Metabolism Flashcards
what is metabolism
Metabolism is all the chemical reactions in an organism.
They are organized into pathways:
what are anabolic and catabolic pathways
Anabolic pathways: biosynthetic
Build complex molecules and use energy
Catabolic pathways: degradative process
break down complex molecules and release energy
what are the forms of energy
Energy is used to do work
KE: Kinetic energy = energy of motion
- thermal energy = random movement of atoms and molecules
PE: Potential energy = stored energy based on position or structure
- Chemical energy = potential energy of molecules
Organisms are energy transformers:
cells transform energy from one form to another.
what is thermodynamics
Thermodynamics: Study of energy transformation
Organisms are open systems, they exchange energy and matter with the surroundings.
what are the 1st and 2nd law of thermodynamics
1st law of thermodynamics: Principle of conservation of energy → energy is always constant
2nd law of thermodynamics: Every energy transformation increases the entropy of the universe.
Entropy = randomness, disorder
Some energy is converted to thermal energy and lost as heat
If entropy is high: Spontaneous process, energetically favourable
If entropy lower: non-spontaneous process, occurs only if energy is supplied
what is Gibbs free energy
Gibbs free energy: ∆G = Gf - Gi
→ ∆G is negative if energy is lost
→ final state if more stable
∆G = ∆H - T∆S
H = enthalpy, S = entropy, T = absolute temperature in kelvin
what are Exergonic vs Endergonic reactions
If ∆G is negative: process is spontaneous → exergonic
If ∆G is positive: process is non-spontaneous → endergonic
Exergonic reaction = net release of free energy. Ex: respiration: C6H12O6 +6O2 → 6CO2 + 6H2O ∆G = -2840KJ
Endergonic reaction = net absorption of free energy. Ex: photosynthesis: 6CO2 + 6H2O → C6H12O6 + 6O2 ∆G = 2840 KJ
what are isolated systems
Isolated system:
- eventually equilibrium is reached
- no more work
- doesn’t happen in a living cell
what are Open systems
Open systems:
- Alive cells
- constant flow of materials in and out
- never in equilibrium
- never stops working
- more realistic, multi step system
what is ATP used for
Cells couple energy by using exergonic processes to drive endergonic processes.
How? by using ATP
ATP + H2O → ADP + Pi + energy
Used for chemical work, transport work, mechanical work
Regeneration of ATP
- Add P to ADP
- Energy comes from exergonic catabolic reactions
We use about 10 million ATP / second
what do Enzymes do
Without Enzymes something like turning sucrose into Glucose + Fructose takes years. With an enzyme, like Sucrase, it takes seconds.
Enzymes: Catalyst → speeds up reacting without being consumed.
what is activation energy
In an exergonic reaction a certain activation energy is necessary to get the reactions into a transition state, then they can be turned into the products.
The activation energy can be overcome with heat, but in a cell heat can denature proteins, or cause other reactions to occur at the same time. So that technique is not great.
how do enzymes affect Ea
Instead cells use enzymes. Enzymes lower the energy of activation while not affecting the ∆G
How do enzymes do this?
- Orientation
- Stretch substrate
- Active site = microenvironment (can have different pH or other factor)
- Amino acids of enzymes may participate
how do Enzymes and substrates react
Enzymes + substrate ← → Enzyme-substrate complex ← → Enzymes + products
Ex: Sucrase + sucrose + H2O ← → Sucrase-sucrose-H2O complex ← → Sucrase + Glucose + fructose
how do enzymes interact with substrate
Enzymes recognize its specific substrate based on 3D shape.
They perform induced fit, when the enzyme reshapes slightly to bind to the substrate.
Can do about 1000 substrates a second.
describe the 6 step catalytic cycle
Catalytic cycle
- Substrate enters active site; enzyme changes shape such that its active site enfolds the substrate (induced fit)
- Substrates are held in active site by weak interactions such as H-bonds and ionic bonds.
- Active site lowers Activation Energy and speeds up reaction.
- Substrate is converted to products
- Products are released
- Active site is available to new substrate molecules
what affects enzyme activity
Enzyme activity depends on temperature: increases at lower temp, decreases at higher temp, has an optimal temperature
It also depends on pH, they have an optimal pH, anything else lowers activity. Ex: Pepsin (stomach) = 2, Trypsin (intestine) = 8
how are enzymes regulated
Enzymes are regulated by gene expression, specific intracellular location of enzymes, and stabilized active/inactive forms.
what is allosteric regulation
Allosteric regulation is where an activator binds to a regulatory site (not an active site) to activate the enzyme.
how can an inhibiter regulate an enzyme
An inhibiter can bind to a non active site and turn the enzyme into a stabilized inactive form.
what is normal regulation of cellular metabolism, competitive inhibitors, and non competitive inhibitors
- Normal regulation of cellular metabolism
- Irreversible due to covalent bonds
- Reversible due to weak bonds
- Competitive inhibitors: bind to active site
- Non competitive inhibitors: don’t bind active site, but cause a shape change that reduces/stops enzyme activity.
Can be countered with more enzymes or substrates.
what is cooperatively
Cooperativity: when a substrate binds to one site of an enzyme that stabilizes it into an active form with multiple active site. Ex: hemoglobin
what is feedback inhibition
Feedback inhibition: when the product binds to the enzyme at the allosteric site, preventing further production. Ex: synthesis of amino acid isoleucine from threonine.
