unit 3 topics 1 and 2*

What is metabolism?

The chemical reactions that occur within an organism to maintain life. They allow growth, reproduction, maintain structures, and respond to their environments. 

What are metabolic pathways?

Sequences of chemical reactions occurring within a cell, starting from a substrate and facilitated by specific enzymes.

Type of metabolic reactions —> Catabolic Reaction:

Reactions that break down complex molecules into simpler ones, releasing energy in the process.

Give an example of a catabolic reaction.

Cellular respiration, where glucose is broken down to produce carbon dioxide, water, and energy.

Type of metabolic reaction —> Anabolic Reaction:

Reactions that build complex molecules from simpler ones, requiring an input of energy.

Give an example of an anabolic reaction.

Photosynthesis, where plants build glucose from carbon dioxide and water using sunlight.

Define kinetic energy.

The energy of motion.

What is thermal energy?

Energy associated with the random movement of atoms or molecules.

Define potential energy.

The energy stored in an object due to its position or structure.

What is chemical energy?

Potential energy stored in chemical bonds, released during chemical reactions.

First Law of Thermodynamics: Energy Conservation

Energy cannot be created or destroyed, only transformed or transferred.

Ex: Cellular respiration where chemical energy in glucose is converted to ATP

Second Law of Thermodynamics (Law of Entropy)

Every energy transfer increases the entropy (disorder) of the universe. During energy transformation, some energy may not be used and instead lost as heat.

Ex: Cells work to maintain order by using energy to build complex structures and perform functions.

What is free energy?

Available energy to do work in a system. Is important since it determines whether a reaction will occur spontaneously without the need of added energy.

What indicates a reaction is exergonic?

Negative change in free energy, meaning the reaction can occur and releases energy.

What indicates a reaction is endergonic?

Positive change in free energy, meaning the reaction cannot occur without an input of energy.

What are exergonic reactions?

Reactions where ATP hydrolysis releases free energy by breaking down ATP into ADP and inorganic phosphate, evident in cellular respiration.

What are endergonic reactions?

The free energy that was released from ATP hydrolysis and is used to drive endergonic reactions by absorbing the energy.

Ex: photosynthesis, synthesizing macromolecules or active transport across membranes. 

What type of work do cells perform that keeps them from reaching equilibrium?

Mechanical work, transport work, and chemical work.

What is mechanical work?

Movements like muscle contraction and the movement of chromosomes during cell division.

Define transport work.

Movement of substances across cell membranes, like pumping ions against their concentration gradient.

What is chemical work?

The synthesis of complex molecules from simpler ones, such as the formation of proteins from amino acids or DNA replication.

What are the components of ATP?

Adenine, ribose, and three phosphate groups.

How does ATP provide energy for cellular processes?

By coupling exergonic reactions with endergonic reactions.

What occurs during ATP hydrolysis?

ATP is broken down into ADP and inorganic phosphate, releasing energy.

What is phosphorylation?

When ATP is hydrolyzed it transfers one of its phosphate groups to another molecule. This transfer changes the shape or energy state of the target molecule, allowing it to perform work.

How is ATP regenerated?

• From ADP and Pi through cellular respiration mainly found in the mitochondria.

• The cycle of ATP hydrolysis and regeneration keeps the energy supply available for cellular functions.

How does the law of thermodynamics relate to reaction rates?

It helps understand whether a reaction can occur without energy input, but not how fast it will happen.

What are enzymes?

Catalysts that speed up chemical reactions by lowering activation energy and are not consumed in the process.

Characteristics of an enzyme:

Proteins: Enzymes are specific proteins that can be identified by the suffix “-ase” like protease, amylase, lipase, etc.

Specificity: Each enzyme catalyzes a specific reaction or type of reaction.

Efficiency: Enzymes can increase reaction rates by millions of times.

Reusable: Enzymes aren’t consumed in the reactions they catalyze and can be used again.

What is the induced fit model?

Enzymes’ active site molds itself around the substrate as they bind, enhancing the enzyme’s ability to catalyze the reaction.

How does temperature affect enzyme activity?

Enzymes have an optimal temperature; extreme temperatures can denature them.

What is competitive inhibition?

A type of reversible inhibition where inhibitors compete with the substrate for the active site.

What is allosteric regulation?

Regulation of enzyme activity where molecules bind to allosteric sites, causing conformational changes that affect enzyme activity. There are allosteric activators and inhibitors.

Define feedback inhibition.

The end product of a metabolic pathway inhibits an enzyme involved early in the pathway, preventing overproduction.

Structure of Enzymes

Globular proteins with a three-dimensional structure that includes an active site where substrates bind.

Functions of Enzymes

Enzymes perform both catabolic (breaks down) and anabolic (builds molecules) reactions. They speed up reactions by lowering the activation energy required.

How does substrate concentration affect enzyme activity?

Increasing this concentration increases the rate of reaction to a point, that the enzyme becomes saturated and the rate levels off. 

How does pH affect enzyme activity?

Enzymes have optimal pH so extreme levels of pH can denature enzymes

How does enzyme concentration affect enzyme activity?

Increasing this concentration increases the reaction rate, leaving an excess of substrate.

Cofactors

Non-protein molecules or ions that are required for enzyme activity

Coenzymes

Organic molecules that bind to enzymes and assist in enzyme activity. 

Enzyme inhibitors

These reduce the activity of certain enzymes and can be permanent or reversible. 

Noncompetitive inhibition

A type of reversible inhibition, where inhibitors bind to a site other than the active site, causing a conformational change reducing enzyme activity. 

What is cooperativity in a regulation of enzyme activity?

Binding of a substrate to one activate site affects the activity at other active sites in a mult-subunit enzyme.