Cellular Respiration How we get energy from food

Cellular Respiration Cellular respiration – glucose molecules are broken down to release energy Used by heterotrophs and autotrophs to gain energy from food The food we eat is broken down into simple sugars like glucose Glucose is broken down to release energy -this energy is used to make ATP

Cellular Respiration – getting the energy from food Cellular respiration has to happen in steps otherwise all the energy would be released at once and most would be lost So it happens in steps and Energy gets released a little at a time

2 Types of Cellular Respiration Aerobic - releases energy from food molecules using oxygen Anaerobic (Fermentation) releases energy from food molecules without oxygen

Equation of Cellular Respiration /aerobic/

3 Stages of Cellular Respiration Glycolysis – 2 ATP Krebs cycle – 2 ATP ETC – Electron Transport Chain ~ 32 ATP TOTAL Energy gain for Aerobic Respiration ~ 36 ATP

- Glucose (has 6 carbon atoms) is split into 2 pyruvates (each has 3 carbons) - 2 ATP molecules are used in this process and 4 are made giving us a net gain of 2 ATP - From this process you get 2 NADH – energy storing compound 2 ATP 2 Pyruvates – used in the next step to release energy In Cytoplasm

Why is Glycolysis important? Only releases 2 ATP but the process happens very fast in the cell So cells can make thousands of ATP molecules in a few seconds Doesn’t need oxygen so it can make energy fast without oxygen

Krebs Cycle Happens in the matrix of the mitochondria Pyruvate is transformed into acetly-CoA which enters this cycle In the cycle a set of reactions breaks down acetyl-CoA to: CO2 – carbon dioxide (we breathe out) 2 ATP – what cells use as energy to do work NADH – energy storing compound FAHD2 – energy storing compound For each turn of the cycle a phosphate is added to ADP to make ATP Each pyruvate causes one turn of the cycle creating one ATP So 2 molecules of ATP are made for each 2 pyruvates (=1 glucose) that enters the cycle

Electron Transport Chain Energy is transferred from NADH (from glycolysis) and FADH2 and NADH from the Krebs cycle into the ETC This step requires oxygen that is why this is aerobic respiration! Electrons move from NADH to FADH2 down the chain on the inside membrane of the mitochondria Just as in Photosynthesis -as they move ATP is generated - 32 molecules of ATP Oxygen is the final electron acceptor An enzyme adds the electrons to oxygen and hydrogen to make water

Fermentation Getting energy from Glucose without oxygen Takes place in the cytoplasm Types: Alcoholic fermentation Lactic acid fermentation Both types form 2 ATP molecules

Alcoholic Fermentation Converts pyruvate and NADH (from glycolysis) into carbon dioxide, ethanol and NAD+ Ethanol is an alcohol that is why it is called alcoholic fermentation This is carried out by yeast – bread and beer Animals cannot carry out this type of fermentation

Beer and Bread

Fermentation is your friend

Lactic Acid Fermentation Converts pyruvate and NADH (from glycolysis) to lactic acid and NAD+ Animals use this in their muscle cells When you exercise a lot breathing cannot give your muscles all the oxygen they need When they run out of oxygen they switch to lactic acid fermentation to get energy Have you ever felt the burn while working out, or after an intense workout? That is lactic acid in your muscles

Photosynthesis and Cellular Respiration Photosynthesis and cellular respiration are related processes The products for one are the reactants for the other Look at the formulas: Cellular respiration: Photosynthesis: