Cellular Respiration

What is Cellular Respiration? The process of converting food energy into ATP energy C 6 H 12 O O 2 → 6 CO H 2 O + 36 ATP

Why are both Photosynthesis and Cell Respiration important to Ecosystems? Light is the ultimate source of energy for all ecosystems Chemicals cycle and Energy flows Photosynthesis and cellular respiration are opposite reactions

Why do plants need both chloroplasts and mitochondria? Chloroplasts use energy from the sun to make glucose Mitochondria convert glucose to ATP—the energy currency of the cell yer/ /animations/metabolis m/metabolism.htm

What is ATP? Adenosine Triphosphate  5-Carbon sugar (Ribose)  Nitrogenous base (Adenine)  3 Phosphate groups Energy currency of the cell The chemical bonds that link the phosphate groups together are high energy bonds When a phosphate group is removed to form ADP and P, small packets of energy are released

How is ATP used? As ATP is broken down, it gives off usable energy to power chemical work and gives off some nonusable energy as heat. Synthesizing molecules for growth and reproduction Transport work – active transport, endocytosis, and exocytosis Mechanical work – muscle contraction, cilia and flagella movement, organelle movement

Why use ATP energy and not energy from glucose? Breaking down glucose yields too much energy for cellular reactions and most of the energy would be wasted as heat. 1 Glucose = 686 kcal 1 ATP = 7.3 kcal 1 Glucose → 36 ATP How efficient are cells at converting glucose into ATP?  38% of the energy from glucose yields ATP, therefore 62% wasted as heat.

Cell Respiration can be divided into 4 Parts: 1) Glycolysis 2) Pyruvate to Acetyl CoA 3) The Krebs Cycle 4) The Electron Transport Chain and ATP production

Where do the 4 parts of Cellular Respiration take place? Glycolysis:  Cytosol Pyruvate to Acytyl CoA:  Matrix The Krebs Cycled:  Matrix Electron Transport Chain and Production of ATP:  Cristae

Parts of the Mitochondria

Glycolysis Glucose (C 6 ) is split to make 2 Pyruvates (C 3 ) Glycolysis produces very little ATP energy, most energy is still stored in Pyruvate molecules. Glucose  2 Pyruvate 2 ATP4 ATP (Net 2 ATP) 2 NADH

Pyruvate To Acetyl CoA When Oxygen is present, 2 Pyruvates go to the matrix where they are converted into 2 Acetyl CoA (C 2 ). 2 NADH’s carry electrons and hydrogens to the Electron Transport Chain. CO 2 is given off 2 Pyruvate  2 CO 2 2 NADH 2 Acetyl CoA

The Krebs Cycle / Citric Acid Cycle 8 Enzymatic Steps in Matrix of Mitochondria: Two Turns of the Krebs Cycle are required to break down both Acetyl Coenzyme A molecules. The Krebs cycle produces some chemical energy in the form of ATP but most of the chemical energy is in the form of NADH and FADH 2 which then go on to the Electron Transport Chain. 2 Acetyl CoA  4 CO 2 2 ATP 6 NADH 2 FADH 2

The Electron Transport Chain NADH and FADH 2 produced earlier, go to the Electron Transport Chain. NADH and FADH 2 release electrons to carriers/proteins embedded in the membrane of the cristae. As the electrons are transferred, H + ions are pumped from the matrix to the intermembrane space up the concentration gradient. Electrons are passed along a series of 9 carriers until they are ultimately donated to an Oxygen molecule. ½ O electrons + 2 H + (from NADH and FADH 2 ) → H 2 O. 10 NADH  32 ATP 2 FADH 2 H 2 O Oxygen

Chemiosmotic Phosphorylation Hydrogen ions travel down their concentration gradient through a channel protein coupled with an enzyme called ATP Synthase. As H + ions move into the matrix, energy is released and used to combine ADP + P → ATP. Hydrogens are recycled and pumped back across the cristae using the Electron Transport Chain. ATP diffuses out of the mitochondria through channel proteins to be used by the cell.

ATP Synthase Multisubunit complex with 4 parts:  Rotor – spins as H + ions flow  Stator – holds the rotor and knob complex together in the cristae  Internal Rod – extends between rotor and knob, spins when rotor spins which then turns the knob  Knob – contains 3 catalytic sites that when turned change shape and activate the enzyme used to make ATP

Review ATP Production: 1) Glycolysis → 2 ATP 2) Pyruvate to Acetyl CoA → No ATP 3) The Krebs Cycle → 2 ATP 4) The Electron Transport Chain and Chemiosmotic Phosphorylation:  Each NADH produces 2-3 ATP so 10 NADH → 28 ATP  Each FADH 2 produces 2 ATP so 2 FADH 2 → 4 ATP Total = 36 ATP 1 Glucose = 686 kcal 1 ATP = 7.3 kcal 1 Glucose → 36 ATP How efficient are cells at converting glucose into ATP?  38% of the energy from glucose yields ATP, therefore 62% wasted as heat (used to maintain body temperature or is dissipated)  Ex. Most efficient Cars: only 25% of the energy from gasoline is used to move the car, 75% heat.

All Types of Molecules can be used to form ATP by Cell Respiration: Proteins, Carbohydrates, and Lipids must first be broken down into their monomers and absorbed in the small intestine. Monomers may be further broken down into intermediate molecules before entering different parts of Cell respiration to ultimately form ATP.

Anaerobic Respiration: Fermentation If there is NO oxygen, then cells can make ATP by Fermentation Without oxygen, Oxidation of Pyruvate and the Electron Transport Chain do not operate. Glucose → Pyruvate → Lactate NAD + Glycolysis 2 NADH or 2 ATP Alcohol + CO 2 Fermentation yields a net gain of 2 ATP for every 1 Glucose. (Inefficient) Two Forms of Fermentation: Lactic Acid Fermentation (animals) Alcohol Fermentation (yeast)

Lactic Acid Fermentation

Alcoholic Fermentation