Topic 6 Flashcards
(64 cards)
1
Q
Living cells are
A
miniature chemical factories
2
Q
Cellular respiration extracts energy stored in
A
sugars and other fuels
* Cells apply this energy to perform work
3
Q
Metabolism:
A
the sum of all chemical reactions in an organism
* Transforms matter and energy
* Subject to Laws of Thermodynamics
4
Q
Metabolism is an emergent property of life that arises from
A
orderly interactions between molecules
5
Q
- A metabolic pathway begins with
A
a specific molecule and ends with a product
* Each step is catalyzed by a specific enzyme
* Cascade effect drives conversion from A to D
6
Q
Two types of metabolic pathways
A
Catabolic pathways:
* Release energy by breaking down complex molecules into simpler compounds
* Ie) Cellular respiration, the breakdown of glucose in the presence of oxygen
Anabolic pathways:
* Consume energy to build complex molecules from simpler ones
* Ie) The synthesis of protein from amino acids
7
Q
Bioenergetics:
A
the study of how energy flows through living organisms
8
Q
- Energy:
A
- Capacity to cause change
- Exists in various forms, some of which can perform work
Can be converted from one form to another
9
Q
- Types of Energy:
A
- kinetic
- thermal
- potential
- chemical
10
Q
- Kinetic energy:
A
energy associated with motion
11
Q
thermal energy
A
the kinetic energy associated with random movement of atoms or molecules
heat- thermal enery transferred between objects
12
Q
potential energy
A
energy that matter possesses becuase of its location or structure
13
Q
chemical energy
A
potential energy avaliable for release in a chemical reaction
14
Q
Thermodynamics
A
is the study of energy transformations
15
Q
Isolated vs open systems:
isolated
A
unable to exchnage energy or matter with its surroundings
16
Q
open systems
A
able to exchnage energy or matter with surroundings
- organisms are open systems
17
Q
The First Law of Thermodynamics:
A
- The principle of conservation of energy
- The energy of the universe is constant
- Energy can be transferred and transformed, but it cannot be created or destroyed
18
Q
The Second Law of Thermodynamics
A
- During every energy transfer or transformation, some energy is unusable and is often lost as heat
- Every energy transfer or transformation increases the entropy of the universe
- Entropy is a measure of molecular disorder, or randomness
19
Q
- Entropy
A
a measure of molecular disorder, or randomness
20
Q
Biological Order vs Disorder 1
A
- Living cells convert organized forms of energy to heat
- Heat is a more disordered form of energy
- But, in Topic 01, Order was a Unifying Theme in Biology
21
Q
Biological Order vs Disorder 2
A
- Organisms create ordered structures from less organized forms of energy and matter
- Organisms also replace ordered forms of matter and energy in their surroundings with less ordered forms
- Ie) animals consume complex molecules in their food and release smaller, lower energy molecules and heat into the surroundings
22
Q
Biological Order vs Disorder 3
A
- The evolution of more complex organisms does not violate the second law of thermodynamics
- Entropy (disorder) may decrease in a particular system, such as an organism, so long as the total entropy of the system and surroundings increases
23
Q
Conversion of Energy
A
- Living cells convert organized forms of energy to heat (a more disordered form of energy)
24
Q
- Spontaneous processes:
A
- occur without energy input
- can happen quickly or slowly
- for a proccess to occur spontaneously, it must increase the entropy of the universe
25
non spontaneous process
decrease entropy, need energy to occur
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* Free Energy
energy that can do work when temperature and pressure are uniform, as in a living cell
represented as: G
- Free Energy change indicates whether reaction occurs spontaneously or not
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Free energy is a measure of
a system’s instability - its tendency to change to a more stable state
- During a spontaneous change, free energy decreases, and the stability of a system increases
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* Equilibrium is a state of
maximum stability
* A process is spontaneous and can perform work only when it is moving toward equilibrium
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exergonic reaction:
* Proceeds with a net release
of free energy * Spontaneous * G < 0
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endergonic reaction:
* Absorbs free energy from its
surroundings
* Nonspontaneous * G > 0
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Equilibrium and Metabolism
Reactions in a closed system eventually reach equilibrium and can then do no work
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Cells are not in
equilibrium
* A defining feature of life is that
metabolism is never at equilibrium
* A catabolic pathway in a cell releases free energy in a series of reactions
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* A cell does 3 main kinds of work:
Chemical work: pushing
endergonic reactions
* Transport work: pumping substances against the direction of spontaneous movement
* Mechanical work: such as contraction of muscle cells
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* To perform work, cells use
energy coupling
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Energy coupling:
the use of exergonic processes to drive endergonic processes
* Most energy coupling in cells is mediated by ATP and ATP hydrolysis
36
ATP Hydrolysis
* Bonds between the phosphate groups of ATP’s tail can be broken by hydrolysis
* Energy is released from ATP when the terminal phosphate bond is broken
* This release of energy comes from the chemical change to a state of lower free energy, not from the phosphate bonds themselves
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* Cellular work (mechanical, transport, and chemical) is powered by
the hydrolysis of ATP
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Energy from the exergonic reaction of ATP hydrolysis can be used to drive an
endergonic reaction
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ATP drives endergonic reactions by
phosphorylation, transferring a phosphate group to some other molecule, such as a reactant
The recipient molecule is now called a phosphorylated intermediate
* Overall, the coupled reactions are exergonic and occur spontaneously
40
Transport and mechanical work in the cell are also powered by
ATP hydrolysis
* ATP hydrolysis leads to a change in protein shape and binding ability
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what needs to be regenerated
* ATP hydrolysis is an exergonic reaction, so it occurs spontaneously
* ATP levels become depleted and need to be regenerated by adding a phosphate group to adenosine diphosphate (ADP)
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ATP regeneration
* The energy to phosphorylate ADP comes from catabolic reactions in the cell
* Ie) cellular respiration, photosynthesis
* The ATP cycle is a revolving door through which energy passes during its transfer from catabolic to anabolic pathways
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* Enzymes are
proteins that speed up chemical reactions
* Catalysts:
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* Catalysts:
they speed up reaction without being consumed
* Often have name that ends in ‘ase’
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Every chemical reaction between molecules involves
bond breaking and bond forming
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How enzymes speed up reactions
* Enzymes speed up specific reactions by lowering the EA barrier
* Enzymes do not affect the change in free energy (ΔG)
* Enzymes allow reactions that would eventually occur to occur faster
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* The enzyme binds to its substrate, forming an
enzyme-substrate complex
* While bound, the activity of the enzyme converts substrate to product
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* The active site is the
region on the enzyme where the substrate binds
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* Induced fit of a substrate:
* Brings chemical groups of the active site into positions that enhance their ability to catalyze the reaction
* Lock and Key Model
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* Induced fit of a substrate:
* Brings chemical groups of the active site into positions that enhance their ability to catalyze the reaction
* Lock and Key Model
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* Enzymes are:
* Extremely fast acting
* Catalysts: Emerge from reactions in their original form
* Very small amounts of enzyme can have huge metabolic effects
* Used repeatedly in catalytic cycles
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* The active site can lower activation energy by 4
* Orienting substrates correctly
* Straining substrate bonds
* Providing a favorable microenvironment
* Covalently bonding to the substrate
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* The rate of an enzyme-catalyzed reaction can be sped up by
increasing substrate concentration
* When all enzyme molecules have their active sites engaged, the enzyme is saturated
* If the enzyme is saturated, the reaction rate can only be sped up by adding more enzyme
53
* An enzyme’s activity can be affected by:
* Environmental factors, such as temperature & pH
* Chemicals tha tspecifically influence the enzyme
* Each enzyme has optimal temperature and pH for its function
* Optimal conditions – favor most active shape for enzyme molecule
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* Cofactors
are non-protein enzyme helpers
* Cofactors may be inorganic (a metal in ionic form) or organic
* An organic cofactor is called a coenzyme
* Coenzymes include vitamins
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* Competitive inhibitors:
* Bind to the active site of an enzyme
* Compete with the substrate
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* Noncompetitive inhibitors:
* Bind to another part of an enzyme, causing the enzyme to
change shape
* Makes the active sitel ess effective
* Examples of inhibitors: toxins, poisons, pesticides, and antibiotics
* Not all inhibitors are bad, allows for regulation of enzymatic activity
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* A cell’s metabolic pathways need to be tightly regulated A cell does this by:
* Switching on or off the genes that encode specific enzymes
* Regulating the activity of enzymes
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Allosteric regulation:
* May either inhibit or stimulate an enzyme’s activity
* A regulatory molecule binds to a protein at one site, and affects the protein’s function at another site
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* Most allosterically regulated enzymes are made from
polypeptide subunits, each with its own active site
* The enzyme complex has active and inactive forms
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* The binding of an activator stabilizes
the active form of the enzyme
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* Cooperativity:
a form of allosteric regulation that can amplify enzyme activity
* One substrate molecule primes an enzyme to more easily act on additional substrate molecules
* Cooperativity is allosteric because binding by a substrate to one active site affects catalysis in a different active site
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* Feedback inhibition:
* 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
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* Compartmentalization within the cell help bring
order to metabolic pathways
* In eukaryotic cells, some enzymes reside in specific organelles
* Ie) Enzymes for cellular respiration are in mitochondria
* Ie) Acid hydrolases in lysosome
