Cellular Respiration: Obtainingiris.nyit.edu/~jlee26/pics/rptse/Eng RPTSE Bio Ch. 06.pdf · 2015. 10. 28. · • Cellular respiration is an example of a metabolic pathway: a series

RPTSE Biology – Fall 2015, Dr. Jong B. Lee 1

© Jong B. Lee, Ph.D.

Chapter 6

Cellular Respiration: Obtaining

Energy from Food

RPTSE BIO Fall 2015 Jong B. Lee, PhD, All rights reserved.

Biology and Society: Marathoners versus Sprinters

• It is unusual to find a runner who complete equally well

in both 100m and 1000m races.

• Natural differences in the muscles of these athletes favor

sprinting or long-distance running.

• The muscles that move

our legs contain two main

types of muscle fibers:

Slow-twitch fibers &

Fast-twitch fibers


• Fast-twitch fibers (속근): function

best in sprints

Generate more power

Fatigue much more quickly

Can generate ATP without using oxygen

• All human muscles contain both types of fibers but in

different ratios.

• Slow-twitch fibers (지근): function best in marathons

Generate less power

Last longer

Generate ATP using oxygen


ENERGY FLOW AND CHEMICAL CYCLING IN THE BIOSPHERE

• Fuel molecules in food represent solar energy

• Animals depend on plants to convert solar energy to

chemical energy

:This chemical energy is in the form of sugars and other

organic molecules. 그외 clothing, lumber, paper

• Autotrophs (자가영양생물): called producers (생산자)

– “Self-feeders”: organisms that make all their own

organic matter from inorganic nutrients



• Heterotrophs (종속영양생물)

– “Other-feeders”

– Humans and other animals that

cannot make organic molecules from

inorganic ones

– Depend on autotrophs for their

organic fuel and material for growth

and repair

– Called consumers (소비자)


• The ingredients for photosynthesis are carbon dioxide

and water

– CO2 is obtained from the air by a plant’s leaves

– H2O is obtained from the damp soil by a plant’s roots

• Chloroplasts rearrange the atoms of these ingredients to

produce sugars (glucose) and other organic molecules

– Oxygen gas is a by-product of photosynthesis

Chemical Cycling Between Photosynthesis and Cellular Respiration


• Both plants and animals perform cellular respiration

– Cellular respiration is a chemical process that

harvests energy from organic molecules

– Cellular respiration occurs in mitochondria

– Cellular respiration uses to convert energy extracted

from organic fuel to another form of chemical energy

called ATP, an energy currency in the cell

• The waste products of cellular respiration, CO2 and H2O,

are used in photosynthesis




• Cellular respiration

CELLULAR RESPIRATION: AEROBIC HARVEST OF FOOD ENERGY

– A living version of internal combustion

– The main way that chemical energy is harvested from

food and converted to ATP

– This is an aerobic process—it requires oxygen

– 유기연료에서추출한에너지→ 화학에너지인ATP

에너지로전환하기위해, O2를필요로한다.


Cellular respiration and breathing are closely related

– Cellular respiration

requires a cell to

exchange gases with

its surroundings

– Breathing exchanges

these gases between

the blood and outside

air

The Relationship Between Cellular Respiration and Breathing


• A common fuel molecule for cellular respiration is glucose

– This is the overall equation for what happens to

glucose during cellular respiration

– The series of arrows indicates that cellular

respiration consists of many chemical steps

– The process can produce up to 38 ATP molecules for

each glucose consumed

The Overall Equation for Cellular Respiration


The Role of Oxygen in Cellular Respiration

During cellular respiration, hydrogen and its bonding

electrons change partners

Hydrogen and its electrons go from sugar to oxygen,

forming water (That hydrogen transfer turns out to

be the key to why oxygen is so vital to the harvest of

energy during cellular respiration)

Glucose Oxygen Carbondioxide

Water Energy

H+ + e-



• Chemical reactions that transfer electrons from one

substance to another are called oxidation-reduction

reactions (산화환원반응) : Redox reactions for short

Redox Reactions

• The loss of electrons (and hydrogens) during a redox

reaction is called oxidation

• The acceptance of electrons (and hydrogens) during a

redox reaction is called reduction


• Energy is released when hydrogen and its bonding

electrons change partners, from sugar to oxygen.


Why does electron transfer to oxygen release energy?

– In redox reactions, oxygen is an “electron grabber”.

– When electrons move from glucose to oxygen, it is

as though they were falling.

– Instead of gravity, it is the attraction of electrons to

oxygen that causes the “fall” and energy release

during cellular respiration

– This “fall” of electrons releases energy during

cellular respiration


A very rapid electron fall

• A very rapid electron fall

generates an explosive release

of energy in the form of heat

and light.

ex) A reaction between

hydrogen gas and oxygen gas

• The flame represents energy

released as heat and light



NADH and Electron Transport Chains

Cellular respiration is a more controlled “fall” of electrons:

Instead of liberating food energy in a burst of flame, cellular respiration unlocks chemical energy in smaller amounts that cells can put to productive use

The path that electrons take on their way down from glucose to oxygen involves many steps.


The first stop is an electron acceptor called NAD+

• The transfer of electrons from organic fuel to NAD+

(nicotinamide adenine dinucleotide) reduces it to NADH

• This electron transport chain lead ultimately to the

production of large amounts of ATP

• The rest of the path consists of

an electron transport chain

: This chain involves a series of

Redox reactions


The Metabolic Pathway of Cellular Respiration

• Cellular respiration is an example of a metabolic

pathway: a series of chemical reactions in cells

• A specific enzyme catalyzes each reaction in a

metabolic pathway

• All of the reactions involved in cellular respiration can

be grouped into three main stages

1. Glycolysis (해당과정) in cytoplasm

2. The Krebs cycle in mitochondria matrix

3. Electron transport in mitochondria inner membrane


A Road Map for Cellular Respiration

CytosolMitochondrion

High-energyelectronscarriedby NADH

High-energyelectrons carriedmainly byNADH

Glycolysis

Glucose2

Pyruvicacid

KrebsCycle

ElectronTransport



Stage 1: Glycolysis (해당과정)

• A molecule of glucose is split into two molecules of

pyruvic acid in cytosol (but not mitochondria)

cf) pyruvic acid (피브루산) formula: CH3-C-COOH

• Meanings of this metabolism (생화학적인 의미)

- These molecules then donate high energy electrons to

NAD+, forming NADH (Generate two NADH

molecules per glucose)

- Generate two ATP molecules: by substrate-level of

phosphorylation (기질수준의인산화과정에의해서)



Glycolysis makes some ATP directly when enzymes

transfer phosphate groups from fuel molecules to ADP

(substrate level of phosphorylation , 기질수준의인산화 )

Enzyme

Substrate level of phosphorylation


Stage 2: The Krebs Cycle (= The citric acid cycle)

• The Krebs cycle completes the breakdown of sugar This

cycle completes the breakdown of sugar produce CO2

• Generate three NADH and one FADH2 (function as

electron donor for electron transfer system)

• Generate two ATP molecules

(by substrate level of phosphorylation)

이 과정에 참여하는 효소들은 mitochondria 내부의 액체에

존재한다. 즉, mitochondria matrix에서 수행됨.



• In the citric acid cycle, pyruvic acid from glycolysis is

first “prepped” into a usable form, Acetyl CoA.


Kre

bs

cycle

RPTSE BIO Fall 2015 Jong B. Lee, PhD, All rights reserved. RPTSE BIO Fall 2015 Jong B. Lee, PhD, All rights reserved.

Stage 3: Electron Transport

• Electron transport (전자전달) releases the energy your

cells need to make the most of their ATP

• The molecules of

electron transport chains

are built into the inner

membranes of

mitochondria (electron

transport chain을구성하는

단백질과그밖에분자들은

mitochondria의내막에존재)



• The entire electron transport chain functions as a

chemical machine that uses energy released by the “fall”

of electrons to pump hydrogen ions across the inner

mitochondrial membrane

• By pumping H+ ions,

electron transport chains

store potential energy

by making the ions more

concentrated on one side

of the membrane than on the other (these H+ ions store

potential energy)


• The energy stored by electron transport behaves

something like the electron reservoir of water behind a

dam

• The membrane, analogous to the dam, temporarily

restrains the H+ ions.

• There is a tendency for the H+ ions to gush back to

where they are less concentrated, just as there is a

tendency for water to flow downhill.


Space between

membranes

Inner

mitochondrial

membrane

Electron

carrier

Protein

complex

Electron

flow

Matrix Electron transport chain ATP synthase

NADHNAD

FADH2 FAD

ATPADP

H2OO2

H

1

2

HHH

H

H

H

H

H

H

H

HH

HH

HH

HH

H 2

P


• When the hydrogen ions flow back through the

membrane, they release energy

– The ions flow through ATP synthase. This action spin

a component of the ATP synthase and activate

catalytic action. ATP synthase takes the energy from

this flow and synthesizes ATP

– ATP synthase는ADP 분자에 Phosphate-group을

부착시켜ATP를재발생시킨다.

– Some of deadliest poisons (CO and HCN) do their

damage by disrupting electron transport (blocking the

transfer of electrons to oxygen



The Versatility of Cellular Respiration

• Cellular respiration (versatile metabolic furnace) can

“burn” other kinds of molecules besides glucose

– Diverse types of carbohydrates

– Fats

– Proteins



Adding Up the ATP from Cellular Respiration

A summary of ATP yield during cellular respiration


ATP 생성 상황

Glucose 2 pyruvic acid + 2 ATP + 2 NADH

2 pyruvic acid 6 CO2 + 6 H2O + 2 ATP + 8 NADH + 2 FADH2

10 NADH x 3 ATP/NADH = 30 ATP

2 FADH2 x 2 ATP/FADH2 = 4 ATP

4 ATP + 30 ATP + 4 ATP = 38 ATP



FERMENTATION: ANAEROBIC HARVEST OF FOOD ENERGY

• Some of your cells can actually work for short periods

without oxygen

– For example, muscle cells can produce ATP under

anaerobic conditions

• Fermentation (발효): The anaerobic harvest of food

energy


• Human muscle cells can make ATP with and without

oxygen

– If you start to run because you’re late for class your

muscle forced to work under anaerobic conditions.

– They have enough ATP to support activities such as

quick sprinting for about 5 seconds

– A secondary supply of energy

(creatine phosphate) can keep muscle

cells going for another 10 seconds

– To keep running, your muscles must

generate ATP by the anaerobic process of fermentation

Fermentation in Human Muscle Cells


• Glycolysis is the metabolic pathway that provides ATP

during fermentation

– To harvest food energy during glycolysis, NAD+ (not

NADH) must be present as an electron acceptor

– This is no problem under aerobic condition, because

the cell regenerates its NAD+ when NADH drops its

electron cargo down electron transport chains to O2

– However, this productive recycling of NAD+ cannot

occur under anaerobic conditions because there is no

O2 to accept the electron


• Glycolysis produces just two ATPs

– Is not efficient compared with 38 ATPs under the

aerobic condition

– Your cells have to consume more glucose fuel

– Instead, NADH disposes of (처분하다) electrons by

adding them to pyruvic acid produced by glycolysis

– 즉, 해결책: Pyruvic acid is reduced by NADH,

producing NAD+, which keeps glycolysis going



• Lactic acid (젖산) as a by-product after fermentation in

muscle cells

– A temporary accumulation of lactic acid in muscle cells

contributes to the soreness or burning you feel after

exhausting run

– The lactic acid eventually transported in the blood from

muscles to the liver, where liver cells convert it back to

pyruvic acid

– Oxygen debt: O2 that metabolic pathway requires after

you’ve stopped vigorous activity (you breathe hard even

after stopping exercise). The extra oxygen is used to

generate glucose from lactic acid (gluconeogenesis)



• Various types of microorganisms perform fermentation

– Fermentation products: cheese, sour cream, yogurt

(주로젖산때문에이러한맛이발생)

– 그밖에 soy source (soybean), pickle cucumbers,

pepperoni, salami 등이있다.

Fermentation in Microorganisms


• Yeast (효모), a microscopic fungus

– Yeast cells are capable of both cellular respiration

and fermentation but a slightly different type of

fermentation

– This pathway (=alcohol fermentation) produces CO2

and ethyl alcohol

Fermentation in Microorganisms


RPTSE BIO Fall 2015 Jong B. Lee, PhD, All rights reserved. RPTSE BIO Fall 2015 Jong B. Lee, PhD, All rights reserved.

• The food industry uses yeast to produce various food

products


• 산소의 사용능력에 따라 생물체의 분류

- Facultative anaerobe: an organism that harvest food

energy by either cellular respiration or fermentation

- Obligate anaerobe: 산소접촉시사망, 깊은토양속미생물, 캔속의미생물, 늪지대에사는미생물

- Obligate aerobe: 산소를절대적으로필요로하는생명체


Ancient bacteria probably used glycolysis to make ATP

long before oxygen was present in Earth’s atmosphere

EVOLUTION CONNECTION:

LIFE ON AN ANAEROBIC EARTH

– Glycolysis is a metabolic heirloom from the earliest

cells that continues to function today in the harvest of

food energy

– Krebs cycle & electron transport chain은산소가

존재하는 aerobic condition에서만작동하지만

glycolysis는 aerobic과 anaerobic condition에서모두

작동할수있다. 그러므로아마도고대의 bacteria들은

지구의대기에산소가없을때 glycolysis를사용하여ATP를만들었을것으로추정한다.

Documents

Cellular Respiration: Obtainingiris.nyit.edu/~jlee26/pics/rptse/Eng RPTSE Bio Ch. 06.pdf · 2015. 10. 28. · • Cellular respiration is an example of a metabolic pathway: a series