CHAPTER 8-HOW CELLS RELEASE ENERGY
I. All organisms require energy to survive and function properly.
A. Autotrophs-
1. What are some examples of autotrophs?
2. Some autotrophs can produce their carbohydrates from inorganic compounds. This
usually occurs in some bacteria.
B. Heterotrophs-
C. Both autotrophs and heterotrophs can breakdown carbohydrates to generate their supply of
ATP.
D. Cellular Respiration-a process in which living organisms breakdown carbohydrates (primarily
glucose) to generate their ATP.
II. CELLS CAN PRODUCE ATP IN 2 WAYS:
A. Phosphorylation-the addition of a phosphate group to ADP to produce ATP.
B. Chemiosmosis-occurs when electrons are used in the production of ATP by living cells.
III. OVERVIEW OF CELLULAR RESPIRATION
A. Broadly defined, cellular respiration is the conversion of chemical energy into ATP.
B. ALL living organisms must undergo some type of cellular respiration to generate ATP.
1. Different organisms use different carbohydrates as fuels for respiration. Some
organisms can use things other than carbohydrates as fuels for cellular respiration.
2. 2 Types of Cellular Respiration
a. Aerobic Cellular Respiration-occurs only in the presence of oxygen. Oxygen
is highly involved in the reactions of aerobic cellular respiration. Most living
organisms undergo this type of respiration.
b. Anaerobic Cellular Respiration-occurs in the absence of oxygen.
1) What kinds of organisms can undergo this process?
IV. AEROBIC CELLULAR RESPIRATION
A. Equation for Aerobic Cellular Respiration
B. In aerobic cellular respiration, cells breakdown glucose to produce ATP. Most of this process
occurs in a cell’s ____________________.
C. Overall, aerobic cellular respiration generates ____________ ATP molecules from every
single glucose molecule.
D. 4 Major Stages in Aerobic Cellular Respiration:
E. The Stages and Events in Glycolysis
1. Glycolysis-a series of reactions that breakdown glucose molecules into 2 pyruvate
molecules. Pyruvate is a small, three carbon molecule.
a. Glycolysis occurs in the cytoplasm of ALL living cells.
b. Glycolysis requires an input of 2 molecules of ATP to occur.
c. Glycolysis is regulated by a number of enzymes.
d. Steps/Events in Glycolysis
1) 2 ATP molecules donate phosphate groups to glucose to produce
fructose 1,6-bisphosphate.
2) Next, the fructose 1,6-bisphosphate splits to form 2 3-carbon
molecules of Glyceraldehyde 3-Phosphate (PGAL).
3) Both PGAL molecules undergo a series of reactions to produce
2 Pyruvate molecules. In these reactions, PGAL donates a phosphate
to ADP to produce ATP (via phosphorylation). A total of 2 ATP
molecules are produced from each PGAL involved in the reaction.
a) Recall that there are 2 molecules of PGAL in this process;
therefore, a total of 4 ATP molecules are generated in this
step.
4) The coenzyme NADH serves as an electron and hydrogen acceptor.
e. The Net Production of ATP in Glycolysis is _____________ ATP molecules.
1) Can you explain this?
2. Pyruvate Oxidation
a. In the presence of oxygen, pyruvate diffuses into a cell’s mitochondria. Once
in the mitochondria, pyruvate is oxidized to form acetyl co-a.
b. There is a loss of carbon dioxide in this process (known as deacarboxylation).
1) What do animals do with this carbon dioxide?
c. No ATP molecules are generated in this stage of glycolysis.
3. The Kreb’s Cycle (Citric Acid Cycle)
a. This cycle occurs in a cell’s mitochondria.
b. Steps/Events in The Kreb’s Cycle
1) Acetyl co-a combines with oxaloacetate to form citrate.
2) Citrate undergoes a number of reactions to eventually reform
oxaloacetate.
a) Through the course of these reactions, NAD+ and FAD+ gain
electrons to form the electron carriers NADH and FADH2.
3) The Kreb’s Cycle generates a total of 2 ATP molecules.
c. NADH and FADH2 are electron carriers. The electrons generated
during the Kreb’s Cycle will be used in The Electron Transport System.
1) In general, The Kreb’s Cycle serves as a major source of electrons.
Remember that these electrons contain a small supply of energy. This
energy will be used in the formation of ATP in The Electron Transport
System.
4. The Electron Transport System (ETS)
a. Much of the ETS occurs at the membrane that surrounds the mitochondria.
b. FADH2 and NADH from The Kreb’s Cycle are used here.
c. Steps/Events in The ETS
1) FADH2 and NADH carry their electrons to the mitochondrial
membrane.
2) At the membrane, the energy associated with these electrons is used to
turn on special proton pumps in the membrane.
3) The proton pumps function by pumping hydrogen ions out of the
mitochondria.
4) This creates a situation in which the concentration of hydrogen ions is
greater on the outside of the mitochondria than on the inside.
5) Once this concentration gradient is formed, the hydrogen ions begin to
diffuse back into the mitochondria.
6) As these hydrogen ions reenter the mitochondria, a small supply of
heat (energy) is released.
7) The enzyme ATP Synthase captures this energy and used it to
generate ATP. This ATP is produced via Chemiosmosis.
8) Oxygen combines with electrons and free hydrogen ions at the end
of electron transport to produce water. Oxygen is a final electron
acceptor.
d. How much ATP is produced in The Electron Transport System?
F. How much ATP is generated in each stage of Aerobic Cellular Respiration?
1. Glycolysis2. Oxidation of Pyruvate3. The Kreb’s Cycle4. The Electron Transport SystemV. ANAEROBIC CELLULAR RESPIRATION
A. This process occurs in the absence of oxygen. It occurs in
B. Many of the organism that undergo this process live in harsh environments.
C. Examples of Anaerobic Cellular Respiration
1. Alcoholic Fermentation
a. Occurs in microorganisms, including some bacteria and yeasts.
b. In this process, the microbes use sugars to generate ATP.
c. Steps in Fermentation
d. What can the CO2 produced in this process be used for?
2. Lactate Fermentation-occurs in human muscle cells when oxygen levels are low.
a. When would oxygen levels be low in human muscle cells?
b. Steps in Lactate Fermentation
c. Lactic Acid-