A&P Chapter 3

Energy

Capacity to do work

Potential energy

Stored energy (energy of position)

Kinetic energy

Energy of motion

Chemical energy

Energy stored in a molecule’s chemical bonds is the most important form of energy in the human body

What is chemical energy used for

Movement, molecular synthesis, and concentration gradients

When is chemical energy released

When bonds break during reactions

Electrical energy

Movement of charged particles

Mechanical energy

Exhibited by objects in motion due to an applied force

Sound energy

Molecular compression caused by a vibrating object

Radiant energy

Energy of electromagnetic waves

Heat energy

Kinetic energy associates with random motion of atoms, ions, or molecules; usually not available to do work; waste or by-product

Thermodynamics

Study of energy transformation

First law

Energy cannot be created or destroyed, only converted from one form to another

Second law

Every time energy is transformed, some of it is converted to heat

Chemical reactions

Occur when chemical bonds in existing molecular structures are broken, rearranged, or formed

Reactants

Substances present prior to start of a chemical reaction, written on the left

Products

Substances formed from the reaction, written on the right side

Decomposition reaction

Initial large molecule broken down into smaller structures, AB→ A+B, catabolism or catabolic reactions

Synthesis reaction

Two or more structures combine to form a larger structure, A+B→ AB, anabolism

Exchange reaction

Groups exchange between two chemical structures, AB+C→ A+BC, has both decomposition and synthesis components, most prevalent in human body

Oxidation-reduction reaction (redox reaction)

Type of chemical reaction where electrons are moved from one structure to another

Structure that loses an electron (electron donor)

Oxidized

Structure that gains an electron (electron acceptor)

Reduced

Exergonic reactions

Reactants have less energy within bonds than products, energy must be released, decomposition or catabolic

Endergonic reactions

Reactants have less energy in bonds than products, energy must be put in (needed), synthesis or anabolic

Irreversible reaction

Reaction that results in a net loss of reactants and a net gain in products; A+B→ AB or AB→ A+B

Reversible reaction

Does not proceed only to the right, reactants become products and products become reactants at equal rates

Equilibrum

No net change in concentration of reactants or products in a reaction

Activation energy (E_a)

Energy required to break existing bonds

Overcoming reaction rate

Presence of an enzyme lowers E_a, in lab increasing temperature significantly will denature proteins

Functions on enzymes

Decrease activation of cellular reactions, act as biological catalysts

Uncatalyzed reaction

No enzyme present

Catalyzed reaction

Enzyme present

Enzyme diversity

Enzymes can stay within cells, become embedded in plasma membrane, be secreted from cells

Active site

Unique 3-D structure in a protein chain

Enzyme-substrate complex

Temporarily forms when enzyme meet at active site

Enzyme catalysis

Substrate enters active site, forms enzyme substrate complex, enzyme shape changes, binds to substrate, chemical bonds formed or broken from stress, products releases, enzyme available for new substrate

Conformational change

Enzyme changes shape slightly

Induced fit model

Enzyme binds tightly to substrate

Accelerate reaction rates

Increase enzyme or substrate concentration, temperature increase, pH

Inhibitors

Bind to enzymes and prevent enzymatic catalysts

Competitive inhibition

Resembles substrate and binds to active site

Noncompetitive inhibitor

Does not bind to active site, binds to allosteric site to produce a small conformational change preventing the substrate from binding

Cofactors

Helps existing enzymes work properly, existing enzymes may be turned on by adding

Metabolic pathway

Series of enzymes that convert substances to products, product of on enzyme becomes the substrate of the next

Multienzyme complex

Group of enzymes that are physically attached, work in a sequence, produce one reaction serves as substrate for another

Multienzyme complex advantages

Less likely for substance to diffuse away, slowly or failing to complete pathway, single multienzyme complex can be regulated rather than individual enzymes

Cellular resiration

Exergonic multistep pathway, energy released to make ATP, oxygen required, organic molecules are oxidized and disassembled by series of enzymes

Glucose oxidation

Step by step breakdown of glucose to release energy, CO₂ and H₂O formed

Glycolysis

Does not require oxygen, occurs in cytosol

Glycolysis inital substrate

1 glucose

Glycolysis products

2 pyruvate, 2 ATP, 2 NADH

Intermediate stage

Requires oxygen, occurs in matrix of mitochondria

What enters intermediate stage

2 pyruvate

Intermediate stage products

2 Acetyl CoA, 2 NADH, 2 CO₂

Citric acid cycle

Requires oxygen, occurs in matrix of mitochondria

What enters citric acid cycle

Acetyl CoA

Citric acid cycle products

1 ATP, 3 NADH, 1 FADH₂ , 2 CO₂

Two turns of citric acid cycle products

2 ATP, 6 NADH, 2 FADH₂ , 4 CO₂

Electron transport system

Transfer of stored energy from NADH and FADH₂ to make ATP

Electrons from NADH enter at the top of the first hydrogen H+ pump

3 ATP produced

Electrons from FADH₂ pass through the second hydrogen H+ pump

2 ATP produced

ATP production

38 ATP produced, actual yield is 30 ATP due to steps requiring energy