BIOL 1117 Lecture Notes - Lecture 6: Web Of Science, Exergonic Reaction, Ionic Bonding
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Question 1
Plasma membranes are selectively permeable. This means that
| A. | glucose cannot enter the cell. | |
| B. | the plasma membrane allows some substances to enter or leave a cell more easily than others. | |
| C. | plasma membranes must be very thick. |
Question 2
Oxygen molecules O2 crosse a plasma membrane by
| A. | passive transport | |
| B. | osmosis | |
| C. | active transport |
Question 3
Facilitated diffusion across a biological membrane requires ________ and moves a substance ________ its concentration gradient.
| A. energy and channel proteins; against (up) | ||
| B. transport proteins that make channels ; down | ||
| C. energy ; down |
Question 4
When two aqueous solutions that differ in solute concentration are placed on either side of a semipermeable membrane and osmosis is allowed to take place, the water will
| A. move to the side with lower water concentration | ||
| B. | move to the side with higher water concentration | |
| C. | move to the side with lower solute concentration |
Question 5
Kinetic energy differs from chemical energy in that
| A. | chemical energy is a particular form of kinetic energy. | |
| B. | kinetic energy is the energy of a moving object, whereas chemical energy is the potential energy of molecules. | |
| C. | kinetic energy is stored energy that has the potential to do work, and chemical energy is the energy of movement. |
Question 6
When a cell uses chemical energy to perform work, it uses the energy released from a(n) ________ reaction to drive a(n) ________ reaction.
| A. | exergonic; endergonic | |
| B. | endergonic; exergonic | |
| C. | spontaneous; exergonic |
Question 7
When an enzyme catalyzes a reaction
| A. it raises the activation energy of the reaction. | ||
| B. it lowers the activation energy of the reaction. | ||
| C. it is used once and discarded. |
Question 8
Which of the following statements regarding enzyme function is false?
| A. An enzyme's function depends on its three-dimensional shape. | ||
| B. Enzymes are very specific for their substrates. | ||
| C. Enzymes are used up when they catalyze a chemical reaction so must be synthesized for each new chemical reaction |
As entropy increases there will be more useful energy to doâworkâ. True or false?
False. As entropy increases, there will generally be less usefulenergy to do work. We can think of entropy as usually being presentin the form of heat energy. Imagine a car motor, which attempts toturn chemical potential energy into kinetic energy (movement). Lessefficient motors will get hotter for the same amount of fuelconsumed. When you drive a car you hope that most of the fuelenergy is converted into kinetic energy and not lost as heat(entropy). The hotter the car (and thus the more entropy) the lessefficient the ability to do âworkâ (the moving of the vehicle). |
| True. As entropy increases, there will generally be more usefulenergy to do work. We can think of entropy as usually being presentin the form of heat energy. In most biological and mechanicalsystems it is heat energy which is captured to do useful 'work'.Heat energy, the random movement of molecules, and increases inentropy are central to doing useful work. |
Biological systems sometimes appear on the surface to break theSecond Law of Thermodynamics â by seemingly increasing the order inthe overall system. They donât. Why?
| a. Earth (and living things on it) are not a closed system. Thesun's constant input of energy in the form of photons is harnessedby living things to create internal order within themselves. Butwithout such a constant input of energy, most biological systems onearth would break down. |
| b. The Second Law tells us that no natural process can occurunless it is also associated with an increase in the entropy of theuniverse. A living organism (such as an animal or plant) brings inmatter and energy from its environment and uses this to creategreater order within its body: the processes of life. But it isimportant to keep in mind that all animals and plants are also partof a larger system of the environment around them. While creating asmall âpocketâ of order, the processes of life (metabolism,movement, etc..) releases heat into the environment â thusincreasing the entropy of the universe and following the2nd law. |
| c. Living things, by harnessing energy to create order (withinand around themselves) actually create a paradox in questionssurrounding the first and second laws of thermodynamics andseemingly violate many previously held assumptions. |
| d. Both a and b above are correct. |
When plants capture energy in the photons of sunlight andconvert that energy into the chemical bonds of organic molecules,are they creating new energy?
| No, the energy is being transferred from one form into another.But no new energy is being created. |
| No, the overall total energy is decreasing over time. |
| Yes, by capturing photons, the plants are creating newenergy. |
| Yes, by capturing photons, the plants are creating new energy -of a different wavelength. |
