Chapter 5: Metabolism

Energy

Energy

the ability to perform work

Potenial Energy

Stored energy that is available to do work (gravitational, chemical - stored in bonds)

Kinetic energy

energy of motion (moving objects, muscle contractions)

Thermodynamics

study of energy transfers between bodies of matter

System

the specific portion of matter being studied

Surroundings

everything else outside the system

biologic systems

transfer both energy and mass with the surroundings

first law of thermodynamics (law of conservation of energy)

Energy can be transferred and transformed but it cannot be created or destroyed. Total amount of energy in the universe does NOT change.

Entropy

A measure of disorder or randomness. the more disorder=the higher entropy

second law of thermodynamics

100% efficient energy conservation is impossible since heat energy is lost, increasing universal entropy

Heat

form of kinetic energy that is transferred between two objects w/ different temperatures

Chemical Reactions

consist of the making and/or breaking of chemical bonds leading to changes in matter

Reactants:

the starting material in a chemical reaction

Products:

the ending material in a chemical reaction

Endergoinc reactions:

requires an input of energy (energy ENters)

Exergonic Reactions:

releases energy (energy EXits)

Adenosine Triphosphate (ATP)

a high energy molecule used to "power" cellular activities

ATP molecule structure:

-Chain of 3 phosphate groups
-pentosesugar
-adenine nitrogenous base

ATP hydrolysis:

energy-releasing; breaking bonds between phosphate groups generating chemical energy and ADP

ATP formation:

energy-requiring

Energy Coupling:

when energy released bu an exergonic reaction is used to power/drive an endergonic reaction

ATP hydrolysis is coupled to

endergonic reactions to provide the energy input they need to proceed

Phosphorylation

transfer of a phosphate group from ATP to another molecule to provide energy

Enzymes:

molecule that catalyzes a chemical reaction without being consumed

Substrates:

the reactants of a chemical reaction that is catalyzed by an enzyme

Enzyme Functions:

-Building proteins
-Copying DNA
-Digestion of Food

Environmental Factors for Enzymes:

-Temperature
-pH
-Concentration of reactants

activation energy (Ea)

the difference in energy between the reactants and the transition state of a reaction

Ea is the minimum amount of energy required

to start a chemical reaction

the higher the Ea, the

slower the reaction

Transition State

a temporary state of maximum energy in a reaction

Enzymes catalyze chemical reactions by

lowering their activation energy barrier

Enzyme-Substrate Complex

Substrate binds an enzyme at the active site

Active Site

SPecific region of an enzyme that binds substrates

Cofactors:

non-protein substances required for catalysis to occur

Coenzyme:

an organic molecule cofactor derived from vitamins

Enzyme Inhibitors

compounds that interfere w/ and selectively inhibit the catalysis of specific enzymes

Competitive Inhibitors

Compete w/ the substrate for an active site

noncompetitive inhibitor

does not compete with the substrate and binds at an allosteric site on the enzymes

Allosteric site

an alternative site for inhibitor binding that is NOT in the active site

Metabolism

All of an organisms chemical reaction

Metabolic Pathways

series of reactions that alters a substrate multiple times before the final product

Two types of metabolic pathways:

catabolic and anabolic

Catabolic Pathways (catabolism)

releases energy by breaking down molecules into smaller ones

Anabolic Pathways (anabolism)

Spends energy to build up larger molecules (like DNA and Proteins)

Negative Feedback:

when the final product of a metabolic pathway inhibits an earlier step in the same pathway

Positive Feedback:

when the final product of a metabolic pathway stimulates an earlier step in the same pathway

Oxidation-Reduction (Redox) Reaction:

transfers electrons between molecules

Oxidation

the process of losing one or more electrons

Reduction

the process of gaining one or more electrons

Oxidation and Reduction reactions occur

simultaneously

LEO

Lose Electrons Oxidation

GER

Gain Electrons Reduction

NADH and FADH2

Electron Carriers that each carry/transport 2 electrons

NADH oxidized

NAD+

FADH2 oxidized

FAD

NADPH

an electron carried involved in biosynthetic reactions for biosynthesis

Aerobic Cellular Respiration

the aerobic process of breaking down glucose to make ATP

Aerobic

requires presence of oxygen

Aerobic Cellular Respiration in prokaryotes occurs in the

cytoplasm

Chemical Equation for Aerobic cellular respiration

C6H12O6 + 6O2 --> 6H20 + 6CO2 + 36ATP

Stages of Aerobic Cellular Respiration

1. Glycolysis
2. Pyruvate Oxidation
3. Krebs Cycle
4. Electron Transport Chain and Chemiosmosis

Types of phosphorylation

-substrate level
-oxidative

Substrate Level Phosphorylation

Uses an enzyme and a substrate to directly transfer a phosphate group to ADP, creating ATP

Substrate Level Phosphorylation is used to make

a small amount of ATP during Glycolysis and the Krebs Cycle

Oxidative Phosphorylation

uses energy from redox reactions in the Electron Transport Chain to phosphorylate ADP

Oxidative Phosphorylation builds

a H+ concentration gradient, which is used to make large amount of ATP

1st step of aerobic cellular respiration

glycolysis

Glycolysis

breaks down glucose into 2 pyruvate molecules

Glycolysis does not require

oxygen

Energy Investment Phase of Glycolysis

requires an input of energy by using 2 ATP molecules

Energy Harvest Phase of Glycolysis

produce energy by forming 2 NADH & 4 ATP molecules

In glycolysis, 1 single glucose molecule =

2 pyruvate, 2 NADH, and 2 ATP molecules

Entner-Doudoroff pathway

alternative glycolysis pathway producing NADPH

2nd step of aerobic cellular respiration

pyruvate oxidation

pyruvate oxidation

converts each pyruvate into a molecule of Acetyl-CoA

pyruvate oxidation Produces

2 acetyl-CoA, 2 NADH, and 2 CO2 molecules

3rd stage of aerobic cellular respiration

Krebs cycle (citric acid cycle)

Krebs Cycle (Citric Acid Cycle)

Oxidizes acetyl-CoA producing energy int he form of ATP, NADH, and FADH2

1st phase of Krebs cycle

Acetyl-CoA entry: 2 carbons enter and react with oxaloacetate producing citrate

2nd phase of Krebs cycle

Citrate Oxidation: rearrangement and oxidation of citrate. Produces 1 ATP, 2 NADH, and 2 CO2 molecules

3rd phase of Krebs cycle

Oxaloacetate Regeneration: Regeneration of oxaloacetate by oxidation. Produces 1 NADH and 1 FADH2 molecules

How many rounds of Krebs Cycle for 1 glucose molecule?

2

4th step of aerobic cellular respiration

electron transport chain

Prokaryotic ETC is found in the

plasma membrane

ETC uses energy from electrons to generate

a H+ gradient by pumping H+ into the intermembrane space

Final Electron Acceptor

Oxygen

When oxygen serves as a final electron acceptor, it interacts with H+ to form

H2O

Chemiosmosis is the

the diffusion of ions across a membrane down their concentration gradient (high to low)

How is potential energy captured in the ETC?

through chemiosmosis

ATP Synthase

enzyme that facilitates chemiosmosis and synthesizes ATP

oxidative phosphorylation =

electron transport chain + chemiosmosis

Without Oxygen, ______ CANNOT occur

aerobic cellular respiration

Fermentation

process that uses electrons from NADH to reduce pyruvate and regenerate NAD+

Pyruvate can be reduced to

lactic acid or alcohol

Fermentation makes very little

ATP

Regeneration of NAD+ allows

glycolysis to continue without O2

Lactic Acid Fermentation

pyruvate is reduced by NADH to form lactic acid/lactate and NAD+

Alcohol Fermentation

pyruvate is reduced by NADH to form ethanol and NAD+

Anaerobic Respiration

uses other molecules instead of oxygen as the final electron acceptors of ETC