Carbohydrate Metabolism Flashcards

Flashcards about carbohydrate metabolism, glycolysis, and gluconeogenesis.

Ingested carbohydrates

Hydrolyzed by digestive enzymes to hexose monosaccharide sugars before absorption.

Mechanisms by which monosaccharides are absorbed from the jejunum

Passive and Active Transport

How is glucose taken up by tissue cells

Facilitated transport (type of passive transport)

Which GLUT transporter maintains a basal constant rate of glucose uptake?

GLUT 1 & 3

Where is GLUT-2 located?

Liver and Pancreas

What is the function of GLUT-2?

Glucose sensing

What is the function of GLUT-4?

Insulin-sensitive uptake of glucose

Where is GLUT-4 located?

Skeletal & Cardiac Muscles and Adipose Tissue

What are the major metabolic fates of glucose?

Glycolysis, Glycogenesis, Lipogenesis

What is the main role of Glycolysis?

ATP production

What does the Pentose Phosphate Pathway provide?

NADPH and 5-carbon sugars

Where does glycogenesis occur?

In liver and skeletal muscles

To what is glucose converted during lipogenesis?

Glycerol and fatty acids

What is glycolysis?

Oxidation of glucose

What is glucose broken down into during glycolysis?

Two molecules of pyruvate or lactate

Where does glycolysis occur within the cell?

The cytosol

What makes Glycolysis unique as an ATP-producing pathway?

It doesn't need mitochondria

What are the two phases of glycolysis?

Energy utilization and recovery

How many ATPs are consumed during the energy utilization phase of glycolysis?

Two ATPs

What molecules does glucose convert into during phase one of glycolysis?

Glyceraldehyde 3-phosphate (GAP) and Dihydroxyacetone Phosphate (DHAP)

What are the two molecules of glyceraldehyde 3-P converted to in phase two?

Two molecules of pyruvate or lactate

Where does NADH produced during glycolysis go under aerobic condition?

Mitochondria via the respiratory chain (ETC)

What shuttles are required to transfer the reducing power of NADH to the mitochondria?

Glycerol-3-phosphate and malate-aspartate shuttle

What enzyme catalyzes the reoxidation of NADH to NAD under anaerobic conditions?

Lactate dehydrogenase (LDH)

What are the three key regulatory enzymes of glycolysis?

Hexokinase/glucokinase, phosphofructokinase-1, and pyruvate kinase

What is the role of hexokinase and glucokinase in glycolysis?

Traps glucose inside cells

Which enzyme catalyzes the committed step of glycolysis?

Phosphofructokinase-1 (PFK-1)

What does a pyruvate kinase deficiency cause?

Inherited hemolytic anemia

Which AMP levels activate glycolysis?

High levels of AMP

Which ATP levels inhibit glycolysis?

High levels of ATP

What effect does insulin have on glycolysis?

Stimulates

What effect does glucagon have on glycolysis?

Inhibits

What is the net gain of ATP under anaerobic conditions?

2 ATP molecules

What is the net gain of ATP under aerobic conditions?

7 ATPs

What enzyme catalyzes the conversion of pyruvate to lactate?

Lactate dehydrogenase

What enzyme catalyzes the conversion of pyruvate to oxaloacetate?

Pyruvate carboxylase

What enzyme catalyzes the conversion of pyruvate to alanine?

Aminotransferase

What is gluconeogenesis?

Formation of glucose from non-carbohydrate substances

Where does gluconeogenesis primarily occur?

Liver and Kidneys

What are the major gluconeogenic substrates?

Lactate, glycerol, glucogenic amino acids, and odd chain fatty acids