gen bio 1 exam 3 Flashcards
cellular metabolism
The chemical reactions that occur in cells, including those
that use and release energy
metabolic pathways
ordered series of chemical reactions that build or break
down a molecule
ways cells respond to the environment:
*Building and breaking down macromolecules
* Transporting proteins across cell membranes
* Packaging materials into vesicles,
* Dividing, mutating, dying, etc.
catabolism reaction
starts from a larger molecule and breaks down to a smaller one and releases energy
anabolism reaction
starts from a smaller molecule and combines with energy to create a larger molecule
1st law of thermodynamics
Energy is conserved. Energy cannot be created nor destroyed, but only transferred and transformed.
kinetic energy
energy in motion
Ex: thermal energy, electricity, electromagnetic radiation (e.g. light/photons), sound waves
potential energy
stored energy
Ex. gravity or chemical bonds
what happens to energy when a chemical bond is broken
may be converted into light, heat, new chemical bonds
By breaking a bond, potential energy can be converted to kinetic energy such as light and
thermal energy (heat)
total energy in a molecule is measured in…
Enthalpy (H)
ΔH =
potential energy of product – potential energy of reactant
A chemical reaction that has reactants of high potential energy and low kinetic energy can result in products with…
low potential energy and high kinetic energy. This produces a –ΔH
exothermic reactions have a…
–ΔH; usually produces heat
A chemical reaction that has reactants of low potential energy and high kinetic energy can result in products with…
high potential energy and low kinetic energy. This produces a +ΔH
endothermic reactions have a…
+ΔH
high entropy means..
high disorder
Entropy, S =
amount of disorder
ΔS =
Entropy of product – Entropy of reactant
high entropy reactants and low entropy products result in a…
–ΔS
Gibbs free energy describes…
determines whether a chemical reaction is spontaneous or non-spontaneous and whether energy is stored or released
ΔG =
ΔH - TΔS
the symbols in the gibbs free energy equation:
ΔH = Potential energy of product – Potential energy of reactant
ΔS = Entropy of product – Entropy of reactant
T = Temperature
Conversion: T in Kelvin = Celsius +273
more energy is unavailable to do work when a reaction occurs at higher temperature because….
an increase in temperature increases entropy
a spontaneous reaction (exergonic), has a..
-ΔG and releases energy
a non-spontaneous reaction (endergonic), has a…
+ΔG, requires an input of energy to proceed; stores energy
a +ΔH means +ΔG and vice versa
…
Chemical energy can drive non-spontaneous
reactions via:
- Harnessing energy by breaking
(cleavage) of chemical bonds (ATP to
ADP or AMP) - Electron transfer (via redox reactions)
ATP stores a large amount of potential energy
in the form of…
phosphanyhydride bonds
when ATP is hydrolyzed…
energy is released
ATP hydrolysis (breaking a phosphoanhydride
bond)…
releases free energy (-ΔG), an exergonic
reaction
Exergonic reactions can provide energy for
endergonic reactions like cellular
respiration
…
Redox reactions transfer energy via…
electrons
redox reaction
chemical reaction involving the loss or
gain of one of more electrons
oxidation
loss of electrons; when product has less electrons than reactant
reduction
gain of electrons; when product has more electrons than reactant
catalyst
a substance that increases the rate of a reaction
without being consumed
enzyme
a catalyst that speeds up the rate of a biochemical
reaction
* most are proteins
substrate
Substance the enzyme acts upon
When a substrate binds to the
active site of an enzyme, the
enzyme slightly changes its
shape to better accommodate
the substrate → creates a
more precise fit → facilitates
the chemical reaction
…
conformational change
a change in the shape of a molecule such as a protein
Enzymes lower the activation energies of chemical
reactions → Amount of enzymes and enzyme activity
determine which biochemical reactions will proceed
…
Enzyme levels and activity are tightly regulated in cells in order to…
maintain homeostasis and organismal health
3 mechanisms for enzyme regulation:
- molecular regulation
- Compartmentalization
- Feedback inhibition
Molecular regulation of enzymes
Mechanism that regulates enzyme activity through the action of inhibitors or activators
enzyme inhibitors
molecules or substances that reduce the activity of an
enzyme
- Leads to reduction in amount of products
- Substrates may accumulate
3 Mechanisms for enzyme inhibition:
- Competitive inhibition
- Non-competitive inhibition
- Allosteric inhibition
competitive inhibition
A molecule or substance competes with the substrate for binding to an active site (substrate unable to bind to enzyme)→ decreased enzyme activity
* A competitive inhibitor usually resembles the structure or shape of a substrate
non-competitive inhibition
An inhibitor binds to the enzyme in a location other than the active
site (allosteric site) → decreased enzyme activity
allosteric site
a location in an enzyme other than the active site that allows for
regulation of enzyme activity
non-competitive inhibitors prevent the substrate from binding to the active site via
a number of mechanisms including
1. conformational change in the active
site (allosteric inhibition)
2. crowding
enzyme activators
molecules or substances that increase the activity of
an enzyme
- Leads to an increase in the amount of
products
allosteric activators
bind to locations on an enzyme away from the active site →
conformational change → increased binding of substrate to active site
Many enzymes require helpers such as … for optimal conformation and function (activity)
coenzymes and cofactors
cofactors
inorganic ions
coenzymes
organic molecules comprised of carbon and hydrogen
Compartmentalization
regulates enzyme activity (certain biochemical reactions only occur within specific areas in the cell → more efficient biochemical reactions)
feedback inhibition
Mechanism by which the reaction’s end product inhibits or controls the enzyme’s function that helped make it
feedback inhibition prevents…
overproduction of product or depletion of a substrate
cellular respiration
A pathway for the production of ATP involving the transfer of
electrons from compounds with high potential energy through
an electron transport chain involving electron carriers and
ultimately to a final electron acceptor
Sites of cellular respiration in prokaryotes:
cytoplasm, inner cell membrane
Sites of cellular respiration in eukaryotes:
cytoplasm, mitochondria
aerobic respiration
cellular respiration pathway that requires oxygen
anaerobic respiration
cellular respiration pathway that does not require oxygen
Aerobic and anaerobic respiration both use glycolysis as the first major step to produce ATP
…
Under what conditions cellular respiration will proceed to all 4 steps
aerobic conditions
4 steps of cellular respiration
- glycolysis
- transition reaction
- Kreb’s cycle
- electron transport chain
what does glycolysis do
break down glucose with ATP
transition reaction
pyruvate converted to acetyl CoA releasing CO2
where does the krebs cycle happen
the matrix
what does the krebs cycle do
oxidize acetyl CoA to CO2. releases ATP and coenzymes (NADH, FADH2)
where does the electron transport chain happen
inner membrane
what does the electron transport chain do
uses high energy electrons from NADH and FADH2 to create a proton gradient that powers ATP synthesis
photoautotroph
converts energy in light to build carbohydrates
chemoautotroph
can use inorganic energy to produce carbohydrates and energy
photosynthesis
use of light to manufacture carbohydrates
photosynthesis chemical reaction
6CO2 + 6H2O -> C6H12O6 + 6O2
2 components of photosynthesis
- light capturing reactions
- calvin cycle (dark reaction)
light producing reactions
triggered by light, produces O2 from H2O; produces ATP and NADPH
Calvin cycle (dark reaction)
uses products from light capturing reactions (ATP and NADH); produces sugars from CO2
where does photosynthesis occur
chloroplast
the thylakoid membrane contains …
pigments (e.g. chlorophyll)
clorophyll
most abundant pigment in thylakoid membrane
granum
stack of thylakoids
stroma
fluid between thylakoid and inner membrane of chloroplast
how does chlorophyll absorb light energy
excited electrons of oxygen atoms
light
a type of electromagnetic radiation; behaves both as a particle (photon) and wave
how is electromagnetic radiation measured
in wavelength
violet has the shortest wavelength and the highest photon energy
chlorophylls absorb…
violet to blue to red. transmits green
carotenoids absorb…
blue and green. transmit yellow, orange, or red
blue photons excite electrons to a higher energy state
red photons excite electrons to a high energy state
the 4 things that can happen when ana electron gets excited:
- fluorescence
- heat
- resonance energy transfer
- redox
how do electrons fluoresce and/or give off heat
they drop back to low energy state
how do electrons resonance energy transfer
energy in electron is transferred to a nearby pigment to the reaction center
how do electrons undergo a redox reaction
electron is transferred to a new compound (electron acceptor) from the reaction center
photosystem
functional unit of photosynthesis; located within the thylakoids; site where light dependent reactions take place
components of a photosystem
antenna complex
reaction center
antenna complex
chlorophyll molecules the harvest light and are organized in an array of proteins
reaction center PSII (P680)
contains specialized chlorophyll pigments that can donate high energy electrons to an electron acceptor; located in the thylakoid membrane
plastoquinone
electron carrier in photosystem II, carries electrons to cytostome complex and H+ to the thylakoid lumen
cytochrome complex
bridge from photosystem II to photosystem I
photosystem II overall process
feeds excited electrons to an electron transport chain (cytochrome complex) which is used to produces ATP via an electrochemical gradient
events in PS II
energy in light is used to oxidize water to produce oxygen, hydrogen ions, and
pheophytin
transfers electrons to PQ
reaction center in PS I (P700)
overall process in PS I
energy from light is used to excite the electrons and move them to an electron transport chain to reduce NAD+ to NADPH
ferredoxin
electron acceptor in photosystem I
why is the linkage of photosystems important
- captures light more efficiently
- protects from excessive ROS production when there is too much light
- regulate the amount of electrons transported
- PSI serves as a backup if PSII is damaged by UV light
what light does PSII absorb better
blue
what light does PSI absorb better
red
3 phases of the calvin cycle
- fixation
- reduction
- regeneration
carbon fixation
process by which inorganic carbon is converted to organic compounds by living organisms
reduction phase in the calvin cycle
regeneration phase in Calvin cycle
One phosphate in ATP is transferred to G3P -> regenerates RuBP -> cycle repeats
how does CO2 enter plant cells
stoma
C3 plants
- use the calvin cycle
- temperate climates
- disadvantage in hot climates
- stoma open
C4 pathway
- tropical environments
- can fix CO2 when CO2 is low
CAM pathway
- close their stoma during the day and take upCO2 at night, when air temperature is lower
- prevents excessive water loss
