Lecture Notes-18 Biology 1004

North Arkansas College

Topic: Energy Production: Respiration

1. Respiration requires energy.
2. Respiration is the primary route of energy production. Respiration occurs in most living systems including plants.
3. C₆H₁₂O₆ (glucose) & 6 O₂ - 6 CO₂ & 6 H₂O & ATP.
4. This process occurs in 4 key reactions:

1. Glycolysis
2. Transition reaction
3. Kreb's Cycle (e.g. Citric Acid Cycle)
4. Respiratory chain

1. Anaerobic - occurs in absence of molecular oxygen (O₂).
2. Glucose (6-C sugar) is broken down by a series of enzymes to produce pyruvic acid (3-C).
3. In this process, 2 ATP are used to initiate the reaction sequence. A total of 4 ATP's are produced for a net of 2 ATP of energy (not very energy efficient).
4. The enzymes make ATP, and they also remove electrons as 2 H+. Each pair of electrons (2 H+) ultimately makes 3 ATP molecules when passed through the respiratory chain.

3-C pyruvic acid loses CO₂ to form a 2-C compound (acetyl coenzyme A). No energy is produced, but one NADH+H+ is produced.

2 pyruvic acid (3-C) ------------------= 2-C acetyl coenzyme A

1. 2-C acetyl coenzyme A combines with the end product of the cycle which is a 4-C compound (oxaloacetic acid - OAA) to form 6-C citric acid.
2. A series of enzymes now convert citric acid (6-C) back to the 4-C compound used to start the cycle. This cyclic reaction continues.
3. This cycle produces a net of 3 ATP (substrate level Phosphorylation) and several NADH+H+ (potential for 3 more ATP).

1. Each pair of electrons removed is transferred from the cytoplasm into the mitochondria where they combine with O₂.
2. The electrons are transferred through a series of carrier molecules that are oxidized (+) (can take on another electron) to eventually combine with O₂ and make H₂O & 3 ATP.
3. This process is called oxidative phosphorylation and/or respiration using respiratory chain.
4. 1 molecule of glucose produces a net of 36 ATP if degraded all the way through the anaerobic and aerobic process of energy.

Glycolysis nets = 2 ATP

Oxidative nets = 34 ATP

Both reactions net = 36 ATP

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