Chapter 3 Flashcards
What are the basic requirement of a cell?
- A system to encode/transmit information
- A membrane to separate inside from out
- ENERGY
What is energy?
The capacity to do work to be transferred as heat or the ability to promote change.
Takes energy to move sucrose or proteins across a membrane, or to replicate DNA, and many, many other cellular processes.
What are the two types of energy?
Kinetic and potential
What is kinetic energy?
The energy of motion
· Ocean waves, falling rocks, moving hockey puck
· Electricity (flow of electrons)
· Light (photons)
What is potential energy?
- Stored energy
· Object, because of its position (boulder at the top of a hill)
· Molecule because of its structure (electrons of chemical bonds)
Can energy be converted readily from one form to another?
Yes
- Example: chemical energy to electrical energy
Can energy be measured or weighed directly?
No
We can detect it through its ability to do work.
What are the different types of energy?
Heat, chemical, electrical, mechanical, and electromagnetic.
What is an example of energy conversions?
Chemical energy from the battery is converted to electrical energy that passes into a lightbulb, which is transformed into light energy and heat energy.
Photosynthesis, in which light energy (a form of kinetic energy) is converted into chemical energy in the form of complex sugars and other organic molecules - - which are forms of potential energy
What are the energy levels of the electrons of an atom?
Atomic nucleus:
first energy level (lowest)
second energy level
third energy level Highest)
What happens when an electron gains energy? Loses energy?
Moves to the highest energy level that is farther away from the nucleus
Moves to a lower energy level closer to the nucleus.
Electrons further away from the nucleus possess more…
Potential energy
What are thermodynamics?
Study of energy and its transformations
What types of systems are included in thermodynamics?
Isolated system
Closed system
Open system
System?
The object being studied
Surroundings?
Everything outside the system
What is an isolated system?
Does not exchange matter or energy with its surroundings
Entire universe; insulated thermos
What is a closed system?
Exchanges energy but does not matter with its surroundings
Saucepan with lid heating on the stove, Earth
What is an open system?
Exchanges energy and matter with surroundings are the most important in biology
An ocean, a cell/organism
What is the First Law of Thermodynamics?
Energy can be transferred or transformed from one form into another but it cannot be created or destroyed (Conservation of Energy)
▪ When energy changes form, the total amount of energy remains constant
(cubes of energy can be converted into a line of energy)
What is entropy (S)?
· The tendency of energy to become dispersed or spread out
· Measure of disorder or randomness
· Most entropy increase occurs through transformations of energy into heat
· Energy tends to spread out—to become more dispersed over time.
· The thermodynamic measure of energy dispersal is called entropy.
· The tendency of energy to disperse (or spread out) is a very important principle of thermodynamics
· Entropy is the measure of how much energy and matter has moved from being localized to becoming more widely dispersed
What is low entropy (low disorder)?
Energy is not spread apart, compacted and remains close together
Glucose is highly ordered
What is high entropy (high disorder)?
Energy is spread out and dispersed.
Individual molecules between bonds (carbon dioxide and water)
What is the Second Law of Thermodynamics?
The transfer or transformation of energy increases the entropy of a system and its surroundings (entropy is always increasing).
▪ When energy changes form, the total amount of energy remains constant — However the energy available to do work decreases, and disorder increases. (some is lost ay entrophy, becomes unabilble to do work)
Entropy of a system and the surroundings will always increase
What does energy increase?
Entropy (energy often in form of heat)
How much energy in the gas is converted into mechanical energy?
Approximately 25%
How much energy in glucose is converted to do the work in muscle contractions?
40%
What is the reason why energy transformations are never 100% efficient?
Energy is defined as the capacity to do work; but some energy is lost to entropy, which is really energy that is NOT available to do work.
Does the concept of Entropy form the basis of the 2nd law of thermodynamics?
Yes
What are spontaneous reactions?
Occur without a constant input of energy
doesn’t necessarily imply quick; it means energetically favourable
Reactions tend to be spontaneous if products have less potential energy than reactants and when products are less ordered than reactants
As the term thermodynamics implies, what is a form of energy that is an important property of thermodynamic systems?
Heat
What does Total Energy/Thermal Energy/Entropy = ?
usable energy + unusable energy
Can a thermodynamic system be a cell, organelle, organism or membrane?
Yes
What is H = G + TS?
· Total Energy is called Enthalpy (H)
· Usable Energy is called Free Energy (G)
· Unusable Energy is Entropy (S)
· T = temperature
What are the two groups of reactions?
Exergonic and endergonic
What is an exergonic reaction?
Free energy is released, products have less free energy than reactants, and the reaction proceeds spontaneously
where ΔG is negative because products contain less free energy than reactants
- Spontaneous
- Releases energy
- Energy reactants > products
- ΔG negative (amount of energy released)
What is an endergonic reaction?
Free energy is gained from products that have more ee energy than reactants and the reaction is not spontaneous.
where ΔG is positive because products contain more free energy than reactants
- Non-spontaneous
- Requires input of energy
- Energy products > reactants
ΔG positive (amount of energy required)
What do both types of reactions require?
An initial input of energy called activation energy
Do molecules have stored energy in their chemical bonds (chemical potential energy)?
Yes
What do concentration gradients represent?
A form of stored potential energy
What do transformations (reactions, processes) result in?
Changes in enthalpy (ΔH)
What is diffusion across a membrane?
Driven by an increase in entropy and the energy associated with the molecules is spread out. Molecules will move spontaneously across a membrane from a region of high concentration to a region of lower concentration because the energy associated with the molecules becomes more dispersed.
(top to bottom>bottom to top)
What happens when the conversion of glucose 1-phosphate (blue) to glucose 6-phosphate (pink) courrs (notes)?
No matter what quantities of glucose 1-phosphate and glucose 6-phosphate are dissolved in water when equilibrium is attained, there will always be 95% glucose 6-phosphate and 5% glucose 1-phosphate. At equilibrium, the number of reactant molecules being converted to products equals the number of product molecules being converted back to reactants.
Energy relationships between catabolic and anabolic pathways
What do open systems do?
Bring in both energy and matter from surroundings and use them to maintain an ordered/organized state (low entropy) state. The release of heat and waste gases into the environment increases the entropy of the surroundings.
The flow of energy through the biosphere?
Living systems constantly bring in concentrated forms of energy and use them to do the work required to maintain a highly organized state. Organisms give off heat and gases (high-entropy energy).
Open systems give off heat and waste byproducts, that are used to increase the entropy of surroundings.
What is photosynthesis? Cellular respiration?
Captures light energy and uses it to convert carbon dioxide into carbohydrates.
Cellular respiration breaks down carbohydrates and transforms the energy into ATP.
Photosynthesis uses the energy in sunlight to build sugar molecules from carbon dioxide and water, releasing oxygen as a by-product. The process of cellular respiration breaks down the products of photosynthesis and releases usable energy.
What is ATP hydrolysis?
Releases free energy that can be used as a source of energy for the cell.
- Exergonic
- Spontaneous reaction
- Releases energy (-ΔG)
ΔG = -7.3 kcal/mol
Chemical structure of ATP (adenosine triphosphate)
Clarify that the bonds are NOT actually “high energy phosphate bonds”; but that they are relatively unstable because of the overlapping negative charges, and that ADP and Pi are more stable.
What is included in the hydrolysis of the phosphate bonds?
The formation of new bonds in products results in the net release of free energy that can be used by a cell.
ATP: 3 phosphate group, sugar (ribose) and nucleic base (adenine)
Hydrolysis of Atp and Coupling reactions require enzymes
What is the ATP cycle?
Continuous breakdown and resynthesis of ATP
ATP is used in coupling reactions and is replenished. reactions replenishing ATP link ATP synthesis to catabolic reactions
Enzyme specificity?
Model of the enzyme hexokinase shows the catalysis of glucose with phosphate, forming glucose-6-phosphate. The glucose is represented by black (carbon) and red (oxygen) spheres, and the phosphate group is shown with the phosphorus atom (yellow sphere) bonded to four oxygens (red).
What is the activation energy?
The initial input of energy to start a reaction, even if it is spontaneous
EA: Initial energy investment required to start a reaction
Molecules that gain necessary activation energy occupy the transition state
What is the catalytic cycle of enzymes?
Shown is the enzyme β-galactosidase, which cleaves the sugar lactose to produce glucose and galactose.
- Bringing the reacting molecules into close proximity?
- Exposing the reactant molecules to altered environments that promote their interactions?
- Changing the shape of a substrate molecule
What occurs in the presence of excess substrate?
The rate of catalysis is proportional to the amount of enzyme
What is the relationship between enzyme activity and pH?
Changes in pH affect the charged groups in the amino acids of the enzyme
Effects of pH on enzyme activity. An enzyme typically has an optimal pH at which it is most active; at pH values above or below the optimum, the rate of enzyme activity drops off. At extreme pH values, the rate drops to zero.
What is competitive inhibition?
The inhibitor competes with the normal substrate for the active site
differ in how strongly they bind to the active site:
- reversible: weak
-Irreversible: strong, covalent bonds, highly toxic (cyanide)
The inhibition of enzyme activity by a competitive inhibitor can be overcome by increasing the amount of substrate relative to the inhibitor.
What is noncompetitive activator?
Allosteric activators convert an enzyme from the low to the high-affinity state
reversible
What is noncompetitive inhibition?
Inhibitor does not compete with the normal substrate for the active site but combines with sites elsewhere on enzyme
What is feedback inhibition?
The product of the enzyme-catalyzed pathway acts as a regulator of the reaction
Helps conserve cellular resources
The mechanism is allosteric regulation
Feedback inhibition in the pathway that produces isoleucine from threonine. If the product of the pathway, isoleucine, accumulates in excess, it slows or stops the pathway by acting as an allosteric inhibitor of the enzyme that catalyzes the first step in the pathway.
