Bio 004, College of the Desert

Photosynthesis: process in which light energy from the sun powers chemical processes that assemble organic molecules in plants

Chloroplasts: Site of photosynthesis.

Chlorophyll: Green pigment in leaves.

Autotrophs: organisms that produce all their own organic matter from inorganic matter. [Generally green plants, algae, & photosynthetic bacteria].

Heterotrophs: organisms incapable of producing organic matter from inorganic matter. [Generally animals, fungi, protozoans, and non-photosynthetic bacteria].

Cellular Respiration: Aerobic harvesting of chemical energy from fuel molecules.

Aerobic: Process that requires oxygen.

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP

• Note: Redox (oxidation-reduction reaction) – reaction during respiration in which glucose is oxidized and oxygen is reduced.
• Oxidation: the loss of electrons Reduction: the gain of electron

• NAD (Nicotinamide Adenine Dinucleotide): An electron acceptor.
• NAD + H+ (electron) → NADH
• NAD is reduced by accepting a H electron which is then carried to the electron transport chain.

Electron Transport Chain: a series of molecules that collect and carry electrons in order to release energy used to make ATP. Locate in: mitochondria of all organisms, chloroplasts of green plants, the plasma membrane of prokaryotes.

• Process of Electron Transport Chain
• 1. H is accepted from NADH.
• 2. H passes through the ETC until it is accepted by O at the end of the process.
• 3. ATP is made from ADP producing energy

• Metabolic Pathway of Cellular Respiration
• Stage 1: Glycolysis
• Stage 2: Krebs Cycle
• Stage 3: Electron Transport Chain

• Glycolysis
• 1.During glycolysis, a 6C sugar – glucose – is split into two 3C molecules – pyruvic acid.
• 2.It costs 2 ATP molecules to activate this reaction.
• 3.NAD accepts electrons from the splitting glucose.
• 4.4 ATP are generated during glycolysis.

• Krebs Cycle
• 1.In preparation for the Krebs cycle, pyruvic acid (3C) is converted into acetic acid (2C) and bonded to Coenzyme A forming acetyl CoA.
• 2.Acetyl CoA (2C) is converted into CO2 (1C).
• 3.Each 2C molecule generates 1 ATP.
• 4.Each 2C molecule generates 3 NADH + 1 FADH2.

• Cellular Respiration Blockers
• A.Cyanide & carbon monoxide (CO) block the transfer of electrons from the ETC to oxygen.
• B.Mitochondria can no longer convert food energy into ATP and the organism dies.

ATP Generation: Net total of ATP generated from 1 molecule of glucose is 36 ATP.

• Lipid Metabolism
• A.Carbohydrates are generally converted into lipids for storage.
• B.Lipids can be used for metabolism and serve better as energy storage.

• Protein Metabolism
• A. Protein molecules used in respiration, but only as a last resort.
• B Protein broken down into amino acid subunits with the removal of the amino group (otherwise converted into toxic ammonia)
• C. Protein metabolism results from starvation and conditions like anorexia nervosa.

• Anaerobic Harvest of Food Energy
• A. Anaerobic: Process that does not require O2.
• B. Fermentation: breakdown of glucose to generate ATP using an electron acceptor other than oxygen

• Fermentation in Muscle Cells
• A.Glycolysis works anaerobically.
• B.A net total of two ATP are generated, (34 less than aerobic cellular respiration).
• C.Without O2, NADH deposits its H electrons with pyruvic acid – continuing the process.
• D. As pyruvic acid gains electrons, lactic acid (waste product) is produced.
• E.As lactic acid accumulates, soreness and muscle burning occurs.
• F.Lactic acid is carried in blood to the liver where it is aerobically converted into pyruvic acid.

• Fermentation in Microorganisms
• A. Microorganisms (bacteria and fungi) also produce lactic acid.
• B. Commercially these microorganisms are used to produce cheese, sour cream, yogurt, soy sauce, pickles, olives, sausage, pepperoni, and salami.
• C. The anaerobic pathway yeast cells follow converts pyruvic acid into ethanol and CO₂ instead of lactic acid
• In bread, CO₂ causes yeast to rise.
• Wine contains ethanol while CO₂ escapes.
• Champagne and beer contain both CO₂ & ethanol.