Metabolism

What is metabolism?

Metabolism is the collection of all of the chemical reactions in a cell and it is broken into metabolic pathways.

What are metabolic pathways?

• A series of chemical reactions that go from one starting molecule to a product 

• Each step is catalyzed/triggered by an enzyme 

Catabolic vs. Anabolic Pathways

• Catabolic: breaking down a complex molecules into simple components and releases energy

• Anabolic: taking really simple building blocks to synthesize complex molecules which requires energy 

Kinetic vs. Potential energy and examples of each type

• Kinetic: movement energy

  • Thermal: kinetic energy generated by movement of molecules

  • Heat: thermal energy being transferred

• Potential: positional energy 

  • Chemical: energy stored in a molecule and is available for release in a reaction; more complex molecule = more energy available for release 

What is ATP and what does it do?

• RNA nucleotide with 3 phosphates 

• Snap off third phosphate to create adenosine diphosphate and release energy 

• Drives cellular work by causing shape changes 

What are exergonic vs. endergonic reactions?

• In exergonic reactions, energy is released, spontaneous, starts with high level energy reactants and ending with low level energy in the products because energy is released

• In endergonic reactions, energy is absorbed, nonspontaneous, starts with low level energy reactants and ending with high level energy because energy is absorbed

What is activation energy and how is it affected by an enzyme catalyst?

• E_A is the energy required to start a reaction 

• Enzyme lowers E_A cost so more molecules can cross E_A barrier; easier reaction to happen so it occurs more often 

Why are enzymes particular about their shape?

• Active site is shaped to bind to substrate

• Substrate is held in active site by weak interactions called enzyme-substrate complex and will do something to lowers E_A and then substrate is converted into products

How are enzymes sensitive about activity conditions? (pH and temperature)

• Optimal temperature or pH depends on where it is (human vs. bacteria or organelle vs. organelle)

• Steep slope after peak because too much energy makes the enzyme break apart

• Slope before peak is a gradual slope because when the temperature is decreased, the enzymes are bumping into the substrates more slowly

• When pH is changed, balance of hydrogen and hydroxide ions is changed so it disrupts hydrogen bonds so secondary and tertiary structure falls apart 

What are inhibitors and their purpose?

• Inhibitors are small molecules that can bind to enzymes and shape their functions

• They exist to regulate enzymes

What is the difference between competitive and non-competitive inhibitors?

• Competitive inhibitors are going to bind to the active site which physically blocks substrate binding and stops reaction/enzyme function

• Non-competitive inhibitors bind at the allosteric state which causes a change in the shape of the enzyme and alters the shape of the active site 

What is the experiment to test which kind of inhibitor is present?

• Experiment: 5 test tubes with same amount of enzyme and inhibitor content with increasing amounts of substrates

  • If inhibitor is competitive, then the reaction rate will increase because more substrates can overcome inhibitors  

  • If inhibitor is non-competitive, then the reaction rate will be the same