Unit 3: Cellular Energetics Flashcards
Metabolism
totality of an organisms chemical reactions; arises from orderly interactions between molecules
catabolic pathways
release energy by breaking down complex molecules into simpler compounds
ex) cellular respiration breaks down glucose
anabolic pathways
consume energy to build complicated molecules from simpler ones
ex) synthesis of an amino acid from simpler molecules and then the synthesis of a protein from amino acids
Exergonic Reaction
proceeds with a net release of free energy
G is negative
spontaneous (does not require energy to begin), so energetically favorable
ex: cellular respiration
endergonic reaction
absorbs FREE energy from its surroundings
G is positive
stores energy, non-spontaneous
ex: photosynthesis
What is ATP made of?
nucleotides: a triphosphate group, adenine base, phosphate group, and ribose
holds energy in its chemical bonds between the phosphate groups
ATP is recyclable after it loses a phosphate (releasing energy), the cell recharges by adding another
Hydrolysis is the process in which the bond breaks by the addition of a water molecule.
catalyst
chemical agent that speeds up a reaction without being consumed by it
Activation Energy
the energy that reactants must absorb before a chemical reaction will start also called free energy of activation
enzymes lower the Ea barrier and enable the reactant molecules to absorb enough energy to reach the transition state even at moderate.
Induced fit
tightening of binding after initial contact.
brings chemical groups of the active site into positions to enhance their ability to catalyze the chemical reaction.
what affects the rate of enzyme action
- initial concentration of substrate: the more substrate available, the more frequently they can be pushed by adding more substrate to a fixed amount of enzyme. at some point, the concentration of substrates will be high enough that the enzyme molecules will be maxed out
- pH- change in pH levels can denature most enzymes
- temperature- up to a point, the rate of an enzymatic reaction increases with temperature partly because substrates collide with active sites more frequently when the molecules move rapidly. Above that temp, the speed of enzymatic reaction drops. Thermal agitation disrupts the hydrogen and ionic and other weak bonds.
Cofactors
any nonprotein molecule or ion that is required for the proper functioning an enzyme
can be permanently bound to the active site or may bind loosely and reversibly along with the substrate
ex: inorganic, metal atoms like zinc, copper and iron
coenzymes
an organic material serving as a cofactor. most vitamins function as coenzymes in metabolic reactions
ex: most vitamins are important in nutrition because they act as coenzymes or raw materials from which coenzymes are made
competitive inhibitors
Competitive inhibitors reduce the productivity of enzymes by blocking substrates from entering active sites. They can be overcome by increasing the concentration of a substrate so that as active sites become available, more substrate molecules than inhibitor molecules are around to gain entry to the sites.
noncompetitive inhibitors
Noncompetitive inhibitors do not directly compete with the substrate to bind to the enzyme at the active site. They impede enzymatic reactions by binding to another part of the enzyme. This interaction causes the enzyme molecule to change its shape in such a way that the active site becomes much less effective at catalyzing the conversion of a substrate to a product.
allosteric regulation
describes any situation in which a protein’s function at one site is affected by the binding of a regulatory molecule to a separate site. may result in either inhibition or enzyme stimulation
feedback inhibition
the end product of a metabolic pathway shuts down the pathway by binding to the allosteric site an enzyme
prevents wasting chemical resources and increases cell efficiency
fermentation
partial degradation of sugars or other organic fuel that occurs without the use of oxygen
cellular respiration
includes both aerobic and anaerobic processes,
redox reactions
LEOGER
loses electrons- oxidation
gains electrons- reduction
Stages of cellular respiration:
I. Glycolysis
:sugar-splitting
no oxygen required
occurs in cytosol
partially oxidizes glucose
Net gain: 2 ATP, 2NADH, makes H2O
Stages of Cellular Respiration:
II. Pyruvate Oxidation and the Citric Acid Cycle
Pyruvate- acetyl CoA; produces CO2 and NADH
Citric Acid Cycle- occurs in the mitochondrial matrix
acetly CoA –> citrate –> CO2 released
net gain: 2 ATP,6NADH, 2FADH2
Stages of Cellular Respiration:
III. Oxidative Phosphorylation (Electron Transport Chain)
occurs in the inner membrane of mitochondria
makes 26-28 ATPs via chemiosmosis
literal chain in the membrane and alternate between reduced/oxidized states of being as they lose and accept electrons
ECT+chemiosmosis=oxidative phosphorylation
oxygen is the terminal electron acceptor
chemiosmosis
Hydrogen atoms are pumped across the inner mitochondrial membrane, diffuse through ATP synthase and become ATP
photosynthesis
converts light energy to chemical energy and food
occurs in the chloroplast of plant cells
photosystem
composed of a protein complex called a reaction-center complex surrounded by several light-harvesting complexes
photosystem term:
I. reaction center complex
organized association of proteins holding a special pair of chlorophyll a molecule and a primary electron acceptor
photosystem term:
II. light-harvesting complex
various pigment molecules bound to proteins
photosystem term:
III. primary electron acceptor
a molecule capable of accepting protons and becoming reduced
Linear electron flow
a. What is the source of energy that requires the electron in photosystem II? P700
b. What compound is the source of electrons for linear electron flow? H2O; This compound is also the source of O2 in the atmosphere.
c. As electrons fall between photosystem I and II, the cytochrome complex uses the energy to pump H+ ions. This builds a proton gradient that is used in chemiosmosis to produce what? ATP
d. In photosystem II, the excited electron is eventually used by NADP+ reductase to join NADP+ and H+ to form NADPH
uses chemiosmosis to generate ATP
cyclic electron flow
Cyclic electron flow is thought to be similar to the first forms of photosynthesis to evolve. In cyclic electron flow, no water is split, there is no production of NADPH and there is no release of O2.
Uses PSI only: produces ATP for calvin cycle and no O2 or NADPH produced
uses chemiosmosis to generate ATP
Calvin Cycle
Uses ATP and NADPH to convert CO2 to sugar
occurs in stroma
uses ATP, NADPH, CO2
produces 3-C sugar
Calvin Cycle Phases:
I. Carbon Fixation
3CO2 + RuBP (5-C sugar ribulose biphosphate)
catalyzed by enzyme rubisco
The Calvin cycle incorporates each CO2 molecule by attaching it to a 5-carbon sugar named ribulose bisphosphate. The enzyme that catalyzes this step is rubisco. The product of the reaction is a six-carbon intermediate so unstable that it immediately splits in half, forming two molecules of 3-phosphoglycerate.
Calvin Cycle Phases
II. Reduction
uses 6 ATP and 6 NADPH to produce 1 net G3P
Calvin Cycle Phases
III. Regeneration of RuBP
uses 3 ATP to regenerate RuBP
As a review, note that the light reactions store chemical energy in ATP and NADPH which…
As a review, note that the light reactions store chemical energy in ATP and NADPH which shuttle the energy to the carbohydrate-producing Calvin cycle.
