Module 6: Making Life Work Flashcards
Why do cells need energy?
they need the energy to do the work of the cell.
- movement, growth, pump ions, perform reactions
Phototroph
Obtain energy form the sun
- plants are most common
Chemotroph
obtain energy from chemical compounds
- animals
Autotroph
organism can convert CO2 into glucose since they make own organic source of carbon
Heterotroph
organism is unable to convert CO2 and must ingest other organisms/molecules for a source of carbon
What is metabolism?
chemical process that occur in a living organism to maintain life
- includes the building up and breakdown of chemical compounds. allows energy to be harnessed or released
- these reactions are continuously happening in cells
- many of these reactions are linked in such a way that the products of one are the reactants of another
What are the two branches of metabolism?
Anabolism:** building** of molecules from smaller units, *requires an input *of energy (ATP)
Catabolism: breakdown of molecules into smaller units, produces energy (ATP)
ATP
Adenosine triphosphate
- provides energy in a form that all cells can readily use to perform work of the cell
- the ATP molecule contains energy in its chemical bonds
Potential energy
Energy that is not associated with movement but rather is stored
Kinetic energy
energy of motion
Chemical energy
chemical bonds between pairs of atoms in a molecule hold onto a form of potential energy
Bond strength and potential energy are…
linked
- strong bonds = less PE
- weak bonds = more PE
ATP has ___ amount of energy. Why?
high.
- the bonds between phosphate groups are weak
- has high PE
- when bonds between the phosphate groups are broken, the potential energy is released for cell to do work
Do cells use all their energy at once?
no.
they keep it stored in a chemical form that is readily accessible to the cell
- most common chemical form used by the cell is ATP, the energy currency of the cell
ADP
two phosphate groups
AMP
one phosphate group
First Law of Thermodynamics
energy can neither be created nor destroyed
- energy can be converted from one form to another
- when e- move from higher to lower energy level, energy released as heat or light
Second Law of Thermodynamics
events in the universe have direction, proceed from higher energy to lower energy
- these events are thermodynamically favourable and are said to to be spontaneous, no input of external energy
- results in a reduction in the amount of usable energy because energy transformations are not 100% efficient
Gibbs free energy
the amount of energy in a system available to do work
- delta G is the symbol for the difference in Gibbs free energy between R and P of a chemical process
Delta G is +
the products of a reaction have more free energy then the reactants
- thermodynamically unfavourable, endergonic
- needs an input of energy
Delta g is -
the reactants have more free energy then the products
- thermodynamically favourable, exergonic
- energy is available for use in another process (release energy)
dG = dH - TdS
d = delta
H = total energy (enthalpy)
G = energy available to do work
S = energy lost to entropy or disorder
T = absolute temperature in Kelvin
What happens when ATP is hydrolyzed?
The reaction of ATP with water is exergonic (spontaneous) and releases energy (-dG)
- at physiological pH the phosphate groups in ATP are negatively charged and resist one another
Activation Energy
- chemical transformations require the breakage of certain covalent bonds within the reactant
- reactants must contain sufficient kinetic energy to overcome the activation energy barrier (Ea)
- enzymes catalyze reactions by decreasing magnitude of Ea barrier so reaction can proceed
- cells can carry out many reactions with a +dG (unfavourable)
What are the two reasons cells carry out a +dG reaction, which is unfavourable?
- relative concentrations of reactants to products is maintained above that defined by equilibrium constant
- coupling endergonic and exergonic reactions
- ex, hydrolysis of ATP drives endergonic reactions
How are chemical reactions catalyzed?
chemical reactions are catalyzed by proteins called enzymes (“ase”= enzyme)
- active site of a an enzyme is formed by the assembly of certain amino acids in a three dimensional structure
- the enzyme active site binds the substrate(s) and converts it to the product
- the active site binds the substrate(s) and helps stabilize the transition state and lowers Ea
Anabolic and catabolic reactions are catalyzed by __
enzymes
Is it possible to affect enzyme activity?
yes
- enzyme activity can be reduced by two different kinds of inhibitors, reversible & irreversible
- enzyme activity can be increased by activators
Negative feedback
- because energy is needed for chemical reactions, many metabolic pathways are regulated
- an example of regulation is where the final product in a pathway inhibits the first step of the reaction known as negative feedback
- important for maintaining balance in the cell and in helping the cell to conserve energy
