CELLULAR RESPIRATIONSECTION7.5 I THINK

3 STAGES OF CELLULAR RESPIRATION (CR)

IN CYTOPLASM

1. Glycolysis

In mitochondria

2. Krebs cycle or citric acid cycle or CAC

3. Electron transport chain

Glycolysis

•Occurs in cytoplasm

•Splits glucose (6 carbon molecule) into 2x 3 carbon molecules pyruvic acid

Requires 2 ATP to get reaction started

•Transfers two electrons and hydrogen ions to carrier molecule NAD+ (making NADH: )x2

Requires 2 ATP to get reaction started

•Transfers two electrons and hydrogen ions to carrier molecule NAD+ (making NADH: )x2

Requires 2 ATP to get reaction started

• (2 ADP changed to 2 ATP )x2 and 2 x 3 carbon pyruvic acid produced

Requires 2 ATP to get reaction started

Stage 2 Krebs cycle – occurs in mitochondria

•Structure of mitochondria

•Has both inner and outer membrane with space between membranes

•Krebs cycle takes place in fluid of inside inner membrane

Krebs cycle – inside inner membrane in mitochondria

•Pyruvic acid diffuses into inner membrane of mitochondria

•Loses a molecule of CO2 forms – 2 carbon molecule

Acetyl coenzyme A or acetyl CoA

Krebs cycle – inside inner membrane in mitochondria

•acetyl CoA – joins a 4 carbon molecule in the Krebs cycle

Krebs cycle – inside inner membrane in mitochondria

•2 more CO2 produced as well as ATP (per cycle remember there are 2 acetyl CoA per cycle)

•Also 2 electron carriers pick up electrons and hydrogen ions

Krebs cycle – inside inner membrane in mitochondria

•End result the 4 carbon molecule recycled with the production of ATP, FADH2:, NADH: (last 2 are electron carriers)

Stage 3 – electron transport chain

•Most productive stage of CR

•Occurs on both sides of inner membrane

Stage 3 – electron transport chain•NADH: from krebs cycle transfers electrons to proteins in electron transport chain•Electrons move from carrier to carrier in chain releasing energy that is used to move H+ outside membrane against concentration gradient

Stage 3 – electron transport chain

•Final stage is the electron transfer is to oxygen which holds them more strongly

•Oxygen also picks up 2 hydrogen ions – forms water

Stage 3 – electron transport chain•H+ ions concentrated outside membrane•Return to inside through ATP synthase (like a turbine in a dam) the energy from turning of the protein put P onto ADP making ATP

Stage 3 – electron transport chain

•Net result of the ATP synthase action is the forming of about 34 ATP

Fermentation

•Occurs when oxygen is not present

•Produces much less ATP than cellular respiration

•By-products include alcohol and lactic acid –depending on the cell type that is being effected

Formation of lactic acid

Glycolysis is first step of lactic acid formation

Net of 2 ATP produced compared to the 38 of CR

Why LAF is important

•When muscles are working hard they are burning lots of ATP and requiring lots of oxygen to do so.

•When oxygen is in short supply LAF kicks in still producing ATP for a short term use of the muscles• Say you had to run to preserve your life (a bolder is

rolling down a hill toward you) – short term use

Price of LAF

•You build up lactic acid

•Lactic acid makes your muscles feel sore

•Takes time to convert the lactic acid to ATP when there is enough oxygen

Formation of ethyl alcohol

How we take advantage of fermentation

•Yeast (a fungus) when kept in an anaerobic environment (without oxygen) produce ethyl alcohol and CO2

•The brewing of beer and wine take advantage of the alcohol

•Baking of bread takes advantage of CO2 to make bread rise (the alcohol evaporates off when the bread is baked)

How we take advantage of fermentation cont.

•Some bacteria and fungi produce lactic acid in the process

•Use the lactic acid to ferment milk into cheeses, yogurt

•Use LA to ferment cabbage to sauerkraut