Chapter 6, 7, and 8 Flashcards
Phototrophs
Capture Energy from sunlight
Chemotrophs
Get energy directly from chemical compounds
Autotrophs
- Able to convert CO2 into glucose
- Make own organic carbon using inorganic carbon
Heterotrophs
Rely on other organisms for their organic forms of carbon
Metabolism
Entire set of chemical reactions that convert molecules into other molecules and transfer energy in living organisms
Catabolism
Set of chemical reactions that break down molecules into smaller units, and in the process produce ATP
Anabolism
Set of chemical reactions that builds molecules from smaller units and requires an input of energy (usually ATP)
Chemical Energy
Form of Potential Energy held in the chemical bonds between pairs of atoms
Entropy
Degree of Disorder
Second Law of Thermodynamics
Transfer of energy is associated with an increase in entropy
Gibbs Free Energy (G)
Amount of energy available to do work
Exergonic Reactions
Release energy and are spontaneous
-G
Endergonic Reactions
Require input of energy and are not spontaneous
+G
Enthalpy
(H) total amount of energy
Equation
H= G + TS
What type of reaction is ATP hydrolysis?
Exergonic (releases energy)
Energetic Coupling
Spontaneous reaction (exergonic) drives a non-spontaneous (endergonic) reaction Net G is negative
Transition State
State between reactants and products
Activation energy
Amount of energy needed to reach transition state
Active Site
Part of the enzyme that binds substrate (reactant) and catalyzes it
Inhibitors
Decrease enzyme activity
Activators
Increase enzyme activity
Allosteric enzymes
- enzymes that are regulated by molecules that bind at sites other than the active site
- found at/near start of a metabolic pathway or at crossroads of multiple pathways
Negative Feedback
Final product inhibits the first step of the reaction
Cofactor
Substance that associates with an enzyme and plays a key role in its function
Enzymes
- Reduce activation energy
- small active site, but very specific arrangement of amino acids
- highly specific
Catalysis
Substrate and product form a complex with the enzyme. Transient covalent bonds and/or weak noncovalent interactions stabilize the complex
Do strong bonds have high chemical energy?
No because it does not require a lot of energy to remain intact
Is energy needed to break covalent bonds ?
Yes, because going from a lower energy state to a higher energy state requires an input of energy. Covalent bonds have low potential energy because they are strong.
Structure of ATP
- Chemical energy in ATP is held in the bonds connecting the phosphate groups because they are negatively charged and tend to repel each other (this means that they have high potential energy)
- When new, more stable bonds form with the phosphate, energy is released
Is cellular respiration anabolic or catabolic?
Catabolic because molecules are broken down
Cellular respiration equation
glucose + oxygen -> carbon dioxide + water + energy
How much ATP is produced from 1 molecule of glucose?
32 on average
How is ATP generated?
- Substrate-level phosphorylation
The hydrolysis of of phosphorylated organic molecule and the addition of a phosphate group to ADP. - Oxidative Phosphorylation (during respiration)
Electron carriers transport electrons released to the electron transport chain, which transfers electrons along a series of proteins to a final electron acceptor (02), Energy is harnessed to produce ATP
Oxidized form of electron carriers
NAD+ and FAD
Reduced form of electron carriers
NADH and FADH2
Electron carrier reduction equations
NAD+ + 2e- + H+ -> NADH
FAD + 2e- + H+ -> FADH2
Electron carrier oxidation equations
NADH-> NAD+ + 2e- + H+
FADH2 -> FAD + 2e- + H+
Glycolysis
-glucose (6 Carbon molecule) split into 2 pyruvate (3 Carbon molecule)
-anaerobic
-10 chemical reactions
-3 phases:
1. Preparatory phase, uses 2 ATP (adds 2 phosphate groups to glucose). Endergonic
2. Cleavage, 6-carbon split into 2 3-carbon
3. Payoff, ATP, NADH, and 2 pyruvate
Products: 2 pyruvate, 4 ATP (2 net), 2 NADH
Pyruvate Oxidation
-Links glycolysis to the citric acid cycle
-occurs in the mitochondrial matrix
-pyruvate turns into acetyl-CoA
Products: 2 CO2, 2 NADH, 2 acetyl-CoA
Citric Acid Cycle
- acetyl group of acetyl-CoA is oxidized to carbon dioxide and the chemical energy is transferred to ATP by substrate-level phosphorylation and to the reduced electron carriers
- takes place in the mitochondrial matrix
- oxaloacetate is regenerated
- produces: 2 ATP, 6 NADH, and 2 FADH2 per molecule of glucose
Why do some organisms run the citric acid cycle backwards?
- Allows an organism to build organic molecules
- some bacteria do this
Electron Transport Chain and Oxidative Phosphorylation
Electrons pass through a chain of protein complexes in the inner mitochondrial membrane to oxygen, the final electron acceptor. The passage of electrons is coupled to the pumping of protons, into the intermembrane space. When electrons are passed it is a redox couple reaction. This creates a concentration and charge gradient which provides potential energy to synthesize ATP.
Complex I
Accepts electrons from NADH
Complex II
Accepts electrons from FADH2
Oxygen in the Electron Transport Chain
When O2 accepts electrons, it is reduced to form water
O2 + 4e- + 4p+ -> 2H2O
catalyzed by complex IV
Coenzyme Q (CoQ) (ubiquione)
accepts electrons from I and II
2e- and 2 p+ transferred to CoQ and create CoQH2
CoQH2
diffuses in membrane to III
@ III, e- from CoQH2 is transferred to cytochrome c and p+ is released into the inner membrane space
cytochrome c is reduced and goes to complex IV
ATP Synthase
couples the movement of protons with the synthesis of ATP
2 subunits: F0 and F1
F0 forms the channel for proton flow
F1 catalyzes the synthesis of ATP
Proton flow causes F0 to rotate, which causes F1 to rotate, which causes conformational changes that catalyze the synthesis of ATP from ADP and Pi.
mechanical rotational energy is converted into the chemical energy of ATP
Fermentation
Breakdown of pyruvate in the absence of oxygen
Lactic Acid Fermentation
Occurs in animals and bacteria
electrons from NADH transferred to pyruvate to produce lactic acid and NAD+
glucose + 2 ADP + 2Pi -> 2 lactic acid + 2 ATP + 2H2O
Ethanol Fermentation
in plants and fungi
pyruvate releases carbon dioxide to form acetaldehyde, and e- from NADH transferred to acetaldehyde to produce ethanol and NAD+
glucose + 2ADP + 2Pi -> 2 ethanol + 2 CO2 + 2 ATP + 2H2O
Excess glucose
starch- plants
glycogen- animals
Fatty Acids
contain triacylglycerols which are an important form of energy storage in cells
breakdown of fatty acids is called beta oxidation
Phosphofructokinase-1 (PFK-1)
has many allosteric activators, including ADP and AMP, and allosteric inhibitors, including ATP and citrate
when ATP levels are low, PFK-1 is activated, allowing glycolysis to continue
when ATP or citrate levels are high, PFK-1 is inhibited and glycolysis slows down
