Energy and the Underlying Organization of Life

Metabolism Cell’s capacity to

Acquire energy

Build-anabolism

Break apart-catabolism

Release substances

Defining Energy Potential Energy-energy

of position

Kinetic Energy-energy of motion

Heat (Thermal) Energy-usually a waste product

Chemical Energy-energy for work (like carbs)

Kilocalories

Total Energy Content Energy content of any system with the environment

remains constant-neither created or destroyed

How Much Energy is Available?

First Law of Thermodynamics Energy cannot be created or destroyed

Second Law of Thermodynamics Total amount of energy in the universe is

flowing from higher to lower quality

Entropy

System’s disorder

This is constantly increasing in the universe

One-Way Flow of Energy

Flow of energy into life and one-way flow of

energy out of it

Doing Cellular Work Mechanical Work

Energy input required

Potential energy released by downhill run

Doing Cellular Work

Reactions Endergonic-

energy used

Exergonic-energy released

Cells couple energy to get the job done

ATP The Cell’s Energy Currency

ATP - Adenosine Triphosphate Ribose

Adenine

Three phosphate groups

Phosphorylation-helps to supply energy

ATP and Cellular WorkA Calcium Pump

Phosphorylation

Electron Transfers

Oxidation-reduction reactions

Donating and acceptance of electrons

Conservation of energy

Metabolic Pathways

Ordered

Enzyme-mediated

Biosynthetic or Degradative

Enzyme Structure and Function

Catalysts speed the rate of chemical reactions

Not permanently altered or used up

Reversible reactions

Selective for the substrates

Enzyme Activation Energy

Enzyme Substrate Interaction

Reaction rate is enhanced by lowering the activation energy

Model of Enzyme at Work

Active site exposed Glucose in site - Reaction takes place

Induced-Fit Model of Enzyme-Substrate Interactions

Four Features of Enzymes

Helping substrates get together

Orienting substrates in positions favoring

reactions

Promoting acid-base reactions

Shutting out water

Factors Influencing Enzyme Activity

Temperature

pH

Salinity

Ranges are specific

Heat sensitiveenzyme controls

melanin production

Control of Enzyme Function

Allosteric control Binding of

substances on enzyme other than the active site

Can activate

Can inhibit

Feedback Inhibition

Shutting down of activity

Product produced shuts down reaction

Reactants, Products, and Cell Membranes

Selective permeability

Small non-polar molecules pass easily

Some molecules need transport proteins

Bulk movement Exocytosis - out of cell

Endocytosis - into cell

Concentration Gradients

Diffusion

Passive transport Transport proteins

Movement occurs both ways across membrane

Active transport Uses ATP

Diffusion

Passive Transport

Active Transport

Movement of Water Across Membranes

Osmosis- diffusion of water

Tonicity

Hypotonic- more solvent than solute

Hypertonic- more solute than solvent

Isotonic- equal solvent/solute

Fluid pressure

Hydrostatic pressure- water pressure keeps earthworms plump

Osmosis and Solute Concentration

Effects of Tonicity

Effects of Fluid Pressure

Loss of Fluid Pressure

Plasmolysis - Plasma membrane moves away from the wall

Exocytosis and Endocytosis

Large moleculesor particles

Receptor-Mediated Endocytosis

Receptor proteins bind solutes

Phagocytosis

Amoebas andmacrophages

engulftheir targets

In Conclusion

The sum of metabolism underlies the survival of organisms

The First and Second Laws of Thermodynamics affect life

Energy can be converted from one form to another but cannot be destroyed

Energy flows from higher to lower quality

In Conclusion

All matter has some form of potential energy which can be converted to kinetic energy

Cells stay organized as long as they balance energy expenditures with energy replacements

Metabolic reactions can release or require energy

In Conclusion

Exergonic reactions end with a net loss of energy

Endergonic reactions end with a net gain of energy

Cells couple exergonic and endergonic reactions

ATP is the main energy carrier in cells

In Conclusion

ATP forms when a phosphate is donated to ADP

Transfer of electrons from one substrate to another involves ATP

Metabolic pathways are orderly, stepwise sequences of enzyme-mediated reactions

Enzymes are catalysts, lower activation energy, and bind substrates

In Conclusion

Enzymes are temperature, pH, and salinity specific

Molecules or ions diffuse down a concentration gradient

Some molecules diffuse across the membrane

Transport mechanisms involve passive and active transports

In Conclusion

Osmosis is the diffusion water across a selectively permeable membrane

Different tonicities influence the movement of water

Cells acquire or get rid of substances in bulk by exocytosis and endocytosis

developed by M. Roig