Metabolism

All the reactions taking place in an organism 

Anabolism

• Anabolic rxn 

• Building up large molecules 

• Using dehydration rxn

Catabolism 

• Catabolic rxn 

• Breaking down large molecules 

• Using hydraulic rxn 

The first law of thermodynamics: 

Energy is neither created nor destroyed; instead, energy changes from one form to another 

The second law of thermodynamics:

Systems are not efficient; energy is always lost to the surroundings, resulting in disorder, which is called entropy, measured in temp 

Living things are constantly working against entropy by trying to maintain their homeostasis, a constant internal environment. We fight disorder and when we begin to lose, we start to age & die. 

Energy is the ability to do work.

Forms of energy 

• Kinetic: increate in KE → inc heat 

• Potential: stored energy located in the bonds; stronger bonds = more energy 

Heat: the amount of collisions particles form with each other & surroundings 

Temperature: the average movement of particles 

Different energy forms of chemicals 

• Ordered with high energy bonds; very reactivity 

  • Exp: ATP dec Δs

• Ordered with low energy bonds; low reactivity 

  • Exp: glucose, glycogen, lipids dec Δs

• Disordered with low energy bonds: low reactivity 

  • Exp: ADP, CO2 Inc Δs

Energy Graph

The most common chemical used in biology is ATP

ATP     → ADP           + Pi

Adenosine triphosphate → adenosine diphosphate + inorganic phosphate 

Coupling reactions

When two rxn are paired together, one is exergonic, supplying energy to the second rxn, which is endorgonic, allowing it to occur. 

Cellular Work

Most common forms of cellular work 

Chemical Work:

• Definition: Chemical work involves the synthesis of complex molecules, the breakdown of larger molecules into simpler ones, and the conversion of one type of molecule into another.

• Example: An essential example of chemical work is the synthesis of adenosine triphosphate (ATP), which serves as the primary energy currency of cells. During cellular respiration, cells break down glucose into carbon dioxide and water, releasing energy that is used to produce ATP.

Transport Work:

• Definition: Transport work involves the movement of substances across cellular membranes. This can include the active transport of ions or molecules against their concentration gradient, requiring energy input.

• Example: The sodium-potassium pump is a classic example of transport work. This pump actively transports sodium ions out of the cell and potassium ions into the cell against their respective concentration gradients, using energy derived from ATP hydrolysis.

Mechanical Work:

• Definition: Mechanical work involves the physical movement or mechanical manipulation of cellular structures. This includes activities such as muscle contraction and the movement of cilia and flagella.

• Example: Muscle cells perform mechanical work during contraction. The interaction between actin and myosin filaments, powered by ATP, leads to the shortening of muscle fibres and the generation of mechanical force.

Enzymes

Proteins (sometimes RNA) that lower the Ea to allow reactions to happen faster 

How is the Ea lowered?

• Enzyme brings reactants close to each other 

• Brings reactants together in the correct orientation 

• Places stress on bonds, allowing them to break and form more readily 

Catalytic cycle of enzymes 

1. Substrates (reactants) enter into the active site of the enzyme in the correct orientation 

   1. The active site is a specific region of the enzyme where the reaction takes place 

   2. receptors/transport proteins do now have an active site; they have a binding site instead. the binding site is for attachment, holding things

Each enzyme is specific to a substrate that is called the lock-and-key mechanism 

Substrates are attached to the active site, and as soon as they enter it, the active site will wrap tightly around the substrates; this is called induced fit

2. Once substrates are in the enzyme, the enzyme-substrate complex is formed, where the substrate is held by weak intermolecular force in the active site 

3. The enzyme lowers the Ea by placing stress on the bonds of the substrate using the weak intermolecular forces

4. The stress on the bonds created by the active site will allow bonds to break and new ones to form, generating products.

5. Products are repelled by the active site, causing them to leave the enzyme 

6. Enzyme returns back to its original conformation, ready to receive a new substrate 

Other chemicals can help enzymes function, such as…

Inorganic chemicals called cofactors 

Exp: zinc, manganese, copper 

Organic chemicals called coenzymes 

Factors that disrupt enzyme function (all stress)

• Pressure 

• Temperature 

• pH 

• Salt concentration 

• Electricity 

• poison/inhibitors 

These change the structure of the enzyme, resulting in denaturation 

Forms of enzymes 

1. In the active form (more common in bio)

   1. Always function and must be turned off when not needed (inhibited) 

2. Inactive form 

   1. Produced in a nonfunctioning form and must be turned on or activated

Controlling the function of active enzymes 

Inhibitors are chemicals that will inactivate enzymes 

Two types… 

1. Competitive inhibitors 

• Will compete with the substrate for the active site

• This can be controlled by changing the substrate concentration 

• More substrate, lower chance of activation 

1. Reversible competitive inhibitor 

   1. Inhibitor temporarily attaches to the active site and can leave 

2. Irreversible competitive inhibitor 

   1. Permanently attaches to the active site and will not leave 

2. Non-competitive inhibitors 

• Will attach to the enzyme at another location called the allosteric site, causing the active site to change in shape so that substrates will not fit properly

• Or blocks the active site so substrates can’t enter 

• Exists as reversible and irreversible 

Reactions are constantly regulated by feedback. 

Positive

• Feedback activation 

• As more products are created, this causes enzymes to work more and produce even more products 
  

Negative 

• Feedback inhibition 

• As products increase in amount, the enzyme will be inactivated 

  • The concentration of the product is the inhibitor 

• Example: threonine (amino acids) changes by a series of reactions to isoleucine, the isoleucine attaches have an allosteric site, inhibiting the cell. When isoleucine is used up, it will detach.