase of glycolysis, how many pyruvate molecules are created for each molecule of glucose
2 pyruvate per 1 glucose
What are the reactants for glycolysis?
Glucose + 2(NAD+) + 2ADP + 2Pi
What are the products of glycolysis?
2 pyruvate + 2NADH + 2H +2ATP + 2H20
The conversion of glucose to pyruvate is (endergonic or exergonic) ?
exergonic = favorable
delta G = -146jk/mol
Under standard cellular conditions, glycolysis is (reversible or irreversible) ?
irreversible
energy stored in pyruvate can be extracted in which two processes?
aerobic and anaerobic processes
Aerobic: oxidative reactions in Krebs, oxidative phosphorylation
Anaerobic: reduction to lactate, reduction to ethanol
What is the purpose of the first step in glycolysis?
To trap glucose inside the cell & to lower intracellular glucose levels so that further glucose uptake can occur
Which steps in glycolysis require ATP?
steps 1 and 3
Which steps in glycolysis PRODUCT ATP?
steps 7 and 10 (substrate level phosphorylations)
Which steps in glycolysis are carried out by isomerases?
steps 2 and 5
What are the functions of phosphoryl groups in glycolysis?
- to prevent glycolytic intermediates from leaving the cell
- to serve as essential components in the enzymatic conservation of metabolic energy
- to lower the activation energy and to increase the specificity of the enzymatic reactions
In what step of glycolysis does an aldose isomerize into a ketose via an enediol intermediate?
Step 2- Isomerization of glucose (an aldose) to fructose (a ketose) via enzyme phosphohexose isomerase
What is the mechanism of the phosphohexose isomerase mechanism in the isomerization of glucose to fructose?
General acid-base catalysis
What is the first committed step of glycolysis?
Step 3 - The Second Phosphorylation of fructose-6-phosphate to fructose-1,6-bisphosphate
**fructose 1,6-bisphosphate is committed to becoming pyruvate
**irreversible reaction
What is the least energetically favorable step of the preparatory phase?
Step 4 - Aldol cleavage
In step 6, DHAP must be oxidized to _____ via triose phosphate isomerase
DHAP OXIDIZED TO GAP
What step completes the preparatory phase of glycolysis?
step 5- triose phosphate isomerization
Enzymes that transfer phosphate groups between ATP and various substrates
Kinases
Define substrate-level phosphorylation
The formation of ATP by phosphoryl group transfer from a substrate
Why does glycolysis need to be regulated?
To ensure proper use of nutrients and to ensure ATP is only produced when it is needed
What two molecules is glucose cleaved from?
Glycogen and Starch
In step 6 of glycolysis, each molecule of glyceraldehyde-3-phosphate is oxidized and phosphorylated by ________ to form 1,3 Bisphosphoglycerate
Inorganic Phosphate (Pi)