CELLULAR RESPIRATION

NOTES

• The transformation of chemical energy in food into chemical energy cells can use: ATP, adenosine triphosphate.

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

• Overall Reaction:• C6H12O6 + 6O2 → 6CO2 + 6H2O

• FLIP THE REACTANTS & PRODUCTS TO GET THE EQUATION FOR PHOTOSYNTHESIS!

Cellular Respiration Overview

Cellular Respiration Overview

• Breakdown of glucose begins in the cytoplasm.

• At this point life diverges into two forms and two pathways• Anaerobic cellular respiration (aka fermentation)

• Aerobic cellular respiration

STEPS OF CELLULAR RESPIRATION

1. Glycolysis• Series of reactions which break

the 6-carbon glucose molecule down into two 3-carbon molecules called “pyruvate”

• This process is an “ancient one” because all organisms from simple bacteria to humans perform it the same way

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

Anaerobic Cellular Respiration

• 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)

Aerobic Cellular Respiration

• Oxygen required=aerobic

• Steps 2 & 3 of cell respiration will occur in succession in the presence of oxygen. This set of reactions will occur in a specialized structure within the cell called the mitochondria• 2. Kreb’s Cycle

• 3. Electron Transport Chain

KREB’s Cycle &The ETC

A Little Krebs Cycle History

Discovered by Hans Krebs in 1937

He received the Nobel Prize in physiology &medicine in 1953 for his discovery

Forced to leave Germany prior to WWII because he was Jewish

2. Kreb’s Cycle / Citric Acid Cycle

• Completes the breakdown of glucose• Takes both pyruvates and simultaneously

completes the reaction needed to break down the each pyruvic acid into CO2 and H2O

• Hydrogens and electrons are stripped and loaded onto NAD+ and FAD to produce NADH and FADH2

• Yields only 2 more ATP but loads up the coenzymes with H+ and electrons which move to Step 3.

What is NAD or NADH?

NAD+ (nicotinadeninedinucleotide) acts as the energy carrier by carrying electrons

NAD+ is a “coenzyme”

It’s Reduced to NADH when it picks up two electrons and one hydrogen atom (hence the name, NAD+H)

INACTIVESTATE

ACTIVESTATE

Coenzymes

Other Electron Carriers

FAD+ (Flavin adenine dinucleotide)

Also a coenzyme!

Reduced to FADH2

• Both NAD & FAD are election carriers. The main difference seen between in the two is in accepting the excess Hydrogen Atoms.

• NAD is reduced when it accepts a single hydrogen whereas FAD is reduced by a two Hydrogen atoms, hence their names NADH and FADH2.

Cytoplasm

Net Gain = 2 ATP Net Gain = 2 ATP

KREB’s Cycle

In Depth Look

Cytoplasm

3. Electron Transport Chain

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

• As electrons drop down stairs, energy released to form a total of 34 ATP

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

• HAPPENS IN THE CRISTAE of the MITOCHONDRIA

Diagram of the Process

Occurs in Cytoplasm

Occurs in Matrix

Occurs across Cristae

Cytoplasm

Energy Tally

• 36 ATP for aerobic vs. 2 ATP for anaerobic

• Glycolysis 2 ATP

• Kreb’s 2 ATP

• Electron Transport 34 ATP38 ATP

- 2ATP to get Glycolysis started! - “TOTAL” ATP produced – 38 ATP- “Net Gain” ATP produced – 36 ATP

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