Cellular RespirationMolecular Biology

_________________________________________________________________________________Cellular Respiration!Cellular Respiration !Glycolysis !Krebs Cycle !Electron Transport Chain !Fermentation !Lactic Acid

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!Life is built on chemical reactions » transforming energy from one form to another

organic molecules → ATP & organic molecules

organic molecules → ATP & organic molecules

sun

solar energy → ATP & organic molecules

Energy Flow

_________________________________________________________________________________Glucose!Glucose

» product of photosynthesis » 6 carbon sugar molecule » main energy source for animals

Glucose

_________________________________________________________________________________Chemical Energy!Releasing energy from sugar requires an

initial input of energy. » activation energy » large biomolecules are stable » must absorb energy to break bonds

energycellulose CO2 + H2O + heat

!ATP is the energy source of cellular processes. ATP ↔ ADP.

_________________________________________________________________________________Adenosine Triphosphate

_________________________________________________________________________________Electron Carriers

!NAD+ and FAD2+ are high-energy electron carriers.

!NAD+ + H+ + e- = NADH

_________________________________________________________________________________Cellular Respiration!Cellular respiration is the process of

breaking down glucose in the presence of oxygen to create ATP.

aerobic means requiring oxygen.anaerobic means without oxygen.

_________________________________________________________________________________Cellular Respiration

_________________________________________________________________________________Photosynthesis

_________________________________________________________________________________MITOCHONDRION

Outer MembraneInner Membrane

Cristae

Matrix

!Breaking down glucose » glyco - lysis (splitting sugar) !!!

» ancient pathway which harvests energy • transfer energy from organic molecules to ATP • starting point for all cellular respiration

_________________________________________________________________________________Glycolysis

glucose → → → → → pyruvate2x6C 3C

Glycolysis occurs in the cytoplasm.

_________________________________________________________________________________Glycolysis

!Glucose is split into 2 pyruvate molecules.

_________________________________________________________________________________Energy Investment

!Glycolysis requires 2 ATP molecules. !Results in 4 ATP molecules !» 4 ATP molecules (net gain of 2 ATP) !

» 2 Pyruvic Acid molecules !

» 2 electrons

!In the cytoplasm. !Quick !Does not require oxygen (anaerobic).

_________________________________________________________________________________Glycolysis

Glucose

Cytoplasm

Pyruvic acid

Electrons carried in NADH

Krebs Cycle

Electrons carried in

NADH and FADH2 Electron

Transport Chain

Mitochondrion

Glycolysis

_________________________________________________________________________________Krebs Cycle

Aerobic Respiration… !Krebs cycle uses oxygen to release energy

from the pyruvic acid molecules.

_________________________________________________________________________________Kreb’s Cycle

Citric Acid Production

Kreb’s Cycle takes place in the mitochondrion.

Glucose

Cytoplasm

Pyruvic acid

Electrons carried in NADH

Krebs Cycle

Electrons carried in

NADH and FADH2 Electron

Transport Chain

Mitochondrion

Glycolysis

_________________________________________________________________________________Krebs Cycle/Citric Acid Cycle!Products of Kreb’s Cycle

» 2 ATP » CO2 » Lots of electrons

_________________________________________________________________________________Respiration and Exercise

!During exercise cells require more energy, so they produce more carbon dioxide.

!Carbon dioxide produces carbonic acid in water.

!Breathing removes thecarbon dioxide.

_________________________________________________________________________________Carbonic Acid

_________________________________________________________________________________Electron Transport Chain

!The electron transport chain uses the electrons from Krebs cycle to create 32 ATP molecules.

_________________________________________________________________________________Electron Transport Chain

Electron TransportHydrogen Ion Movement

ATP Production

ATP synthase

Channel

Inner Membrane

Matrix

Intermembrane Space

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_________________________________________________________________________________From One Molecule of Sugar!Glycolysis nets 2 ATP molecules !Kreb’s cycle gives 2 ATP molecules !ETC produces 32 ATP molecules. !It only took 2 ATP to start cellular

respiration.

_________________________________________________________________________________Fermentation

Glycolysis Krebs cycle

Electron transport

Fermentation (without oxygen)

Alcohol or lactic acid

When oxygen is not present glycolysis is followed by fermentation.

pyruvate → ethanol + CO2 !

_________________________________________________________________________________Alcoholic Fermentation

!Dead end process » at ≈ 12% ethanol kills yeast » can’t reverse the reaction

NADH NAD+

3C 2C 1C

bacteria and yeast

_________________________________________________________________________________Lactic Acid Fermentation

!Reversible process » When O2 becomes available lactate

is converted back to pyruvate by theliver.

animals and some fungi

pyruvate ⇆ lactic acid

NADH NAD+

3C 3C

_________________________________________________________________________________FermentationAnaerobic respiration...

!Produces lactic acid or ethanol !Produces 2 ATP molecules. !Lactic acid is a product of fermentation, which

causes a painful burning sensation.

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