A&P Ch3- Energy, Chemical Reactions, and Cellular Respiration

Energy

capacity to do work

Concentration Gradient: Potential and Kinetic Energy

-potential energy

ex) Na+ ions in high concentration outside of the cell

-kinetic energy

ex) Na+ ions moving to low concentration inside of the cell

4 Types of Kinetic Energy

1) Electrical energy- moving charged particles

2) Mechanical Energy- movement of a structure due to force

3) Sound Energy- movement of compressed molecules through a medium by vibrating object

4) Radiant Energy- movement of electromagnetic waves varying in wavelength and frequency

3 molecules with high chemical energy (potential)

1) triglycerides

2) glucose

3) ATP

Electrical energy def and example

-kinetic

-moving charged particles

ex) electricity, nerve impulses

Mechanical Energy Def and Example

-object in motion due to applied force

ex) contracting muscles for walking, pumping heart to circulate blood

Sound Energy Def and Example

-compression of molecules moving in a medium caused by vibration

ex) vibrating vocal cords

Radiant energy Def and Example

-energy of electromagnetic waves

-higher frequency= more radiant energy

First Law of Thermodynamics

energy can’t be created or destroyed, only transformed or converted

Second Law of Thermodynamics

every time energy is transformed from one form to another, some energy is converted to heat

• usable amount of energy decreases in transfers

Metabolism

all biochemical reactions in a living organism

Catabolism

-decomposition

ex) hydrolysis

Anabolism

-synthesis

ex) dehydration synthesis

Nicotinamide Adenine Dinucleotide

-oxidation-reduction reaction

-2H atoms donated from glucose to the oxidized NAD+ which accepts 1 H and 1 e- to form NADH which is reduced

Example of Exergonic Reactions

-decomposition of glucose to CO2 and H2O

Examples of Endergonic Reactions

-synthesis of amino acids to peptides

ATP cycling

-continuous formation and breaking down of ATP

• formation: ADP + Pi → ATP, energy is supplied from breaking down fuel molec, oxidation

• breaking down: ATP→ ADP + Pi

Reversible Reaction Example

-Blood transport of CO2 and maintaining acid-base balance

• CO2 and H2O combine to form H+ and bicarbonate ion (HCO3-)

• catalyzed by carbonic anhydrase enxyme

Enzymes def

biologically active catalysts that decrease Ea to accelerate physiologic activities

Active Site Function

-grooved region in an enzyme where a substrate binds to form the enzyme-substrate complex

• highly specific

4 Steps of Enzyme Facilitated Reactions: For both Decomposition and Synthesis

1) substrate enters active site of enzyme to form substrate-enzyme complex

2) entry of substrate induces conformation of enzyme for a better fit, induced-fit model

3) stress on chemical bonds caused by changing enzyme shape, lowers Ea, bonds in substrate easier to break

4) product released from enzyme

Cofactor General Function

-nonprotein structure associated with enzymes to facilitate reaction

Inorganic Cofactors Function

-attached to enzyme, required for the enzyme to function properly

Organic Cofactors

-aka coenzymes

-not attached to enzymes but have specific functions to assist

What are the 6 classes of enzymes?

1) oxidoreductase

2) transferase

3) hydrolase

4) isomerase

5) ligase

6) lyase

Oxidoreductase Action and Example

-transfers e- from one substance to another

ex) dehydrogenase uses NAD+ as e- acceptor

Transferase Action and Example

-transfers functional groups

ex) kinase transfers phosphate to diff substance

Hydrolase

-splits chemical bond using water

-phosphatase, protease, lipase, sucrase

Isomerase Action and Example

-converts one isomer to another

ex) mutase transfers atoms within molec

Ligase Action and Example

-bonds 2 molecules together

ex) synthetase bonds 2 molec using ATP

Lyase Action and Example

-splits chemical bond in absence of water

-synthase catalyzes synthesis process

Substrate Saturation

-so much substrate is present so all enzymes are engaged and no further notable increase is observed in reaction rate

Competitive Inhibitor

-resembles substrate and binds to active site of enzyme

Noncompetitive Inhibitor

-binds to allosteric site on the enzyme resulting in a conformational change

Multienzyme Complex Structure

-group of enzymes physically attached through noncovalent bonds, sequence of reactions

-must be regulated to prevent overproduction of product through negative feedback

Multienzyme Complex Regulation

-must be regulated to prevent overproduction of product through negative feedback

-phosphorylation and dephosphorylation

• kinase adds P

• phosphatases remove P

Glucose Oxidation

-loss of e- from breakdown of glucose molecules

-release of energy forms ATP

Substrate-level Phosphorylation

-direct method of synthesizing ATP

Oxidative Phosphorylation

-indirect method, energy first released to coenzymes that transfer energy to form ATP

Glycolysis Overview

-doesn’t require oxygen

-broken down into 2 pyruvate products

-net production of 2 ATP molecules, 2 NADH molecules

Steps of Glycolysis

1-5: split glucose to 2 molecules of G3P, investment of 2 ATP as kinase transfers Pi from ATP to glucose then fructose

6 (occurs 2x): transfer unattached Pi to substrate, 2H released to NAD+ tp form NADH and H+ catalyzed by dehydrogenase

7 (occurs 2x): original Pi transferred to ADP to form ATP by substrate-level phosphorylation by kinase

8 (occurs 2x): isomer formed b/c loss of water

9 (occurs 2x): transfer of remaining Pi to ADP to form ATP by substrate-level phosphorylation by kinase, forms pyruvate

Net Products of Glycolysis

ATP: 2 molecules ( 2 ATP invested, 4 ATP formed)

NADH: 2 NAHD

Regulation of Glycolysis

-regulated through negative feedback

-ATP is allosteric inhibitor turning off phosphofructokinase

What happens to pyruvate if oxygen is not available?

-pyruvate converted to lactate

Where is the multienzyme complex of the intermediate stage and the enzymes of the citric acid cycle located?

in the matrix of the mitochondria (innermost fluid)

Pyruvate Dehydrogenase

-multienzyme complex in intermediate stage

Function of pyruvate dehydrogenase

-converts pyruvate and coenzyme A to acetyl coA and CO2 (released from pyruvate)

-occurs 2x b/c 2 pyruvate from first step

Yield of Pyruvate Dehydrogenase

2 NADH molecules, 2CO2, 2 Acetyl CoA

Citric Acid Cycle Yield

-acetyl CoA converted to 2 CO2 molecules and CoA released

-1 ATP formed, 3 NADH, 1 FADH2 in one cycle

Steps of Citric Acid Cycle

1) formation of citrate- combined acetyl CoA molecule with molecule of oxaloacetate to form citrate

2-3) forms isomer by removing water from citrate and reattaching it to diff location

4-5) CO2 released by decarboxylation, transfer 2e- and H to get NAD+ → NADH, add CoA

6) removal CoA, formation of ATP through substrate-level phosphorylation

7) dehydrogenase that transfers 2 hydrogens to FAD to form FADH2

8) addition of water

9) dehydrogenase transfers hydrogen to NAD+ to form NADH, oxaloacetate regenerated

Electron Transport System

-transfer of electrons from coenzymes NADH and FADH2 to form ATP

H+ pump transport H+ to outer membrane to maintain a gradient

What are the electron carriers?

ubiquinone, cytochrome C located between pumps and transfer electrons

ATP synthase

-enzyme in cristae allowing for H+ from outer compartment back to matrix

What are the 3 steps of the electron transfer system?

1) coenzyme NADH or FADH2 release H and are oxidized, electrons pass through chain to O2 which is the final e- acceptor, O2 combines with 4e- and 4H+ to make 2 water molecules of H2O

2) H+ gradient is established, e- pass through chain and their kinetic energy is harnessed by H+ pumps to move H ions from matrix to outer component to maintain gradient

3) H+ moves down the gradient by ATP synthase from outer compartment to matrix, this kinetic energy is harnessed by ATP synthase and new bond forms between ADP and Pi

How much ATP does each NADH and FADH2 release?

NADH releases 3 ATP and each FADH2 releases 2 ATP

What happens if pyruvate doesn’t have enough oxygen?

1) cellular respiration needing oxygen in the mitochondria decrease

• electron chain activity decrease

• NADH and FADH2 molecules accumulate

2) cell depends on glycolysis

3) low O2 would result in complete shutdown of glycolysis bc lack of NAD+

4) NAD+ has to be regenerated to continue glycolysis

How is NAD+ regenerated?

-transfer of H from NADH and 2 e- to pyruvate and converted to lactate to regenerate NAD+

-enzyme is catalyzed by lactate dehydrogenase

Why is the Conversion of Pyruvate to Lactate not sufficient?

-this process only produces 2 ATP compared to the 30 ATP produced with O2 available

-low O2= low energy

Beta-Oxidation

-fatty acids changed to form acetyl CoA that enters the metabolic pathway at the citric acid cycle

What is a byproduct of fatty acid metabolism?

ketoacids are produced

Deaminated Amino Acids in Metabolic Pathway

-amino acids can enter at glycolysis, intermediate stage, or citric acid cycle

Waste product of deaminated amino acids in metabolic pathway

-amine group

-this amine group is converted to urea and excreted by kidneys