Glycolysis Flashcards by Mia McCombs

Glycolysis is what kind of pathway?

a catabolic pathway for monosaccharides

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In what types of cells is glycolysis?

an ancient metabolic pathway that exists in almost all types of cells

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Where in a cell does glycolysis occur?

in the cytosol

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What does glycolysis oxidize and why?

oxidizes monosaccharides to gather energy and store the energy in ATP and NADH

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The oxidation in glycolysis doesn’t require ____. Instead in step 6, Glyceraldehyde 3-phosphate is oxidized by ___.

The oxidation in glycolysis doesn’t require O2. Instead in step 6, Glyceraldehyde 3-phosphate is oxidized by NAD+.

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How many steps and stages are in glycolysis?

10 consecutive steps
2 stages

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What is stage one of glycolysis?

trapping and preparation stage

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Explain stage one of glycolysis the trapping and preparation stage.

for one molecule of glucose, two molecules of ATP are consumed in order to trap glucose within the cell and prepare for the breaking of glucose ring

two kinases are involved, they consume 2x ATP to break a C-C bond and 2x GA-3P are generated from 1x glucose

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What is stage two of glycolysis?

ATP harvest stage

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Explain stage two of glycolysis the ATP harvest stage.

2x GA-3P generate 4x ATP

the oxidation of aldehydes (GA-3P) into carboxylic acids (pyruvate) releases energy

two kinases use the energy to phosphorylate ADP into ATP

the energy is transferred to NAD+ in form of high energy electrons (4x) in NADH

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Glycolysis connects what?

connects energy generating pathways with biosynthesis pathways

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What are the two major goals of glycolysis?

Goal #1: bioenergetics
- oxidizes C-C/C-O bonds in monosaccharides, extracts energy, and generates ATP vis SUBSTRATE-LEVEL PHOSPHORYLATION

Goal #2: biosynthesis
- generates small molecule building blocks to SUPPORT BIOSYNTHESIS OF LIPIS, NUCLEOTIDES, PROTEINS, AND PROTEIN GLYCOSYLATION

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What is the bioenergetics goal fulfilled by?

stage two of glycolysis

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What is the biosynthesis goal filled by?

stage one and stage two of glycolysis

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GLUT2 Liver and pancreatic B (beta) cells. What is the Km?

15-20 mM

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GLUT4 Muscle and fat cells. What is the Km?

5 mM

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Glucose transporters (GLUT) do what?

transport glucose in/out of cells

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What GLUT had the highest Km value?

GLUT2 (liver and pancreatic B cells)

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What has the second highest Km value?

GLUT4 (muscle and fat cells)

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What is step one of phase one of glycolysis?

Phosphorylation (a regulated step)

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What is achieved by phosphorylation?

1) glucose trapped within cell (GLUCOSE 6-P CANNOT PASS THROUGH GLUTs)
2) increases phosphoryl transfer potential of Glucose facilitating breaking of C-C ring

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Facts and regulation about step 1 phosphorylation:

it is an irreversible step (VERY exogenic) catalyzed by Hexokinase and Glucokinase
consumes ATP
amount of enzyme Hexokinase, is regulated by hypoxia-inducible factor 1A (HIF1 alpha)
-Hexokinase is allosterically inhibited by its product Glucose 6-P

What is step one of glycolysis catalyzed by?

Hexokinase
Glucokinase

In step one, the amount of enzyme Hexokinase, is regulated by what?

hypoxia-inducible factor 1A (HIF1 alpha)

In step one, Hexokinase is allosterically inhibited by what?

its product Glucose 6-P

What are kinases?

enzymes that transfer phosphoryl groups from molecules of high phosphoryl transfer potential to molecules of low phosphoryl transfer potential

What do kinases require?

divalent cations for their activity

What is a general feature of kinases?

substrate-induced cleft closing

In the case of Hexokinase, binding of Glucose (the substrate) induces what?

induces structural changes of Hexokinase (closing the cleft) which repels H2O from the activity site H2O increases the chance of ATP hydrolysis without phosphoryl transfer to glucose (the energy is wasted)

What is step two in phase one of glycolysis?

Isomerazation

What is achieved in step two of glycolysis (phase one)?

glucose is transformed into Fructose which facilitates cleavage of 6-carbon sugar into 3-carbon structures

Due to the very little energy change of isomerazation of step two in glycolysis, what is the step like?

readily reversible

What is step two, isomerazation, catalyzed by?

Phosphoglucose Isomerase (PGI) they catalyze the exchange of chemical groups on different carbons

During step two, an aldose (Glucose) is transformed into what?

a ketose (Fructose)

What is step three of phase one of glycolysis?

Phosphorylation (a regulated step)

What is achieved by step three (phosphorylation) of glycolysis?

the energy level of glycolysis intermediate further increases because of the second phosphoryl transfer as a result, Fructose 1,6-bisphosphate is unstable

In step three of glycolysis, where does phosphorylation occur?

on the hydroxyl group on carbon 1 of Fructose

Step three is catalyzed by what and consumes what?

catalyzed by Phosphofructokinase 1 (PFK 1) consumes ATP

Can step three of phosphorylation be reversed?

NO it is an irreversible and committed step in Glycolysis once Fru 1,6-BP is made the carbohydrate is destined to be cleaved and used for generating energy

What is very important of step three?

it is a HIGHLY regulated step in glycolysis there are many regulators

What is step 4 of phase one of glycolysis?

aldol cleaving

What is achieved by step four (aldol cleaving) of glycolysis?

the unstable Fructose 1,6-bisphosphate breaks into two 3-carbon triose phosphates Glyceraldehyde 3-Phosphat (GA-3P) and Carbon 4 in Fru 1,6-BP is broken

Can step four (aldol cleaving) be reversed?

yes, it is a readily reversible step catalyzed by Aldolase

What is step four of glycolysis catalyzed by?

Aldolase

What happens to the C-C bond in step four?

the C-C bond between carbon 3 and carbon 4 in Fru 1,6-BP is broken

What is step five of phase one of glycolysis?

Isomerization (a side step)

What is achieved by step 5 of glycolysis?

GA 3-P is used for stage 2 glycolysis for energy generation aldose/ketose isomerization

Can step five of glycolysis be reversed?

it is a readily reversible step

What is step five catalyzed by?

Triose Phosphate Isomerase (TPI)

The isomerization makes glycolysis what kind of pathway?

energy-generation pathway

What is step six, stage two?

Phosphorylation coupled to oxidation

What happens in step six phosphorylation coupled to oxidation?

the energy transfer and coupling of a thermodynamically favorable and an unfavorable biochemical reactions

In stage six, a tioester bond formed between an intermediate with the catalyzing enzymes does what?

it "couples" a thermodynamically favorable reaction and an unfavorable reaction together