Studied by 1 personbioenergetics
the study of how energy from the sun is transformed into energy in living things
first law of thermodynamics
energy can’t be created or destroyed // sum of energy in the universe is constant
exergonic reaction
products have less energy than reactants; energy is given off
endergonic reactions
require an input of energy; products have more energy than the reactants
transition state
a high energy molecule that reactants must turn into before becoming products; difficult to achieve
activation energy
certain amount of energy required to reach the transition state
how does activation energy work
chemical bonds must be broken before new ones can form
enzymes
biological catalysts that speed up reactions
enzyme specificity
each enzyme catalyzes only one kind of reaction
substrates
targeted molecules
enzyme-substrate complex
enzymes make the transition state happen by helping substrates get into position
active site
special region on the enzyme where substrates go
how do the structures and active sites relate?
structure (shape and charge) must be compatible with active site of an enzymea
what happens to an enzyme after a reaction
it’s released and goes back to its original state
induced fit
enzyme has to slightly change its shape to fit the substrate
cofactors
factors that sometimes help enzymes catalyze reactions
conenzyme
a type of cofactor; organic molecule, inorganic molecule, ion
what can affect an enzymatic reaction
temperature and pH
what determines reaction speed
concentration of an enzyme and substrate
at what temperature are enzymes denatured?
42 degrees celsius
denatured
what happens when an enzyme is denatured by heat and isn’t able to catalyze reactions anymore
what is the optimum temperature for most human enzymes to function
37 degrees celsius
how does pH alter enzymes
hydrogen bonds are disrupted and structure is altered
what is the optimum pH for most enzymes
7
when there is a high concentration of substrates, what happens to a reaction?
initially speeds up, once all of the enzymes are bound to a substrate, reaction can’t speed up any longer
saturation point
the point where all enzyme are bound to substrates
how does a cell regulate enzyme activity
regulating conditions that influence enzyme shape
allosteric sites
somewhere on the enzyme that substrates can bind to that isn’t the active site
competitive inhibition
a substance binds to the active site in place of the substrate
noncompetitive inhibitor
when an allosteric inhibitor binds to allosteric site
what happens to ATP when a cell needs energy?
the third phosphate is broken off: ATP → ADP + P + energy
how can endergonic reactions be powered
by organisms using exergonic processes that increase energy
cellular respiration
breaking down sugar and making ATP
photosynthesis
how autotrophs get sugar for ATP
what was the earliest photosynthesis done by
prokaryotic cyanobacteria
what is the formula for photosynthesis?
6CO2 + 6H2O → C6H12O6 + 6O2
what happens when light initially strikes a leaf
chlorophyll is activated, electrons are excited
what happens after chlorophyll is activated
sends electrons down electron carriers, which makes ATP and NADPH
What happens to ATP, NADPH, and CO2 during dark reactions
used to make carbs, H2O is split and O2 is released
stroma
fluid filled region
grana
structures in the chloroplasts that look like coin stacks
thylakoids
individual discs within granum; have chlorophyll
chlorophyll
light-absorbing pigment that drives photosynthesis
thylakoid lumen
interior thylakoid
what are the types of reaction centers
photosystem I and photosystem II
photophosphorylation
when light is used to make ATP
absorption spectrum
shows how well a certain pigment can absorb electromagnetic radiation
what happens right after a leaf captures sunlight
energy is sent to P680 and forms active electrons
what is P680
reaction center of PS II
what is P700
reaction center of PS I
photolysis
H2O is split into O2, H2, ions, electrons
where do the electrons from photolysis go
replace missing ones in PS II and replenish those from the thylakoid
what establishes a proton gradient in the ETC
H+ ions being pumped into thylakoid lumen as energized e- from PS II
How is ATP produced during PS II
H+ ions move back into the stroma through ATP synthase
where do e- go after leaving PS II
PS I; they’re passed through a second ETC
when do e- stop on the second ETC
when they reach NADP+ to make NADPH
cyclic electron flow
makes only ATP, no NADPH
what mainly happens during the light independent reactions
use products of light reactions (NADPH and ATP) to make sugar
carbon fixation
CO2 from air is converted into carbs
where does carbon fixation occur?
stroma
what is another term for dark reactions/light independent reactions?
Calvins cycle
stomata
pores on the leaf that allow CO2 to enter the leaf, and O2 and H2O to exit
what do plants do on hot and dry days to their stomata
close them to prevent water loss → limits CO2 access / reduces photosynthetic yield
photorespiration
uses ATP and O2, produces more CO2, doesn’t make sugars
what is the formula for cellular respiration
C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP
aerobic respiration
when ATP is made in the presence of O2
anaerobic respiration
when ATP is made without O2
what are the four stages of aerobic respiration
glycolysis, formation of acetyl-coA, krebs/citric acid cycle (CAC), oxidative phosphorylation
pyruvic acid
3 C molecules that form when glucose (6C) splits, one glucose breaking down results in 2 pyruvic acid and 2 ATP
how is ATp made in glycolysis
combining ADP and an inorganic phosphate (using an enzyme)
how many NADH does glycolysis make?
2; comes from e- transfer to carrier NAD+ (turns to NADH)
where does glycolysis occur
cytoplasm
where does the formation of acetyl co-A occur?
mitochondrion
what types of C molecules are present in the beginning of the formation of acetyl-coA
two 2-C molecules, extras left as CO2
acetyl coA
2C molecule
how many NADH are made for every initial glucose
2
where does the kreb’s cycle occur
matrix of the mitochondria
what happens to both acetyl-coA molecules as soon as they enter the Kreb’s cycle
turned into CO2
electron transport chain
e- take energy from glucose and carry it with themthe
at the start of oxidative phosphorylation, how many NADH, FADH2 have been produced?
10 NADH, 2 FADH2
what do NADH and FADH do
shuttle e- to ETC → forms NAD+, FADH, can be reused
electron transport chain
a series of protein carrier molecules embedded in cristae
what is the final acceptor in the ETC
O2
what happens when the e- get to the final acceptor
O2 + e- + H+ → H2O
what would happen if there weren’t O2 in the ETC
e- wouldn’t move down it, shuts down electron transport
chemiosmosis
H+ ions from original H atom are pumped across inner mitochondrial membrane from the matrix into inner membrane space; pumping/diffusion of ions
when does chemiosmosis happen
at the same time as electron transport, uses energy released from ETC
pH/proton gradient
caused by the pumping of H+ ions; difference of the concentration of H+ across a membrane
what is the only way H+ ions diffuse across a membrane
ATP synthase
oxidative phosphorylation
when e- are given up, it’s ‘oxidation’ and ADP is phosphorylated to make ADP
what must be maintained about an enzyme
the tertiary shape
negative control
not exposed to experimental treatment or any treatment known to have effect
positive control
exposed to treatment that is known to have an affect / no exposed to experimental treatment
controlled variable
aspects of an experiment that could be changed but aren’t intentionally
what does a decrease in temperature do to reaction rate
slows it down; fewer enzyme-substrate collisions
what is the only way reaction rate will stay constant
saturation levels are maintained
how do cells manage energy resources
energy coupling; energy releasing processes drive energy storing processes
what does it mean for pathways in biological systems to be sequential
product of one reaction can be a reactant in the next; allows for more controlled and efficient energy transfer
where is chemical energy temporarily stored during light dependent reactions
NADPH
what transfers stored chemical energy to power production of organic molecules in light dependent reactions
ATP and NADPH
Note
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