Metabolism I - BIO2101 - Lecture 1
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Questions and Answers

What is the primary function of GLUT-3?

  • Regulate insulin levels
  • Transport fructose in the kidneys
  • Transport glucose in the liver
  • Facilitate glucose uptake in neurons (correct)

Which glucose transporter is abundant in skeletal muscle and adipose tissue?

  • GLUT-1
  • GLUT-2
  • GLUT-4 (correct)
  • GLUT-5

Which GLUT isoform functions in both glucose transport into and out of cells based on blood glucose levels?

  • GLUT-5
  • GLUT-3
  • GLUT-2 (correct)
  • GLUT-1

What characteristic defines the movement of glucose during facilitated diffusion?

<p>Transport occurs along a concentration gradient (B)</p> Signup and view all the answers

Which glucose transporter is specifically known for transporting fructose?

<p>GLUT-5 (B)</p> Signup and view all the answers

Which glucose transporter has minimal expression in adult muscle tissue?

<p>GLUT-1 (A)</p> Signup and view all the answers

What is the primary function of catabolic pathways?

<p>To extract energy in the form of ATP (B)</p> Signup and view all the answers

How does insulin affect GLUT-4 transporters?

<p>Enhances their presence and activity in skeletal muscle (D)</p> Signup and view all the answers

What is the general role of glucose transporters in the cell membrane?

<p>To facilitate passive transport of glucose across the membrane (D)</p> Signup and view all the answers

Which enzyme is involved in the phosphorylation of glucose?

<p>Hexokinase (D)</p> Signup and view all the answers

What do GLUT isoforms primarily regulate?

<p>The transport of glucose into cells (A)</p> Signup and view all the answers

What is a key characteristic of catabolic reactions?

<p>They enable the conversion of dietary molecules into building blocks (D)</p> Signup and view all the answers

What role do multienzyme sequences play in metabolism?

<p>They facilitate the pathways that process metabolic intermediates (D)</p> Signup and view all the answers

What is the significance of tissue-specific GLUT gene expression?

<p>It affects how different tissues respond to insulin (B)</p> Signup and view all the answers

What does the phosphorylation of glucose achieve in metabolic processes?

<p>It initiates glycolysis (D)</p> Signup and view all the answers

Which statement best describes catabolic reactions?

<p>They release energy by breaking down complex molecules (C)</p> Signup and view all the answers

What is the primary function of the sodium-dependent glucose transporter (SGLT)?

<p>To transport glucose against its concentration gradient using Na+ (C)</p> Signup and view all the answers

During which phase of glycolysis is ATP consumed for the phosphorylation of glucose?

<p>Energy investment phase (D)</p> Signup and view all the answers

Which enzyme is primarily responsible for the phosphorylation of glucose in most tissues?

<p>Hexokinase (C)</p> Signup and view all the answers

What prevents phosphorylated sugar molecules from diffusing across cell membranes?

<p>Their polarity and lack of specific carriers (A)</p> Signup and view all the answers

What is the net yield of ATP during the energy generation phase of glycolysis for one glucose molecule?

<p>Two molecules of ATP (C)</p> Signup and view all the answers

What happens to glucose once it is phosphorylated into glucose 6-phosphate?

<p>It is trapped in the cytosol and committed to metabolism (C)</p> Signup and view all the answers

What is the primary purpose of catabolic pathways?

<p>To break down complex molecules into simpler components (D)</p> Signup and view all the answers

Which physiological sites utilize the Na+-monosaccharide cotransporter system?

<p>Epithelial cells of the intestine and renal tubules (C)</p> Signup and view all the answers

How does glucose phosphorylation affect hexokinase activity?

<p>It inhibits hexokinase through product accumulation (A)</p> Signup and view all the answers

During which phase of catabolism is acetyl coenzyme A (CoA) produced?

<p>Conversion of building blocks to simple intermediates (D)</p> Signup and view all the answers

What role do coenzymes, such as NAD+, play in catabolic pathways?

<p>They are typically required for oxidative reactions. (C)</p> Signup and view all the answers

Which of the following statements is true regarding anabolic pathways?

<p>They are endergonic and require energy input. (A)</p> Signup and view all the answers

What compound serves as the primary source of reducing power in anabolic reactions?

<p>NADPH (D)</p> Signup and view all the answers

In the TCA cycle, what is primarily generated during the oxidation of acetyl CoA?

<p>Large amounts of ATP via oxidative phosphorylation (D)</p> Signup and view all the answers

What is the outcome of catabolic reactions in terms of molecular conversion?

<p>They yield a limited number of common end products from various inputs. (C)</p> Signup and view all the answers

What is the relationship between anabolic and catabolic pathways?

<p>Anabolic pathways store energy while catabolic pathways release it. (C)</p> Signup and view all the answers

What is the main end product of glycolysis in cells with sufficient oxygen?

<p>Pyruvate (A)</p> Signup and view all the answers

Which of the following best describes anaerobic glycolysis?

<p>Conversion of glucose to lactate in the absence of oxygen (D)</p> Signup and view all the answers

Why is glycolysis referred to as the central process in carbohydrate metabolism?

<p>It converts various sugars into glucose for energy production (B)</p> Signup and view all the answers

Which statement is true regarding the transport of glucose into cells?

<p>Glucose enters cells either by facilitated diffusion or Na+ cotransport (B)</p> Signup and view all the answers

What is a significant outcome of aerobic glycolysis?

<p>Formation of acetyl CoA for the TCA cycle (B)</p> Signup and view all the answers

Which mechanism is NOT a way glucose enters cells?

<p>Direct diffusion through lipid bilayer (C)</p> Signup and view all the answers

What role does NADH play during glycolysis under aerobic conditions?

<p>It is reoxidized to NAD+ (D)</p> Signup and view all the answers

In which type of tissues does anaerobic glycolysis primarily occur?

<p>Tissues that are devoid of mitochondria or are poorly oxygenated (A)</p> Signup and view all the answers

Flashcards

Catabolic pathways

Catabolic pathways break down energy-rich molecules to produce ATP (energy).

Metabolic pathways

Series of enzyme-catalyzed reactions transforming molecules.

Carbohydrate metabolism

The process of converting and using carbohydrates for energy.

ATP

The main energy currency of a cell.

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Glycolysis

A key metabolic pathway for glucose breakdown.

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Glucose Transport

The movement of glucose into cells via specific transporters.

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GLUT isoforms

Different versions of glucose transporters with varying functions.

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Metabolic intermediates

Molecules that are formed and used during metabolic reactions.

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Catabolic Pathways

Metabolic pathways that break down complex molecules into simpler ones, releasing energy.

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First Stage of Catabolism

Hydrolyzes complex molecules (proteins, polysaccharides, fats) into their building blocks (amino acids, monosaccharides, fatty acids/glycerol).

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Second Stage of Catabolism

Further breaks down building blocks from the first stage to simpler molecules like acetyl CoA using enzymes.

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Third Stage of Catabolism

Oxidizes acetyl CoA via TCA cycle, generating a lot of ATP via oxidative phosphorylation.

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Anabolic Pathways

Metabolic pathways that build complex molecules from simpler ones, requiring energy.

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Acetyl CoA

A common intermediate molecule formed during the breakdown of many organic molecules. Crucial for the TCA cycle.

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TCA Cycle

A metabolic cycle that completely breaks down acetyl CoA, generating more energy (reducing equivalents, ATP, etc.).

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Oxidative Phosphorylation

Process that generates ATP by using the energy from electron transfer in an electron transport chain.

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Anaerobic Glycolysis

The process of converting glucose to lactate in the absence of oxygen.

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Aerobic Glycolysis

Glucose breakdown producing pyruvate when enough oxygen is present.

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Glycolysis

Central process in carbohydrate metabolism to break down glucose.

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Glucose transport

Glucose entering cells using transport mechanisms.

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Pyruvate

End product of aerobic glycolysis.

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Metabolic Pathways

Series of reactions transforming smaller molecules to bigger ones or vice-versa.

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Anabolism

Biosynthetic, complex molecule creation from simpler ones, needing energy.

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Glucose

A sugar used as the primary energy source in cells.

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GLUT Transporters

A family of 14 glucose transporters in cell membranes that transport glucose across membranes.

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GLUT-3 transporter

The primary glucose transporter in neurons.

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GLUT-1, GLUT-3, and GLUT-4

Key glucose transporters that regulate glucose uptake from the blood.

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Glucose Transporter Isoforms

Different types of glucose transporters with tissue-specific expression patterns.

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GLUT-2 and liver/kidney

GLUT-2 transporters are found in the liver and kidneys, able to transport glucose in-or-out of these cells based on blood glucose levels.

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GLUT-5

The primary transporter of fructose in the small intestine and testes, rather than glucose.

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Facilitated Diffusion

Glucose movement across cell membranes that occurs along a concentration gradient without energy input.

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Tissue-specific GLUT expression

Different tissues have different levels of different GLUT transporters which helps regulating glucose import/export based on their specific needs.

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Na+-monosaccharide cotransporter

A system that moves glucose against its concentration gradient, requiring energy, using a carrier protein linked to Na+ transport

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SGLT

Sodium-dependent glucose transporter. The carrier protein used in the Na+-monosaccharide cotransporter system

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Energy investment phase (glycolysis)

First phase of glycolysis, where glucose is activated using ATP to create phosphorylated intermediate molecules

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Energy generation phase (glycolysis)

Second phase of glycolysis, where ATP is produced through substrate-level phosphorylation

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Glucose phosphorylation

Irreversible process of adding a phosphate group to glucose, trapping it in the cell for further metabolism

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Hexokinase

Enzyme that catalyzes the phosphorylation of glucose to glucose-6-phosphate, a key regulatory enzyme in glycolysis

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Glucose-6-phosphate

The product of glucose phosphorylation, it inhibits hexokinase and signals the cell to reduce glucose metabolism

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Aerobic glycolysis

Breakdown of glucose in the presence of oxygen to release energy, producing pyruvate

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Study Notes

Metabolism I - BIO2101 - Lecture 1

  • Course: Biotechnology and Genetic Engineering
  • Academic Year: 2024-2025
  • Lecturer: Assoc. Prof. Manar Seleem
  • Topic: Carbohydrate Metabolism

Chapter 1: Contents

  • Carb Metabolism: Introduction to carbohydrate metabolism, catabolic and anabolic pathways

  • Overview of Glycolysis A general concept of Glycolysis.

  • Transport of Glucose into Cell: Tissue specificity of GLUT gene expression, specialized functions of GLUT isoforms, and the Na+-monosaccharide cotransporter system

  • Reactions of Glycolysis Details of the ten reactions

  • Glucose-phosphorylation: Hexokinase and Glucokinase

  • Catabolic Pathways: Process responsible for breaking down larger chemical compounds, releasing energy in the form of ATP from the breakdown of organic molecules

  • Three Stages of Catabolism: Stage 1: breakdown, Stage 2: conversion of building blocks to acetyl-CoA (or other simple intermediates), Stage 3: Metabolism of acetyl-CoA to CO2 and formation of ATP

  • Hydrolysis of Complex Molecules: Complex molecules are broken down into their component building blocks, such as proteins to amino acids. Polysaccharides to monosaccharides and fats to fatty acids and glycerol

  • Conversion of Building Blocks to Simple Intermediates: Diverse building blocks are further converted to acetyl-coenzyme A and a few other simple molecules, with some energy captured as ATP

  • Oxidation of acetyl CoA: The final common pathway is the tricarboxylic acid (TCA) cycle. Acetyl CoA oxidation generates large amounts of ATP via oxidative phosphorylation

Anabolic Pathways

  • Anabolic Pathways: Reactions involve combining small molecules to form larger complex molecules. The breakdown of ATP to ADP and Pi is the major energy source for anabolic reactions. The primary source of reducing power is the electron donor NADPH. Catabolism is a convergent process, while anabolism is a divergent process
  • Overview of Glycolysis: All tissues utilize the glycolytic pathways to breakdown glucose into energy and intermediates for other pathways. The central process in carbohydrate metabolism, converting various sugars into glucose
  • Aerobic Glycolysis: Pyruvate is the end product of glycolysis in cells with mitochondria. Oxygen is required to reoxidize NADH produced during the oxidation of glyceraldehyde-3-phosphate
  • Anaerobic Glycolysis: In the absence of oxygen, pyruvate is converted to lactate

Transport of Glucose into Cells

  • Na+-independent facilitated diffusion transport: A family of GLUT transporters (GLUT-1 to GLUT-14) facilitates glucose transport across cell membranes. Two conformational states facilitate glucose transport across the cell membrane
  • Tissue-specificity of GLUT gene expression: GLUT transporters exhibit expression patterns specific to each tissue (e.g., GLUT-3 in neurons, GLUT-1 in erythrocytes).

Glycolysis

  • Two Phases: Glycolysis comprises initial energy investment and energy generation phases which results in ATP generation after glucose breakdown

Glucose-Phosphorylation

  • Characteristics of the process: No specific carriers, polar molecules, and are trapped as glucose 6-phosphate to be metabolized in the cell
  • Enzyme: Catalyzed by multiple isozymes of hexokinase in mammals

Hexokinase

  • Regulatory Enzyme: One of the three regulatory enzymes in glycolysis catalyzes glucose phosphorylation
  • Affinity for Glucose: Has a high affinity for glucose, which enables the efficient phosphorylation and subsequent metabolism of glucose, even with modest glucose concentrations in tissues
  • Capacity: The enzyme's low Vmax for glucose means the cell cannot effectively utilize more carbohydrates than possible

Glucokinase

  • Primary Enzyme: Responsible for glucose phosphorylation, in liver parenchymal cells and beta cells of the pancreas
  • Function: Serves as a glucose sensor for insulin secretion in beta-cells. In the liver, glucokinase promotes the phosphorylation of glucose during hyperglycemia

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Metabolism I Lecture Notes PDF

Description

This quiz covers the intricate details of carbohydrate metabolism as presented in the first lecture of the Biotechnology and Genetic Engineering course. Key topics include glycolysis, glucose transport mechanisms, and catabolic pathways. Test your understanding of this essential biochemical process and its role in energy production.

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