Bio Quiz 6

metabolism

the totality of all the chemical reactions occurring within an organism. It is an emergent property, in which individual molecules interact with one another in organized ways, and the result is the complex system known as _.

chemical reaction

a process that changes one set of chemical substances into another. Occurs when atoms in molecules are rearranged, breaking some chemical bonds and forming others to create different substances

emergent property

a characteristic/feature that results from the interactions of many smaller parts in an organized system

metabolic pathway

A _ is a series of defined chemical reactions in which a starting molecule is changed through several steps to produce a final product. Each individual step is catalyzed by a specific enzyme.

molecule A (starting material) → molecule B (intermediate) → molecule C (intermediate) → molecule D (final product)

_ are regulated by the following:

a cell can regulate the enzymes responsible for the _, slowing or speeding up particular reactions, that way products are produced at an efficient pace (not too quickly or slowly). This helps the cell balance metabolic supply and demand.

enzyme

a biological catalyst, usually a protein, that speeds up a chemical reaction without being permanently consumed by that reaction. Generally, _ work on particular reactants because their structure and chemical properties suit that reaction.

catabolic pathways

a type of metabolic pathway, in which complex molecules break down into simpler molecules (breakdown pathways). _ release energy that can be captured and used by the cell (downhill)

• energy released can either be captured for cellular work or transferred to the surroundings as heat

ex: cellular respiration. During cellular respiration, cells break down glucose through a series of reactions, using oxygen in aerobic respiration and producing carbon dioxide and water overall.

glucose + oxygen → carbon dioxide + water + usable energy

anabolic pathways

a type of metabolic pathway in which complex molecules are built from simpler molecules (a.k.a biosynthetic pathways). _ require an input of energy (uphill)

ex: protein synthesis

ATP (adenosine triphosphate)

a molecule that cells commonly use to transfer energy to many cellular processes

downhill

refers to a process in which usable energy is released (overall)

uphill

refers to a process that requires a net input of energy (overall)

bioenergetics

the study of how energy flows through living organisms, examining how organisms obtain energy, transform it, transfer it, and use it to power life processes

energy

_ is the capacity to cause change. It allows cells to do work and carry out the processes necessary for life

intermediate

a molecule formed in the middle of the pathway is called an _.

molecule A (starting material) → molecule B (_) → molecule C (final product)

substrate

The molecule an enzyme acts on is called its _.

enzyme + _ → enzyme + product

kinetic energy

energy associated with motion

ex: moving bicycle, flowing water, moving molecules

potential energy

stored energy associated with an object’s position or structure

ex: water held behind a dam, energy associated with the arrangement of electrons in molecules, a book sitting high on a shelf

thermal energy

a type of kinetic energy associated with the random motion of atoms and molecules. everything made of matter contains atoms or molecules that are moving. In:

• solids: particles vibrate around positions

• liquids/gases: particles move more freely

Only works when there’s a suitable temperature difference (2 objects that are the same temperature can’t have a net flow of heat between them, so _ still exits, but there isn’t a temperature difference between the 2 objects for a heat engine to exploit)

heat

thermal energy being transferred from one object or region to another because of a temperature difference. It’s still energy, but the energy spread out as _ is generally less available to do work than energy maintained in a usable chemical or physical gradient.

chemical energy

a type of potential energy, associated with the arrangement of atoms and electrons in molecules that can be released through chemical reactions

ex: glucose contains _ that cells can make available through cellular respiration. provides energy as the formation of new bonds releases more energy than is required to break the original bonds. The overall _ determines whether energy is released or required.

Breaking a chemical bond requires energy

Forming a chemical bond releases energy

energy transformers

Organisms are _. This means that energy isn’t created by organisms, but rather taken, transformed, transferred, and eventually released into their surroundings. This process usually looks like:

light energy from sun → photosynthesis in plants (where light energy produces energy-rich organic molecules) → food (animals obtain chemical energy by eating plants or other organisms) → cellular respiration (cells transfer energy from organic molecules into usable forms) → cellular work and heat (energy supports life processes, while some is transferred to the surroundings as heat)

thermodynamics

the study of energy transformations and transfers. Allows scientists to understand what happens when energy changes form, how much energy is available to do work, and why certain processes can occur without an additional energy input

system

the part of the universe that we are studying

surroundings

everything that surrounds a system

isolated system

An _ exchanges neither matter nor energy with its surroundings (i.e a thermos bottle). Because the system cannot exchange matter or energy with its surroundings, it moves towards equilibrium (ΔG = 0)

ex: an _ hydroelectric system, where the water levels eventually equalize and there’s no longer a height difference to drive the process

open systems

an _ can exchange both matter and energy with its surroundings (i.e organisms)

ex: an _ hydroelectric system, where a river continuously supplies water to the upper reservoir while water leaves the lower reservoir

closed system

A _ exchanges energy (as heat or work) but not matter with its surroundings

energy cannot be created nor destroyed

The first law of thermodynamics states that _. Rather, it’s transferred or transformed. This is also known as the principle of conservation of energy.

The total amount of energy in the universe remains constant, and cannot suddenly appear or disappear

• energy chances form or moves between places

• total energy is conserved

energy transformations increases the total entropy of the universe

the second law of thermodynamics states that _. Energy can’t be recycled to do work forever, as some is lost to the surroundings as heat. Therefore, energy transformations have a direction. The heat lost to surroundings contributes to the total entropy of the universe (increasing). The total energy is still conserved, but there’s now less available to perform additional work.

We consider the system as well as its surroundings.

• total entropy increases in a spontaneous process

• energy becomes more dispersed overall in natural energy transformations

• the availability of energy to perform work generally decreases as energy is dispersed

entropy

a measure of how dispersed energy is and how many microscopic arrangements are available to a system (disorder)

spontaneous process

a process that is energetically favorable under the given conditions and can proceed without a continuous external energy input to drive it (Δ G < 0)

ex: water flowing downhill, rusting, an explosion

nonspontaneous process

a process that is not energetically favorable under the given conditions and requires an energy input or coupling to another process to proceed in that direction

ex: water pumped uphill

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If the change of Gibbs free energy (Δ G) is _ 0, the forward process is thermodynamically favorable.

The final state (products) have less free energy than the initial state (reactants), releasing free energy overall

• a reaction that moves from a higher-free-energy state to a lower-free-energy state

Exemplifies spontaneous processes (in the forward direction)

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If the change of Gibbs free energy (Δ G) is _ 0, the forward process requires energy input or coupling to a favorable process and is not thermodynamically favorable, receives free energy overall

The final state (products) has more free energy than the initial state (reactants)

Exemplifies a non-spontaneous process (in the forward direction)

=

If the change of Gibbs free energy (Δ G) is _ 0, the system is at equilibrium
The forward and reverse reactions continue at equal rates

increasing

_ biological complexity is consistent with the laws of thermodynamics. This is because the second law doesn’t say that every individual system must become less organized at every moment, but rather that the total entropy of the universe increases during spontaneous processes.

• organisms obtain energy from their surroundings and use it to grow, develop, reproduce, and maintain their structures

• the sun supplies the energy that supports most ecosystems. plants capture some of that energy through photosynthesis, and passes it through food webs. energy eventually leaves ecosystems as heat.

organisms become more organized → surroundings receive energy and matter (heat and metabolic waste products) → total entropy increases

biological order

an organism’s entropy can decrease (becoming more organized/complex) while the total entropy of the organism and surroundings increases. This is not a violation of the second law of thermodynamics

Gibbs free energy (G)

_ is used to determine whether a process (or a particular chemical reaction) is thermodynamically favorable under specified conditions.

Also known as free energy, _ is the portion of a system’s energy available to perform work under the relevant conditions, particularly when temperature and pressure are constant.

It’s a measure that helps us determine how much energy is available to do work and whether a reaction is thermodynamically favorable (under particular conditions).

A measure of a system’s tendency to change (the less free energy, the more stable)

free energy, temperature, enthalpy

Δ G means change in _

Δ T means change in _

Δ H means change in _

enthalpy

_ is the total heat content of a thermodynamic system at constant pressure. Tracks energy lost or gained as heat during physical or chemical reactions

chemical equilibrium

the state in which the forward and reverse reactions occur at equal rates, so the concentrations of reactants and products have no net change. The forward and reverse reactions continue at equal rates, exemplifying dynamic equilibrium

net change = 0

Think: a ball rolls downhill, and it’s gravitational PE decreases. Similarly, as a chemical system proceeds spontaneously toward equilibrium, its free energy decreases. Once at equilibrium, a chemical system cannot spontaneously move away from equilibrium in a way that produces net work.

Cannot produce net work by simply allowing the reaction to move forward as there’s no net free-energy decrease available from the reaction itself. A living cell must maintain chemical conditions away from equilibrium to keep doing work

exergonic reaction

An _ is a reaction that free energy overall. Δ G < 0, so the G final < G initial. The reaction is thermodynamically favorable in the forward direction.

Cells can couple an _ to a process that requires energy, as some the free energy released can be harnessed to do work (some is transferred to the surroundings as heat).

The magnitude of the -ΔG tells us the maximum amount of non-expansion work that could be obtained under the specified conditions if the reaction proceeded reversibly. The greater the decrease in free energy, the greater the maximum amount of work the reaction can provide.

ex: cellular respiration: ΔG = -686 kcal/mol (releases free energy), meaning it releases 686 kilocalories of free energy per mole of glucose consumed, some being captured in usable chemical forms (ATP) while some is released as heat

endergonic reactions

An _ is a reaction that requires a net input of free energy to proceed in the forward direction. ΔG > 0, so G final > G initial. The forward reaction is non-spontaneous under the specified conditions.

Ex: building proteins from amino acids, creating and maintaining certain concentration gradients, processes involved in growth and repair

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Standard conditions:

• _ M for each reactant and product

• A temperature of _°C

• A pH of _

The standard free energy change is commonly written ΔG°’

however, in actual cells, the concentrations of molecules differ from standard conditions, so the actual free-energy change can differ from the textbook value

requires, releases

cellular respiration is an exergonic reaction, releasing energy overall, because breaking chemical bonds _ energy, while forming chemical bonds _ energy. The process is:

1. energy is required to break the bonds in the reactants

2. new bonds form as the products are produced

3. forming the new bonds releases energy

4. for the overall reaction, the energy released through bond formation and other energy changes exceeds the energy required to break the original bonds

The products have less free energy available than the reactants under the stated conditions, making ΔG negative. Cellular respiration transfers energy through a series of reactions

reversing a chemical reaction flips the sign of ΔG, so photosynthesis is an endergonic reaction

dead

If a cell is at metabolic equilibrium, it is _. This is because a living cell must continually perform work. It needs to:

• maintain concentration gradients across membranes

• synthesize proteins and other molecules

• transport substances

• repair and maintain cellular structures

• carry out the reactions necessary for survival

These all rely on energy and chemical differences to drive reactions. If the cell’s metabolism reached equilibrium as a whole, it wouldn’t have the sustained free-energy differences needed to perform net metabolic work, and its organized, living processes could no longer be maintained. So, a living cell must remain out of equilibrium.

equilibrium

Some individual reactions can be near equilibrium while the cell remains alive, but metabolism as a whole must remain away from _, maintaining this condition through continuous exchanges with its surroundings, doing so by:

• materials (from a cell’s surroundings) flowing in and out of the cell. These incoming materials can provide energy or serve as reactants in metabolic pathways

• products of one reaction used in the next reaction, and waste products being removed.

  • The removal of intermediate products can help maintain conditions that favor the forward reactions.

  • Removing products and supplying new reactants help maintain the chemical conditions needed for metabolism to continue (i.e CO2 being removed after cellular respiration)

chemical work

A type of work, in which cells use energy to build molecules that would not form spontaneously (i.e small building blocks forming larger molecules, often an endergonic process as it requires an energy input)

transport work

a type of work in which cells use energy to move substances across a membrane against the direction they would naturally move (i.e a protein pump)

Substances naturally spread down their concentration gradients. Moving them against that gradient requires energy, supplied by ATP (active transport)

mechanical work

a type of work, in which cells use energy to create movement

ex: muscle cells contracting, cilia beating to move a cell or fluid, chromosomes moving during cell division, motor proteins carrying materials through a cell

energy coupling

_ means using an energy-