Cellular Respiration Energy and oxygen
REview Energy is: The ability to do work Organelles that produces energy Mitochondria and chloroplasts
Where do organisms get energy? All organisms need energy Plants make some of their energy Animals must eat to get energy
Food contains Energy Energy is held in chemical bonds Energy is released when bonds are broken Review macromolecules in our food
How much energy do we get from our food? The unit of energy we use to express energy is the Calorie 1 calorie = the amount of energy needed to raise 1 gram of water one degree Celsius 1 Calorie (uppercase C) = 1kilocalorie = 1000 calories (lower case c)
The calories listed on food are kilocalories They are released when the food is digested How much is released varies from one food to another.
CELLULAR RESPIRATION IS A BIOCHEMICAL CYCLE In other words, it is a Series of chemical reactions in a living organism The product of one step is the reactant for the next
Cellular respiration uses the products of photosynthesis Photsynthesis uses the products of Cellular respiration
Energy from food is released in a slow, controlled manner through the process of cellular respiration
Cells capture energy as they break down the food molecules Overview : the symbols 6O 2 + C 6 H 12 O 6 6CO 2 + 6H2O + Energy Oxygen + glucose gives Carbon Dioxide + water +energy
Overview: The steps Glycolysis Breaks down glucose into two molecules of Pyruvic acid With oxygen Krebs Cycle Electron transport chain Without oxygen Fermentation
Overview: Brief description of the Stages Purpose: capture energy from food Stage 1: glycolysis Foods have been broken in digestion processes Glycolysis produces 2 molecules of Pyruvic acid and a little bit of ATP Stage 2: Krebs cycle Pyruvic acid is converted into a little more ATP Stage 3: Electron Transport Chain The electron transport chain makes a lot more ATP!
CellularRespiration and Oxygen Why we need to breathe!
At the very end, the electron transport chain uses oxygen This is when the bulk of the ATP is created The oxygen is supplied through the respiratory system of a living organism
https://www.exploringnature.org/db/view/1045
Some important vocabulary Aerobic: in or with air (oxygen) Anaerobic: without air or oxygen
The Details
Location for each step Glycolysis: Cytoplasm Krebs (Citric Acid ) Cycle: matrix of the mitochondria Electron transport chain: membrane of the mitochondria
GLYCOLYSIS: Literally: sugar- splitting 1 molecule of glucose, a 6-carbon compound, is split into 2 molecules of pyruvic acid. Energy is stored in the bonds of molecules, so as the bonds are broken, energy is released This change is accompanied by a net gain of 2 ATP molecules and 2 NADH molecules. Because we start with 2 ATP molecules, and end with 4- it is a net gain of 2 molecules of ATP
GLUCOSE 2ATP Fructose Bisphosphate 2ADP 2NAD+ 4 ADP 2NADH Pyruvic Acid 4 ATP Fermentation Citric acid cycle
One of the reactions in glycolysis results in 4 electrons being freed from their compounds These electrons are high energy electrons We need an electron carrier! In this case it is NAD + Essentially: NAD + + H + + 2 e NADH
Advantages of Glycolysis: A net of 2 ATP molecules are made from ADP Process is very fast Does not require Oxygen
The Krebs Cycle A.K.A The Citric Acid Cycle The 2 molecules of Pyruvic acid begin the journey to the 2 nd stage
Before we get into the cyclic part. 1. Pyruvic acid passes from the cytoplasm, through the double membrane of the mitochondria and into the matrix 2. The 3-carbon molecule splits into two moleculesa. 1-carbon is used to make CO 2 b. 2 carbons are rearranged to form citric acid
3. The citric acid now bonds with coenzyme-a to form Acetyl-CoA Acetyl-CoA is the ticket for the merry-go-round!
Outer mitochondrion Membrane Inner mitochondrion Membrane Acetic Acid Pyruvic acid enters mitochondrial matrix Pyruvic acid splits into Carbon dioxide and Acetic Acid Co-A Co-A Acetyl-Co_A Co-A Off to the Citric acid cycle
6 2
OOOO 4-carbon molecule OOOO 4-carbon molecule OOOO 4-carbon molecule OOOOOO 6-carbon molecule OOOO 4-carbon molecule OOOOO 5-carbon molecule
(OO-CoA) Acetyl Co-A enters the cycle NAD+ NAD+ NADH OOOOOO Citric Acid 6-carbon molecule NADH CO 2 NAD+ NADH FADH 2 FAD CO 2 ATP ADP
The Electric Transport Chain The idea is the same as the ETC in photosynthesis Electrons are carried to the membrane by high energy electron carriers As the electrons are transported along the membrane, they lose energy This energy is used to move protons (H + ) from the mitochondrial membrane to the space in between the two membranes
What does all this have to do with making ATP? Because there are more H+ in the intermembrane space than in the matrix, a concentration gradient has been set up. The H+ want to move from crowded to uncrowded They do this by going through the protein: ATP Synthase ATP synthase spins With each rotation ADP and a phosphate hook up = ATP
What about oxygen? The de-energized electrons have to go somewhere Oxygen is an electron acceptor The electrons join with H+ and O 2 and make water! 4H + + O 2 + 4e- 2H 2 O
Fermentation How do organisms generate energy if there is not enough oxygen for cellular respiration?
When there is no oxygen, there is no place for NADH to bring the electrons it is carrying
This means NADH can t dump its electrons and be converted back into NAD+. Without NAD+, glycolysis stops Without glycolysis, everything stops What s a cell to do?
In the absence of oxygen, glycolysis is followed by a process called fermentation NADH gives its high energy electrons back to pyruvic acid This converts NADH back to NAD+ Now glycolysis can continue until there is sufficient oxygen
2 pathways of fermentation: 1. Alcoholic fermentation (In plants) Pyruvic Acid + NADH Alcohol + CO 2 + NAD + 2. Lactic Acid Fermentation (In animals) Pyruvic Acid +NADH Lactic Acid + NAD +
In plants In animals