Chapter 8 Test Flashcards
Metabolism
The totality of an organism’s chemical reactions
Metabolic Pathway
Begins with specific molecule, which is then altered, resulting in a certain product
Catabolic pathway
Breakdown pathway
Anabolic pathway
Consumed energy to build complicated molecules from simpler ones
Energy
Capacity to cause change
Kinetic energy
Energy associated with relative motion of objects
Thermal energy
Kinetic energy associated with the random movement of atoms or molecules
Heat
Thermal energy in transfer from one object to another
Potential energy
Energy that is not kinetic; energy that matter processes because of its location or structure
Chemical energy
Potential energy available for release in a chemical reaction
1st law of thermodynamics
Energy of the universe is constant. Energy can be transferred and transformed, but it cannot be created or destroyed
Entropy
Measure of disorder, or randomness
The more randomly arranged a collection of matter is, the greater its entropy
2nd law of thermodynamics
Every energy transfer or transformation increases the entropy of the universe
Free energy
Portion of a system’s energy that can perform work when temperature and pressure are uniform throughout the system
🔺G = 🔺H - T🔺S
Exergonic reaction
Proceeds with a net release of free energy
- 🔺G is negative
- occurs spontaneously
Endergonic reaction
Absorbs free energy from its surroundings
- 🔺G is positive (stores free energy)
- non spontaneous
Enzyme
Macromolecule that acts as a catalyst
Catalyst
Chemical agent that speeds up a reaction without being consumed by the reaction
Activation energy
Free energy of activation
The initial investment of energy required to contort the reactant molecules so the bonds can break
Substrate
The reactant an enzyme acts on
Active site
A restricted region of the enzyme molecule that actually binds to the substrate
Induced fit
Binding between the enzyme and substrate become tighter after initial contact
-brings chemical groups of the active site into positions that enhance their ability to catalyze the chemical reaction
Cofactor
Nonprotein helpers for catalytic activity
Coenzyme
An organic molecule cofactor
Competitive inhibitor
Mimics that reduce the productivity of enzymes by blocking substrates from entering active sites
Feedback inhibition
A metabolic pathway is halted by the inhibitory binding of its end product to an enzyme that acts early in the pathway
Cooperativity
Mechanism amplified the response of enzymes to substrates: one substrate molecule primed an enzyme to act on additional substrate molecules more readily
Catabolic are
Anabolic are
Downhill
Uphill
Energy released from __ can be stored and then used to drive the uphill reactions of __
Catabolic pathways
Anabolic pathways
System
Matter under study
Surroundings
Everything outside the system
Isolated system
Unable to exchange either energy or matter with its surroundings
Open system
Energy and matter can be transferred between system and its surroundings
Spontaneous process
If a given process, by itself, leads to an increase in entropy, that process can proceed without requiring an input of energy
Nonspontaneous process
Leaders to decrease in entropy: will happen only if energy is supplies
The free energy change of a reaction tells us
Whether or not the reaction occurs spontaneously
Living systems increase
The entropy of their surroundings
🔺H
Change in system’s enthalpy
🔺S
Change in system’s entropy
T
Absolute temp in Kelvin
🔺G
Represents difference between free energy of final state and free energy of initial state
Spontaneous processes decrease…
System’s free energy
Processes that have a positive or zero 🔺G are
Never spontaneous
Spontaneous process 🔺G
Negative
Equilibrium
State of maximum stability
-a system at equilibrium cannot spontaneously change, it can do no work
Spontaneous implies
That it is energetically favorable, not that it will occur rapidly
Free energy
Measure of a system’s instability
-its tendency to change to a more stable state
Breaking bonds does not __, it __
Release energy
Requires energy
Reversible process cannot be downhill in both directions
Must be opposites: uphill and downhill
3 kinds of work a cell does
Chemical
Transport
Mechanical
Energy coupling
Use of an exergonic process to drive an endergonic process
ATP is responsible for mediating most energy coupling in cells and acts as immediate source of
Energy that powers cellular work
ATP releases energy when
Loses a phosphate group (hydrolysis)
Phosphorylation
Transfer of a phosphate group from ATP to some other molecule
-the recipient molecule with the phosphate group covalently bonded to it: phosphorylated intermediate
ATP is a renewable resource that can be regenerated by
The addition of a phosphate to ADP
-the free energy required to phosphorylate ADP comes from exergonic breakdown reactions in the cell
Activation energy
Amount of energy needed to push the reactants to the top of an energy barrier, or uphill, so that the downhill part of the reaction can begin
Enzymes…
Speed up metabolic reactions by lowering energy barriers
Enzyme-substrate complex
When the enzyme bunds to its substrate
Noncompetitive inhibitors
Do not directly compete with the substrate to bunt to the enzyme at the active site
-binds to another part of the enzyme and causes enzyme molecule to change shape so that the active site becomes less effective
Spontaneous processes occur
Without energy input; they can happen quickly or slowly-happens with energy already there, doesn’t need more energy
Entropy (disorder)
May decrease in an organism, but the universe will increase
2nd law
Every energy transfer or transformation increases the entropy (disorder) of the universe
-energy is often lost as heat
🔺G-Free energy
Energy that can do work when temperature and pressure are uniform
-the change in free energy (🔺G) during a process is related to the change in enthalpy, or change in total energy (🔺H), change in entropy (🔺S) and temp in Kelvin (T)
Only processes with a negative 🔺G are
Spontaneous
During spontaneous
Free energy decreases and the stability of a system increases
Decrease in entropy
Dehydration reactions/synthesis
Most free energy per molecule
Starch
What does not represent an energy transformation?
The coupling of ATP hydrolysis to the production of a proton gradient across a membrane by a proton pump
Greater free energy
Methane
If during a process the system becomes more ordered, then
🔺S is negative
When one molecule is broken down into 6 component molecules, which if the following will always be true?
🔺S is positive
Negative 🔺G
Spontaneous
There is less energy than when you started
Free energy decreases
Stability of a system increases
Which of the following is an example of the cellular work accomplished with the free energy derived from the hydrolysis of ATP, involved in the production of electrochemical gradients?
Proton movement against a gradient of protons
Which of the following statements correctly describes some aspect of ATP hydrolysis being used to drive the active transport of an ion into the cell against the ion’s concentration gradient?
This is an example of energy coupling
Much of the suitability of ATP as an energy intermediary is related to the instability of the bonds between the phosphate groups. These bonds are unstable because
The negatively charged phosphate groups vigorously repel one another and the terminal phosphate group is more stable in water than it is in ATP
The formation of glucose-6-phosphate from glucose is an endergonic reaction and is coupled to which of the following reactions or pathways?
The hydrolysis of ATP
What do the sign and magnitude of the ΔG of a reaction tell us about the speed of the reaction?
Neither the sign nor the magnitude of ΔG have anything to do with the speed of a reaction.
Under most conditions, the supply of energy by catabolic pathways is regulated by the demand for energy by anabolic pathways. Considering the role of ATP formation and hydrolysis in energy coupling of anabolic and catabolic pathways, which of the following statements is most likely to be true?
High levels of ADP act as an allosteric activator of catabolic pathways
What is meant by induced fit?
The binding between the enzyme and the substrate become tighter after initial contact
Explain how protein structure is involved in enzyme specificity
The specificity of an enzyme results from its shape, which is determined by its amino acid sequence
Many factors affect the rate of enzyme action.
Explain
Initial concentration of substrate: the more substrate molecules that are available, the more frequently they access the active site of the enzyme molecules
pH - 6-8 is best/optimal
Temperature: increase of temperature can increase rate, but too high temps can denature the protein molecule
Why can extremes of pH or very high temperatures affect enzyme activity?
Extreme temperatures denature proteins and kill cells
Cofactor
Nonprotein helpers for catalytic activity
Coenzyme
If the cofactor is an organic molecule
Allosteric regulation
Describes any case in which a protein/s function at one site is affected by the binding of a regulatory molecule to a separate site
Allosteric regulation vs. Noncompetitive inhibition
They are similar in that allosteric inhibition may inhibit enzyme activity like nonconmpetitive, but different because it may also stimulate enzyme activity
Allosteric activator vs. Allosteric inhibitor
The binding of an activator to a regulatory site stabilizes the shape that has functional active sites, whereas the binding of an inhibitor stabilizes the inactive form of the enzyme
Explain the role of catabolic and anabolic pathways
Energy released from downhill reactions of catabolic pathways can be stored and then used to drive the uphill reactions
Describe the relationship between free energy and equilibrium
The tendency for a reaction to reach equilibrium is driven by the Gibbs free energy
Describe 3 main kinds of cellular work
Chemical work: pushing endergonic reactions
Transport work: pumping of substances across membranes against the direction of spontaneous movement
Mechanical work: movement of and within the cell
3 components of ATP
Contains 3 phosphate groups, adenine, and ribose
Describe the relationship between enzyme structure and enzyme specificity
The specificity of an enzyme results from its shape, which results from its amino acid sequence. The specificity of an enzyme is attributed to a compatible fit between the shape of its active site and the shape of the substrate
Cell does 3 main types of work
Chemical Transport Mechanical -cells manage energy resources by energy coupling -powers by the hydrolysis of ATP
The energy from the __ of ATP hydrolysis can be used to drive __
Exergonic reaction
Endergonic reaction
-couples reactions are exergonic
Enzyme’s substrate
The reactant that an enzyme acts on
Enzymes have high
Specificity
Induced fit of a substrate
Brings chemical groups of the active site into positions that enhance their ability to catalyze the reaction
Rate of reaction increases as
Substrate concentration increases
Transcription factor
Factors whether or not you can transcript it
Enzymes can be controlled at
Transcription and concentration levels, shape and structure of enzyme can change
- where you change it matters
- changing the active site is what matters
In an enzymatic reaction, the substrate
Binds to the active site of the enzyme
The active site can lower an Ea barrier by:
Orienting substrates correctly -locking magnets into place
Straining substrate bonds
Providing a favorable micro environment
Enzyme’s activity can be affected by
General environmental factors
-temp. and pH
Chemicals that specifically influence the enzyme
-enzymes have optimal temps and pH in which it can function
Cofactors are nonprotein enzyme helpers
May be inorganic or organic
Coenzyme
Organic cofactor
Enzymes are proteins encoded by genes
-changes in genes lead to changes in amino acid composition of an enzyme
Allosteric regulation
May either inhibit or stimulate an enzyme’s activity
- occurs when a regulatory molecule brings to a protein at one site and affects the protein’s function at another site
- can be inhibitor or activator
Most allosterically regulated enzymes are made from
Polypeptide subunits -> quaternary
Each enzyme has
Active and inactive forms
The binding of an activator stabilizes the active form of an enzyme
Inhibitor/inactive
Feedback inhibition
End product of a metabolic pathway shuts down the pathway
-prevents a cell from wasting chemical resources by synthesizing more product than needed
Active site may resemble
A groove/pocket in protein into which the substrate fits
Activation energy is changed
By presence of an enzyme
Energy coupling
Exergonic reactions drive endergonic reactions
Enzyme inhibitors: the action of inhibitors may be
Reversible or irreversible
If the entropy of a living organism is decreasing
Energy input into the organism must be occurring to drive the decrease in entropy
ATP drives mechanical work inside a cell by
Binding to motor proteins
Hydrolysis
The activity of an enzyme and how effectively it functions is
Affected by general environmental factors
-temp and pH
ATP drives transport work by
Phosphorylating a transport protein
Competitive inhibitors bind…
While noncompetitive inhibitors…
To the active site of an enzyme
Bind away from the active site on an enzyme
Allosteric regulation
Process of stabilizing the structure of an enzyme in its active form by the binding of a molecule
-describes any case in which a protein’s function at one site is affected by the binding of a regulatory molecule to another site
ATP allosterically inhibits enzyme’s in ATP producing pathways. Result is called
Feedback inhibition
ATP is a renewable resource because
ATP can be regenerated by the addition of a phosphate group to ADP
🔺S would be positive for
Catabolism
Energy in an ATP molecule is released through
Hydrolysis of one of the phosphate groups
Enzymes speed up the rate of the reaction without
Changing the 🔺G for the reaction
ATP in cellular metabolism
Free energy released by ATP hydrolysis may be coupled to an endergonic process via the formation of a phosphorylated intermediate
Cofactors and coenzymes are both
Nonprotein helpers, but most cofactors are metal ions, and coenzymes are organic molecules that are a specific type of cofactor
Enzymes can lower the activation energy of reactions, but they
Cannot change the net energy output
Hydrolysis of ATP drives cellular work by
Releasing free energy that can be coupled to other reactions
