Cellular Respiration

The Energy in Food

The Energy in Food

Cellular Respiration Cellular Respiration – A chemical process that uses oxygen to convert the chemical energy stored in foods (organic molecules) into another form of chemical energy.

• ATPATP – Adenosine Triphosphate – Cells in plants and animals use ATP

as their main energy supply

The Energy in Food

Rapid Oxidation Rapid Oxidation – the release of chemical energy

by burning• This reaction is not controlled by

enzymes– Results consist of an uncontrolled

energy release

The Energy in Food

Slow Oxidation Slow Oxidation – the release of energy in a controlled

fashion. • Enzymes catalyze a sequence of

events that cause covalent bonds to break one at a time.

• This is MetabolismMetabolism!

Photosynthesis / Cellular Respiration

Recycle a common set of chemicals:

• Water• Carbon Dioxide

• Oxygen• Glucose (Organic

Compounds)

ATPPhosphate part is most

important

Because of the negative charge on all the attached oxygens, there is a lot of potential energy in these bonds

Removing the last phosphate group makes the molecule much “happier” (chemically stable)

ATP to ADP

“renewable” molecule; ATP ADP, energy to do this comes from food you eat

Three Types of work that Cells Perform “Review”

1. Chemical Work• Building large molecules like proteins

– ATP provides energy for Dehydration Synthesis

Three Types of work that Cells Perform “Review”

2. Mechanical Work• Muscle Contraction

– ATP causes change in shape of protein which then opens the door for Potassium (K) and Calcium (Ca) to cause the binding of Actin and Myosin.

Three Types of work that Cells Perform “Review”

3. Transport Work• Pumping Ions across a membrane

RespirationOrganic compounds contained stored

(potential) chemical energy in their bonds

When that energy is released, cells can use it for metabolism

Glucose (from glycogen stores) typically used first as the source of energy

No glucose? Lipids next then amino acids/proteins (only in

extreme cases- i.e. starvation)

RespirationControlled release of energy from

organic compounds in cells to form: Adenosine Triphosphate (ATP)

Glycolysis is the first step in respiration

Two types of respiration: Two types of respiration: Aerobic (uses oxygen) Anaerobic (without oxygen)

2 types of anaerobic respiration: Lactic Acid Fermentation Lactic Acid Fermentation (Humans /

Mammals) Alcoholic Fermentation (yeast)

Anaerobic RespirationAnaerobic RespirationLactic Acid FermentationLactic Acid Fermentation

Normally in aerobic organisms that find themselves in a situation where oxygen is no longer available—why you breather harder when you work out

When O2 becomes available, lactate converted back to pyruvate and then pushed through the aerobic pathway

Pyruvate converted to lactate (3-C), no CO2 produced, no ATP produced

Anaerobic RespirationAnaerobic RespirationLactic Acid FermentationLactic Acid Fermentation

• DOES NOT MAKE YOU SORE• NO ATP IS MADE SO IT DOES

CAUSE FATIGUE

Anaerobic RespirationAlcoholic Fermentation

• Occurs in yeast cellsThis is a “normal” situation for

the yeast

Pyruvate converted to ethanol (2-C) and CO2 is released…both waste products for the organismBakers’ and brewers’ yeast allows bread to rise and beer to be carbonated (most commercial beer is forcibly carbonated as well)

Fermentation in Microorganisms

Oxygen and Cellular Respiration

• Breathing and Cellular Respiration

Aerobic Process Aerobic Process – means it requires oxygen• Cells Exchange:

– Oxygen into the cell– Carbon Dioxide out of the cell

• Body: In your lungs – Blood Exchange:– Oxygen (in)– Carbon Dioxide (out)

Cellular Respiration

Chemical Formula:• Each glucose molecule yields 38 ATP 38 ATP

molecules

Reviewing the Mitochondria

• Found in almost all Eukaryotic Cells– The Mitochondria structure is key to its role

in cellular respiration– Have their own DNA– Have their own ribosomes

Mitochondria

Structure: Made – up of two membranes– There is a space between the inner and the

outer membrane

Matrix – the highly folded inner membrane enclosing a thick fluid • Inside the inner membrane you find many of

the enzymes involved in cellular respiration– folds of the membrane allows a Large

Surface Area for reactions to occur.– MAXIMIZES the area for ATP production

Cellular RespirationFirst:Metabolism – all chemical processes in a cellMetabolic Pathways – Term given to cellular respiration; because it

is made up of a series of reactions (thus the

term pathways)• Specific enzymes catalyzes each reactions in a

pathways

The Metabolic PathwaysThree Steps or Stages

Stage 1: Glycolysis = “Splitting Sugar”• First stage in breaking down glucose molecule• Takes PLACE outside the mitochondria in the cytoplasm• 2 ATP molecules are actually used to get things started.

– 2 ATP’s split the glucose molecule in half.

Investment Stage

Electrons are then transferred to a carrier molecule called NAD• NAD then turn into NADH • At this point 4 ATP are produced• Now your up by 2 ATP

The Metabolic PathwaysGlycolysis (Payback Stage)• Remember you used 2 ATP’s to start

– Gained 4 (net gain)

• End Result are:• Two Pyruvic Acid Molecules

Glucose + 2ATP 2 Pyruvic Acid molecules

+ 4ATP

Pyruvic Acid Molecules still hold most of the energy of the original glucose molecules

The Metabolic PathwaysStage 2: The Kreb Cycle• Named after biologist Hans Krebs

Blame this guy

The Metabolic PathwaysThe Kreb CycleThe Kreb Cycle

• Finishes the breakdown of Pyruvic Acid molecules to CO₂ - releasing more energy.– Pyruvate loses a C as CO2, becomes

acetyl-CoA

• Enzymes are dissolved in the Matrix inside the Matrix– Called the Fluid Matrix

The Metabolic Pathways

• Acetyl Co A joins a 4 Carbon Acceptor molecule

• Produces 2 CO₂ + 1 ATP per Acetyl CoA– NADH and FADH₂ (another electron

carrier) trap most of the energy– At the end you are left with a 4 carbon

acceptor molecule • So the cycle can continue

The Kreb Cycle

The Metabolic Pathways

The Metabolic PathwaysThe Kreb Cycle

Results:• Glycolysis produces 2 Pyruvic Acid

molecules from 1 glucose molecule• Each Pyruvic Acid molecule makes 1

Acetyl CoA• Cycle turns 2 TIMES• Producing: 4 CO₂ + 2ATP’s

The Metabolic Pathways

Electron Transport Chain & ATP Synthase ActionFirst: (carrier molecules) NADH transfers electrons from

the original glucose molecule to an electron transport chain.

Remember: eˉ move to carriers that attract them more strongly– This is why they move from carrier to carrier

• One carrier attracts them more than the one carrying; moving the eˉ to the inner mitochondria

– Finally being pulled by oxygen at the end of the chain.

– 2 H⁺ combines with oxygen forming H₂O

The Metabolic PathwaysElectron Transport Chain & ATP Synthase Action

The Metabolic PathwaysElectron Transport Chain & ATP Synthase Action

ATP Synthase – Protein structures inside the mitochondria that receives the H⁺ uses that flow to convert ADP into ATP.

• Can make up to 34 ATP’s

The Final Count

Glycolysis 2 ATPKreb Cycle 2 ATP

Electron Transport Chain 34 ATP• Maximum ATP for 1 Glucose

Molecule = 38• Notice most ATP is made after Glycolysis and

Kreb Cycle – which are anaerobic (without O₂)

Aerobic respiration

Types of Respiration

Occurs in the absence of OxygenOccurs in the absence of Oxygen

Aerobic RespirationAerobic Respiration

Occurs in presence of OxygenOccurs in presence of Oxygen

Occurs in the cells’ cytoplasmOccurs in the cells’ cytoplasm

Occurs in the cells’ mitochondria Occurs in the cells’ mitochondria

Yields small amount of ATP (2 molecules) per molecule of glucose

Yields small amount of ATP (2 molecules) per molecule of glucose

Yields large amount of ATP (38 molecules) per molecule of glucose

Yields large amount of ATP (38 molecules) per molecule of glucose

Does not involve fermentationDoes not involve fermentation

Involves fermentation of pyruvate to lactate in muscles/CO2 & ethanol in plant & yeast

Involves fermentation of pyruvate to lactate in muscles/CO2 & ethanol in plant & yeast

Anaerobic RespirationAnaerobic Respiration

Comparison between Aerobic & Anaerobic Respiration -Animals