Chapter 6: Metabolism Flashcards
(92 cards)
1
Q
bioenergetics
A
study of energy flowing through living systems
2
Q
metabolism
A
all the chemical reactions that happen inside of cells
3
Q
metabolic pathway
A
series of biochemical reactions that convert a substrate into its final product
4
Q
What are the two main metabolic pathways?
A
Anabolic and catabolic
5
Q
anabolic pathway
A
synthesises complex molecules from simple ones
6
Q
catabolic pathway
A
breaks down complex molecules into simple ones
7
Q
kinetic energy
A
energy an object has when in motion
8
Q
potential energy
A
energy an object has when it has a potential to do work
9
Q
chemical energy
A
potential energy that exists between molecular bonds
10
Q
Gibbs free energy
A
refers to the usable energy in a chemical reaction after entropy is taken into account
11
Q
delta G
A
change in free energy
12
Q
delta S
A
energy lost to entropy
13
Q
delta H
A
total energy change in a system
14
Q
enthalpy
A
total energy change in a system
15
Q
What is the formula for calculating the change in free energy?
A
ΔG = ΔH − TΔS
16
Q
What does ‘T’ represent in ΔG = ΔH − TΔS?
A
absolute temperature in Kelvin
17
Q
What units express change in free energy?
A
Amount of energy (in kilojoules or kilocalories) per mole of reaction product under standard conditons
18
Q
What is the conversion rate for kilocalories to kilojoules?
A
1 kcal = 4.184 kJ
19
Q
What are the factors for standard conditions for calculating free energy?
A
Standard pH, temperature and pressure
20
Q
What is the standard pH value?
A
pH 7
21
Q
What is the standard temperature value?
A
25 degrees Celsius
22
Q
What is the standard pressure value?
A
100 kilopascals
23
Q
How much pressure is 1 atmosphere?
A
100 kilopascals
24
Q
What will the value delta G be if energy is released in a reaction?
A
It will be negative
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exergonic reaction
reaction that releases free energy
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Are exergonic reactions spontaneous?
Yes, they require no energy input
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endergonic reaction
reaction that results in a gain of free energy
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Are endergonic reactions spontaneous?
No, they require an energy input to happen
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chemical equilibrium
when there is no net change in amount of reactants and products in a chemical reaction
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In what condition is there the lowest amount of free energy and maximal entropy?
In equilibrium
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What would happen if a cell was in a closed environment?
Its chemical reactions would reach equilibrium and it would run out of energy and die
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Do chemical reactions in a cell ever reach equilibrium?
No, they move towards equilibrium but never reach it
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Why do cells never reach equilibrium?
They are in an open environment and materials are constantly being moved in and out
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activation energy
energy necessary to start a reaction
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What is activation energy abbreviated to?
EvA
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transition state
high-energy, unstable form between the substrate and product
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Why do exergonic reactions need energy to start?
Reactants must be slightly contorted first for bonds to break and need energy to reach this state of contortment
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Where does the activation energy for a reaction come from?
From the heat in the surrounding area
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How does heat energy provide the activation energy for a reaction?
When the reactants absorb enough heat, they will reach the transition state and the reaction will occur
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How does amount of activation energy needed affect the rate of reaction?
The greater the activation energy, the slower the reaction
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Why are catalysts important in chemical reactions?
They lower the activation energy required and prevent the body from producing too much heat to overcome the original activation energy
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What does the first law of thermodynamics state?
Energy cannot be created or destroyed
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What does the second law of thermodynamics state?
The total entropy of the universe is always increasing
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entropy
the measure of disorder in a system
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What is the relationship between entropy and energy
High entropy means low energy
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nucleoside
a nitrogenous base attached to a sugar
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adenosine
nucleoside made of adenine and ribose
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How are the phosphate groups in ATP named?
In order of closest to furthest from the ribose sugar, they are named alpha, beta and gamma
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Where are the high-energy bonds in ATP located?
Between the gamma and beta phosphate, and the beta and alpha phospahte
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phosphoanhydride bond
high-energy bonds that hold together the phosphate groups in ATP
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How is ATP converted to ADP?
Through hydrolysis
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How is an inorganic phosphate group as a chemical formula?
Pi
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What is the chemical equation for ATP being converted into ADP?
ATP + H20 -> ADP + Pi + free energy
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Is the conversion of ATP into ADP reversible?
Yes
55
What is the chemical equation for ADP being converted into ATP?
ADP + Pi + free energy -> ATP + H2O
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What is the change in Gibbs free energy for hydrolysis of one ATP under standard conditions?
-7.3 kcal/mole or -30.5 kJ/mole
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What is the change in Gibbs free energy for hydrolysis of one ATP under cellular conditions?
-14 kcal/mole or -57 kJ/mole
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How stable is ATP?
It is highly unstable and will spontaneously dissociate into ADP and Pi if not used
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In what form is energy released when ATP dissociates spontaneously?
It is released as heat energy
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energy coupling
when the energy from an exergonic reaction is used to drive another reaction
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phosphorylation
when a phosphate group binds to another molecule
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Do enzymes alter the free energy of a reaction?
No, they only change the activation energy required to start the reaction
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substrate
the reactants that bind to an enzyme
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active site
the location where the substrate binds with the enzyme
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How specific are enzymes for each substrate?
They is generally a unique enzyme for each substrate
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Why are enzymes so specialised?
Due to the complexity of enzymes as most of them are intricately composed and folded proteins
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What can happen to an enzyme if conditions are too extreme?
The enzymes can denature and lose its properties as an enzyme
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Which model previously describes how an enzyme binds to its substrate?
The "lock-and-key" model
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induced fit
model that describes how an enzyme binds to its substrate
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What does the induced fit model describe?
As the enzyme and substrate come together, the enzyme conforms to fit the substrates shape
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enzyme-substrate complex
when an enzyme binds to its substrate
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How does an enzyme promote chemical reactions through orientation?
Enzymes bring reactant substrates together in an optimal orientation for reacting
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How does an enzyme promote chemical reactions through environment?
The particular arrangement of certain amino acids can create an ideal environment for a reaction to occur
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How does an enzyme promote chemical reactions by altering the substrate directly?
It can contort the substrate to reach its transition state
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How does an enzyme promote chemical reactions by getting directly involved in the reaction?
It can provide the necessary substances for the chemical reaction to occur
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What ways can an enzyme promote chemical reactions?
1. Orient substrates in an ideal position for reacting
2. Create an ideal reacting environment
3. By contorting the substrates into their transition state
4. By taking part in the reaction itself
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Does an enzyme change after a chemical reaction?
No, it always reverts to its original form
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competitive inhibition
inhibitor molecules bind to the active sites of enzymes to prevent substrates from binding instead
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noncompetitive inhibition
inhibitor molecules bind to the enzyme in places other than the active and allosteric site and still prevents the substrate from binding to the active site
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How does competitive inhibition affect rate of reaction?
It slows the initial rate but does not affect the maximal rate
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How does noncompetitive inhibition affect rate of reaction?
It slows the initial rate and lowers the maximal rate
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allosteric site
site at which the inhibitor molecule binds to during allosteric inhibition
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allosteric inhibition
inhibitor molecule binds to a site other than the active site which conforms the active site to decrease affinity for the substrate
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allosteric activation
activator binds to allosteric site which conforms the active to increase affinity for the substrate
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How many polypeptide chains comprise most allosterically regulated enzymes?
More than one polypeptide
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What are the two types of enzyme helper molecules?
Cofactors and coenzymes
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cofactor
inorganic ions that act as enzyme helper molecules
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What cofactor does DNA polymerase need to function?
Zn++
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coenzyme
organic molecules that act as enzyme helpers
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What is the most common source of coenzymes?
Dietary vitamins
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How can enzymes be further regulated in cells?
They can be compartmentalised into cell organelles
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feedback inhibition
using an enzyme's reaction products to regulate its own production
