Unit 3: Energy and Living Systems Flashcards
metabolism
the totality of an organism’s chemical reactions
-as a whole, manages the material and energy resources of the cell
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
catabolic pathways
metabolic pathways that release energy by breaking down complex molecules to simpler compounds
-ex. cellular respiration
anabolic pathways
consume energy to build complicated molecules from simpler ones
-ex. synthesis of amino acids and proteins
bioenergetics
study of how energy flows through living systems
energy
the capacity to cause change or rearrange a collection of matter
kinetic energy
energy associated with the relative motion of objects
thermal energy
kinetic energy associated with the random movements of atoms or molecules
potential energy
energy matter possesses because of its location
chemical energy
refers to the potential energy available for release in a chemical reaction
thermodynamics
the study of energy transformations that occur in a collection of matter
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)
entropy
- a measure of disorder
- increased by a loss of usable energy (heat given off)
- sometimes visible as a physical disintegration of a structure
Second Law of Thermodynamics
every energy transfer or transformation increases the entropy of the universe
spontaneous process
a process that can occur without an input of energy
-must increase entropy of universe to occur
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)
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)
chemical equilibrium
when forward and backwards reaction occur at the same rate
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
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
Endergonic reaction
- absorbs free energy from surrounding (+^G)
- non-spontaneous
- ^G= energy required to drive the reaction
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)
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
energy coupling
use of an exergonic process to drive a endergonic one
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
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
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
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
phosphorylated intermediate
recipient of the ATP phosphate group. More reactive than the original molecule
Regeneration of ATP
-energy from catabolic pathways is used to add a phosphate group to ADP, creating ATP
carrying capacity
(K), the maximum population size that a particular environment can sustain
The Logistic Growth Model
per capita rate of increase (r) approaches zero as carrying capacity is reached
Allee effect
-individuals may have a more difficult time surviving or reproducing if population is small
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
semelparity
organisms reproduce only once but produce a large number of offspring
iteroparity
organisms that produce relatively few but large offspring each time they reproduce and provision offspring better
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)
K-selection
selection for traits that are sensitive to population density and are favored at high densities
r-selection
selection for traits that maximize reproductive success at low-densities
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
primary producers
autotrophs who ultimately support all other trophic levels
-most are photosynthetic organisms
heterotrophs
depend directly or indirectly on the outputs of primary producers for their energy
primary consumers
herbivores
secondary consumers
carnivores that eat herbivores
tertiary consumers
carnivores that eat carnivores
detritivores
- aka decomposers
- get energy from detritus
- break down organic material
- recycle chemical elements
detritus
nonliving organic material
primary production
the amount of light energy converted to chemical energy (organic compounds) in an ecosystem for at period of time
Ecosystem Energy Budgets
-total amount of photosynthetic production sets ecosystems “energy budget”
gross primary product
the amount of energy from light (or chemicals) converted to the chemical energy of organic molecules per unit of time
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
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
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)
limiting nutrient
the element that must be added for primary production to increase
-usually nitrogen or phosphorous
eutrophication
nutrients become highly concentrated in water, causing a great increase in growth of organisms
-causes loss of fish species in lakes
Primary Production in Terrestrial Ecosystems
- controlled mainly by temperature and moisture
- also limited by mineral nutrients (phosphorous or nitrogen)
secondary production
the amount of chemical energy in consumers’ food that is converted to their own biomass during a given period
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
net secondary production
total energy stored in biomass
assimilation of primary production
the total energy taken in, not including losses
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
turnover time
[standing crop (g/m^2)]/[production (g/m^2 times day)]
