Cellular Respiration & Fermentation 4.4, 4.5, & 4.6

4.4 – Overview of Cellular Respiration Key Concept: The overall process of cellular respiration converts sugar into ATP using oxygen. 4.5 – Cellular Respiration in Detail Key Concept: Cellular respiration is an aerobic process with two main stages.

Purpose of Cellular Respiration To make ATP from the energy stored in glucose Glucose comes from an organism doing photosynthesis themselves or from eating foods containing glucose Remember: the purpose of photosynthesis was just to get glucose

Cellular Respiration has 2 parts Anaerobic (does not require oxygen) Glycolysis Aerobic (requires oxygen) Kreb’s Cycle (Citric acid Cycle) Electron Transport Chain (ETC)

Glycolysis Takes place in cytoplasm (eukaryotes and prokaryotes do this step since all cells have cytoplasm) Splits one glucose molecule into two pyruvate molecules Costs the cell 2 ATP molecules to do this 4 ATP molecules are produced (only gain 2 ATP) 2 NADH molecules are formed

Kreb’s Cycle (Citric Acid Cycle) Takes place in matrix of mitochondria (only in eukaryotes) 2 pyruvate (made during glycolysis) enter the mitochondrion Each pyruvate is broken down to create 1 ATP, 3 CO2, NADH, & FADH2 Total products of Kreb’s cycle (because of 2 pyruvates): 2 ATP 6 CO2 NADH FADH2 Will carry energy to the next step

Electron Transport Chain (ETC) Takes place in inner membrane of mitochondria (cristae) Folded to create more surface area for reactions to produce more ATP in a small space NADH & FADH2 (from Kreb’s) donate their energy (electrons) to the electron transport chain Oxygen is the final electron acceptor and it picks up hydrogen ions Oxygen and hydrogen ions combine to form water (released as a waste product) 32 ATP are made

ATP from Cellular Respiration 4 from Glycolysis (uses up 2, so really only gain 2 ATP) 2 ATP from Kreb’s cycle 32 ATP from ETC GAIN 36 ATP from one glucose molecule

Equation for Cellular Respiration C6H12O6 + 6O2 6CO2 + 6H2O + 36ATP  Like the reverse of photosynthesis

What happens when there’s no/not enough oxygen or there are no mitochondria? Answer: Fermentation Two Kinds: Lactic Acid Fermentation Alcoholic Fermentation

Allows glycolysis to continue making ATP without oxygen

Lactic Acid Fermentation Anaerobic Occurs in muscle cells Produces burning feeling in muscles Occurs when body is worked to the point that more oxygen is being used than what is being taken in This is why you breathe harder when you’re exercising is to get more oxygen to keep making ATP Produces Lactic Acid and 2 (net) ATP

Alcoholic Fermentation Anaerobic Occurs in some bacteria and yeast Produces CO2, ethyl alcohol, and 2 (net) ATP Used in food production (bake bread and make wine)