Lecture 6 - Deriving Energy From Food – Cellular Respiration

Energy: 

• The capacity to bring about movement against a force; the ability to do work. 

Forms of Energy: 

• Potential Energy: Stored Energy 

  • Chemical Energy 

  • Ex: Hydroelectric dam, food 

• Kinetic Energy: energy in motion 

  • Running, biking, flying, etc.

1rst Law of Thermodynamics 

• Energy can not be created or destroyed, only transformed. 

  • Excess energy released as heat 

2nd Law of Thermodynamics 

• Energy conversions increase the entropy of the universe 

  • Entropy: the amount of the disorder. 

Exergonic Reactions:

• Reactants contain more energy than the products 

  • Ex: Energy released 

  • Ex: Cellular respiration

Endothermic Reactions: 

• Products contain more energy than reactants 

  • Ex: Energy captured 

  • Ex: Photosynthesis 

Photosynthesis

Cellular Respiration

Adenosine triphosphate (ATP):

• Energy transfer molecule 

Adenosine diphosphate (ADP)

• an essential organic compound in cellular metabolism, formed when ATP releases energy

Phosphorylation: 

• Addition of a phosphate ion to a molecule 

Oxidation: 

• The process of removing electrons 

Reduction: 

• The process of adding electrons 

  • Reduction in charge 

Reduction & Oxidation are always linked 

• Redox reaction: the transfer of electrons from one molecule to another. 

Macromolecules & Energy 

• Through the cellular respiration process, stored energy in chemical bonds of sugar and other macromolecules is captured and converted into the bonds of ATP.

Cellular Respiration 

3 part process that converts a single glucose molecule to energy/ATP

1. Glycolysis 

   1. 2 ATP 

2. Krebs cycle 

   1. 2 ATP

3. Electron transport chain 

   1. 32 ATP 

Glycolysis

• Breakdown of 1 glucose molecule into 2 pyruvate molecules 

• Present in cytoplasm/cytosol 

• Two Stages 

  • Energy investment stage: requires 2 ATP

  • Energy harvesting stage: produced 4 ATP & NADH 

Steps for Glycolysis

1. 2 ATP are used to attach two phosphate groups to the 6-carbon glucose molecule.

2. 6-carbon glucose split into two 3-carbon molecules.

3. Phosphate added with energy from NAD+ oxidation.

• Two NADH molecules produced.

4. Phosphate groups lost to ADP.

• Four ATP produced.

5. Pyruvate end product.

Transition Phase 

• Coenzyme A (acetyl CoA) added to pyruvate producing Acetyl Coenzyme A.

  • Carbon Dioxide (CO2) byproduct 

• One NADH molecule produced from each pyruvate molecule.

Krebs Cycle 

• Inner compartment of mitochondria (matrix) 

• One glucose molecule: 

  • = 2 pyruvate 

  • = two cycles produces 

    • 4 CO2 

    • 6 NADH 

    • 2 ATP 

    • 2 FADH2

Electron Transport Chain 

• Energy from electrons (e - ) used to push H + ions from inner compartment to outer compartment against concentration and electrical gradient.

  • Inner membrane of mitochondria.

  •  Oxygen is the final electron acceptor.

Chemiosmosis

• Movement of ions across semi-permeable membranes, down their electrochemical gradient. 

  • ATP Synthase: enzyme uses energy from H+ ions to spin, which add phosphate to ADP making ATP.

Anaerobic

• without the use of oxygen.

  •  Glycolysis.

  • Fermentation

Aerobic

•  with the use of oxygen.

  • Cellular respiration

Fermentation:

• metabolic pathway that regenerates NAD+ from NADH and allows for glycolysis to continue making ATP in the absence of oxygen.

Alcohol fermentation:

• Yeast in an anaerobic environment.

Lactic acid fermentation:

•  Occurs in muscle when ATP use exceeds oxygen uptake

Lactic acid fermentation:

•  Occurs in muscle when ATP use exceeds oxygen uptake

Alcohol Fermentation

• Ethanol (drinking alcohol) is produced when acetaldehyde (pyruvate derivative) accepts electrons from NADH

Lactic Acid Fermentation

• produced when pyruvate accepts electrons from NADH 

• Occurs when oxygen delivery to cells is lagging 

  • Cause burning in muscles 

Anaerobic and Aerobic Contributions

•  Energy from anaerobic respiration is used for short bursts of activity.

Homeostasis

•  a physiological state where internal conditions are regulated.

 Regulators:

•  use internal mechanisms to minimize external fluctuations.

Conformers: 

• allow internal conditions to change due to external fluctuations.

Thermoregulation 

• Process by which animals maintain their body temperature within a normal range 

Endothermic: 

• Body temperature maintained by metabolism 

  • Birds, mammals, & insects 

Ectothermic: 

• Body temperature controlled by environment 

  • Most reptile, fish, & invertebrates 

Poikilotherm: 

• Animals whose body temperature fluctuates with the environment 

Homeotherm

• Animals with a relatively constant body temperature. 

Conduction: 

• Transfer of heat via touch 

Convection: 

• Transfer of heat by the movement of particles across a surface 

Radiation:

• Emission of electromagnetic waves 

Evaporation:

• Loss of heat from changing a liquid into a gas 

Adaptations for Thermoregulation 

• Insulation

• Behavior Responses

• Evaporative heat loss

Insulation: 

• Hair 

• Feathers 

• Fat (blubber)

Behavior Responses:

• Basking.

• Huddling.

•  Burrowing.

• Hot tubbin’.

Evaporative heat loss:

• Sweating.

•  Panting.

•  Defecating.

Torpor

• physiological state of decreased activity and metabolism.

Hibernation

• long term torpor and a decreased body temperature in response to winter cold and food scarcity

Estivation

• decreased metabolic rate and activity during hot summer months

Vasodilation: 

• The widening of superficial blood vessels 

  • Increase heat transfer 

Vasoconstriction 

• Reduces the diameter of superficial blood vessels 

Adaptations for Thermoregulation 

Countercurrent heat exchange:

1. Warm blood in arteries from an animal's core comes in close contact with veins returning from extremities.

2. Blood in arteries remains slightly warmer than blood in veins resulting in heat transfer.

3. Returning blood is almost as warm as arterial blood.

Animal Diets: 

All animals are heterotrophic: 

• Herbivores.

• Carnivores.

• Omnivores.

• Insectivores.

3 Nutritional Needs: 

• Energy for cellular processes.

• Organic building blocks for macromolecules.

• Acquisition of essential nutrients.

Trade-offs of Thermoregulatory Strategy

• Smaller endotherms have a greater surface area to volume ratio.

  • Lose more heat to the environment.

  •  Must produce more energy to maintain a constant body temperature.