Packet #25 Chapter #9 Introduction to Cellular Catabolism

Laws of Thermodynamics

Energy is defined as the capacity to do work and takes a number of forms Light; heat; chemical The 1 st law of thermodynamics Energy cannot be created or destroyed but changed from one form into another. When scientists used the term that energy is lost, they are simply stating that it (energy) has been converted into a form which cannot be usefully available for a particular purpose. The 2 nd law of thermodynamics All natural processes tend to proceed in a direction which increases the randomness or disorder of a system. All natural processes tend to high entropy.

Metabolism

Energy & Chemical Reactions I The summation of chemical reactions, via the use of enzymes, that occur within living organisms is called metabolism. Metabolism is divided is divided into two groups Anabolism Catabolism

Energy & Chemical Reactions II The reactions that make up these processes may either be termed exogonic or exergonic. Exogonic Chemical reactions that release energy Exergonic Chemical reactions that absorb free energy.

Entropy & Living Organisms Living organisms maintain low entropy by taking their chemical energy in the form of food. This food is converted into a form of energy called ATP.

ATP

Functions of ATP In a metabolically active cell, up to 2 million molecules of ATP are required every second. The ATP is used for a variety of purposes. Anabolic processes Active Transport Movement Activating reactants Chemicals often require the addition of phosphate groups from ATP to make them more reactive Phsophorylation of glucose at the beginning of glycolysis. Secretion ATP provides energy for the secretion of cell products.

ATP & Energy Yields Adenosine triphosphate (ATP) is the form in which energy is temporarily stored from the breakdown of glucose. The removal of the final phosphate, when changing ATP to ADP, releases 30.6 kJ mol -1 of energy. ATP + H 2 O -> ADP + phosphate kJ

Respiration

Types of Respiration Gaseous Exchange External respiration (Organ System—Respiratory System) Processes involved in obtaining oxygen needed for respiration and the removal of gaseous waste such as carbon dioxide. Cellular Respiration Internal/tissue Biological processes which take place within living cells that release energy

Cellular Respiration Cells require a constant supply of energy to generate and maintain the biological order that keeps them alive. The energy is derived from the chemical bond energy in food molecules. Sugars, such as glucose, are particularly important fuel molecules. Animal cells obtain sugars, and other molecules such as starch that are converted to sugars by eating other organisms. Heterotrophs

Types of Cellular Respiration Aerobic Respiration The oxidation of glucose to produce energy via the use of oxygen. Sugar molecule is broken down and oxidized to CO 2 and H 2 O. Energy is derived from the chemical bond energy stored in the sugar. Anaerobic Respiration Production of energy without the use of oxygen.

Aerobic Cellular Respiration Cellular respiration is a complex metabolic process of over 70 reactions that can be divided into three stages Glycolysis Kreb’s Cycle (Tricarboxylic acid cycle) Electron transfer system Chemiosomosis

Electron Carrier Molecules

Electron (Hydrogen) Carriers Electron (Hydrogen) carriers are also known as acceptor molecules. Electrons are collected by electron carriers molecules and passed to electron carriers at lower energy levels. The electrons are at lower energy levels. The energy released, as the electrons move to lower energy levels, is used to form ATP from ADP.

Electron (Hydrogen) Carriers II The electrons are initially part of a hydrogen atom. Hydrogen coming directly, or indirectly, from glucose. Hydrogen atom eventually splits into a proton and an electron.

Electron (Hydrogen) Carriers Examples Nicotinamide adenine dinucleotide NAD Nicotinamide adenine dinucleotide phosphate NADP Flavine adenine dinucleotide FAD Cytochromes

Respiratory Quotients

A respiratory quotient (RQ) is a measure of the ratio of carbon dioxide evolved to the oxygen consumed: RQ = CO2 evolved / O2 consumed For a hexose sugar, such as glucose, used during cellular respiration, it can be seen from the equation C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O The ratio is 6CO2 / 6O2 = 1.0 For a fat such as steric acid, RQ = 0.7 Other RQ’s Malate = 1.33 Proteins = 0.9 (varies slightly based on particular protein)

The Role of Vitamin B

Vitamin B The group of vitamins, called vitamin B, plays a major role in cellular respiration— particularly by acting as coenzymes. Found in green and leafy vegetables.

Vitamin B Vitamin Role in Cellular Respiration B1B1 Thiamine Involved in formation of some Kreb’s cycle enzymes; forms part of ACOA B2B2 Riboflavin Forms part of the hydrogen carrier FAD B3B3 Niacin (nicotinic acid) Forms part of the coenzyme NAD and NADP; forms part of ACOA B5B5 Pantothenic acidForms part of ACOA