Exam 3 Flashcards
Metabolism
sum total of all chemical reactions occurring in a biological system at a given time
2 types of metabolism
Anabolic reactions - complex molecules made from simple molecules, Energy required
Catabolic reactions - complex molecules broken down to simpler ones, Energy released
Energy
capacity to do work, or the capacity for change
Examples of different forms of energy
Chemical - stored in bonds
Electrical - separation of charges
Heat - transfer due to temperature difference
Light - electromagnetic radiation stored as protons
Mechanical - energy of motion
Law of thermodynamics
apply to all matter and all energy
transformations in the universe, helps us understand how cells harvest and transform energy to sustain life
1st law of thermodynamics
Energy is neither created nor destroyed
2nd law of thermodynamics
When energy is converted from one form to another, some of that energy becomes unavailable to do work
Potential vs. Kinetic energy
Potential - stored energy (stored as chemical bonds, concentration gradient, or charge imbalance)
Kinetic - energy from movement
Entropy
(S) measure of disorder in a system it takes energy to impose order on a system, unless energy is applied to the system, it will be randomly arranged or disordered
Enthalpy
(H) total energy
Free energy
(G) usable energy that can do work
How is change in energy measured
Change in energy measured in calories or joules, ΔG = ΔH – TΔS
(-) ΔG
free energy is released
(+) ΔG
free energy is required
If free energy not available
reaction doesn’t occur
Endergonic vs. Exergonic reactions
Exergonic reactions: release free energy (‐ΔG), catabolic
Endergonic reactions: consume free energy (+ΔG), anabolic
Why is ATP important?
energy transfer in biochemical reactions, important because it acts as the primary energy carrier within living cells, providing readily available energy to power all essential biological processes
Is ATP formation exergonic or endergonic
captures and transfers free energy, so an endergonic reaction
What about ATP hydrolysis
ATP can by hydrolyzed to ADP and Pi, releasing a lot of energy for endergonic reactions
ATP hydrolysis reaction equation
ATP + H2O ADP + P i + free energy
What two characteristics of ATP allow for release of free energy when it’s hydrolyzed
Phosphate groups have negative charges and repel each other, and Free energy of the P~O bond is much higher than energy of the O‐H bond that forms after hydrolysis
What is meant by “coupling” reactions
an energetically favorable reaction (like ATP hydrolysis) is directly linked with an energetically unfavorable (endergonic) reaction
Enzymes
biological catalysts that act as a framework in which reactions can take place
– Most are proteins
What do enzymes do/don’t do
they do speed up chemical reactions in the body, making them essential for many processes, including digestion, blood clotting, and growth, they don’t change the overall equilibrium of a chemical reaction, whether the reaction is endergonic or exergonic
Activation energy
amount of energy required to start a
reaction, can come from heating the system
Transition state
reactive mode of the substrate (aka – reactant) after there has been sufficient input of energy to initiate the reaction
Transition state intermediate
unstable reactants with higher free energy
Substrates
reactants: molecule(s) on which an enzyme exerts its catalytic action
Active site
place on an enzyme where substrate binds
3 mechanisms of enzyme action
- Enzymes can orient substrates so they can react
- Enzymes can induce strain by stretching substrate, which makes bonds unstable and more reactive to other substrates
- Enzymes can temporarily add chemical groups
2 ways to regulate enzymes
- Regulation of gene expression – how many enzyme molecules are made
- Regulation of enzyme itself – enzyme shape may change, or enzyme can be blocked by regulators
Reversible vs. irreversible inhibition
Reversible inhibition: inhibitor bonds noncovalently to the active site, preventing substrate binding
Irreversible inhibition: inhibitor covalently bonds to side chains in active site and permanently inactivates the enzyme
Competitive inhibitors
compete with natural substrate for binding sites
Uncompetitive vs. noncompetitive inhibitors
Uncompetitive inhibitors: bind to enzyme‐substrate complex, preventing release of products
Noncompetitive inhibitors: bind to enzyme at site other than the active site
Allosteric regulation
an effector binds an enzyme at a site different from the active site, changing the enzyme’s shape
Commitment step and feedback inhibition
Commitment step: first reaction, followed by other reactions in sequence
Feedback inhibition: final product acts as
noncompetitive inhibitor of the first enzyme, shutting down the pathway
Do pH and temperature affect enzymes and what happens at high temperatures
Yes, it does, higher temperatures cause denaturation in enzymes since most are proteins, causing noncovalent bonds to break and the 2nd and 3rd structures are destroyed
5 principles of metabolic pathways
- Complex transformations occur in a series of separate reactions
- Each reaction is catalyzed by a specific enzyme
- Many metabolic pathways are similar in all organisms
- In eukaryotes, metabolic pathways are compartmentalized in specific organelles
- Key enzymes can be inhibited or activated to alter the rate of the pathway
Burning/metabolism of glucose equation
C6 H12 O6 + 6 O2 6 CO2 + 6 H2 O + free energy, very exergonic, G= ‐686 kcal/mol, drives endergonic formation of ATP molecules
3 catabolic processes that harvest energy from glucose
- Glycolysis (anaerobic)
- Cellular respiration (aerobic)
- Fermentation (anaerobic
Redox reactions
one substance transfers electrons to
another substance, oxidation and reduction always occur together, OIL RIG, when a molecule loses hydrogen atoms (H), it is considered to be oxidized
Electron carrier molecules
NADH - Nicotinamide Adenine Dinucleotide + H+
FADH2 - Flavin Adenine Dinucleotide + H+
NADPH - Nicotinamide Adenine Dinucleotide Phosphate + H+
5 energy yielding metabolic pathways
Glycolysis (Either one)
Fermentation (Anaerobic)
Citric Acid Cycle (Aerobic)
Pyruvate Oxidation (Aerobic)
Respiratory chain (Aerobic)
