Unit 3: Energy and Living Systems Flashcards Preview

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Flashcards in Unit 3: Energy and Living Systems Deck (62):
1

metabolism

the totality of an organism's chemical reactions
-as a whole, manages the material and energy resources of the cell

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metabolic pathway

begins with a specific molecule which is then altered in a series of defined steps (enzyme catalyzed reactions) resulting in a certain product

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catabolic pathways

metabolic pathways that release energy by breaking down complex molecules to simpler compounds
-ex. cellular respiration

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anabolic pathways

consume energy to build complicated molecules from simpler ones
-ex. synthesis of amino acids and proteins

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bioenergetics

study of how energy flows through living systems

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energy

the capacity to cause change or rearrange a collection of matter

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kinetic energy

energy associated with the relative motion of objects

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thermal energy

kinetic energy associated with the random movements of atoms or molecules

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potential energy

energy matter possesses because of its location

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chemical energy

refers to the potential energy available for release in a chemical reaction

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thermodynamics

the study of energy transformations that occur in a collection of matter

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First Law of Thermodynamics

-energy can be transferred and transformed but it cannot be created or destroyed
-during every transfer or transformation some energy becomes unavailable to do work (lost as heat)

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entropy

-a measure of disorder
-increased by a loss of usable energy (heat given off)
-sometimes visible as a physical disintegration of a structure

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Second Law of Thermodynamics

every energy transfer or transformation increases the entropy of the universe

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spontaneous process

a process that can occur without an input of energy
-must increase entropy of universe to occur

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Free energy

the portion of a system's energy that can perform work when temp and pressure are uniform throughout the system
-can be seen as a measure of a system's instability (tendency to change to a more stable state)

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Free energy change, ^G

^G= ^H-T^S
^H= change in enthalpy
^S= change in systems entropy
T= absolute temperature (K)
-only processes with negative ^G are spontaneous (spontaneous process decrease system's free energy)

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chemical equilibrium

when forward and backwards reaction occur at the same rate

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Free Energy and Euilibrium

free energy decreases, as a reaction proceeds toward equilibrium
-a reaction in equilibrium cannot perform work
-a process is spontaneous and can perform work only when it is moving toward equilibrium

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Exergonic reaction

negative change in G
-proceeds with a net release of free energy
-reactions that occur spontaneously
-^G = maximum amount of work a reaction can perform

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Endergonic reaction

-absorbs free energy from surrounding (+^G)
-non-spontaneous
-^G= energy required to drive the reaction

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Equilibrium and Metabolism

-reactions in an isolated system will eventually reach equilibrium
-constant flow of material into and out of a cell keeps metabolic pathways from reaching equilibrium
-product of one reaction becomes a reactant in the next step (occurs in cellular respiration)

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Cell does 3 kinds of work

-chemical work: pushing of endorgonic reactions that would not occur spontaneously
-transport work: actively pumping substances across membrane
-mechanical work: cell movement

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energy coupling

use of an exergonic process to drive a endergonic one

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ATP

-adenosine triphosphate
-contains sugar ribose, the nitrogenous base adenine, and a chain of three phosphate group
-chain of three negative phosphates act as spring
-plays a role in energy coupling and is used to make RNA

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Hydrolysis of ATP

-the bond between phosphate groups is broken by hydrolysis. ATP becomes ADP and energy is released
-exergonic and releases about 7.3 kcal of energy per mole ATP

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How the Hydrolysis of ATP performs work

-generates heat which may be use to warm body
-most energy is harnessed by the cells proteins to perform work
-coupling
-drives transport and mechanical work by changing shape of proteins

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ATP and coupling

-energy created by ATP hydrolysis is used to drive reaction which, by themselves, are endergonic
-usually involves transfer of a phosphate group to another molecule

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phosphorylated intermediate

recipient of the ATP phosphate group. More reactive than the original molecule

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Regeneration of ATP

-energy from catabolic pathways is used to add a phosphate group to ADP, creating ATP

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carrying capacity

(K), the maximum population size that a particular environment can sustain

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The Logistic Growth Model

per capita rate of increase (r) approaches zero as carrying capacity is reached

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Allee effect

-individuals may have a more difficult time surviving or reproducing if population is small

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life history

made up of the traits that affect an organism's schedule of reproduction and survival
-when reproduction begins
-how often organisms reproduce
-how many offspring produced per reproductive episode

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semelparity

organisms reproduce only once but produce a large number of offspring

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iteroparity

organisms that produce relatively few but large offspring each time they reproduce and provision offspring better

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Factors that contribute to evolution of semelparity or iteroparity

-survival rate of offspring. If low semelparity is favored
-likelihood adult will survive to reproduce again (if unlikely semelparity is favored)

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K-selection

selection for traits that are sensitive to population density and are favored at high densities

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r-selection

selection for traits that maximize reproductive success at low-densities

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conservation of mass in ecosystems

-mass is neither created or destroyed
-allows us to determine how much of a chemical element cycles within an ecosystem
-elements can also be gained or lost by environment
-most elements are recycled within an ecosystem

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primary producers

autotrophs who ultimately support all other trophic levels
-most are photosynthetic organisms

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heterotrophs

depend directly or indirectly on the outputs of primary producers for their energy

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primary consumers

herbivores

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secondary consumers

carnivores that eat herbivores

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tertiary consumers

carnivores that eat carnivores

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detritivores

-aka decomposers
-get energy from detritus
-break down organic material
-recycle chemical elements

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detritus

nonliving organic material

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primary production

the amount of light energy converted to chemical energy (organic compounds) in an ecosystem for at period of time

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Ecosystem Energy Budgets

-total amount of photosynthetic production sets ecosystems "energy budget"

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gross primary product

the amount of energy from light (or chemicals) converted to the chemical energy of organic molecules per unit of time

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net primary product

equals the gross primary production minus energy used by primary producers for "autotrophic respiration" (Ra)
-amount of new biomass added in a given period of time

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net ecosystem production

a measure of the total biomass accumulation during that time
-GPP-total respiration of all organisms in the system (Rt)
-determines whether an ecosystem is gaining or losing carbon over time
-may be estimated by measuring the flow of CO2 or O2 into and out of an ecosystem

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Nutrient Limitation

-nutrients limit primary production more than light in most lakes and oceans
-areas of upwelling (deep-nutrient rich waters circulate to the oceans surface)

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limiting nutrient

the element that must be added for primary production to increase
-usually nitrogen or phosphorous

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eutrophication

nutrients become highly concentrated in water, causing a great increase in growth of organisms
-causes loss of fish species in lakes

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Primary Production in Terrestrial Ecosystems

-controlled mainly by temperature and moisture
-also limited by mineral nutrients (phosphorous or nitrogen)

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secondary production

the amount of chemical energy in consumers' food that is converted to their own biomass during a given period

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production efficienty

-the percentage of energy stored in assimilated food(not including the undigestable parts) that is not used for respiration
=(net secondary production/ assimilation of primary production)
-mammals and birds have the lowest (around 1-3%) as they must maintain body heat

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net secondary production

total energy stored in biomass

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assimilation of primary production

the total energy taken in, not including losses

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Trophic efficiency

the percentage of production transferred from one trophic level to the next
-typically around 10%
-loss of energy along a food chain limits the abundance of top-level consumers an ecosystem can support

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turnover time

[standing crop (g/m^2)]/[production (g/m^2 times day)]