Bioenergetics: Energy Transformations in Cells (Vocabulary Flashcards)

A set of vocabulary flashcards covering key concepts from energy transformations, thermodynamics, and enzyme/metabolic regulation.

Bioenergetics

The study of energy transformations in living organisms and how cells convert energy to do work.

Thermodynamics

The science of energy transformations and the relationships between heat, work, and energy.

What system is an organism?

A open system that exchanges energy (and often matter) with its self and its surroundings.

First Law of Thermodynamics (Conservation of Energy)

Energy cannot be created or destroyed; it can be transferred or transformed.

Second Law of Thermodynamics

In every energy transfer, disorder (entropy) tends to increase; not all energy is usable, and is lost as heat

Entropy

A measure of disorder or randomness in a system; tends to increase in natural processes.

Spontaneous process

A process that can occur without external energy input and happens when the process increases the universe’s entropy. (doesn’t happen quickly just means it’s more favorable as it follows laws)

Free energy

The energy in a system available to do work under constant temperature and pressure.

Gibbs Free Energy (ΔG)

The energy available to do work; ΔG = ΔH − TΔS for a process.

Entropy change (ΔS)

The change in a system’s entropy during a process.

Endergonic reaction

A reaction that absorbs energy (positive ΔG).

Ex: photosynthesis

Slope starts from bottom, goes to top and slows down

Exergonic reaction

A reaction that releases energy (negative ΔG).

Slope starts from top, increases little bit, before coming all the way to bottom

Ex: cell respiration

Activation energy

Amount of energy needed to destabilize the bonds of a molecule. catalysts lower it.

Energy coupling

Using energy released by one reaction to drive another endergonic reaction.

Catalyst

A substance that lowers activation energy and speeds up a reaction without being consumed.

Enzyme

A biological catalyst, typically a protein (or RNA) that speeds a chemical reaction.

Reduce activation energy without being consumed

doesn’t change free energy released or absorbed

Highly specific

Controls reactions of life

Substrate

The molecule that binds to an enzyme’s active site and is transformed.

Active site

The region of the enzyme where the substrate binds; its shape enables the reaction.

Enzyme-substrate complex

The temporary complex formed when the substrate binds to the enzyme.

Lock-and-key model

A simple model where the substrate fits exactly into the enzyme’s active site. H bonds between substrate and enzyme.

Induced fit model

A more accurate model in which the enzyme changes shape to better fit the substrate after binding. Bring r groups into position to catalyze reaction

Substrate concentration

The amount of substrate available; higher concentrations raise reaction rate until enzymes saturate.

Enzyme concentration

The amount of enzyme present; more enzyme generally increases reaction rate until substrate is limiting.

Optimal temperature

The temperature at which an enzyme’s activity is maximal.

Denaturation

Loss of an enzyme’s 3D structure and function due to heat or extreme conditions, beyond optimal temp. Distrusted bonds in enzyme and bonds between substrate.

pH

A measure of acidity/alkalinity; enzymes have optimal pH ranges for activity.

Optimal pH

The pH at which an enzyme works best.

Human enzymes (6-8)

pepsin (stomach) (2-3)

Trypsin (intestine) (8)

Salinity

Salt concentration; extreme salinity can disrupt attractions between charged amino acids resulting in change of enzyme structure and function.

Activator

Cofactors, non-protein, small, inorganic compounds and ions that bind with enzyme molecule. Helps enzymes

Coenzyme

Non-protein organic molecule that bind temporarily or permanently to enzyme near active site (e.g., NAD+, FAD, CoA). Helps enzymes

Competitive inhibitor

A molecule that competes with the substrate for the active site; can be overcome by increasing substrate concentration. Ex: penicillin blocks enzyme bacteria. Disulfiram blocks enzyme that breaks down alcohol

Noncompetitive inhibitor (allosteric inhibitor)

An inhibitor that binds away from the active site, binds to allosteric site, changing enzyme shape and reducing activity.

Conformational change: active site is no longer functional binding site, keeping it inactive

Usually temporarily but could be permanent

Ex: anti cancer drugs

Allosteric regulation

Regulation of enzyme activity via allosteric sites, causing conformational changes.

Irreversible inhibition

An inhibitor that permanently deactivates an enzyme, often by covalent modification.

Competitive inhibitor: binds to active site

Allosteric inhibitors: binds to allosteric site

Metabolic pathway

A series of linked enzymatic reactions (pathways and small steps) converting a starting material to a product. Increased efficiency, control

Feedback inhibition

Negative feedback where a product inhibits an earlier enzyme to regulate production. No unnecessary accumulation of product

Gibbs free energy change (ΔG)

The change in free energy of a system; ΔG < 0 indicates spontaneity, ΔG > 0 indicates non-spontaneity.

ΔH (Enthalpy)

The total energy content (heat content) of the system.

Example of feedback inhibition

Synthesis of amino acid, isoleucine from amino acid, threonine. Isoleucine becomes allosteric inhibitor of the first step in pathway. Isoleucine collides with enzyme more than substrate does.

Biological order

Cells create ordered structures from less ordered materials and vice versa.

Entropy may decrease in an organism, but the universes total entropy always increases.

Free energy and stability

Free energy measures a systems instability. Free energy decreases during any spontaneous process, and increases stability

Equilibrium

State of maximum stability

Process is spontaneous and only works when moving towards equilibrium

When equilibrium is reached, organism is dead

Properties of enzymes

each enzyme works with a substrate (chemical fit) h and ionic bonds between r groups of amino acids in active site and substrate

Enzymes can catalyze thousands or more reactions

Affected by cellular conditions

Synthesis reactions

Active site orient substrates in correct position for reaction. Enzymes brings substrates closed together

Digestion (hydrolysis reactions)

Active site binds substrate and puts stress on bonds that must be broken, making it easier to separate molecules

Rearrangement

Active site crates micro environment different from rest of solution

Factors that affect enzyme function

Enzyme concentration

Substrate concentration

Temperature

pH

Salinity

Activators

Inhibitors

Optimum temp for human enzymes

35-40

37 Celsius is body temp

Decrease in temperature effect

Molecules move slower, decrease collisions between enzyme and substrate (NO DENATURATION)

Bacteria temperature

Extreme hot temp is optimal temperature

Catalase

An enzyme that catalyzes the decomposition of hydrogen peroxide into water and oxygen, playing a crucial role in protecting cells from oxidative damage.