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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 C6H12O6
+ 6O2
YIELDS
6CO2 + 6H20 + 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 6CO2 and 6H2O •  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 + Pi Each day, you hydrolyse 1025 ATP molecules ATP-ase
ATP Synthetase
HYDROLYSIS (Adding H2O) H2O
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 • 
• 
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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 •  Aerobic respira,on enter the completely oxidises a mitochondrion glucose molecule •  Pyruvate loses a CO2 •  Anaerobic respira,on molecule and becomes does not completely acetyl CoA oxidise glucose – ethanol, lactate and •  Krebs cycle produces 2 carbon dioxide are by-­‐
ATP and 4 CO2 products •  Electron transport chain produces 34 ATP and water 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 CO2?
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 CO2?
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)