Ch. 6 Metabolism: Energy & Enzymes

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Biology Fundamentals 1308

Why is energy not recyclabe?

One energy is released as heat it cannot be recaptured.
-when as it transforms it will eventally become heat, which is unusable. Also b/c the 1st law "energy can neither be created nor destroyed, it can only be transformed form one form to the other."

If cells become more organized, what has become less organized in the universe in order to fulfill the second law of thermodynamics?

The energy from the sun which is lost as heat

Kinetic Energy

Energy of motion; all moving objects have kinetic energy
e.g. a ball rolling down a hill

Potential Energy

Stored Energy- its capacity to accomplish work is not being used a the moment

Mechanical Energy

A type of Kinetic Energy such as walking or running
e.g. a rolling ball and a contractin muscle are forms of mechanical energy.

Chemical Energy

Energy associated with the interaction of atoms in a molecule.
e.g. Food is chemical energy that contains poteintial energy.

First Law of Theromodyamics (Also called the law of conservation of energy)

Energy cannot be created or destroyed; it can change from one form to another.
e.g. This law implies that the total amoutn of energy in a closed system remains constant. Energy neither enters nor leaves a closed system, energy can change.

Second Law of Thermodyamics

Energy cannot be changed from one form into another without a loss of usable energy.
e.g. This law implies the amount of available energy in a closed system is decreasing constantly. Energy becomes unavaliable for use by living things because of entropy.

Entropy

Is a measure of disorganization.

Why dose energy flow through an ecosystem?

We say energy flows b/c it moves from one level to the next and some of this energy is lost as heat.

State the two laws of Thermodynamics and how these laws apply to cells

-two energy laws are basic to understanding energy-use patterns in the cells and ecosystem.
-The 1st law states that energy cannot be crated or destroyed but can only be changed form one form to another.
-The 2ed law states that one useable form of energy cannot be converted into another form without loss of usable energy. Therefore every energy transformation makes the universe less organized.

The fact that energy transformation is never 100% efficient is stated in the ...... law of thermodyamics.

Second law of thermodyamics
-As a result ot the 2nd law, no process requiring a converson of energy is ever 100% efficient. Much of the energy is lost in the form of heat.

Which has more potiental energy: Gluose or CO2 and H2O?

Glucose
-Energy within an atom lies an arragement of its molecules; glucose has more energy thatn its break down componets, carbon dioxide and water.

Entropy is a termed used to indicate the level of ......?

Disorganization
-entropy is hte measureof randomness or disorder. Entropy is used to indicate the realative amount of disorganization.

Metabolism

All of the chemical changes that occur within a cell

Catabolism

Metabolic process that breaks down large molecules into smaller ones. "Breaking down of molecules"

Anabolism

Metabloic process by which larger molecules are synthesized from smaller ones. " building up(synthesis) of molecules."

Reactants

Substance that participates in a reaction
e.g. A+B-->C+D ; A and B are the reactants

Products

Substance that forms as a result of a reaction.
e.g. A+B--> C+D; C and D are the products

Free Energy

Energy in a system that is capable of performing work
- Change in free energy is noted as ( G), a neg. ( G) means that products have less free energy than reactants, the reaction occurs spontaneously

Exergoinc Reactions

Chemical reaction that release energy; opposite of endergoinc reaction
- have a negative ( G) and energy is released
e.g. Cellular respiration

Endergonic Reactions

Chemical reaction that requires an input of energy
-have a negative ( G), products have more energy than reactants, such as reactions can only occur with an input of energy.
e.g. protein synthesis, nerve impulse conduction, muscle contraction.

ATP (adenosine triphosphate)

Energy for cells; Necleotide with three phosphate groups. The breakdwon of ATP into ADP +P makes energy available for energy-requiring processes in cells.

ADP ( adenosine diphosphate)

Nucleotide with two phosphate groups that can accept another phosphate group and become ATP

Structure of ATP

-ATP is a nucleotide composed of the base adenine and the 5-carbon sugar ribose adn three phosphate groups. Held together by high energy bonds

Coupled Reactions

Reactions that occur simultaneously; one is exergonic reaction that releases energy, and the other is an endergonic reaction that reqires an input of energy in order to occur.
-energy is released by an exergonic reation is used to drive an endergonic reaction.
-ATP breakdown is often coupled to cells reactions that require inergy.
-when ATP breaks sown to drive reactions, some energy is lost aas heat; overall reaction become exergonic.
e.g. Muscle contraction occurs only when it is coupled to ATP breakdown.

Function of ATP

Chemical work, Transport work and Mechanical work

Chemical Work

ATP supplies energy to synthesize macromolecules that make up the cell.

Transport Work

ATP supplies energy to pump substances across the plama membrane

Mechanical Work

ATP supplies energy needed to perform muscles contractions, propel cilia, etc.

Determine wheher a chemical reaction will go foward as written

Free energy is the amount of energy avaliable. The change in free energy after a reaction occurs is calculated by subracting the free energy content of the reactants from the products. A negative result means that the product will have less free energy than the reactants, and the reaction will go foward.

Describe how ATP is used in metabolism

ATP, a crucial chemical in human metabolism that has been called "chemical currency" because the cells use it as a direct source of energy.

Is an anabolic reaction likely to be exergonic or endergonic? To have a positive or negative value for ( G)?

Endergonic

How is ATP like currency (money)?

It is avaliable as small packets of energy that are spent to perform work.

ATP is a

Nucleotide

If the reaction A + B --> C + D + energy occurs in a cell....

- The reaction is exergonic
-an enzyme could still speed the reaction
-ATP is not needed to make the reaction go
-A and B are reactants; C and D are products

Metabolic pathway

Series of linked reactions, beginning with a particular reactant and terminating with an end product.
-reactions in cells are orderly
-this is an orderly sequences of linked reactions; each step is catalzed bya a specific enzyme.

Enzyme

Organic catalyst, usually a protein, that speeds up a reaction in cells due to its particular shape
-speed up the chemical reaction without the enzyme being changed.
-they catalyze chemical reactions by lowering the activation energy.

Substrates

Reacant in a reaction controlled by an enzyme
-reacant for an enzymatic reaction

Energy of activation (Ea)

Energy that must be added to cause molecules to react with one another

Active Site

Region on the surface of an enzyme where the substrate binds and where the reaction occurs

Induced fit Model

Change in the shape of an enzyme's active site that enhances the fit between the active site and its substrate(s).

What is the advantages of having a particular chemical reaction (such as the breakdown of sugar) proceed via a metabolic pathway instead of in just one reaction?

So that the energy can be captured and used to perform work instead of being lost as heat, so the reaction can be regulated by the cells

Why is the induced fit model more accurate for enzyme substate interaction than the lock-and-key model?

The enzyme actually dose not change shape slightly when the substrate binds.

List the componets of a metabolic pathway,and state why such pathways are useful

-Catabolic pathways break down complex molecules to make energy available for biological work. Cellular respiration is an example of a catabolic process.
-Anabolic pathways build complex molecules from simpler components. Protein synthesis is an example of an anabolic process.
-Different pathways interact with one another to control the rate at which they operate.

Describe how an enzyme binds its substate

When a substrate binds to enzyme, active site undergoes a slight change in shape that facilitates the reaction----this is called the induced-fit model.

Explain how an enzyme increases the rate of a reaction, and list factors that affect enzyme speed.

Catalysts are substances that speed up chemical reactions. Organic catalysts are called enzymes.
-Temperature and pH

Name 2 facts about biochemical pathways

-they are very well organized and structured
-they convert an initial substrate via a series of steps into an end product

Consider the biochemical pathway: A - E1 -> B - E2 -> C
Enzyme 1 can utilize

only A as substrate.

Consider the biochemical pathway: A - E1 -> B - E2 -> C
If Enzyme 2 is inactive, which of the following compounds will accumulate?

B only

In a biochemical pathway, the product of the first reaction becomes the substrate in the second reaction. True/False

True

All biochemical pathways have the same number of enzymatic reactions? T/F

False

Sometimes a particular reactant(s) produces more than one type of product(s) when?

a. Presence or absence of an enzyme determines which reaction takes place
b. if reactants can form more than one product, enzymes present determine product produced.

Denatured (denaturation)

Loss of normal shape by an enzyme so that it no longer fucntions.

Enzyme inhibition

Means by which cells regulate enzyme activity; may be competitive or noncompetitive.

Cofactors

Nonprotein adjuct required by an enzyme in order to function

Coenzymes

Nonprotein organic molecule that aids the action of the enzyme to which it is loosely bound

Vitamins

Essential organic reqirement in the diet, needed in small amounts. Vitamins are often part of coenzymes.

What factors could denature an enzyme and cause it to cease functioning?

Heat and pH

What is the advantage to inhibiting a metabolic pathway by feedback inhibition?

The pathway is inhibited at the very first step so energy is not wasted going through the remaining steps.

Enzymes are

Proteins

What binds to the active site of an enzyme?

substrate

What correctly represents the mechanism of enzyme function?

E + S -> E-S -> E-P -> E + P

An enzyme can only bind one reactant at a time. T/F

False

An enzyme speeds up a chemical reaction in the cell, but can only be used once. T/F

False

Which of the following is an example of potential energy?

A big piece of chocolate cake
-undigested and a source of energy not currently being broken down or in motion.

Reactions which require an input of energy ___________.

are endergonic

In the reaction A + B --> C + D, the reactant(s) is/are ______________.

A and B

Enzymes _____.

bring together specific molecules and causes them to react with each other

Cells that do a lot of active transport have many _____.

mitochondria

The coenzyme ____ accepts electrons during cellular respiration.

NAD+
-NAD+ serves as an electron carrier during cell respiration.

During cellular respiration, glucose loses hydrogen ions so it is _____.

oxidized

The speed of a reaction that involves an enzyme increases as ______.

substrate concentration increases
-as the substrate concentration increases, this also increases the opportunity for the enzyme to create enzyme substrate complexes.

A very high fever (105 degrees F) is dangerous because enzymes can become _________.

denatured
-denaturation is a probable side effect of high fevers as proteins are broken down.

The nitrogen base in ATP is _____________.

adenosine
-adenosine is the nucleotide which forms adenosine triphosphate.

Energy is constantly supplied to ecosystems by _____.

the Sun
-the primary source of energy for all living systems

The sodium-potassium pump, associated with muscle and nerve cells, moves ______ to the outside of the cell and ______ to the inside of the cell.

Na+, K+
-sodium moves out of the cell while potassium moves inward.

Without __________ organisms, life as we know it could not exist.

photosynthetic
-photosynthetic organisms supply energy for primary exergonic reactions to take place

Electron transport systems used to make ATP are located in the _____.

mitochondria
-electron transport systems are found in mitochondria in the cristae.

ATP production in the electron transport system depends on _____.

-the establishment of an electrochemical gradient
- carrier proteins
-ATP synthase

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