Respiration

Chapter 6

Cellular Respiration - Basics

• releases energy from glucose• released energy is chemical energy• occurs in cell

cytoplasmmitochondria

• works better with oxygen (aerobic) than without oxygen (anaerobic)

Cellular Respiration - Process

glucose oxygen +water energycarbon dioxide ++

CO2C6H12O6 H2OO2 ATP+ + +

Aerobic Respiration

aerobic = with oxygenC6H12O6 + O2 -----> CO2 + H2O + ATP

Three process occur in aerobic respiration1. Glycolysis

occurs in the cytoplasm

oxygen is not requiredelectron acceptor is nicotinamide adenine

dinucleotideNAD --> NADH

glucose 2 pyruvic acid

CCC

CCC

CCC C

CC

PEP

CO2

Aerobic Respiration cont’d

2. Krebs Cycle (citric acid cycle)

pyruvic acid(3C)

(in cytoplasm)

acetyl-coenzymeA(2C)

(in mitochondron)

Krebs Cycle

CO2

CO2

ATP

NADH

FADH2

occurs in:

mitochondria

electron acceptors are

NAD and FADH2

CCC

CC

C

C

C

Kreb’s Cycle

Aerobic Respiration cont’d

3. Electron transport• electrons transferred from

NADH, FADH2 to oxygen and water is formed

• oxidative phosphorylation• ATP synthase complex• protons pumped across

membrane

• occurs in mitochondria• conversion equivalents:

NADH = 3 ATPFADH2 = 2 ATP

Aerobic Respiration cont’d

• Energy from aerobic respiration• Glycolysis

• net gain of 6 ATP

• pyruvic acid --> acetyl-CoA• 2 NADH = 6 ATP

• Krebs Cycle• 2 ATP

• Electron Transport• 6 NADH = 18 ATP• 2 FADH2 = 4 ATP

• oxidative phosphorylation

•Total = 36 ATP / glucose

•39% of energy available

•61% of energy is lost as heat

Anaerobic Respiration

(without oxygen)

1. ethanol fermentation

glucose ---> pyruvic acid ---> ethyl alcohol + CO2 + ATP

C6H12O6 ----> 2C2H5OH + 2CO2 + 3ATP

• 25% of energy of aerobic respiration

• occurs in some plants and microorganisms including yeasts

Alcohol Fermentation• Ancient Eqyptian wall painting: historical record of wine-

making• ~ 5000 yrs ago, perhaps earlier• Grapes were picked, crushed by foot, juice collected in jugs,

then fermented producing wine.

Anaerobic Respiration cont’d

2. lactic acid fermentation glucose ---> pyruvic acid ---> lactic acid + ATP

C6H12O6 ----> 2C3H6O3 + 2ATP

• 22% of energy of aerobic respiration

• mammalian muscle and some microorganisms

Organic Macromolecules

• four groupsCarbohydrates

built from monosaccharidesProtein

built from amino acidsLipids

built from glycerol & fatty acidsNucleic acids

built from nucleotides

Carbohydratesmonosaccharides

disaccharides

polysaccharide

Lipids

Protein

Biochemical Pathways

• note catabolic and anabolic pathways

• note production and use of:• proteins• lipidsbesides carbohydrates

Biochemical Pathways

• note catabolic and anabolic pathways

• note production and use of:• proteins• lipidsbesides carbohydrates

Biochemical Pathways

• note catabolic and anabolic pathways

• note production and use of:• proteins• lipidsbesides carbohydrates

Biochemical Pathways

• note catabolic and anabolic pathways

• note production and use of:• proteins• lipidsbesides carbohydrates

Biochemical Pathways

• note catabolic and anabolic pathways

• note production and use of:• proteins• lipidsbesides carbohydrates

What is the connection between respiration and photosynthesis?

• Is atmospheric CO2 in “equilibrium”?• Absorption by plants and the oceans• Accumulating in the atmosphere as carbon dioxide

• CO2 emission into the atmosphere by fossil fuel combustion dramatically changed “equilibrium”CARBON (oil, coal, natural gas, etc) + OXYGEN + COMBUSTION -> CO2 + heat

Carbon Cycle

Numbers = approximate carbon exchange (Gt/year)

Air samples at Mauna Loa, Hawaii are collected continuously from air intakes at the top of four 7-m towers and one 27-m tower. Four air samples are collected each hour for the purpose of determining the CO2 concentration

Conclusion: carbon released from the burning of fossil fuels has increased exponentially over the last century!

Global Warming Contributors

Consequences of CO2 increase• CO2 as a Greenhouse Gas

• third most abundant gas in atmosphere

• absorbs heat energy reflected by earth• acts as a blanket around earth• produces the greenhouse effect

• This is normal, and good!

• Excessive greenhouse gas accumulation?• increase GH gas; increase

heat absorption• increased heat of earth• Global Warming

CO2 in atmosphere

key component of nature’s thermostat

If carbon cycle removes excessive

CO2

earth cools

If carbon cycle generates excessive

CO2

earth warms

Carbon Flow: Living Systems

• Life is carbon based• All organisms use carbon compounds for

• Energy: • Glucose primarily, is converted to ATP in cells

• Structural components:• Cell membrane & wall; cellulose, proteins,

• Regulatory components:• DNA,enzymes, hormones, neurotransmitters, etc.

• Thus: • energy flow is tied to carbon• life is tied to carbon

Carbon Flow: Living Systems

• Goals for you as student:• Trace carbon • from atmosphere• through photosynthesis in autotrophs• through cellular respiration in autotrophs

and heterotrophs• back into atmosphere