Life at the Cellular Level 3 Flashcards
What is the basic rule of energy?
Energy cannot be created or destroyed, it merely changes its form
What are the two laws of thermodynamics?
- Energy can be converted from one form to another but the total energy of the universe remains constant
- All energy transformations ultimatelty lead to more disorder in the universe, ie, increase in entropy
What is entropy?
Degree of disorder in a system, quanitity representing the unavailability of a systems therman energy for conversion into work (measures in J/K)
What happens as usable energy decreases and unusable energy decreases?
Entropy increases
How do cells create and maintian order?
By performing lots of chemical reactions which require energy
How do the reactions within cells obey the second law of thermodynamics (leads to an increase in disorder/entropy)?
Chemical reactions used to create order generate heat which is discharged into the surrounding environment and disorders it, leading to an increase in total entropy
What is Gibb’s free energy?
Amount of useful, free energy in a system that can be used for work (measured in kJ/mol)
What are the 3 quantities that can define free energy?
Enthalpy (H)
Entropy (S)
Absolute temperature (T)
What formula expresses free energy?
G = H - TS
What is enthalpy?
Total heat content of a system
What is absolute temperature?
Temperature measured from absolute zero in kelvin
What does enthalpy reflect?
The number/kinds of bonds being broken or formed
When can spontaneous reactions occur?
If a system gives up energy
Becomes more random and increases in entropy
Why must spontaneous reactions have a negative value for delta G (change in G)?
Because they must decrease enthalpy and/or increase entropy
What does a positive and negative delta G mean?
Delta G positive means the reaction requires energy
Delta G negative means the reaction releases energy
Why do most biological reactions require a positive delta G?
Because they require order
What is energy coupling?
Transfer of energy from catabolism to anabolism
How do cells carry out energetically unfavourable reactions?
By using energy coupling
How does energy coupling allow energetically unfavourable reactions to happen?
The unfavourable reaction with a positive delta G is driven by the favourable reaction with a negative delta G as the net free energy change is less than 0
What is catabolism?
Metabolic pathways that break down moelcules into smaller units releasing energy (negative delta G)
What is anabolism?
Synthesis of complex molecules from simper ones using energy (positive delta G)
Why do reactions never reach the equilbrium?
Because delta G = 0 is incompatible with life, this doesn’t happen because energy is passed from the envionment to the organism and vice versa
What is the dyamic steady state?
Flow of energy between molcules, a continuous series of reactions
Why do the concentrations of intermediate molecules in a dynamic steady state remain constant?
Because as soon as they are made they are used
What does a simple dynamic steady state system look like?
When a=b the system is in a dynamic steady state due to maintaning the concentration of intermediate molecules
What is metabolism?
Chemical processes in a living organism where food is broken down and used for energy production
What happens during metabolism in terms of free energy?
Flows between catabolic and anabolic processes, with energy being lost as heat
Each step of a metabolic pathway is catalysed by an enzyme, what are some of their properties?
They are selective
They can be regulated
Why is glucose often used as a food molecule
It has a high potential energy
Why does the breakdown of glucose occur in a series of small reactions?
To allow the energy to be extracted in stages, as if it was broken down in one step to much energy would be produced and most of it would be lost to heat
How does glucose metabolism begin?
A small amount of energy must be inputed, activated carrier molecules store released energy
What does endergonic mean?
Anabolic pathway is supplied with free energy
What does exogonic mean?
Catabolic pathway releases free energy
How is free energy supplied and stored?
Using the interconversion of ATP and ADP
ATP + H2O ⇔ADP + Pi
Is ATP to ADP + Pi exogonic or endogonic?
Exogonic
Decrease in free energy
Delta G is negative
Is ADP + Pi to ATP exogonic or endergonic?
Endergernic
Requires free energy input
Delta G is positive
How to enzymes allow us to do reactions that would otherwise be impossible?
By lowing the activation energy
Why does potential energy in food molecules arise?
Because they contain large amounds of H atoms
What steps following the oxidaiton (breakdown) of glucose?
Releases electrons that flow through a series of intermediate steps to another spiecies, such as O2
Can be described as an electromotive force (EMF)
What carrier molecules do cellular redox reactions use?
NAD+
FAD+
NADP+
What do activated carriers acts as in biochemical pathways to fuel oxidation and biosynthesis?
Coenzymes
