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25 Cards in this Set
- Front
- Back
- 3rd side (hint)
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In what types of cells does glycolysis occur?
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All cell types
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Where in the cell does glycolysis occur?
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cytosol
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Does glycolysis require oxygen? What does that tell us about how life arose?
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-No
-Life arose without oxygen, glycolysis is an ancient pathway |
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Describe transport of glucose across intestinal epithelial wall into the blood
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-active transport into liver epithelial cells, using Na/glucose cotransporter
-because active transport/unfavorable to transport glucose, transport is coupled to Na via [Na] gradient -then into blood via passive transport by GLUT2 |
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Describe glucose uptake by most cells
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-passive b/c [glucose] in cell is lower than outside cell
-uses GLUT1 (glucose transporter) because glucose is hydrophilic whereas cell membrane is hydrophobic -reversible |
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How is energy conserved in glycolysis?
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Stored in ATP, making ATP
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What is the oxidizing agent in glycolysis?
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NAD+
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What is the first stet of glycolysis? Why is it important?
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-hexokinase phosphorylates glucose to G6P
-phosphorylation tags glucose for glycolysis; traps G6P in cell b/c GLUT1 can't transport G6P; destabilizes glucose for cleavage; energy storage b/c P will be used to phos ADP later -irreversible |
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Why is the first step irreversible (why is delta G so negative)?
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[ATP] inside of cell is really high which drives the reaction
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How are unfavorable reactions driven in a cell?
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concentration of reactants to products
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Describe the difference between the hexokinase isozymes found in most tissues and the isozyme found only in the liver
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In most tissues
-traps glucose in cells -low Km -nonspecific, can bind to diff sugars |
In liver only
-regulates glucose in blood, so removes glucose from blood -high Km -specifically binds glucose -cooperative effect (enzyme activity increases with increasing [glucose] |
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In what step is glucose committed to glycolysis?
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-step 3, phosphofructokinase-1 phosphorylates fructose 6-phosphate to make fructose 1,6-bisphosphate
-irreversible -Fructose 6-phosphate can only go into glycolysis |
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How does [ATP] affect activity of PFK-1?
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high [ATP] will decrease PFK-1 because cell already has enough energry, doesn't need to activate PFK (@ committed step) to break down glucose
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low [ATP] will stimulate activity of PFK-1
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What are the 2 active amino acids involved in aldolase?
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Lysine and glutamate
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NADH resulting from oxidation via glyceraldehyde 3-phosphate is used where?
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Citric acid cycle
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Compare 1,3-bisphosphoglycerate to ATP
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BPG has a much higher phosphate bond than ATP
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If BPG is so high in energy, how are cells able to generate it?
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BPG produced by glyceraldehyde 3-phosphate dehydrogenase can happen because this oxidation reaction is coupled with reducing NAD+ to NADH form
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What are the 2 active enzymes of glyceraldehyde 3-phosphate dehydrogenase?
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histidine and cysteine
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What is the reaction performed by phosphoglycerate mutase and why is it so unfavorable?
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3-phosphoglycerate --> 2-phosphoglycerate
-so unfavorable because phosphate group moved closer to negative charges |
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How does phosphoglycerate mutase transfer phosphate group?
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never removes phospho-ester bond
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Which form of pyruvate is initially formed?
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enol
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How does step 10 (pyruvate kinase) drive step 9 (enolase)?
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PEP is the produce of enolase and it is constantly in low concentration in the cell because it is quickly dephosphorylated to make ATP in step 10
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Why do cancer cells have such high rates of glycolysis?
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As cancer cells grow, don't have as many blood vessels as want, so works in hypoxic (low oxygen) conditions; glycolysis doesn't require oxygen and gives cancer cells energy source, so cancer cells undergo lots of glycolysis
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Describe the difference in products made from NADPH and NADH
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NADPH: used in biosynthesis of RNA, DNA, enzyme cofactors
NADH: ATP |
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What are the 3 irreversible steps of glycolysis?
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step 1: hexokinase
Step 3: phosphofructokinase-1 Step 10: pyruvate kinase |
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