Biology 1115 Chapter 8 Part 2
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Reactions in a closed system eventually reach equilibrium and then ___________
do no work
Do cells reach equilibrium? why?
cells are not in equilibrium because they are open systems experiencing a constant flow of materials
What is a defining feature of metabolism in life?
Metabolism is never at equilibrium
How does a catabolic pathway in a cell release free energy?
in a series of reactions
What are the three main kinds of work a cell does? give an example for each?
- Chemical: breaking down of food
- Transport: diffusion
- Mechanical: movement in cytoskeleton
How do cells manage energy resources to do work?
by energy coupling, which is the use of an exergonic process to drive an endergonic one
How are most energy coupling in cells mediated?
What class of large biological molecule is ATP?
What type of molecule is adenosine?
How can the bonds between the phosphate groups of ATP be broken?
by hydrolysis, adding water to break the bonds
How is energy released from ATP?
When the terminal phosphate bond is broken
Where does the release of free energy come from?
comes from the chemical change to a state of lower free energy, not from the phosphate bonds themselves.
What is the free energy if the hydrolysis of ATP?
What are the 3 types of cellular work powered by?
hydrolysis of ATP
Overall, what are coupled reactions, endergonic or exergonic?
ATP drives endergonic reactions by ___________.
Define phosphorylation. What is the recipient molecule called?
- involves the transfer of a phosphate group to some other molecule
- It's now called a phosphorylated intermediate
ATP is a renewable resource that is regenerated by _______________________________.
addition of phosphate group to adenosine diphosphate (ADP)
Where does the energy to phosphorylate ADP come from?
catabolic reactions in the cell
What are the three processes that ATP is regenerated by?
- substrate-level phosphorylation
- oxidative phosphorylation
How do enzymes speed up metabolic reactions?
by lowering energy barriers (activation energy)
What is a catalyst?
a chemical agent that speeds up a reaction without being consumed by the reaction
What is an enzyme?
a catalytic protein
What is the initial energy needed to start a chemical reaction called?
- free energy of activation or activation energy (EA)
- barrier that reaction must overcome
How do enzymes catalyze reactions?
by lowering the activation energy barrier
What is the enzyme's substrate?
the reactant that an enzyme acts on
What is the active site on an enzyme?
the region on the enzyme where the substrate binds
The active site can lower an activation energy barrier by:(4)
- orienting substrates correctly
- straining substrate bonds
- provide a favourable microenvironment
- covalently bonding to the substrate
How can an enzyme's activity be affected? (2)
- general environmental factors such as pH and temperature
- chemicals that specifically influence an enzyme
Each enzyme has an optimal _________ and _________ in which it can function
temperature and pH
What are cofactors? (2)
- non-protein enzyme helpers
- may be inorganic (such as metal in ionic form) or organic
What is a coenzyme, give an example?
- organic cofactor
- example is vitamins
What are competitive inhibitors?
they bind to the active site of an enzyme, competing with the substrate
What are non-competitive inhibitors?
They bind to another part of an enzyme, causing the enzyme to change shape and making the active site less effective
How is a cell's metabolic pathways regulated?
A cell does this by switching on or off the genes that encode specific enzymes or by regulating the activity of enzymes
What is allosteric regulation?
occurs when a regulatory molecule bonds to a protein at one site and affects the protein's function at another site
What are the two things that allosteric regulation can do?
may either inhibit or stimulate an enzyme's activity
What does the activator in allosteric regulation stabilize?
stabilizes the active form of the enzyme
What does the inhibitor in allosteric regulation stabilize?
stabilizes the inactive form of the enzyme
It's a form of allosteric regulation than can amplify enzyme activity.
What happens in feedback inhibition?
The end product of a metabolic pathway shuts down the pathway
What does feedback inhibition prevent?
It prevents a cell from wasting chemical resources by making product than needed.
What would you like to do?
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