Bio Exam Study Part 2

Front 1

What is necessary for cellular respiration but not necessary for fermentation?

Back 1

Oxygen.

Front 2

What are two common forms of fermentation? Describe each.

Back 2

Two common types of fermentation are alcohol fermentation and lactic acid fermentation. In alcohol fermentation, pyruvate gives off carbon dioxide and is converted to ethyl alcohol (ethanol) in a two-step process. In lactic acid fermentation, pyruvate is converted to lactate (lactic acid). The figure below depicts both types.

Front 3

adenosine triphosphate (ATP)

Back 3

a major source of chemical energy for chemical work.

Front 4

bioenergetics:

Back 4

the area of thermodynamics that deals specifically with the energetic reactions that occur in an organism

Front 5

chemical work:

Back 5

non-spontaneous reactions between molecules

Front 6

endergonic reaction:

Back 6

refers to the change in free energy when energy enters a system

Front 7

endothermic reaction

Back 7

has a positive delta H and will absorb heat

Front 8

energy

Back 8

that which can or does move matter (i.e., the capacity for doing work)

Front 9

energy coupling:

Back 9

the use of an exergonic (energy-releasing) process to drive an endergonic (energy-requiring) process

Front 10

enthalpy (H):

Back 10

he total energy in a system

Front 11

entropy (S):

Back 11

disorder

Front 12

exergonic reaction:

Back 12

refers to the change in free energy when energy leaves a system

Front 13

exothermic reaction:

Back 13

has a negative delta H and will release heat

Front 14

free energy (G):

Back 14

the energy available (or required) to do work in a given system

Front 15

kinetic energy:

Back 15

refers to energy that is associated with moving matter

Front 16

mechanical work:

Back 16

work such as contracting muscle cells; the amount of energy transferred by force.

Front 17

metabolism:

Back 17

all of the chemical reactions that occur in an organism

Front 18

non-spontaneous reaction:

Back 18

a reaction which has a positive delta G

Front 19

potential energy

Back 19

refers to energy that is stored

Front 20

spontaneous reaction:

Back 20

a reaction which has a negative delta G

Front 21

system:

Back 21

any collection of matter under thermodynamic scrutiny

Front 22

thermodynamics:

Back 22

the physics of energy transformations that occur in a collection of matter

Front 23

transport work:

Back 23

transporting substances across a cell membrane

Front 24

work:

Back 24

the act of moving matter

Front 25

What is one of the major characteristics of life pertinent to this tutorial?

Back 25

One of the major characteristics of a living organism is that it can obtain and process energy.

Front 26

What is metabolism? Review anabolic and catabolic reactions and relate them to metabolism in living organisms.

Back 26

Metabolism refers to all of the chemical reactions that occur in an organism. Metabolic reactions can be subdivided into those that result in the formation of molecules (anabolic) versus those that result in the breakdown of molecules (catabolic).

Front 27

Name some processes done by living organisms which classify as anabolic reactions. Name some which classify as catabolic reactions.

Back 27

During photosynthesis, photoautotrophs (e.g., land plants) convert the energy found in sunlight into chemical energy via a series of anabolic reactions that result in starch being formed and stored within the plant. Chemoheterotrophs (e.g., humans) eat starch and break it down via a series of catabolic reactions to obtain the stored chemical energy.

Front 28

What is energy? Name and describe two types of energy. Give examples which compare the two.

Back 28

Energy refers to that which can or does move matter (i.e., the capacity for doing work). Let's consider two forms of energy. Kinetic energy refers to energy that is associated with moving matter. Potential energy refers to energy that is stored. The Hoover Dam on the Colorado River (shown here) blocks the normal flow of water and stores potential energy behind its walls. When released, the kinetic energy of the swiftly flowing water is harnessed to provide electricity for 1.3 million people a year. There are many other possible examples.

Front 29

Discuss how temperature relates to energy. What is heat? What is cold? What do we actually feel when something is hot or cold?

Back 29

The temperature of an object is a reflection of the kinetic energy of its atoms or molecules. Fast molecules = high kinetic energy = high temperature. Boiling water has a much higher temperature (and higher kinetic energy) than ice. Our bodies sense the kinetic energy of the molecules.

Front 30

Name some molecules in which humans and other living organism store energy.

Back 30

Carbohydrates, fats, proteins (though these are broken down by the body less often).

Front 31

Describe what chemical bonds do, and how they are structured. What are the necessary components of a chemical bond? What is the key part of a chemical bond, and also one of the key components of metabolic reactions?

Back 31

Chemical bonds hold atoms together and these bonds form as a result of electron behavior (either directly or indirectly). Electrons have mass and hence, their movement requires energy. In addition, electrons contain varying amounts of potential energy. Without electrons, chemical bonds could not exist, nor could many metabolic reactions.

Front 32

Does it take energy to create chemical bonds? What about breaking bonds?

Back 32

No, energy is released when bonds are formed. However, it takes energy to break chemical bonds.

Front 33

Differentiate between a Calorie and a calorie.

Back 33

1 Calorie = 1,000 calories, or 1 kcal = 1 Calorie.

Front 34

What is the study of thermodynamics? How is it studied in life? What is a system in biological and non-biological terms?

Back 34

Thermodynamics is the physics of energy transformations that occur in a collection of matter (formally, any collection of matter under thermodynamic scrutiny is defined as a "system"). Bioenergetics is the area of thermodynamics that deals specifically with the energetic reactions that occur in an organism; energetically, an organism is a "system." (FYI: collections of organisms and abiotic components can also be systems, i.e. “ecosystems.”)

Front 35

What are the laws of thermodynamics? Explain why energy is actually “converted” instead of made.

Back 35

The first law of thermodynamics states that energy is neither created nor destroyed. In other words, the amount of energy in the universe is constant. This first law could be considered "bookkeeping." It states that the energy used and released in any reaction must be balanced. The second law of thermodynamics deals with the ordering of matter, and states that all energy-affected matter in the universe is becoming random. Energy can only be “converted” instead of made because there is only a set about of energy in the universe, as stated by the first law. If the amount of energy in the universe is constant, then creating more energy would change the amount of energy in the universe.

Front 36

What is the concept of entropy? Explain how it relates to the second law of thermodynamics.

Back 36

The second law of thermodynamics states that all energy-affected matter in the universe is becoming more and more random—in other words, it is increasing in entropy

Front 37

What is required for order? How can everything be moving towards greater randomness, yet life still be very ordered?

Back 37

Energy input is required to create order. Systems can become ordered as long as they are "open" to the universe. Life exists as a system that is open to the universe and ultimately, the energy that organisms obtain is used, in a sense, to reverse entropic change.

Front 38

Descibe—in thermodynamic terms—why someone can starve to death.

Back 38

If you stop eating you will die because there is no input of energy from outside your body (i.e., your system) to reverse the natural tendency of matter to disorder.

Front 39

How does entropy change with temperature? Think about the state of matter at different temperatures and the order of that matter.

Back 39

The entropic state of a given system is proportional to temperature. At absolute zero (in degrees Kelvin), the entropic state of any system is zero. (Right now, science has not yet been able to achieve a state of zero disorder i.e. 0 degrees Kelvin.)

Front 40

What is free energy? How is work done by a system? How is work done on a system?

Back 40

Free energy (G) is the energy available (or required) to do work in a given system. If a given system releases free energy, then it can do work. Conversely, if it absorbs free energy, then work can be done on it.

Front 41

What are endergonic and exergonic reactions? Is a spontaneous reaction endergonic or exergonic?

Back 41

The change in free energy (delta G) is endergonic if energy enters the system, and exergonic if it leaves the system. Moreover, an exergonic reaction is unstable, has a negative delta G and is therefore, a spontaneous reaction.

Front 42

Name one very important reason why energy transfer is not 100% efficient?

Back 42

Friction exists, and energy can thus be lost to heat.

Front 43

How do free energy changes relate to life? Describe briefly, on a molecular level, how energy flows through a living organism. How does a release of free energy usually affect the entropy of a system, and why?

Back 43

The free energy changes (delta G) associated with life's metabolic energy involve the movement of matter. This free energy comes from a series of metabolic reactions that result in work being done at the molecular level (i.e., the movement of electrons, atoms, or molecules). Recall the relationship between free energy and stability; a given reaction (i.e., a system) that has the potential to do a lot of work (i.e., release a lot of free energy) is inherently unstable; it typically has a low relative entropy and tends to change spontaneously to a more stable, disordered state.

Front 44

What is more likely to release free energy, a system with high entropy or a system with low entropy? Why?

Back 44

A system that has the potential release a lot of free energy is inherently unstable; therefore, it typically has a low relative entropy and tends to change spontaneously to a more stable, disordered state. A system with a lower entropy is more likely to release free energy.

Front 45

What is the difference between total energy and free energy? What is “total energy” of a system called, and how is it denoted in shorthand?

Back 45

Not all of the energy in a system (i.e. total energy) is energy that is available to do work (i.e. free energy). Enthalpy (H) is the total energy in a system.

Front 46

What terms are used to describe and measure a change in enthalpy? What reactions are associated with the changes?

Back 46

If enthalpy is negative, then some energy (typically heat) will leave the system. If this value is positive, then energy will enter the system (typically heat will be absorbed from outside). An exothermic reaction has a negative delta H and will release heat, whereas an endothermic reaction has a positive delta H and will absorb heat.

Front 47

How is a change in entropy expressed? What abbreviations are used?

Back 47

The entropic state of the system is denoted S. If the reaction results in an increase in entropy, then this value is positive. If the reaction decreases in entropy, then this value is negative.

Front 48

Write out the free energy equation. Describe each term within the free energy equation. By re-ordering the equation, discuss how each value is related or changed by another.

Back 48

delta G = delta H - T(delta S)

change in free energy = change in total energy – temperature times change in randomness

This equation reveals that not all of the energy stored in a system is available for work; free energy is less than the total energy of a system. The free energy concept can be used to determine whether a specific process or reaction will occur spontaneously.

A change in total energy = the change in free energy + the temp * change in randomness

Temperature = (change in total energy – change in free energy) / change in randomness

A change in randomness = (change in total energy – change in free energy)/ temperature

Front 49

What does a more negative value of ΔG mean in the free energy equation? What does a more positive value mean?

Back 49

The more negative the value of delta G, the more free energy released by the reaction, and the more work that can be done. Conversely, as delta G becomes progressively more positive, the energy required for the reaction to proceed also increases.

Front 50

What is the major source of stored energy in cells? Describe or draw this molecule, and describe how it stores this energy (i.e. what features of the molecule make it “easy” to release energy”)

Back 50

A major source of chemical energy for this work is adenosine triphosphate (ATP). ATP is a 5-carbon sugar (ribose) attached to a nitrogenous base (i.e., adenine; recall our discussion of the nucleotides DNA and RNA) and a group of three phosphates. The three phosphates are the triphosphate component of adenosine triphosphate, and they are very unstable. This instability is due to the three negative charges that induce an intramolecular strain in one area of the molecule. Most reactions that involve ATP depend on the hydrolysis of the third phosphate to liberate the potential energy that can be used to do work.

Front 51

Write out the equation for the hydrolysis of ATP. Draw the products of the hydrolysis reaction. How much energy is usually released by the hydrolysis of ATP? Is this a catabolic reaction or an anabolic reaction? An exergonic or endergonic reaction?

Back 51

The hydrolysis of ATP is an exergonic reaction (which is a catabolic reaction). The hydrolysis of ATP releases 7.3 kilocalories per mole.

Front 52

What is energy coupling and why is ATP an integral part of energy coupling in living organisms? Can you think of any examples of energy coupling in other systems (even non-living ones)?

Back 52

he use of an exergonic (energy-releasing) process to drive an endergonic (energy-requiring) process is called energy coupling. In many living organisms, ATP undergoes hydrolysis (an exergonic reaction) to create enough energy to drive endergonic reactions, such as protein building. There are many examples of energy-coupled systems, including gasoline-fueled vehicles, etc.

Front 53

What are the three main types of work cells do? How is ATP involved?

Back 53

A cell does three types of work: mechanical (e.g., contracting muscle cells), transport (e.g., moving substances across the cell membrane), and chemical (e.g., non-spontaneous reactions between molecules; discussed in the next section). A major source of chemical energy for this work is adenosine triphosphate (ATP), which fuels this work in a energy coupling process.

Front 54

proton:

Back 54

positively charged hydrogen atoms (H+)