Download Chapter 9 - Cellular Respiration

Chapter 9 - CELLULAR RESPIRATION
9.1 – Catabolic pathways – metabolic pathways that release stored energy by breaking down complex
molecules
A. fermentation – partial degradation of sugars without oxygen (anaerobic respiration_
B. Aerobic respiration – oxygen is consumed as reactant along with organic fuel (glucose)
C. Cellular respiration is the enzymatic breakdown of glucose (C6H12O6) in the presence of oxygen (O2) to
produce cellular energy (ATP)
C6H12O6 + 6O2 -->6 CO2 + 6H2O + 36 ATP
glucose + oxygen --> carbon dioxide + water + ATP
D. Redox reactions – transfer of electrons from one reactant to another
1) oxidation – loss of electrons from one substance
2) reduction – addition of electrons to another substance
C6H12O6 + 6O2 -->6 CO2 + 6H2O
Glucose becomes oxidized to CO2
6O2 becomes reduced to 6H20
E. Electron Transport Chain - breaks fall of electrons to oxygen into several energy releasing steps
9.2 Glycolysis – (sugar-splitting)
a) 6 carbon glucose is split into two 3 carbon pyruvates
b) anaerobic (without oxygen) - proceeds whether or not O2 is present ; O2 is not required
d) net yield of 2 ATP per glucose molecule
e) net yield of 2 NADH per glucose ---> sent to the ETC in mitochondria
The pyruvic acid diffuses into the inner compartment of the mitochondrion where a transition
reaction occurs that serves to prepare pyruvic acid for entry into the next stage of respiration, this
converts them an acetyl CoA which enters the Kreb's cycle.
If oxygen is not present, pyruvate is converted to lactic acid in the cytoplasm -- anaerobic respiration
9.3 Citric Acid or Krebs Cycle
a)occurs in the inner mitochondrial matrix
b) an aerobic process; will proceed only in the presence of O2
c) net yield of 2 ATP per glucose molecule
d) net yield of 6 NADH and 2 FADH2 (NAD+ is reduced to NADH, FAD+ is reduced to FADH)
e) in this stage of cellular respiration, the oxidation of glucose to CO2 is completed.
9.4 – Electron Transport System
a) consists of a series of enzymes on the inner mitochondrial membrane
b) electrons are released from NADH and from FADH2 and as they are passed along the series of
enzymes, they give up energy which is used to fuel a process called chemiosmosis, which drives the
process of ATP synthesis using an enzyme called ATPase.
c) net yield of 32 ATP per glucose molecule
d) 6 H2O are formed when the electrons unite with O2* at the end of electron transport chain.
* Note: This is the function of oxygen in living organisms!
At end of cellular respiration: 2 ATP (glycolysis) + 2 ATP (Citric Acid Cycle) + 32 or 34 ATP (Oxidative
phosphorylation [electron transport and chemiosmosis) = 36 or 38 ATP
9.5 Fermentation
A. fermentation – way of obtaining chemical energy without using oxygen or electron transport (i.e.
without using cellular respiration
1) Alcohol fermentation – pyruvate is converted to ethanol
a) bacteria carry out fermentation when oxygen not present
b) yeast (fungus) - use alcohol fermentation; as releases CO2 creates bubbles, causing bread to
rise
2) lactic acid fermentation – pyruvate is reduced directly by NADH to form lactate, no CO2
released
a) used to make cheese, yogurt by bacteria or fungus
b) occurs in muscles when oxygen is depleted
Food for Thought
1. What is the purpose of cellular respiration?
2. Where does cellular respiration occur within the cell?
3. What is the waste product of cellular respiration?
4. Comparing photosynthesis to respiration
a) Where does each occur?
b) What are the products of each?
c) What compounds are needed to start the process
d) What is the function of the Electron Transport Chain in each process
e) Describe the role of ATPase in photosynthesis and cellular respiration.
Case Study: The Mystery of the Seven
Deaths: http://sciencecases.lib.buffalo.edu/cs/files/cellular_respiration.pdf
In this case study, students learn about the function of cellular respiration and the electron transport
chain and what happens when that function is impaired. Students play the role of
medical examiner as they analyze the autopsy results to determine the cause
of the mysterious deaths of these seven victims.
Loosely based on the Chicago Cyanide Poisonings in 1982