Cellular Respira,on Topic 3.7 and 3.8
Defini,on of cellular respira,on Controlled release of energy from organic compounds to produce ATP Chemical energy is stored in covalent bonds Cells break down organic compounds by SLOW oxida,on By releasing energy in a controlled way, it can be trapped in the useful form of ATP
Cellular Respira,on: Standard level How does the process of cellular respira,on yield ATP (chemical energy) from food? 1. What do you already know about cellular respira7on? 2. What organelle in the cell is the powerhouse that makes energy for the cell?
You must be able to write all equa,ons for aerobic respira,on
Equa%on for Cellular Respira%on C 6 H 12 O 6 + 6O 2 YIELDS 6CO 2 + 6H 2 0 + e - + 36-38ATP + heat
Cellular Respira%on Complete breakdown of one glucose results in 36 to 38 ATP molecules Process is exergonic (energy- releasing) as high- energy glucose is converted to 6CO 2 and 6H 2 O Process is catabolic: glucose is converted to smaller molecules
What is ATP? Energy currency used by all cells Adenosine triphosphate Organic molecule containing high- energy phosphate bonds
Chemical Structure of ATP Adenine Base 3 Phosphates Ribose Sugar
How Do We Get Energy From ATP? By breaking the high- energy bonds between the last two phosphates in ATP ATP hydrolase (ATP ase) catalyses the breakdown of ATP into ADP + P i
Each day, you hydrolyse 10 25 ATP molecules ATP-ase ATP Synthetase
H 2 O HYDROLYSIS (Adding H 2 O)
How is ATP re- made during respira,on? Substrate- level phosphoryla@on (using enzymes: in the cytoplasm of the cell and the matrix of the mitochondrion) Chemiosmosis (in the mitochondria, using ATP synthase)
The major organic nutrients (carbohydrates, proteins and lipids) can all act as sources of ATP
Stages of Cellular Respira%on 1. Glycolysis ALWAYS OCCURS 2. Anaerobic pathways if no oxygen available (Lac@c acid and Ethanol fermenta@on) 3. Aerobic pathways if oxygen available (Link reac@on, Krebs cycle, electron transport chain)
Where Does Cellular Respira%on Take Place? glycolysis occurs in the cytoplasm Krebs Cycle & ETC Take place in the mitochondria
Glycolysis: Always the ini7al stage of respira7on Loca,on: cytoplasm Substrate: glucose Requires input of 2 ATP Products: pyruvate, (NADH), 4 ATP Glycolysis is an anaerobic process: no oxygen required the movie...
Glycolysis
If no oxygen is available, glycolysis (anaerobic) is followed by fermenta,on (anaerobic)
Anaerobic respira,on
Why fermenta,on? In the absence of oxygen, glycolysis will stop unless there is an alterna,ve acceptor for the electrons produced from the glycoly,c pathway
Fermenta%on 1. Alcoholic fermenta%on Pyruvate is converted into ethanol plus carbon dioxide and NAD + 2. Lactate fermenta%on Pyruvate is converted into lactate and NAD +
Alcoholic fermenta,on in yeast
Alcoholic fermenta,on in yeast Pyruvate is produced from glycolysis 3- carbon pyruvate is converted to 2- carbon ethanol and carbon dioxide Genera7on of carbon dioxide helps bread products to rise Yeast is used to produce ethanol
Lactate fermenta,on in mammals Lactate is a 3- carbon molecule NAD + is regenerated to allow glycolysis to con,nue
Aerobic respira,on Takes place in the mitochondria of eukaryo,c cells Substrate: pyruvate Produces LOTS of ATP (28 38 ATP): 90% of total ATP from respira%on Also produces carbon dioxide, water and heat Oxygen is the final electron acceptor
Aerobic respira,on: the most efficient pathway for ATP genera,on
Aerobic respira,on 2 pyruvate molecules enter the mitochondrion Pyruvate loses a CO 2 molecule and becomes acetyl CoA Krebs cycle produces 2 ATP and 4 CO 2 Electron transport chain produces 34 ATP and water Aerobic respira,on completely oxidises a glucose molecule Anaerobic respira,on does not completely oxidise glucose ethanol, lactate and carbon dioxide are by- products
Some prac,ce ques,ons on respira,on 1. How do cells capture the energy released by cell respiration? A. They store it in molecules of carbon dioxide. B. They produce glucose. C. The energy is released as pyruvate. D. They produce ATP. (Total 1 mark)
Some prac,ce ques,ons on respira,on 2. Which process produces the most ATP per molecule of glucose? A. Anaerobic respiration in a yeast cell B. Aerobic respiration in a bacterial cell C. Glycolysis in a human liver cell D. The formation of lactic acid in a human muscle cell (Total 1 mark)
Some prac,ce ques,ons on respira,on 3. Which of the following is the best definition of cell respiration? A. A process needed to use energy, in the form of ATP, to produce organic compounds B. A process used to provide oxygen to the atmosphere C. A controlled release of energy, in the form of ATP, from organic compounds in cells D. A controlled release of energy in the production of food from organic compounds (Total 1 mark)
Some prac,ce ques,ons on respira,on 4. Which of the following processes produces CO 2? I. Glycolysis II. Alcohol (ethanol) fermentation III. Lactic acid production A. I only B. II only C. I and II only D. I, II and III (Total 1 mark)
Some prac,ce ques,ons on respira,on 4. Which of the following processes produces CO 2? I. Glycolysis II. Alcohol (ethanol) fermentation III. Lactic acid production A. I only B. II only C. I and II only D. I, II and III (Total 1 mark)
Some prac,ce ques,ons on respira,on 4. State a word equation for anaerobic cell respiration in humans. (1 mark)