Biology Exam 3 Chapter 8
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What is metabolism? What processes is it responsible for? What does it require?
All chemical reactions within the cell; digestion, growth, reproduction, photosynthesis, healing, etc; energy
What is energy? What is its relation to work?
Energy is the capacity to cause a change; work is specific energy transfer causing a change.
What process is the responsible for the transformation or transfer of energy?
Within a cell or organism, what is responsible/needed for the synthesis or movement of molecules?
What happens when energy is lost within a cell?
Energy radiates out as heat and is lost
What are some different types and sources of energy?
Light/photons (sun), chemical (bonds broken/formed), electrochemical potential (charges equalizing, ions diffusing)
What type of energy is photosynthesis and how does this process work?
light energy; chlorophyll absorb energy which excites electrons; excited electrons fuel synthesisof organic molecules from CO2
What type of energy is responsible for cision and archaea ATP synthesis?
How does light energy affect retinal?
- Light energy causes change between cis- &
- trans- isomers
How can light energy cause DNA damage?
- It can cause p53 gene mutations and is
- responsible for Dimers within DNA
What is the process of catabolism? What type of
energy is it responsible for? What are some examples of catabolism in action?
- Catabolism is the process of breaking down
- molecules; chemical energy; hydrolysis of macromolecules to release energy to
- make NADH or ATP, glycolysis, lipolysis, citric acid cycle
How are NADH/NADPH used for chemical energy?
- They donate electrons (energy transfer) to other
How is ATP used for chemical energy?
It donates a phosphate to other molecules
Explain the process of chemosynthesis. Who uses this?
Chemosynthesis is the process of fixating CO2without sun energy. Simple molecules/ions like H2 or Fe2+ donate electrons totransfer energy to other molecules; deep sea vents
What process makes use of energy from the
diffusion of protons to make ATP?
Chemiosmosis/proton motive force
What is anabolism?
The synthesis of molecules
What is the first law of thermodynamics?
Energy can be transformed and transferred but it can’t be created or destroyed
What is the transfer of energy? What is the
transformation of energy?
- Energy that stays as the same type but is moved
- to a different object; one form of energy changing into another form
What is a byproduct of the
transfer/transformation of energy? Which direction does it go?
Does heat do work? How is it transferred?
- No; movements, vibrations, collisions,
- compressions, friction
What is the second law of thermodynamics?
Energy us always dissipating and diffusing
Define the terms enthalpy and entropy.
- Enthalpy is the energy present within
- macromolecules; entropy is the energy lost as heat
What is enthalpy? Where is this energy found?
- The energy stored within a cell; chemical bonds,
What is entropy? How can this process happen?
- All the energy that is leaving the cell; heat
- dissipating, molecules breaking into smaller molecules, diffusion of
How do enthalpy and entropy work simultaneously
in the process of cell metabolism?
- Energy is turned into macromolecules (enthalpy),
- but at each step in this process, energy is lost (usually as heat) (entropy)
How can we measure a change in enthalpy?
- By examining the chemical energy within the
- reactants vs the chemical energy in the products
What is an endothermic reaction and how does it affect the change in enthalpy?
- An endothermic reaction involves the absorption
- of heat energy. The reactants have less energy and the products have more
- energy (deltaH is positive)
What is an exothermic reaction and how does it
affect the change in enthalpy?
- An exothermic reaction involves the release of
- hear energy. The reactants have more energy than the products (less chemical
How does the second law of thermodynamics relate to entropy?
- If energy is always dissipating or diffusing,
- then entropy is always increasing and energy is becoming more and more spread
What is free energy? What is the formula for
free energy? What does a plus or minus value for free energy mean?
- The amount of energy available for work after
- compensating for H (enthalpy) and S (entropy) (8-34); ΔG=ΔH-TΔS
- (8-33); Plus is an endergonic process and energy is available to do work, negative
- is an exergonic process and energy is lost
Because of the second law of thermodynamics, are
all processes of the universe endergonic or exergonic? What is the consequence
of this process?
- Exergonic (8-36); Less energy is available to
- work so we must eat to supply more energy or plants must receive more sunlight
How is enthalpy put to use as free energy to do
work if every process in the universe is exergonic? Give an example of this
- Energy coupling (8-39), An exergonic process is
- used to drive an endergonic process; Glutamate is synthesized into glutamine-An
- exergonic reaction occurs when ATP hydrolysis releases energy which is then
- used to create bonds (an endergonic reaction) between Glutamate and an amino
- group; the overall free energy of the reaction is still negative though so it
- is an overall exergonic process
Is sunshine an endergonic or exergonic process?
- Exergonic; most is radiated as heat and only a
- small amount is used in photosynthesis (an endergonic process)
What is an enzyme used for? How does it do this?
- It makes reactions easier to take place (8-43);
- It does this lowering the energy of the transition state or stabilizing the
What is a transition state?
- A transition state represents the stage in which
- a reaction occurs. This process requires an endergonic process (needs to take
- in energy) before settling into a net exergonic reaction
What is a catalyst? What are two common types and how do they work?
A catalyst is something that increases the rateof a reaction; Heat energy increases collisions of molecules and the chances ofreaching the transition state; enzymes are proteins that stabilize or lower theenergy of the transition state
How can enzymes lower activation energy?
- By orienting two substrates to favor a specific
- interaction, by putting stress on bonds to induce transition state, and by
- making transient bond
True or false: Enzymes are modified after they
are used making them unusable again
True or false: Enzymes affect the overall deltaG
What is the process of an enzyme modifying a
- The substrate (the molecule being modified)
- binds to the active site of the enzyme
What is the common naming procedure for enzymes?
- They often end in –ase and are generally named
- for the substrate they bind
What is an allosteric site?
- A spot where other molecules (regulators) bind
- to affect enzyme function
How might an enzyme be allosterically modified?
- A regulator binds to the allosteric site of an
- enzyme and modifies the active site of the enzyme by either activating it or
- inhibiting it.
Describe the process of feedback inhibition.
- The product of an enzymatic reaction acts to
- inhibit the same enzyme
Besides a regulator allosterically inhibiting an
enzyme, how else might the enzyme become inhibited?
- Through competition inhibition when an inhibitor
- binds to the active site of the enzyme
Describe the difference between allosteric and
- In an allosteric inhibition, a molecule binds to
- the allosteric site and modifies the active site of the enzyme. In competitive
- inhibition, a molecule binds to the active site, preventing the substrate from
What is the purpose of a cofactor for an enzyme?
What are some examples?
- Ions/molecules required for an enzyme to
- function; many essential vitamins and minerals
What can affect the rate of an enzyme-catalyzed
pH and heat
Describe the flow of energy
- Cells obtain energy by either converting light energy to chemical energy or through
- the catabolism of nutrients. The energy is then converted into usable form such
- as ATP. The energy is
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