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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.