Chapter Eight Flashcards
What is metabolism?
it is the sum total of all chemical reactions occurring in a biological system at any given time, their reactions involve energy changes
What are the two types of metabolism?
Catabolism - involves catabolic reactions - complexity decreases (generates disorder = more entropy) i.e complex molecules give free energy and become small molecules
Anabolism - involves anabolic reactions - complexity increases (generates order) i.e free energy is combined with small molecules to make complex molecules
What is energy?
it is the ability to do work (the capacity for change)
What are the forms of energy?
- Chemical energy
- Heat energy
- Electrical energy
- Light energy
- Mechanical
What is chemical energy?
potential energy, stored in chemical bonds, usually covalent bonds - released during hydrolysis
What is electrical energy?
kinetic energy, or (potential energy when it involves an electrochemical gradient i.e separation of charges), one example is how electrical gradients help drive movement of ions.
What is heat energy?
kinetic energy, an energy transfer due to temperature difference, can be released by chemical reactions. usually unusable energy
What is light energy?
both kinetic and potential energy and is electromagnetic radiation stored as photons, example is light energy being captured by plant pigments in photosynthesis.
what is mechanical energy
kinetic energy that is the energy of motion, an example would be muscle movements
What are the two types of energy?
- Potential energy - stored energy (chemical bonds, concentration gradient, or an imbalance in charges)
- Kinetic energy - energy of movement
What are the laws of thermodynamics?
in biology, they are a set of laws that help us understand how cells harvest and transform energy to sustain life
they apply to all matter and all energy transformations in the universe
What is the first law of thermodynamics?
energy is neither created or destroyed - when energy is converted from one form to another the total energy (delta H) remains the same
What is the second law of thermodynamics?
when energy is converted from one form to another, some of that energy becomes unavailable to do work i.e no energy transformation is 100% efficient, some energy is lost to disorder (entropy)
What is entropy?
is the measure of disorder in a system, disorder is the amount of states a system can have unit is (S)
more entropy = more unusable energy
energy must be applied to a system to keep the entropy in check
What is enthalpy?
is the sum of all free energy plus the unusable energy in a biological system unit is (H)
H (enthalpy) = T (absolute temperature) x S (entropy) + G (free energy)
What is free energy?
it is the usable energy that can do work unit is (G)
How is a change in energy measured?
it is measured in calories or joules, delta symbol (triangle) means (a change in)
formula for change in free energy goes as follows:
∆ G = ∆H - T∆S
What does a -∆G mean?
when the change in energy is negative, energy is released
What does +∆G mean?
when the change in energy is positive, energy is required
What happens if free energy isn’t available?
reactions don’t occur
What are exergonic reactions?
they are reactions that release energy (-∆G)
example is catabolism - complexity decreases (breakdown) (generates disorder)
complex molecules are broken down into smaller molecules and -∆G
What are endergonic reactions?
they are reactions that consume (require) free energy (+∆G)
example is anabolism - complexity increases (generates order)
∆G + small molecules = complex molecules
Why is ATP important?
ATP transfers and captures free energy in biochemical reactions
Can be hydrolyzed to release lots of energy for endergonic reactions
What type of reaction is ATP formation?
it is an endergonic reaction which means it requires energy
it involves active transport, cell movement and anabolism and has a +kcal/mol (positive energy = energy is needed, it needs to be gained)
What type of reaction is ATP hydrolysis?
it is an exergonic reaction which means it releases energy
it involves cellular respiration and catabolism and has a
-kcal/mol of energy (negative energy= energy lost from the bond gained elsewhere)
What is meant by coupling reactions?
When the free energy RELEASED from one reaction (exergonic) and is used for/ coupled with another reaction that REQUIRES (endergonic) OR when one molecule is reduced SO THAT another can be oxidized.
What are the two characteristics of ATP that allow so much energy to be released?
- phosphate groups have negative charges and repel each other - the energy that is needed to get them close is in the P-O bond
- The free energy of the P-O bond is much higher in ATP than is the O-H bond that forms after hydrolysis on the ADP
What do enzymes do?
enzymes act as biological catalysts and provide the framework for reactions to take place
How do enzymes function?
enzymes lower the energy barrier E(a) AKA activation energy AKA the amount of ΔG needed to jumpstart the reaction
When activation energy is lowered, the reactions speed up
What are things enzymes do not do?
enzymes do not make a reaction happen that could not already happen
enzymes do not change the difference in Δ G between the reactants and the products i.e the final equilibrium
What is activation energy?
is the amount of energy required to start a reaction, can come from heating the system
What are transition state intermediates?
are unstable substates/reactants with higher free energy, any substate with a +ΔG
What are substrates?
are the reactants or molecules that the enzyme exerts its catalytic function i.e lowering the activation energy.
What is the active site?
it is the location on the enzyme in which the substrate/reactant binds, which are highly specific in nature
What are the three mechanisms of enzyme action?
- Chemical change - enzymes can temporarily add chemical groups to itself
- Orientation - enzymes can align/position the substrate so they can react
- Physical strain - enzymes can induce strain by stretching substrate, and by consequence make the bonds of the substrate more reactive
What are the two ways enzymes can be regulated?
- Regulation of gene expression - how many enzyme molecules are made (works slowly)
- Regulation by the enzyme itself - enzyme shape may change (adding phosphate group/enzyme inhibitor may close/open the active site)
What is an enzyme inhibitor?
part of the second way enzymes can be regulated
are molecules that bind to the enzyme and slow reaction rates, and can be naturally occurring or artificial
What is an irreversible inhibitor?
when an inhibitor covalently binds to side chains in active site and PERMANENTLY inactivates the enzyme.
What is a reversible inhibitor?
when an inhibitor bonds non non-covalently to the side chains on the active site and temporarily prevents substrate binding
What is a competitive inhibitor?
reversible inhibitor that directly COMPETES with natural substrate for the active site / binding site.
the degree of the inhibition depend on what type of substrate and what type of inhibitor
What is an uncompetitive inhibitor?
reversible inhibitor that binds to the enzyme substrate complex (when the enzyme has substrate bound to it) and prevents the substrates release, freezes the reaction of substrates
UN = eNzyme sUbstrate
What is a non-competitive inhibitor?
a reversible inhibitor that binds to the enzyme at site that isn’t the active (allosteric site)
this changes the shape of the shape of the enzyme and alters the active site (allostery)
What is allosteric regulation?
when an effector (non competitive inhibitor) binds an enzyme at the allosteric site (different from the active site), changing the shape
active form - can bind substrate = product
inactive form - can’t bind substrate = no product
What is feedback inhibition?
when the final product acts as a noncompetitive inhibitor of the first enzyme, which shuts down the pathway.
this makes sure we don’t make too much of something or waste energy/materials making something in excess
Does pH affect enzyme function?
short answer is yes, because in low pH there is high H+ concentrations and high pH H+ concentration is low, and this can affect functional groups / side chains and then affects the shape and the function of the enzyme
Does temperature affect enzyme function?
short answer is yes, because when temperatures are cold enzymes have less action
all enzymes have an optimal temperature where they function with the most efficiency
high temperatures disrupt the non covalent bonds and make the enzyme useless
What happens at high enzyme temperatures?
when there are high temperatures ionic and hydrogen bonds break and the enzyme becomes denatured (loses tertiary and secondary structure)
human enzymes are more stable at high temperatures than those of bacteria, so a moderate fever tends to denature bacterial enzymes but but our own
what is the transition state?
it is the reactive status of the substrate/reactant, after there has been a good enough input of energy to start the reaction.
What is the commitment step and how can it regulate enzymes?
first reaction, followed by other reactions in sequence
it regulates metabolic pathways by requiring a process to become fully committed and not venture off into other pathways
