BIO110 Chapter 5: Energy and Life

5.1 What is energy?

The ability to do work or bring about change.

5.1 What are the two states energy exists in?

Potential energy & kinetic energy.

5.1 What is potential energy?

Energy with the potential to do work; stored energy.

5.1 What is kinetic energy?

The energy of motion.

5.1 What is the most convenient way to measure energy?

As heat

5.1 Why is heat the most convenient way to measure energy?

All forms of energy can be converted to heat.

5.1 What is thermodynamics?

The study of energy or heat changes.

5.1 What are chemical reactions?

The making or breaking of chemical bonds.

5.2 What are the laws of thermodynamics?

Principles that govern energy changes involved with any activity by an organism.

5.2 What is the first law of thermodynamics?

Energy cannot be created or destroyed, but it can change from one state to another.

5.2 What does the first law of thermodynamics say about the total amount of energy in the universe?

It is constant.

5.2 What is heat energy?

A form of kinetic energy; a measure of the random motions of molecules.

5.2 How can heat energy be harnessed for work purposes?

There must be a heat gradient, which is a temperature difference between two areas that allows heat to flow.

5.2 Does all energy flow during energy conversions?

Some energy is dissipated as heat, which is later replaced by energy from the sun.

5.2 In short, what is the second law of thermodynamics?

Entropy increases.

5.2 What is the second law of thermodynamics?

The amount of disorder in the universe is increasing.

5.2 What is entropy?

A measure of the degree of disorder of a system; a measure of energy that’s become so randomized & uniform in a system that the energy is no longer available to do work.

5.2 What does increasing entropy mean in terms of energy conversion?

Potential energy is transforming into heat energy and becoming less available to do work.

5.3 What are reactants?

Also called substrates, they are the original molecules in a chemical reaction before the reaction occurs.

5.3 What are products?

The molecules in a chemical reaction that result after the reaction.

5.3 What are the two kinds of chemical reactions?

Endergonic & exergonic.

5.3 What is an endergonic reaction?

A reaction that requires energy input to proceed, resulting in products with more energy than the reactants; not spontaneous.

5.3 What is an exergonic reaction?

A reaction that releases energy, resulting in products with less energy than the reactants; usually spontaneous.

5.3 What is activation energy?

The extra energy required to destabilize existing chemical bonds & so initiate a chemical reaction.

5.3 How can reactions become more spontaneous?

If the activation energy is lowered.

5.3 What is catalysis?

The enzyme-mediated process in which the subunits of polymers are positioned so their bonds can undergo chemical reactions.

5.3 Do catalyzed reactions proceed faster or slower than non-catalyzed reactions?

Faster.

5.4 What are enzymes?

Proteins capable of speeding up specific chemical reactions by lowering the energy required to activate or start the process but that remains unaltered in the process; a biological catalyst.

5.4 What is a catalyst?

A general term for a substance that speeds up a specific chemical reaction by lowering the energy required to activate or start the reaction.

5.4 What is an active site?

The region of an enzyme surface to which a specific set of substrates binds, lowering the activation energy required for a particular chemical reaction and so facilitating it; the site on the surface of an enzyme that binds to a substrate.

5.4 What is a binding site?

The site on a substrate or reactant that binds to an enzyme.

5.4 Why is the non-rigid nature of enzymes important to their shape?

During the process of an enzyme & reactant binding, the enzyme’s shape will slightly change.

5.4 What does “induced fit” describe?

The binded enzyme and substrate’s tight fit together as a complex that occurs as a result of the enzyme’s change in shape.

5.4 Do enzymes lower or raise the activation energy of a particular reaction while bound to a reactant?

They lower it because they are catalysts.

5.4 What happens to enzymes after a chemical reaction?

They are unaffected and able to be reused.

5.4 What is a biochemical pathway?

A series or sequence of catalyzed chemical reactions.

5.4 What two conditional changes affect an enzyme’s shape?

Temperature & pH.

5.4 What happens to enzymes when their environmental temperature rises?

The shape-determining bonds within it become too weak to hold its peptide chains in proper position, leading to it denaturing.

5.4 What is the best temperature for enzymes in the human body?

37ºC, or near normal body temperature,

5.4 What happens to enzymes when the pH of their environment lowers?

The shape-determining polar interactions of enzymes become disrupted.

5.4 What pH range do most human enzymes function at?

6-8.

5.4 What is the pH of human blood?

7.4.

5.4 What is an exception to the preferred pH range of human body enzymes?

Stomach enzymes function in acidic ranges (ex: pepsin).

5.5 What are allosteric enzymes?

Enzymes affected by the binding of signal molecules.

5.5 What are signal molecules?

Molecules that transmit information between cells.

5.5 Where do signal molecules bind on an enzyme?

The allosteric site.

5.5 What are repressors?

Signal molecules (proteins) that regulate the transcription of mRNA from DNA by binding to the operator and so preventing RNA polymerase from attaching to the promoter.

5.5 What do repressors do to enzymes?

They bind and alter the shape of the enzyme’s active site so it cannot bind the substrate.

5.5 What are activators?

Signal molecules (regulatory proteins) that bind to DNA and make it more accessible for transcription.

5.5 What do activators do to enzymes?

Some enzymes require them to be able to bind the substrate.

5.5 How do some drugs/antibiotics work regarding enzymes?

They inhibit them. Some drugs and antibiotics work by mimicking substrates or binding to active sites, preventing enzyme activity.

5.6 What is ADP?

Adenosine triphosphate; a molecule made of ribose, adenine, and a triphosphate group; the chief energy currency of all cells.

5.6 What substance do cells focus all energy resources on manufacturing?

ATP, which is generated from ADP & phosphate).

5.6 How many kcal obtained from photosynthesis do cells need to use to form 1 mole of ATP?

7kcal.

5.6 Besides kcal obtained from photosynthesis, where else can cells get resources to form 1 mole of ATP?

From electrons stripped from foodstuffs.

5.6 What do cells use ATP for?

To drive endergonic reactions.

5.6 What happens when the endermost phosphate group is broken off an ATP molecule?

Energy is released and the reaction converts ATP to adenosine diphosphate (ADP).

5.6 What is the equation to get ADP?

ATP ← → ADP + P_i + energy.

5.6 What does P_i represent?

Inorganic phosphate.

5.6 What is the equation to get AMP?

2ADP → ATP + AMP.

5.6 What are coupled reactions?

When exergonic reactions are used to pay for the initiation of endergonic reactions.

5.6 Exergonic reactions require ___ energy, endergonic reactions require more, so reactions in the cell are usually coupled with the breaking of ___ in ATP.

1) activation 2) phosphate bonds.

5.6 Why is heat given off during the breakdown of ATP?

More energy than needed is released by its breakdown.

5.6 Does ATP flor or cycle?

It cycles in the cell with respect to its energy needs, continually from ADP & P_i through the ATP-ADP cycle.

5.6 What two complimentary processes convert energy from the sun and potential energy into ATP?

Photosynthesis & cellular respiration.

5.6 How does photosynthesis play a role in converting energy into ATP?

Some cells convert energy from the sun into ATP and then se it to make sugar (where the energy is stored in its potential form).

5.6 How does cellular respiration play a role in converting energy into ATP?

Cells break down potential energy in sugars and convert it into ATP.