How Cells Harvest Chemical Energy

Cellular Respiration

O2 CO2

BREATHING

Lungs

CO2O2

Bloodstream

Muscle cells carrying out

CELLULAR RESPIRATION

Sugar + O2 ATP + CO2 + H2O

Breathing and Cell Respiration are related

Muscles get oxygen from breathing and sugar from food to produce energy during cellular respiration.

Is a series of reactions where fats, proteins, and carbohydrates, mostly glucose, are broken down to make CO2, water, and energy.

Glucose Oxygen gas Carbon dioxide

Water Energy

recall that reactions have two parts› reactants (the ingredients needed for the

reaction to happen)› products (the molecules produced by the

reaction) they are separated by an arrow that

points towards the products

Glucose Oxygen gas Carbon dioxide

Water Energy

Burning glucose in an experiment

Energy released from glucose

(as heat and light)

100%

Energy released from glucose

banked in ATP

“Burning” glucosein cellular respiration

About 40%

Gasoline energy converted to movement

Burning gasolinein an auto engine

25%

How efficient is cell respiration?

energy released fromglucose as heat and light = 100% if you burn glucose

energy released fromglucose stored in ATP = 40% burned during cellular respiration

gas energy converted to movement 25% if burned in an auto engine

These reactions proceed the same way in plants and animals. Process is called cellular respiration

Overall Reaction:› C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP

Transformation of chemical energy in food into chemical energy cells can use: ATP

Most of the energy from cell respiration is converted into ATP

ATP is a substance that powers most cell activities.

Get energy by breaking the bond between the last 2 phosphates of ATP

An enzyme is needed to break the bond.› ATPase› This makes ATP into ADP (triphosphate into

diphosphate = took away one phosphate atom)

To remake ATP, another enzyme is used › ATP synthetase

Breakdown of glucose begins in the cytoplasm outside the mitochondria

smaller molecules enter the liquid matrix inside the mitochondria for further breakdown.

locate the matrix in the next slide

The matrix where 3-carbon pieces, called pyruvate, (that came from carbohydrates) are broken down into CO2 and water

The cristae is where ATP is made

Glycolysis› Series of reactions which break the 6-

carbon glucose molecule down into two 3-carbon molecules called pyruvate

› Process is an ancient one-all organisms from simple bacteria to humans perform it the same way

› Yields 2 ATP molecules for every one glucose molecule broken down

› Yields 2 NADH (enzyme) per glucose molecule

Cellular RespirationStage One: Breakdown of Glucose

• Glycolysis Glucose is broken down into pyruvate during glycolysis, making some ATP.• happens in the cytoplasm outside the mitochondrion.• pyruvate can go one of two ways: aerobic or anaerobic respiration

At this point, life diverges into two forms and two pathways› Anaerobic cellular respiration (aka

fermentation)› Aerobic cellular respiration

› We’ll look at anaerobic respiration first› also called fermentation

Some organisms thrive in environments with little or no oxygen› Marshes, bogs, gut of animals, sewage treatment ponds

No oxygen used = ‘an’aerobic Results in no more ATP, final steps in these

pathways serve ONLY to regenerate NAD+ so it can return to pick up more electrons and hydrogens in glycolysis.

End products such as ethanol and CO2 (single cell fungi (yeast) in beer/bread) or lactic acid (muscle cells)

Fermentation in the Absence of Oxygen•Fermentation (aka anaerobic respiration) When oxygen is not present, fermentation (used in making alcohol) follows glycolysis, regenerating NAD+ needed for glycolysis to continue.•Lactic Acid Fermentation In lactic acid fermentation, pyruvate is converted to lactic acid which is what makes your muscles burn during exercise.

Oxygen required=aerobic 2 more sets of reactions which occur in

a specialized structure within the cell called the mitochondria› 1. Kreb’s Cycle› 2. Electron Transport Chain