Metabolic processes

Metabolism

The sum of all chemical reactions in a cell or organism

Kinetic energy

The energy of motion (waves in the ocean)

Potential energy

The stored energy that an object possesses as a result of its position relative to other objects or to its internal structure

First Law of Thermodynamics

The total amount of energy in any closed system is constant. Energy cannot be created or destroyed, only transformed from one form to another.

Conversions in bio

• sunlight into chemical energy during photosynthesis

• chemical energy to mechanical energy as animal breaks down food and uses the energy to move around

Activation Energy

the minimum amount of energy that chemical reactants must absorb to start a reaction (spark is required for combustion reaction)

Transition State

The temporary condition during a chemical reaction in which the bonds in the reactants are breaking and the bonds in the products are forming

Free energy (Gibbs free energy)

Energy that can do useful work

• change in free energy G (final state) - G (initial state)

• reactions are sorted into two groups based on free energy in product and reactant

Exergonic reactions

• the energy of the products is less than the energy of the reactants

• release of free energy (negative)

• ex. exothermic reaction (cellular respiration)

Endergonic reactions

• The energy of the products is more than the energy of the reactants

• absorb free energy (positive)

• ex. endothermic reaction (photosynthesis)

coupled reactions

• transfer of energy from 1 reaction to another to drive the second reaction

• Catabolic (cellular respiration): series of reactions where energy is released and complex molecules are broken down into simple

• Anabolic (photosynthesis): series of reactions where energy is supplied to build complex molecules from simple ones

ATP (adenosine triphosphate)

• directly supplies energy for cell functions

• Contains large amounts of free energy due to the three negatively charged phosphate molecules

• these bonds are easily broken during a hydrolysis reaction - the terminal phosphate group is broken off, producing ADP and a molecule of inorganic phosphate

• the energy that is released is usually coupled with an endergonic process that attaches the inorganic phosphate group to another molecule directly associated with the work the cell needs to do. This is called phosphorylation.

• this results in the molecule gaining free energy and becoming more reactive

• Two types:

1. Substrate-level Phosphorylation

2. Oxidative Phosphorylation

Substrate-level Phosphorylation

• A simple way to create ATP

• ATP is formed directly in an enzyme-catalyzed reaction

• A phosphate-containing compound transfers a phosphate group directly to ADP, containing ATP

Oxidative Phosphorylation

• ATP is formed indirectly through a series of enzyme-catalyzed redox reactions involving oxygen as the final electron acceptor

• Involves two molecules: nicotinamide adenine dinucleotide (NAD+) and flavin adenine dinucleotide (FAD)

Cellular respiration

C6H12O6 (aq) + 6O2 (g) → 6CO2 (g) + 6H2O (l)

• series of enzyme-controlled redox reactions to break the covalent bonds in glucose and rearrange them into new and more stable configurations

• exergonic process

• results in a transfer of electrons from glucose to oxygen (glucose is oxidized to FO2 and oxyge is reduced to water)

• yields 2870kJ of energy per mile of glucose

• glucose and oxygen are fairly stable

• living cells use enzymes for activation energy

• energy released in repiration is transferred to a number of energy-carrier molecules, including ATP

Mitochondria

• double memberane composed of a smooth outer membrane and folded inner membrane (cristae)

• outer membrane: role similar to cell membrane

• inner membrane: conatins many proteins and enzymes attached to its inner surface or embedded in the phospholipid layer

• matrix: protein rich liquid that fills the innermost space of a mitochondrion

• intermembrane space: lies between the two membranes

• mitochondria have their own DNA (mtDNA), RNA and ribosomes and can reproduce by binary fission

Glycolysis

• Sugar splitting

• thought to be the earliest form of energy metabolism

• series of 10 reactions

• overall → 1 glucose molecule is split into two pyruvate molecules

• produces ATP and NADH

• initial steps require energy followed by a production of energy

• occurs in the cytoplasm

• anaerobic process

Pyruvate Oxidation

• The two pyruvate molecules formed in glycolysis are transported to the matrix of the mitochondria

• The pyruvate molecules are converted to acetyl-CoA

Citric Acid Cycle (Krebs Cycle)

• occurs in the mitochondrial matrix (twice for each molecule of glucose)

• Discovered in 1937 by Sir Hans Krebs

• 8-step cyclic process

• Entire glucose molecule is consumed by the end of this cycle (carbon is released as CO2)

• 2 ATP

• 6 NADH

• 2 FADH2

The electron transport chain and che