Metabolism and ATP Overview

Metabolic Pathways and Energy Production

• Metabolic pathways are a series of chemical reactions that provide energy and the necessary substances for continued cell growth
• Two types of metabolic reactions are catabolic and anabolic
• Catabolic reactions break down complex molecules into simpler ones, releasing energy
• Anabolic reactions build large molecules from simpler ones, requiring energy
• ATP is a high-energy compound that stores the energy released from the oxidation of food in cells

Learning Objectives

• Understand the process of catabolism and the structure of ATP
• Identify the components and functions of coenzymes (NAD+, NADP+, FAD, and coenzyme A)
• Explain the processes of glycolysis, the citric acid cycle, and the electron transport chain
• Create an audio-visual presentation showcasing metabolic pathways

Metabolism and ATP Energy

• Metabolism encompasses all chemical reactions essential for cellular processes and growth
• During catabolism, nutrients are broken down to release energy in the form of ATP
• During anabolism, energy drives the synthesis of complex molecules, like proteins, from simpler building blocks
• ATP is the primary energy currency of cells, storing and transferring energy

Digestion of Foods

• Food is broken down into smaller units for absorption and utilization
• Fats are emulsified by bile salts, breaking them into smaller droplets for enzyme action
• Carbohydrates are broken down by enzymes into monosaccharides for absorption
• Proteins are broken down into amino acids for digestion

Digestion of Carbohydrates

• Salivary enzymes initially break down carbohydrates, and digestion continues in the stomach
• Smaller carbohydrates like maltose, glucose are produced in the digestive process by enzymatic hydrolysis
• Absorbed into bloodstream and converted into glucose, enabling utilization throughout the body

Digestion of Fats

• Bile salts emulsify fats into smaller droplets
• Pancreatic enzymes like lipase hydrolyze fats, forming fatty acids and glycerol
• These components are absorbed into the lymphatic system and later into the bloodstream enabling cell use

Digestion of Proteins

• Stomach acid (HCl) denatures proteins and activates enzymes like pepsin in hydrolysis to polypeptides
• Small intestine enzymes (trypsin, chymotrypsin) further hydrolyze polypeptides into amino acids
• Absorbed into the bloodstream for cellular use

Coenzymes in Metabolic Pathways

• Oxidation involves hydrogen loss, electron loss, or oxygen gain
• Reduction involves hydrogen gain, electron gain, or oxygen loss
• Coenzymes facilitate these reactions by aiding in electron transferring. Examples include NAD+ and FAD.

NAD+

• NAD+ (nicotinamide adenine dinucleotide) facilitates oxidation-reduction reactions in the body
• The B3 vitamin niacin provides the nicotinamide group, forming NAD+ molecule
• NAD+ is reduced to NADH during reactions, utilizing stored energy

NAD+ (Metabolic reactions)

• NAD+ is required for metabolic reactions involving carbon-oxygen (C=O) bonds
• The body uses NAD+ in oxidation of alcohols to aldehydes and ketones
• NADH is produced when ethanol is converted to ethanal

FAD

• FAD (flavin adenine dinucleotide) is a coenzyme involved in electron transfer
• It's derived from the B2 vitamin riboflavin and flavin ring structure
• Involved in dehydrogenation reactions where single bonds become double bonds

Coenzyme A (CoA)

• CoA, not involved in redox reactions, is made of pantothenic acid (vitamin B5), ADP, and aminoethanethiol
• The key component is the thiol group, enabling CoA to bind with acetyl groups
• CoA formation creates energy rich thioester acetyl CoA enabling transport

Types of Metabolic Reactions

• The main categories are anabolism and catabolism
• Metabolic reactions synthesize complex molecules (anabolism) or break them down (catabolism)
• Anabolic reactions utilize energy to build; catabolic reactions release energy

Glycolysis: Oxidation of Glucose

• Glycolysis is an anaerobic process, using glucose to generate energy
• It involves multiple reactions, including substrate-level phosphorylation
• Glucose (6 carbons) is converted to 2 molecules of pyruvate, each with 3 carbons
• Byproducts like NADH are created, while 2 ATP are produced per glucose molecule

Importance of Glycolysis

• Important for highly energy demanding tissues like muscles & brains
• Glycolysis provides rapid energy when oxygen is limiting
• Pyruvate products enter the mitochondria if oxygen is available; it may be converted into lactate if oxygen is limited & converted to lactate

Regulation of Glycolysis

• Glycolysis is regulated at key points; there are 3 primary control points in glycolysis (hexokinase, phosphofructokinase, pyruvate kinase)
• These points act as control centers, ensuring that glycolysis adapts based on energy needs, ensuring energy is provided as needed.

ATP Yield from the Complete Oxidation of 1 mol of Glucose

• Different reactions produce variable amounts of ATP during glucose oxidation
• Various steps of glucose oxidation, from the initial steps of Glycolysis to the citric acid cycle and electron transport chain generate variable levels of ATPs (depending on efficiency step)

Pathways for Pyruvate

• Pyruvate is converted to acetyl CoA during aerobic conditions
• Pyruvate is converted into lactate under anaerobic conditions
• Lactate buildup can cause muscle fatigue and pain following workout activity

Krebs Cycle (Citric Acid Cycle)

• Acetyl CoA combines with oxaloacetate to form citrate starting the cycle
• The cycle runs in multiple stages through various steps
• The cycle releases two CO2 molecules per cycle
• Energy carriers (NADH, FADH2) are produced & carry energy for later ATP production, via electron transport chain

Importance of Krebs Cycle

• Critical for transferring electrons via coenzyme NADH and FADH2, which are essential for ATP production
• The cycle plays a vital role in oxidizing carbohydrates, fats, proteins for energy requirements of the body

Electron Transport Chain

• NADH and FADH2 molecules formed during glycolysis and Krebs cycle are pivotal in electron transfer processes along the chain.
• Electrons are transferred through complexes embedded in the inner mitochondrial membrane
• During electron transfer, protons and energy is captured and delivered to build ATP. This mechanism is very efficient

Oxidative Phosphorylation

• As electrons pass between complexes in electron transport chain, protons are pumped from the mitochondrial matrix to the intermembrane space generating proton gradient
• Protons flow back from intermembrane space to the mitochondrial matrix via a protein complex
• Movement produces enough energy to synthesis ATP, from ADP and phosphate molecules. This conversion is efficient.

Importance of Electron Transport Chain

• A major ATP producer, powering various cellular functions
• Requires oxygen, & stops ATP production when oxygen is not available
• Essential for organs with high energy demands like heart and brain; muscle contractions and nerve impulses depend on it.

ATP Yield from the Complete Oxidation of 1 mol of Glucose

• The complete oxidation of a single glucose molecule generates a significant amount of ATP, which comes from various steps
• Details of how much ATP is produced at each step

Overview of Glucose Metabolism (Overview)

• Glucose is broken down in stages, yielding ATP byproducts
• Key stages of glycolysis, Krebs cycle, and electron transport chain are clearly defined steps. Each producing varying amounts of ATP.
• The entire pathway is regulated which ensures sufficient production and utilization of energy

This quiz explores the intricacies of metabolic pathways and energy production within cells. It covers the catabolic and anabolic reactions, the structure of ATP, and essential coenzymes involved in these processes. Enhance your understanding of glycolysis, the citric acid cycle, and the electron transport chain.