Unit 3 Test Review Flashcards
what is a substrate?
substance(s) / reactant(s) and enzyme works on
what is an active site?
the location where the substrate binds to an enzyme
what is an enzyme-substrate complex?
a combination of enzyme and substrate. they are connected by weak bonds (usually ionic or hydrogen bonds) that trigger shape changes in the enzyme and as the enzyme changes shape, more weak bonds form to allow the two to fit even more closely together
what is induced fit?
the tightening of binding after original contact
different enzymes link to different molecules based on their ____ and ____
aa composition and tertiary structure
for an enzyme-mediated chemical reaction to occur, the ____ and ____ must be compatible with the active site of the enzyme
the shape and charge
the structure and function of enzymes contribute to the ____
regulation of biological processes
enzymes are biological catalysts that facilitate ____ in cells by lowering the ____
chemical reactions and activation energy
what is a catalyst?
a chemical agent that speeds up a reaction without being used up by the reaction
most cellular catalysts are ____ but some RNA molecules called ____ can also act as cellular catalysts
proteins and ribozymes
all chemical reactions involve ____
the breaking and reforming of bonds
converting molecules from one format to another usually involves ____
altering the starting molecule to an unstable form before the reaction
reactants require ____ to get to an unstable state
energy
____ is released when new bonds of product form
heat energy
what is activation energy?
an energy investment to start a reaction
once enough activation energy has been absorbed, molecules reach the ____ when the reaction will occur
transition state
what is catalysis?
when enzymes lower the activation energy for a specific reaction
- describe how enzymes catalyze reactions
as the substrate is held in place, r-groups of the aa in the active site aid in the conversion of the substrate from reactant to product. the product enters and is converted and released quickly (typically 1,000 substrate molecules converted per second by a single enzyme).
describe the ways enzymes lower activation energy
moving two substrates into prime orientation for bonding, pulling/distorting a single molecule to aid in breaking apart, or providing a microclimate (ex: lower pH to aid the transfer of h+ ions to the substrate without lowering the overall cell pH)
increasing the concentration of a substrate can increase the ____
rate of a reaction
more substrate ____ odds of collision of substrate and enzyme
increases
once substrate concentration is large enough that all enzymes active sites are engaged with substrate, the enzyme is said to be ____
saturated
change to the molecular structure of a component in an enzymatic system may result in ____
a change in the function or efficiency of the system
denaturation of an enzyme occurs when ____
the protein structure is disrupted, eliminating the ability to catalyze rections
environmental temperatures and pH outside the optimal range for a given enzyme will ____, altering the efficiency with which it catalyzes reactions
cause changes to its structure
temperature and pH can change ____
an enzyme’s shape
temperature can ____ speed of molecules, ____ collisions and providing activation energy
increase and increasing
pH can change enzyme conformation by ____
interacting with Ionic bonds
depending on their ____, different enzymes work best in differing conditions
aa makeup
some enzymes require ____ molecules to bind them to function properly (some bond permanently, others loosley and temporarily)
non-protien
what is a coenzyme?
an organic cofactor
what is competitive inhibition?
when a substance competes with a substrate for position in an active site
what is non-competitive inhibition?
when a substance bonds to a site on the enzyme other then the active site but causes shape change that lowers active site functionality or stops it
what is an allosteric site?
any bonding sit on an enzyme that is not at the active site
what is metabolism?
all the chemical reactions in an organism
what is anabolic?
reactions that take in energy to build more complex molecules from simpler ones
what is catabolic?
reactions that degenerate or break down molecules and release energy
what is kinetic energy?
energy of motion
what is thermal energy?
energy associated with the random movement of atoms or molecules
what is potential energy?
energy of position or structure
what is chemical energy?
potential energy available for release in a chemical reaction
what is thermodynamics?
the study of energy transfer in a collection of matter
what is the first law of thermodynamics?
matter and energy cannot be created nor destroyed
what is the second law of thermodynamics?
every energy transfer increases the state of entropy or disorder of a system
what is chemical work?
providing activation energy to drive chemical reactions
what is transport work?
providing energy for active transport
what is atp composed of?
ribose sugar, the nitrogenous base adenine, and three negatively charged phosphates
hydrolysis of a phosphate group releases ____
energy
uncoupled hydrolysis of atp releases ____
heat
phosphorylation can make a substance ____
more reactive
hydrolysis of atp is ____ and results in the products ____ and ____
exergonic, adp, and pi
atp synthesis is ____ and requires energy to fuse ____ back onto ____
endergonic, pi, and adp
photosynthesis capture ____ from the sun and produces ____
energy and sugars
photosynthesis first evolved in ____ organisms
prokaryotic
scientific evidence supports the claim that ____ was responsible for the production of an ____
prokaryotic photosynthesis and oxygenated atmosphere
when chlorophyll absorbs ____, those wavelengths are no longer ____ or ____
light, transmitted, and reflected
as photons are absorbed, an ____ in the pigment is boosted from ____ to an ____
electron, ground started, and excited state
high energy state of an electron is ____
unstable
what is a photosystem?
a reaction center complex surrounded by many light-harvesting complexes
what is a reaction center complex?
a special pair of chlorophyll a molecules paired with proteins and a primary energy electron acceptor that revives any excited electrons
what is a light harvesting complex?
several pigments that transfer energy to the reaction center complex
what is photosystem l?
discovered first but actually acts second in linear electron flow and reaction center (most effectively absorbs light at wavelength of 700nm)
what is photosystem ll?
discovered second but actually acts first in linear electron flow and reaction center (most effectively absorbs light at a wavelength of 680nm)
what is the difference in photosystem l and photosystem ll due to?
differing associated proteins in the reaction center
describe linear flow
light energy exciting photosystem ll causes an electron to become excited in the antenna until it passes the energy to excite an electron in the reaction center. the electron leaves the pair of chlorophyll a molecules in the reaction center and passes to a primary electron acceptor. an enzyme splits a water molecule releasing oxygen gas, protons (h+), and electrons to replace those lost at the reaction center. each photoexcited electron is passed from the primary electron acceptor though an electron transport chain that use the energy of the excited electrons pump protons into the thylakoid space. the potential energy of the proton gradient is used to make atp in a process called chemiosmosis. low energy electrons entering photosystem l are excited again by photons of light hitting the antenna complex of photosystem l. photo excited electrons leaving photosystem l are passed to a primary electron acceptor. an enzyme passes the excited electrons and a proton to nadp+ forming the energized molecule nadph
describe chemiosmosis in thylakoids
the protons from both the splitting water and actions of the electron transport chain fill the thylakoid and dropping the pH to around 5. protons (h+) want to exit the thylakoids to diffuse down their chemical gradient and due to charge difference. the enzyme atp synthase allows protons to exit the thylakoid space and uses the energy of their movement to fuse the adp and pi to form atp
the calvin cycle uses ____ and ____ energy to convert ____ to sugar
atp, nadph, and co2
where does the calvin cycle occur?
in the stroma of a chloroplast
fermentation and cellular respiration use energy from ____ to produce ____
biological macromolecules and atp
organic macromolecules contain ____ due to the arrangement of ____ in their bonds
potential energy and electrons
what is a catabolic reaction?
reactions that break bonds
