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

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

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 follows glycolysis, regenerating NAD+ needed for glycolysis to continue.•Lactic Acid Fermentation In lactic acid fermentation, pyruvate is converted to lactate 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

Cellular RespirationStage Two: Production of ATP

•Krebs Cycle The Krebs cycle is a series of reactions that produce energy-storing molecules during aerobic respiration. •Electron Transport Chain During aerobic respiration, large amounts of ATP are made in an electron transport chain.

Completes the breakdown of glucose› Takes the pyruvate (3-carbons) and breaks it

down, the carbon and oxygen atoms end up in CO2 and H2O

› Hydrogens and electrons are stripped and loaded onto NAD+ and FAD (coenzymes) to produce NADH and FADH2

Production of only 2 more ATP but loads up the coenzymes with H+ and electrons which move to the 3rd stage

Electron carriers loaded with electrons and protons from the Kreb’s cycle move to this chain-like series of steps (staircase).

As electrons drop down stairs, energy released to form a total of 32 ATP

Oxygen waits at bottom of staircase, picks up electrons and protons and in doing so becomes water

click here for ETC animation

36 ATP for aerobic vs. 2 ATP for anaerobic

› Glycolysis 2 ATP

› Kreb’s 2 ATP

› Electron Transport 32 ATP 36 ATP

Anaerobic organisms can’t be too energetic but are important for global recycling of carbon

Cellular Respiration is a metabolic process like burning fuel› Releases much of the energy in food to

make ATP› This ATP provides cells with the energy

they need to carry out the activities of life.

› C6H12O6+O2 CO2 + H2O + ATP

•Cellular respiration works opposite of the photosynthesis carried out by autotrophs.

•The products of respiration are used as the reactants for photosynthesis.