Biology cha 8 Flashcards

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created 10 years ago by Veronica_Guzman
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Define catabolic pathways.

breakdown pathways" - Releases energy by breaking down complex molecules to simpler ones.


Define anabolic pathways.

Construct molecules from smaller units. Consume energy to build complicated molecules.


Explain the role of catabolic and anabolic pathways in the energy exchanges of cellular metabolism.

They are the "downhill" and "uphill" avenues of the metabolic map - energy released from the downhill reactions of catabolic pathways can be stored and then used to drive the uphill reactions of anabolic pathways.
*Catabolic releases energy - Anabolic consumes energy


Explain the first and second law of thermodynamics.

The first law, also known as Law of Conservation of Energy, states that energy cannot be created or destroyed in a chemical reaction. The second law of thermodynamics states that the entropy of any isolated system not in thermal equilibrium almost always increases.


Distinguish between exergonic and endergonic reactions i terms of free energy change.

Exergonic reaction proceeds with a net release of free energy and is spontaneous. Endergonic reactions are nonspontaneous; they must absorb free energy from the surroundings


Explain how feedback inhibition prevents a cell from wasting chemical resources

The product of a pathway acts as an allosteric inhibitor of an enzyme early in the pathway


ATP (adenosine triphosphate)

Consists of nitrogenous base adenine bonded to the sugar ribose, which is connected to a chain of three phosphate groups.


Distinguish between kinetic and potential energy

Potential energy is stored energy; kinetic energy is energy in motion that is doing work.


Distinguish between an isolated and an open system. Explain why an organism is considered an open system

An isolated system is a physical system without any external exchange. It's total energy and mass stay constant. An open system is a system which continuously interacts with its environment. The interaction can take the form of information, energy, or material transfers into or out of the system boundary, depending on the discipline which defines the concept (see below). An open system should be contrasted with the concept of an isolated system which exchanges neither energy, matter,nor information with its environment.


Explain the first and second laws of thermodynamics in your own words

First -- energy cannot be created or destroyed, but can be transformed from a more useful form to a less useful form, such as from wood to smoke and ashes
Second -- Energy moves towards entropy -- the potential energy of a system will be less than the initial energy, if there are no inputs of energy.


Explain why highly ordered living organisms do not violate the second law of thermodynamics

this increase in organization over time in no way violates the second law. The entropy of a particular system, such as an organism, may actually decrease, so long as the total entropy of the universe-the system plus its surroundings-increases. Thus, organisms are islands of low entropy in an increasingly random universe. The evolution of biological order is perfectly consistent with the laws of thermodynamics.


Write and define each component of the equation for free-energy change.

Gibbs free energy equation determines if a chemical equation will be spontaneous or not. If ΔG comes out negative, it is spontaneous, if positive, it's not spontaneous. ΔH is change in enthalpy, or energy in a system, and TΔS is difference in entropy multiplied by temperature, and entropy is the energy that is not used for work and accumulates as waste heat. So if difference in enthalpy is greater than difference in entropy times temperature, that means that energy was added to the system, and if difference in enthalpy is less than difference in temperature times difference in entropy, that means that energy left the system.


Distinguish between exergonic and endergonic reactions in terms of free energy change

In an exergonic reaction, energy leaves the system and the reaction is spontaneous, ΔG is negative. In an endergonic reaction, ΔG is positive -- energy was added to the system and it is not spontaneous. If ΔG is zero, the equation is in equilibrium


Explain why metabolic disequilibrium is one of the defining features of life

When a cell reaches metabolic equilibrium, it can no longer do cellular work. When it reaches equilibrium, it is dead; free energy equals 0; no work is being made


List the three main kinds of cellular work. Explain in general terms how cells obtain the energy to do cellular work

Chemical work: the pushing of endergonic reactions
- Transport work: the pumping of substances across membranes against the direction of spontaneous movement.
- Mechanical work: the contraction of muscle cells and the movement of chromosomes during cellular reproduction.
Cells manage their energy resources to do this work through energy coupling, the use of an exergonic process to drive an endergonic one.


Describe the structure of ATP and identify the major class of macromolecules to which ATP belongs

ATP contains the sugar ribose, with the nitrogenous base adenine and a chain of three phosphate groups bonded to it. ATP is also one of the nucleoside triphosphates used to make RNA. macro=nucleotide


Explain how ATP performs cellular work

In this role, ATP transports chemical energy within cells for metabolism. It is produced as an energy source during the processes of photosynthesis and cellular respiration and consumed by many enzymes and a multitude of cellular processes including biosynthetic reactions, motility and cell division.


Describe the function of enzymes in biological systems

An enzyme acts as a catalyst, which speeds up reactions. Enzymes are proteins in biological systems used to regulate the metabolism.


Explain why an investment of activation energy is necessary to initiate a spontaneous reaction

Molecules are stable. In order to be reactive, they must be unstable. Therefore, energy must be added to molecule in order for them to reach the transition state where their bonds can be broken. The bonds break only when the molecules have absorbed enough energy to be unstable.


Explain how enzyme structure determines enzyme specificity

its like a lock and key mechanism where the substrate (this substance the enzyme acts on) is the lock and the enzyme is the key; so only the enzymes with the structure that fits perfectly into the substrate can act on the substrate; hence specific enzymes act on specific substrates.


Explain the induced-fit model of enzyme function

A model for enzyme-substrate interaction to describe that only the proper substrate is capable of inducing the proper alignment of the active site that will enable the enzyme to perform its catalytic function. It suggests that the active site continues to change until the substrate is completely bound to it, at which point the final shape and charge is determined.


Describe the mechanisms by which enzymes lower activation energy

enzyme molecule holds one of the reactants in an orientation appropriate for successful collision. The other reactant molecule approaches, and most collisions result in a reaction.


Explain how substrate concentration affects the rate of an enzyme-catalyzed reaction

As the concentration of substrate increases, the rate of reaction also increases until the point saturation occurs. It means as you increase the concentration, rate keeps increasing and then one point comes when the maximum rate is achieved and there is no free enzyme to bind with substrate and all the active sites of enzyme are bound to the substrate. So after that point, increasing the concentration wont have any effect.


Explain how temperature, pH, cofactors, and enzyme inhibitors can affect enzyme activity.

Temperature affects enzyme activity because enzymes are made of proteins and as the temperature raises, the protein's molecular structure will be more and more unstable until it denatures and breaks apart. The pH works essentially the same where the enzyme will denature if it is in too acidic or too basic of an environment. Cofactors are molecules that will fit into the active site of an enzyme and active/deactivate. Enzyme inhibitors are little molecules that will fit into an enzyme and prevent the cofactor from reaching it and activating it.


Describe how allosteric regulators may inhibit or stimulate the activity of an enzyme

allosteric regulators, such as the inhibitors and the activators, respectfully stabilizes the inactive form of the enzyme's active site and stabilizes the active forms of the functional active sites.


Explain how the binding of oxygen to hemoglobin illustrates cooperativity

the cooperative binding of oxygen by hemoglobin enables it to deliver 1.7 times as much oxygen as it would if the sites were independent. The homotropic regulation of hemoglobin by its ligand oxygen dramatically increases its physiological oxygen-carrying capacity


Explain how feedback inhibition prevents a cell from wasting chemical resources

By synthesizing more product than is necessary


Describe how localization of enzymes within a cell may help order metabolism

The cell is compartmentalized: The organization of cellular structures helps bring order to metabolic pathways; A team of enzymes for several steps of a metabolic pathway may be assembled as a multienzyme complex;The product from the first reaction becomes the substrate for an adjacent enzyme in the complex until the final product is released; Some enzymes and enzyme complexes have fixed locations within the cells as structural components of particular membranes; Others are confined within membrane-enclosed eukaryotic organelles; Metabolism, the intersecting set of chemical pathways characteristic of life, is a choreographed interplay of thousands of different kinds of cellular molecules.