III. WHAT IS CELLULAR RESPIRATION?
A. A series of chemical reactions that are universally used by living organisms to
transfer ENERGY from one form to another (Fig. 4.6)
B. That is:energy in the bonds between C & H in the glucose molecule is
transferred to the energy in the bonds in the ATP molecule
C. The chief source of energy in living things
D. Glucose catabolism (glucose oxidation) is cellular respiration (Fig. 4.6)
E. C6 H12O6+6O2à
6CO2+6H2O+Energy+Heat
F. If oxygen is not available, C6H12O6 is broken down to lactic acid in humans.
IV. WHY DO WE NEED CELLULAR RESPIRATION?
A. In order to maintain life, cells must make enzymes and other proteins; they must repair cell membranes, divide and grow. All of these anabolic processes require raw materials(in the form of nutrients) and ENERGY.
B. Cells must have a way to release the chemical energy stored in nutrients in a safe, controlled manner. This potential energy is stored in the chemical bonds between C & H atoms in glucose molecules.
C. Cellular respiration allows the cells of all living things to reorganize these molecules so that usable energy is released or new molecules are formed.
V. WHEN IS CELLULAR RESPIRATION USED?
A. Universal activities that are used by all living organisms from microbes to mammals require energy.
1. Humans use cellular respiration when they jog around the track, or sit & read, eat, or sleep.
2. Their pets use cellular respiration when they eat, play, or take a nap.
3. The worm in their gardens uses cellular respiration as it wriggles in the dirt.
4. The microbes growing in the chicken sandwich left on the table use cellular
respiration as they metabolize, multiply, and spoil the food.
B. In all 4 cases, the organisms are using glucose & oxygen to obtain the energy to fuel life's processes.
VI. WHERE DOES CELLULAR RESPIRATION OCCUR?
A. Cellular respiration occurs in all cells in our bodies except RBC.
B.The phases of cellular respiration take place in different areas of the cell.
1. Glycolysis, in which glucose is broken into 2 pyruvic acid molecules (3 C each),
occurs in the cytoplasm, outside a mitochondrion.
2. Krebs Cycle (TCA) occurs in the matrix of a mitochondrion.
3. The Electron Transport System occurs on the cristae of the mitochondrion.
VII.WHAT ARE THE STEPS INVOLVED IN CELLULAR RESPIRATION?
A. There are 4 subpathways of cellular respiration, all occurring at the same time.
1. The first step:**GLYCOLYSIS � occurs in the cytoplasm (Fig. 4.9)
2. Glucoseà
2 pyruvic acid molecules( 3 C atoms each)
a. ENERGY is released as H atoms are removed
b. 2 ATP molecules are required to start glycolysis
c. 4 ATP molecules are produced. NET == 2 ATP
3. C6H12O6à
2 CH3-CO-COOH+2 NADH+2H++2 ATP
B. The 2nd step: TRANSITION REACTION �occurs in matrix of mitochondrion, removes hydrogen atoms from substrates and releases CO2(Fig. 4.11)
1. 2 Pyruvic acid+CoAà
2 Acetyl CoA+2NADH+2 H++2 CO2
C. The 3rd step: **KREBS CYCLE(Fig. 4.10)
1. Occurs in the matrix of a mitochondrion
2. Removes hydrogen from substrate; releases 4 CO2;
3. Produces 2 ATP,6 NADH+6H+and2 FADH2
D. The 4th step:**ELECTRON TRANSPORT SYSTEM(Fig. 4.11)
1. Occurs on inner membrane of the mitochondrion
2. ETS accepts H from other pathways; passes electrons to oxygen
3. Forms H2O
E. Steps of the ETS: (Fig. 4.11)
1. The ETS begins with NADH (a coenzyme that carries H atoms to the ETS).
2. Then molecules that carry electrons take over.
3. Electrons are removed from hydrogen and then passed from one electron carrier to
another until the electrons are accepted by the final acceptor, oxygen.
4. Two hydrogen ions (protons) then combine with ionic oxygen to form H2O .
5. Note that the **ETS uses oxygen as the final acceptor to accept the H atoms that are broken off glucose. As electrons are handed from electron carrier to
carrier to carrier to carrier, hydrogen ions build up behind the inner membrane like
water behind a dam and then diffuse through channels from a greater concentration
>to lesser concentration. In the process, ENERGY is given off and trapped by ADP
and PO4-3 forming ATP. As the 12 electrons (carried by the 12 hydrogen ions) are
transferred from glucose to oxygen, 6 molecules of water are formed.
6. Thus, when the highly reduced molecule of glucose (full of energy) is
catabolized to 6 molecules of CO2 and 6 molecules of H2O, 36 molecules of ATP
are formed and over half of the energy that was contained in glucose is lost in the form
of heat.
7. Hydrogen carriers: (Fig. 4.10)
a. NAD+ (nicotinamide adenine dinucleotide � derived from niacin)
b. FADH2 (flavine adenine dinucleotide)
c. Both combine with electrons (REDUCTION) from hydrogen. Energy once in
bonds of original glucose molecule is now carried by NADH and FADH2
d. Both release electrons (oxidation). (Fig. 4.11)
VIII. WHAT ARE THE RESULTS OF CELLULAR RESPIRATION?
A. When organisms catabolize glucose to 6 CO2 & 6 H2O molecules, they transform the C to a more oxidized state.
B. C6H12O6+6 O2à
6 CO2+6 H2O+36ATP+HEAT
C. Carbons highly reduced highly oxidized electrons
D. Energy rich energy poor from glucose
E. The energy that was between the C and H atoms in glucose is now stored in the high energy phosphate bonds of the ATP molecules.
IX. LIPID PATHWAYS (Fig. 4.13 (old book))
A. Note discussion of formation of **ketone bodies in text
B. What ultimately happens to **fats from foods that we eat
X. PROTEIN PATHWAYS
A. Proteins digested to form _________________
B. Fig. 4.14 (old book)
XI. SUMMARY OF CATABOLISM (Fig. 4.14)
XII. NUCLEIC ACIDS AND
***PROTEIN SYSTHESIS
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