[2] Class 7: Glycolysis And Gluconeogenesis Flashcards by John Pate

3 components to monosaccharide:

Carbon number
Functional group
Stereoisomer form

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Only 5 carbon sugar to know:

D-ribose

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3 carbon sugars to know:

Dihydroxyacetone

D-glyceraldehyde

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6 carbon ketose sugar?

D-fructose

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Major component of DNA

Deoxyaldose

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Theyre components of glycoproteins and glycolipids: cell signaling and adhesion

Acetylated amino sugars

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Glycosaminoglycans and proteoglycans. Present in cell membrane and ECM

Acidic sugars

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Constituted the gangliosides in oligodendrocyte of the NS

Sugar esters

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Food additives, gains importance in uncontrolled diabetes leading to cataracts and peripheral neuropathy, used in synthesis of lipids

Sorbitol, mannitol

Sugar alcohols

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Ex of sugar alcohols:

Sorbitol, mannitol, and xylitol

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Sugar alcohols that can be converted to fructose and metabolized normally, their slow metabolism is what helps reduce calories and weight gain.

Sorbitol, mannitol, and xylitol

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Non-sugar based artificial sweeteners trick the receptors on tongue and aren’t metabolized like sugar. How does this effect endocrine?

Disrupts insulin signaling

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Giving a phosphate generally…

Activates

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Disaccharide

2 monosaccharides glycosidic linkage

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Starch amylose

Polysaccharide of glu residues w/ alpha-1,4 glycosidic bonds

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Amylopectin

Amylose w/ addition of alpha-1,6 glycosidic branch points

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A major plant polysaccharide

Unbranded polymer of glucose residues joined by beta-1,4 linkages, allowing to form very long and straight chains

Dietary fiber

Cellulose

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Metabolizes one molecule of glucose to 2 molecules of pyruvate w/ 2 net ATP

Glycolysis

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Glycolysis and oxygen

Anaerobic

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Glucose is the only fuel that: 2 things…

The brain uses under nonstarvation conditions and the only fuel that red blood cells can use at all.

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How can pyruvate and lactate be salvaged?

By being resynthesized to glucose in gluconeogenesis

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Sources of glucose in diet:

Starch, glycogen, disaccharides (esp. sucrose and lactose)

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Complete oxidation efficiency > …

Anaerobic glycolysis

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The only insulin dependent glucose uptake GLUT4

In skeletal, muscle, heart, adipose

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Why would GLUT 2 [main transporter for liver] have a low affinity for glucose uptake:

The liver doesnt want to store glu. It wants to maintain it throughout body.

Ubiquitous but high in RBC's and brain High affinity for glucose

GLUT1

The main glucose transporter in neurons

GLUT3

How many stages to glycolysis?

3; 1st is 6 carbons-investment 2nd: is converting into 3 carbons and conversion of DHAP to G3P 3rd: converting to pyruvate- gaining ATP

Traps glucose in the cell

Hexokinase

Which stage in glycolysis, the conversion of glucose to fructose 1,6-bisphosphate

Stage 1

Strategy to stage 1 glycolysis:

Traps the glucose in cell, for a A compound that can be readily cleaved into 2 phosphorylated 3- carbon units

What enzyme does liver use to convert glucose into glu-6-P?

Glucokinase

What are the 2 steps involving energy investment in stage 1 glycolysis?

Glucose->G6P by hexokinase/glucokinase F6P-> F1,6BP by phosphofructokinase

What regulates hexokinase?

Negative feedback inhibition by product- G6P

Regulation of glucokinase:

Stimulated by glucose, F-1P, and insulin Inhibited by glucagon and F6P

Regulation of phosphofructokinase

Stimulated by AMP and F2,6-BP Inhibited by ATP and Citrate

Which stage of glycolysis? | Fructose 1,6-BP into 2 3-C fragments by Aldolase reaction And isomerase Products are readily interconvertible

Stage 2

What conditions represent high energy? (3)

High ATP High NAD+ Low NADH

When there's high energy which of the products of stage 2, DHAP and GAP (G3P) is favored?

DHAP is favored under high energy conditions b/c it is converted to glycerol 3 phosphate- that way it can form triacylglycerols -FAT

What percentage of f1,6BP becomes GAP, usually?

Usually, 99% becomes GAP to continue glycolysis....in the event of high energy conditions the reaction will regress to DHAP for fat storage

Glyceraldehyde 3-P creates:

NADH (x2) that will be used in oxidative phosphorylation

1,3-BPG is converted to 3-PG by

Phosphoglycertae kinase and this forms the first ATP (x2) of glycolysis

2-PG is converted to_______ by:

Phosphoenolpyruvate by dehydration rxn by enolase

Phosphate is removed from phosphoenolpyruvate by:_________ creating:

Pyruvate kinase; Pyruvate (x2)

Pyruvate is what type of molecular structure?

Stable ketone

3 irreversible steps of glycolysis:

1- glu-G6P 3-F6P-F1,6BP 10-PEP- Pyruvate

Regulation of pyruvate kinase:

Stimulated by insulin and Fructose 1,6-BP Inhibited by Alanine, ATP, and glucagon

After glycolysis, aerobic: Anaerobic?

Pyruvate to TCA; Pyruvate to lactate--then, hopefully cori cycle...

Disaccharide of glucose and fructose makes=

Sucrose

Disaccharide composed of glucose and galactose =

Lactose

Fructose and galactose are converted to:

Glycolysis intermediates

In times of high energy, fructose quickly turns to:

FAT

Why would fructose quickly turn to fat in times of high energy?

Remember that GAP is readily interconvertible w/ DHAP, and although GAP is formed 99% of the time...this isn't the truth when there is high energy conditions b/c the GAP is converted to DHAP which becomes triacylglycerols- it is the backbone of fat.

3 regulated steps in glycolysis for ATP need

Hexokinase PFK Pyruvate kinase

Main organ in glucose regulation

Liver

NO hexokinase in liver: it is glucokinase....how is this regulated?

Glucose is permanently trapped in liver cell. It is not inhibited by G3P (product of glucokinase)

What type of regulation is used for pyruvate kinase:

Allosteric effectors and covalent modification

Pyruvate kinase is more ________ when phosphoirylated

Inactive- under conditions of low BG

Pyruvate kinase is more ________ when dephosphorylated

ACTIVE - under conditions of high BG

Glucokinase has a ____ Km

High = low affinity

Hexokinase Km is significantly ________ than glucokinase

Lower

Fates of pyruvate

Lactate TCA -other micoorganisms can convert pyruvate to ethanol

What must occur before pyruvate can enter TCA cycle?

Pyruvate must undergo oxidative carboxylation to form acetyl CoA

Pyruvate can be reduced to lactate w/ the regeneration of:

NAD+

Precursor for pentose phosphate pathway

glucose-6-phosphate

Which organ(s)depends on glucose as primary fuel or only fuel

Brain and RBCs- only use glucose

Brains daily glucose req'ment amt.: Whole body req'ment:

120 g 160g

Glucose always has ____ g in body fluids, but there's about _____g available from glycogen

20 g; 190 g

How long would glucose reserves last a person?

About a day or so.

What bodily process is important during a long period of fasting or starvation?

Gluconeogenesis

Synthesis of glucose from noncarbohydrate precursors Major precursors are lactate, AA's, and glycerol (but not FA's) Pathways convert pyruvate to glucose Pathway is not a reversal of glycolysis

Gluconeogenesis

Enzymes of irreversible reactions in the liver:

Glucokinase Phosphofructokinase Pyruvate kinase

What are the 4 enzymes used in gluconeogenesis to 'bypass' irreversible steps of glycolysis:

Pyruvate carboxylase (pyruvate->OAA) Phosphoenolpyruvate carboxykinase (OAA->PEP) Fructose-1,6-BPtase (F-1,6-BP->F-6-P) Glucose-6-phosphatase (G-6-P->glu)

Regulation of pyruvate kinase:

Stimulated by insulin and F-1,6-BP Inhibited by alanine, ATP, and glucagon

Stimulation of glucose-6-phosphatase

Stimulated by cortisol

Regulation of fructose-1,6-BPtase:

Stimulated by citrate and cortisol Inhibited by AMP and F-2,6-BP

Regulation of PEP carboxylase

Stimulated by cortisol, glucagon, thyroxine

Regulation of pyruvate carboxylase

Stimulated by acetyl CoA and cortisol Inhibited by ADP

First step of gluconeogenesis:

Pyruvate is converted to OAA

Source of OAA in gluconeogenesis: How about pyruvate:

Some AA's source of OAA and pyruvate Lactate also is a source of pyruvate

Generation of free glucose For glucose to leave the liver the phosphate must be removed from glucose-6-phosphate Which reaction? Enzyme?

G-3-P to glucose Glucose 6-phosphatase

Where is glucose-6-phosphatase located?

In the lumen of the endoplasmic reticulum

G3P is transported to the ER by

A specific protein (T1) and another protein (T2) then transports glucose back to the cytoplasm

Glycolysis __________ ATP; Gluconeogenesis __________ ATP

Generates; Consumes

What is the best way to determine which pathway will be most active btw glycolysis and gluconeogenesis:

Energy charge (ATP/ADP ratio)

Gluconeogenesis and glycolysis are _____________ regulated

Reciprocally

Lactate produced in skeletal muscle and RBC's can be converted back to pyruvate in the liver

Cori cycle

What is the benefit of the cori cycle?

Since lactate is able to be converted back to pyruvate, the pyruvate can be used in gluconeogenesis to form glucose in times of low energy.

[2] Class 7: Glycolysis And Gluconeogenesis Flashcards

(88 cards)