Lecture 5: Energy, ATP, Enzymes Flashcards
What is metabolism?
All of the chemical reactions that take place in our body
What is Anabolism?
Reactions that link simple molecules together into more complicated molecule
What is Catabolism?
Breaks down complex molecules into simpler ones.
Which requires energy anabolism or catabolism?
Anabolism
Which releases energy anabolism or catabolism?
Catabolism
How do cells acquire energy?
From their environment(ex. eating food)
What law explains energy conversions?
Second Law of Thermodynamics
What is the second law of thermodynamics?
The drive of energy to be evenly distributed/dispersed
Two ways energy is dispersed into the environment?
- Increasing disorder inside the cell
- Increasing disorder outside the cell
How can disorder be increased inside the cell?
-Doing a chemical reaction that increases the disorder of the chemicals inside the cell
-Ex. Breaking down highly ordered molecules such as polypeptides
How can disorder be increased outside the cell?
-Releasing heat
What is an increase of disorder inside a cell called?
Entropy (delta S)
What is an increase of disorder outside a cell called?
Enthalpy (delta H)
Equation for delta G?
delta G = delta H - T(delta S)
What does a negative delta G indicate?
Energy is released/dispersed
-There is disorder inside the system
-Reaction is spontaneous
What does a positive delta G indicate?
- Energy is required and the reaction cannot occur on its own
What happens when heat is released and disorder is increased (spontaneous?)(Anabolic/Catabolic)
-ALWAYS spontaneous(delta H = -, delta S = +)
-Catabolic
-Exergonic
What happens when heat is released and disorder decreases?(spontaneous?)
- Spontaneous at low temperatures (delta H = -, delta S = -)
- Non-spontaneous at high temperatures
What happens when heat is used and disorder increases?(spontaneous?)
- Spontaneous at high temperatures (delta H = +, delta S = +)
- Non spontaneous at low temperatures
What happens when heat is used and disorder decreases?(spontaneous?)
-NEVER spontaneous (delta H = +, delta S = -)
- Anabolic
-Endergonic
How are endergonic reactions able to occur?
-By coupling endergonic reactions with exergonic reactions
How is energy transferred in cells?
Through ATP
How does ATP create free energy?
Through ATP hydrolysis
-ATP is converted into ADP and Pi and releases free energy
Why is ATP used as energy currency?
Its ΔG is intermediate between what you gain in respiration and what you expend in anabolism
Examples of anabolism reactions?
- DNA replications
- Protein synthesis
- Making of Starch
Examples of catabolic reactions?
- Digestion of food
- Any hydrolysis reaction (ATP – ADP +Pi)
True or False: Energy conversions always result in a state of more disorder.
True
Explain complication 1 of thermodynamics(reversible reactions)
All reactions are reversible, therefore delta G is dynamic and changes depending on how much reactant and product is in the system
-Concentrations are necessary in order to find the true value of delta G
What is delta G of ATP in a cell?
-12 kJ/mol
Another complication of thermodynamics(not knowing reaction rates)
If you know delta G, you still do not know how fast the reaction will proceed
-Many exergonic reactions occur extremely slowly
What do catalysts do?
Increase the rate of spontaneous reactions with negative delta G
What is a catalyst?
A protein, called an enzyme
- Can sometimes be RNA’s
How do enzymes work?
They lower the activation energy required for reactions to proceed
What is an enzyme-substrate complex?
When a reactant(substrate) binds to the active site of an enzyme it creates an enzyme-substrate complex
What is a transition state and how do enzymes get substrates there?
Transition: characterized by a lower activation energy.
After the substrate binds to the enzyme the enzyme undergoes a conformational bringing the substrate into a transition state
What happens after the substrate leaves the enzyme?
The enzyme reverts back to its original shape
What can induce the enzyme to transfer the substrate to the transition state?(3 ways)
- Binding substrates in the correct orientation
- Exposing the reactants to altered charge environments
- Inducing strain on the substrate facilitating breaking of bonds
Why is pH important to maintain in terms of enzymes and charged environments?
Enzymes may no longer be able to bring substrates to the transition state if there is too high of pH or too low of a pH due to a lack of charged environment
What are cofactors?
- Anything that is not an amino acid
- Binds to enzymes and is necessary for enzyme activity
When is an enzyme saturated?
When all of its active sites are full
