Cellular Respiration

Energy and Life8-1

Page 201

The sun is the

original source of

energy for all living

things.

To live and perform life functions all organisms need…

Autotrophs

Able to make their own food using the sun’s energy.

Heterotrophs

Get their energy from feeding on autotrophs or

other heterotrophs.

The food eaten must be turned into a chemical form to be used for life processes.

Adenosine Triphosphate (ATP)the main chemical compound that cells use

to store and release energy

• Energy from ATP powers:- active transport across cell membranes- synthesis of proteins & nucleic acids- responses to chemicals at the cell surface - can even be used to produce light

ATP is made up 3 parts:– adenine – 5-carbon sugar called ribose– three phosphate groups

adenine ribose phosphate groups

• Phosphate groups are the key to ATPs ability to store and release energy.

• Energy is stored in the bond between the 2nd and 3rd phosphate.

adenine

ribose

phosphate groups

When the 3rd phosphate breaks off it is called

ADP (adenosine diphosphate)

adenine

ribose

phosphate groups

• Breaking the chemical bond between the 2nd & 3rd phosphate RELEASES energy.

adenine

ribose

phosphate groups

ATPADP

• Adding the chemical bond between the 2nd and 3rd phosphate STORES energy.

• Breaking the chemical bond between the 2nd & 3rd phosphate RELEASES energy.

adenine

ribose

phosphate groups

ADPATP

ADP ATP

Energy

EnergyAdenosine diphosphate (ADP) + Phosphate Adenosine triphosphate (ATP)

Partiallychargedbattery

Fullychargedbattery

• Most cells have only a small amount of ATP, enough to last them for a few seconds of activity.

• ATP’s ability to “recharge” is very important to its usefulness.

• ATP is great for transferring energy, not good for long term energy storage.

– A single molecule of glucose stores 90 times the chemical energy of one molecule of ATP.

• Cells regenerate ATP from ADP as needed.

Figure 9–2 Cellular Respiration: An OverviewFigure 9–2 Cellular Respiration: An OverviewElectrons carried in NADH

Glucose

Cytoplasm

Glycolysis

Pyruvic acid

Krebs Cycle

Mitochondrion

Electrons carried in

NADH and FADH2 Electron

Transport Chain

Mitochondrion

Cellular Respiration

Net gain of 2 ATP

Net gain of 34 ATPTotal ATP molecules formed during cellular respiration = 36 ATP

CELLULAR RESPIRATION

6O2 + C6H12O6 6CO2 + 6H2O + Energy

Oxygen + Glucose Carbon + Water + Energy (ATP) Dioxide

Where did that glucose come from?

?

CELLULAR RESPIRATION

After glycolosis, there are two possible pathways depending on the presence or absence of O2

Chemical Pathways of Cellular Respiration

Glucose

Glycolysis Krebs cycle

Electrontransport

Fermentation (without oxygen)

Alcohol or lactic acid

CELLULAR RESPIRATION If oxygen is present aerobic respiration will

begin

If oxygen is not present anaerobic respiration will occur

After Glycolysis cont.If oxygen is not present one of two types of anaerobic respiration or Fermentation takes place;

Alcoholic Fermentation Lactic Acid Fermentation

Requires NADH to convert pyruvic acid into lactic acid

The Krebs CycleIf oxygen is present aerobic respiration begins

The Krebs Cycle begins when the two molecules of pyruvic acid produced in glycolysis enter the Mitochondria and with the help of enzymes form Citric Acid. As a result the Krebs cycle is also referred to as the Citric Acid

The Krebs Cycle cont.

Energy Extraction;The citric acid is broken down into carbon compounds and the following are released;

2 ATP 6 molecules of CO2Electron carriers

(NADH and FADH2 )

The Krebs Cycle cont.

Citric Acid Production

Mitochondrion

Electron Transport Chain The electron transport chain uses the high-energy

electrons (donated electron carriers NADH and FADH2) from the Krebs cycle to convert ADP into ATP.

High-energy electrons from NADH and FADH2 are passed along the electron transport chain (carrier proteins).

An enzyme at the end of the electron transport chain combines electrons with hydrogen ions and oxygen to form water.

Oxygen is the final electron acceptor. Releases 6H2O and 32 molecules of ATP

Cellular Respiration

Total ATP produced= 36