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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