Chapter 8 Flashcards
Catabolism
- releasing energy by breaking down complex molecules into simpler ones
- energy is stored or released as heat; needed for anabolic processes
Anabolism
- consuming energy to build complex molecules from simpler ones
Bioenergetics
- the study of how organisms manage their energy resources
Cellular metabolism
- the processes of sustaining a cell
- each step is catalyzed by a SPECIFIC ENZYME, ends with a product
- two types: anabolism and catabolism
- almost all metabolic reactions take place non-spontaneously (why they need enzymes)
What type of molecule is an enzyme?
What dictates the structure of this type of molecule?
- catalytic protein
- sequence of amino acids in polypeptide chain, during primary structure ; including active site shape
Energy
- the capacity to change
- exists in various forms, some can perform work
- 2 types: Kinetic Energy and Potential Energy
- can be converted from one form to another (i.e. cellular respiration)
Kinetic energy
- associated with motion
- includes thermal energy (heat) which involves random movement of molecules
Potential energy
- energy in matter because of its location/structure (height usually)
- includes chemical energy as energy available to be released during reactions
- cells convert chemical energy for heat
Thermodynamics (and its 3 laws)
- the study of energy transformations
1) the energy of the universe is constant (principle of conservation of energy) - it can be transformed or transferred but not created or destroyed
2) unusable energy, usually lost in heat, is a product of energy transformations or transfers - every transformation/transfer increases universal entropy
3) irrelevant ig
Entropy (S)
- entropy = disorder
- may decrease in an organism, but universe’s total entropy increases
- decreased entropy makes an organism “lower” and unstable (more reactive)
Closed system
- a system that is isolated from its surroundings
- self sufficient
- like an aquarium (even if its not technically fully self sufficient)
- reactions eventually reach equilibrium and do no work (death…?) ; not in equilibrium = constant flow of materials (good! alive!)
Open system
- a system open to its surroundings
- energy and matter can be transferred between system and surroundings
- example: organisms
Spontaneous
- a reaction that occurs without energy
- happens quickly or slowly
- increases the entropy (disorder)
- have a negative delta G
- harnessed to perform work only when it is moving toward equilibrium
Nonspontaneous
- a reactions that must have an energy input
- increases enthalpy (order)
- positive delta G
Cells make ordered structures from —- ——- materials. Organisms replace ordered forms of —— and —— with less ——- forms.
1) less ordered
2) matter, energy, ordered
Enthalpy (H)
- order
- sum of the system’s internal energy and the product of its pressure and volume
- decreased enthalpy makes an organism “higher” more stable (which means less reactive)
(Gibbs) Free energy
- energy that can do work when temperature and pressure are uniform (like in a cell)
- how energy changes are studied to see if a reaction is spontaneous or not
- relates to change in enthalpy (aka total change in energy, delta H) and change in entropy
- ∆G = ∆H - T∆S
- measure of a system’s instability
Stability and instability
1) equilibrium is a state of MAXIMUM stability, less reactive
2) the tendency to change to a more stable state, more reactive
Exergonic
- exothermic
- releases energy, so reactants have more energy than products
- net release of free energy
- is spontaneous
- delta G is negative (i.e.: -7.3 kcal/mol)
Endergonic
- endothermic
- intakes free energy from surroundings, so reactants have less energy than products
- nonspontaneous
- delta G is positive (i.e.: 3.4 kcal/mol)
- after atp drives an endergonic reaction, adp is left
3 kinds of cellular work
- mechanical, transport, and chemical
- powered by hydrolysis of atp (breaking apart phosphate group)
ATP
- adenosine triphosphate
- powers work by using exergonic processes to drive endergonic ones ; overall EXERGONIC (delta G = negative)
- the cell’s energy shuttle
- provides energy for cellular functions
- nucleic acid
- renewable resource ; regenerated by addition of a phosphate group to ADP
One example of how atp uses an exergonic process to drive an endergonic one
- bonds between ATP tail phosphate groups can be broken by hydrolysis which RELEASES ENERGY
- energy comes from chemical change to a state of lower free energy, not the phosphate group
Phosphorylation
- transferring a phosphate group to some other molecule, such as a reactant
- how atp drives endergonic reactions
- if phosphorylating adp, the energy comes from catabolic reactions
Enzymes
- speeds up metabolic reactions by lowering energy barriers
- can be denatured and permanently unusable because of temperature, pH, inhibitors, specific chemicals, etc.
- example of enzyme-catalyzed reaction: hydrolysis of sucrose by sucrase enzyme
- do not affect the change in free-energy
- reusable
- each enzyme has an optimal pH and temperature it can function at
Activation energy
- initial energy needed to start a chemical reaction
- the energy used bond breaking and bond forming (every chemical reaction)
- often supplied as heat from surroundings
- enzymes catalyze by lowering this activation energy barrier
Substrates
- reactant that an enzyme acts on
- when it binds to an enzyme on its active site, its an enzyme-substrate complete
- usually only 1 or 2 substrates can fit into their enzyme’s active site
- converted into products in enzyme
induced fit of the substrate
- enhances chemical groups’ ability to catalyze the reaction by putting them in certain positions
Cofactors
- nonprotein enzyme helpers
- examples: ions - Ca+2, Mg+2, etc.
- coenzymes are organic cofactors (i.e. vitamins)
- can determine how quickly reactions proceed from their reactant to their product
Inhibitors
- two types: competitive and noncompetitive
- competitive: binds to the active site of an enzyme thus competes with substrate for it
- noncompetitive: binds to another part of an enzyme which makes it change shape which decreases the active site’s efficiency
Why is enzyme regulation important?
- chemical chaos would result if metabolic pathways are not tightly regulated
- although enzymes can help make materials, making TOO much can hurt the cell just as much as having too little
- reduces material waste
Enzyme regulation
- the cell switches on or off the genes that encode the synthesis of specific enzymes to regulate them
Allosteric regulation
- cases where an enzyme’s function at one site is affected by a regulatory molecule binding at another site (of the same enzyme, again just at different places or sites)
- may either inhibit or stimulate an enzyme’s activity
- essential for enzymatic regulating
- allosterically regulated enzymes are made from polypeptide subunits
Allosteric regulation
- cases where an enzyme’s function at one site is affected by a regulatory molecule binding at another site (of the same enzyme, again just at different places or sites)
- may either inhibit or stimulate an enzyme’s activity
- essential for enzymatic regulating
- allosterically regulated enzymes are made from polypeptide subunits
Active and inactive enzyme forms
- all enzymes have a form of both
- being binded to an activator stabilizes the active form (functioning)
- being binded to an inhibitor stabilizes the inactive form (not functioning)
Feedback inhibition
- where the end product of a metabolic pathway shuts down the pathway
- prevents a cell from wasting chemical resources by synthesizing more product than is needed
- the product realizes enough of itself is made and then acts as the inhibitor to cut off production
Structures and enzymes
- some enzymes are structural components of membranes
- some enzymes reside in specific organelles
- example: enzymes for cellular respiration being located in mitochondria
Chemical potential energy
- energy that can be absorbed or released due to a change of the particle number in a chemical reaction or phase transition
- stored in the chemical bonds of a substance (ATP!!!)
Catalyst
- a substance that increases the rate of a chemical reaction without undergoing any permanent chemical change itself
- enzyme
Why do highly ordered living organisms do violate the second law of thermodynamics?
- because the earth is an open system, not a closed system
Why cant most cells harness heat to perform work?
Because the temperature is usually consistent throughout the cell
Some bacteria are metabolically active in hot springs because?
They have high optimal temperatures
Which statements is a logical consequence of the 2nd Law of Thermodynamics?
Every chemical reaction must increase the total entropy of the universe
true or false: hydrolysis decreases the entropy of a system
FALSE
dehydration reactions do
true or false: rna nucleotides are the most similar to atp structure
true
Increasing the substrate concentration in an enzymatic reaction could overcome what?
competitive inhibition
How does zinc affect enzymes
it is a cofactor necessary for enzyme function
structure of atp
a ribose sugar, the nitrogenous base adenine, and a chain of three phosphate groups.
When a cell uses an energy releasing process to drive an energy consuming process, this is known as?
energy coupling
allosteric regulation
a molecule that impedes enzymatic action by binding to the enzyme outside of the active site casing a conformational shape change that renders the active site less effective.
If an enzyme is added to a solution where its substrate and product are in equilibrium, what will occur?
nothing, the reaction will stay the same
