Cellular Respiration Chapter 7 Miss Colabelli Biology CPA

Cellular Respiration o Complex process that our cells make ATP by breaking down organic compounds o Organisms that use cellular respiration are known as heterotrophs

Cellular Respiration o Cellular Respiration is the process that releases energy by breaking down food molecules in the presence of oxygen o C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O + ATP o Same equation for photosynthesis JUST BACKWARDS!

Glycolysis o Process where one molecule of glucose is broken in half, producing two 3-carbon molecules of pyruvic acid o Creates a small amount of ATP and NADH o Process is anaerobic o Does not require oxygen

Aerobic Respiration o If oxygen is present in cell environment o Pyruvic acid is broken down to make a large amount of ATP o If no oxygen is available for the pyruvic acid o Fermentation

Fermentation o Releases energy from pyruvic acid without oxygen o Two types o Lactic Acid o Alcoholic

Lactic Acid Fermentation o Lactic Acid is produced by muscles during rapid exercise when the body cannot supply enough oxygen

Alcoholic Fermentation o Alcoholic fermentation is done by yeasts and some microorganisms o Produces an alcohol & Carbon dioxide

Glycolysis o Glucose  2 pyruvic acid molecules o Step 1: o Glucose molecule uses two ATP molecules to make a 6-carbon molecule with two phosphates

Glycolysis o Step 2: o Glucose molecule breaks in half to make two G3P molecules

Glycolysis o Step 3: o Each G3P molecule gets a phosphate added and 2 NAD+ are reduced and gain an electron to become NADH

Glycolysis o Step 4: o Each 3-Carbon molecule loses their phosphates to make 4 molecules of ATP, 2 molecules of water, and 2 molecules of pyruvic acid

Fermentation o Anaerobic process after glycolysis o Pyruvic acid is used to become either lactic acid or ethyl alcohol o This process is important because it regenerates NAD+ molecules for glycolysis to continue to work

Lactic Acid Fermentation o Pyruvic acid  lactic acid o NADH  NAD+ o Important for making dairy products o Produces certain cheeses and yogurts o Occurs naturally in your muscles when you work out o Muscle soreness

Lactic Acid Fermentation o Muscles use up all available oxygen o Switch to anaerobic respiration o Increases acid levels in muscles causing the fatigue o Eventually gets processed in liver back to pyruvic acid

Lactic Acid Fermentation

Alcoholic Fermentation o Pyruvic acid  ethyl alcohol o NADH  NAD+ o Ethyl alcohol is a 2-carbon molecule o Pyruvic acid loses a carbon by releasing CO 2

Alcoholic Fermentation o Yeast needs to get food to survive such as sugars from fruit o Yeast breaks down to ferment the pyruvic acid into ethyl alcohol and CO 2 o If CO 2 is released, you get regular alcohol o Ex: wine o If CO 2 is not released, you get sparkling alcohol o Ex: Champagne

Efficiency of Glycolysis o Glycolysis uses 2 ATP in order to create G3P molecules o Makes 4 ATP at the end of the process o As a process to make energy, the efficiency is about 2% o Very low for necessary energy o This is why we need cellular respiration!!

The Krebs Cycle o During the Krebs Cycle, pyruvic acid is broken down into carbon dioxide in a series of energy-extracting reactions o Citric Acid is created in this cycle thus giving it the nickname Citric Acid cycle o Net ATP Production is 2 ATP

Electron Transport Chain o The electron transport chain uses the high- energy electrons from the Krebs Cycle to convert ADP to ATP o Total ATP produced: 32

Aerobic Respiration o Only occur in the presence of oxygen o Two stages o Krebs Cycle o Electron Transport Chain with chemiosmosis o Prokaryotes o Occur in cytosol o Eukaryotes o Occur in mitochondria

Aerobic Respiration o After glycolysis, pyruvic acids are produced o Pyruvic acid moves inside mitochondria into mitochondrial matrix (space between two membranes) o Pyruvic acid + CoA  Acetyl CoA + CO 2

The Krebs Cycle o Acetyl CoA  CO 2 + H + ATP o The H produced reduce NAD+  NADH o Five steps in the Krebs Cycle o Occurs in mitochondrial matrix o Citric Acid is made in Step 1 therefore this is also called the Citric Acid cycle o Net ATP produced is 2 ATP

Krebs Cycle - Step 1 o Acetyl CoA + oxaloacetic acid  Citric Acid o This step releases CoA back into the mitochondrial matrix for pyruvic acid to be fixed again

Krebs Cycle – Step 2 o Citric acid releases CO 2 and H o Becomes a 5-carbon compound o The H released, reduces the NAD+ to NADH

Krebs Cycle – Step 3 o Five carbon compound releases another CO 2 and H o Becomes a 4-Carbon compound o Another NAD+ is reduced to NADH o Produces an ATP

Krebs Cycle – Step 4 o 4 carbon compound releases H atom o This time, FAD is reduced to FADH 2 o Similar molecule to NAD+

Krebs Cycle – Step 5 o 4-Carbon compound releases H atom o Reduces NAD+ to NADH o This reaction regenerates initial oxaloacetic acid

Don’t let this happen to YOU!

Electron Transport Chain o Uses the high-energy electrons from the Krebs Cycle to convert ADP to ATP o Total net ATP produced is 34!! o Prokaryotes o Occurs on cell membrane of organism o Eukaryotes o Occurs in the mitochondria membrane called cristae membrane called cristae

ETC – Step 1 o NADH & FADH 2 are used to power this chain of reactions o NADH & FADH 2 are oxidized (lose electrons) to the electron transport chain o Also donate H atoms o NADH  NAD+ o FADH 2  FAD+

ETC – Step 2 o Electrons from NADH & FADH 2 are passed down chain o Lose some energy each time passed on

ETC – Step 3 o Lost energy from electrons transferring down the chain pump protons (H + ) o This creates high concentration of H + between inner and outer membranes o Creates a concentration gradient & electrical gradient since H + are positive

ETC – Step 4 o Concentration & electrical gradients in membranes produce ATP molecules by chemiosmosis o ATP synthase is protein embedded in membrane that pumps protons out and creates ATP

ETC – Step 5 o The electrons move to final acceptor down the chain o Oxygen is the final acceptor o Oxygen also accepts protons provided by NADH & FADH 2 o The protons, electrons, and oxygen all combine to produce H 2 O

Importance of Oxygen o The only way to produce ATP is by the movement of electrons in the ETC o Oxygen is the final acceptor o Without oxygen, the ETC would halt

Efficiency of Cellular Respiration o Glycolysis 2 ATP o Krebs Cycle 2 ATP o Electron Transport Chain 32 ATP o Total = 36 ATP

Efficiency of Cellular Respiration o Depends on conditions of the cell o How ATP are transported o Aerobic respiration is 20 times more efficient than anaerobic respiration

Summary o Cellular respiration o Glycolysis o Glucose  pyruvic acid + ATP + NADH o Aerobic respiration o Pyruvic acid  CO 2 + H 2 O + ATP

Comparing Photosynthesis & Respiration Photosynthesis Cellular Respiration Function Energy Storage Energy Release LocationChloroplastsMitochondria Reactants CO 2 and H 2 O C 6 H 12 O 6 and O 2 Products CO 2 and H 2 O Equation 6CO 2 + 6H 2 O  C 6 H 12 O 6 + 6O 2 C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O