Unit 3: Lecture 11

Define energy.

Define energy.

The capacity to cause change/ do work (e.g. chemical energy, thermal energy, mechanical energy)

Define potential energy.

The energy stored by matter as a result of its location or spatial arrangement (e.g. ATP, anything w/ a chemical bond, free energy); energy available for release in a chem rxn

Define kinetic energy.

Energy of motion (e.g. heat [thermal nrgy]); associated with random movement of atoms or molecules

What does all work carried out by living organisms involve?

The transformation of potential energy to kinetic energy

What is fuel?

Molecule that stores chemical energy in its bonds

What can all forms of energy be converted to?

Heat

The matchstick is converted from _______ energy to ________ energy when struck.

Chemical; thermal

Humans are an ______.

Open system- exchanging energy w/ environment

What is thermodynamics?

The study of energy transformations

What is the first law of thermodynamics?

Conservation of energy: Energy cannot be created or destroyed. It can only be converted from one form into another

The energy of the universe is _________.

Constant

What is energy most often measured as?

Lost "heat energy" = a calorimeter

What is the second law of thermodynamics?

-In all spontaneous processes, the total entropy increases

-In living organisms, energy transformation increase the entropy of the universe (it does not increase entropy of an organism)

Define entropy.

Disorder and chaos happens spontaneously

Why do energy transformations increase the entropy of the universe but not the organism?

Life increases order within the organism, but increases overall universal disorder b/c all energy transformations in the body (to create order) will produce waste AKA heat

Why can life not "break even?"

Anabolic rxns required to make 1 kg of your body requires 10 kg of food. 90% is "waste"

Why is heat considered waste?

It is rarely useful for performing work

Why do we eat?

We need energy

A burning candle converts _________ energy into __________ energy.

Chemical; heat

Define metabolism.

The sum of the chemical processes that occur in living organisms, resulting in growth, production of energy, elimination of waste, etc. (Catabolism+anabolism)

Define catabolism.

The process of breaking down large molecules to smaller components

Define anabolism.

The synthesis of new molecules from smaller components

What is an acronym to remember the parts of metabolism?

ABCD: Anabolism= Building Catabolism= Degradation

Outline a metabolic pathway for food.

Input: food (i.e. complex sugars)-> catabolic pathways (breaks down input)-> useful forms of energy + lost heat + building blocks (i.e. monosaccharides)-> anabolic pathway (uses useful forms of nrgy + building blocks to build)-> Output: essential molecules (i.e. glycogen, phospholipid bilayer)

Is "Sucrose + H2O -> Fructose + glucose" catabolic or anabolic?

Catabolic (b/c glucose is a monosaccharide; water is added [hydrolysis: polymer-> monomer])

What do enzymes do?

1. Maintain balance between catabolism and anabolism

2. Catalyze metabolic rxns and maintain homeostasis

3. Control chemical transformations

Describe characteristics of a metabolic pathway.

1. Begins w/ a specific molecule, ends with a product

2. Each step is catalyzed by a specific enzyme

3. Most metabolic pathways are similar between organisms

4. Pathways are compartmentalized in organelles (in eukaryotes)

Is energy a form of matter or molecule?

No, it is a measurement

What is free energy (G)?

Energy available for doing work in a cell; measures a system's instability, its tendency to change to a more stable state

What are exergonic reactions?

-Release free energy (nrgy output)

-Reactants have a lot of potential nrgy (& a lot of free nrgy)

-Products have a little potential nrgy

-Downhill, spontaneous

-△G is negative

-these processes can be harnessed to do cellular work

Where did the "energy" for exergonic reactions come from?

Bonds (broken)

What are exergonic reactions used for?

Cellular process

What are endergonic reactions?

-Require the input of free energy

-Reactants have a little potential energy

-Products have a lot of potential energy

-△G is positive

-uphill, nonspontaneous

What is a state of maximum stability?

Equilibrium

What happens to free energy in a spontaneous change?

Decreases

What is enthalpy?

The total heat content of a system

Exothermic vs. Endothermic

Exo: △H < 0 ; Endo: △H>0

The change in "free energy" (△G) is proportional to the change in...

Enthalpy (△H), entropy (△S), and temperature (in Kelvin):

△G = △H - T△S

What is the difference between catabolic and exergonic?

Catabolic: polymer->monomer; exergonic: refers to the energy transformation that occurs during a catabolic reaction

Cellular respiration is an __________ process.

Exergonic

Photosynthesis is an ___________ process.

Endergonic

Why is photosynthesis the process that it is?

-It uses energy-poor reactants (CO2 and H2O)

-Energy absorbed from sunlight

-Energy-rich sugar molecules are produced

What does energy coupling do?

Uses the energy released from exergonic reactions to drive endergonic reactions, typically using the energy stored in ATP

Can life be at equilibrium?

No, equilibrium is not compatible w/ life

Describe ATP synthesis in terms of endergonic and exergonic reactions.

Enters: energy from cellular respiration (exergonic)-> ATP (its synthesis is endergonic and its hydrolysis is exergonic)-> Exits: energy for cellular work (endergonic)-> ADP+P (ATP is hydrolyzed)

What are three main types of cellular work (cells that need energy)?

1. Chemical (e.g. endergonic rxns)

2. Mechanical (e.g. flagella for movement)

3. Transport (e.g. active transport)

What do exergonic reactions replace?

Ordered forms of matter w/ less ordered b/c chaos is created by breaking down a stable molecule

What does it mean to be a spontaneous process?

A process that can occur w/o outside intervention (i.e. w/o energy input)

What do catalysts do?

Speed up chemical reactions (endergonic & exergonic); increase rates w/o being altered or consumed by the rxn

What is the most common type of catalyst?

Enzymes (usually a protein); other types of catalyst: RNA or heat

How do reactants bind to substrates?

Reactants (substrates) bind to groove in the enzyme (active site)

What forms when an enzyme binds to its substrate?

Enzyme-substrate complex

What is induced fit?

Entry of the substrate induces the enzyme to change shape slightly, making the a snug fit (not the same as lock and key)

What does lock and key refer to?

Specificity; each enzyme recognizes a substrate (e.g. sucrase only recognizes sucrose)

What is the one purpose of an enzyme?

To lower the activation energy barrier

What must be overcome for a reaction to begin?

Activation energy barrier

What is activation energy?

The initial energy needed to start a reaction (spontaneously); the larger it is-> the longer the rxn takes; from the reactants to the top of the hurdle

Define transition state.

A temporary, unstable intermediate between substrate and product

Do enzymes affect the amount of free energy in reactants/ products?

No

How does the active site of an enzyme lower the activation energy barrier of a substrate?

1. Providing a favorable environment

2. Orienting molecules correctly

Do enzymes have a covalent or noncovalent interaction with the substrate?

Noncovalent interactions b/c it requires reversible bonds

Why are many cellular reactions considered unfavorable?

1. Use catalysts

2. Couple reactions

What are cofactors/coenzymes?

Helpers used by enzymes to turn it into an active molecule

What is the difference between cofactors and coenzymes?

Cofactors- smaller (e.g. ions); Coenzymes- larger

Can enzymes bind to more than one type of substrate?

No, usually the same type of substrate, not multiple types