biology - carnes ap bio · form inactive form oscillation ... enzyme 4 enzyme 2 enzyme 3 initial...

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

PowerPoint® Lecture Presentations for

Biology

Eighth Edition

Neil Campbell and Jane Reece

Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp

BIG IDEA IV Biological systems interact, and these systems and

their interactions possess complex properties.

Enduring Understanding 4.B

Competition and cooperation are

important aspects of biological systems.

Essential Knowledge 4.B.1

Interactions between molecules affect their structure and function.


Essential Knowledge 4.B.1: Interactions between molecules affect their structure and function.

• Learning Objectives:

– (4.17) The student is able to analyze data to

identify how molecular interactions affect

structure and function.


Change in the structure of a molecular system may result in a change of the function of the system.

• Consider the following molecular system:

– Signal transduction begins with the recognition of a chemical

messenger, a ligand, by a receptor protein.

– A receptor protein recognizes signal molecules, causing the

receptor protein to change shape, which initiates transduction.

– During transduction, the signal is converted to a cellular response

– whereby signaling cascades relay signals from receptors to cell

targets.

– This generally involves protein modifications or phosphorylation

cascades that lead to a cellular response within the cytosol or

nucleus.

• A change in the structure of any part of this particular molecular

system will change the function of the overall system.


The shape of enzymes, active sites and interaction with specific molecules are essential for basic functioning of the enzyme.

http://www.sumanasinc.com/webcontent/animations/content/enzymes/enzymes.html

http://www.sumanasinc.com/webcontent/animations/content/enzymes/enzymes.html

Progress of the reaction

Products

Reactants

∆G < O

Transition state

EA

D C

B A

D

D

C

C

B

B

A

A

Progress of the reaction

Products

Reactants

∆G is unaffected by enzyme

Course of reaction without enzyme

EA

without

enzyme EA with

enzyme is lower

Course of reaction with enzyme


Substrate Specificity of Enzymes

• The reactant that an enzyme acts on is called the

enzyme’s substrate.

• The enzyme binds to its substrate, forming an

enzyme-substrate complex.

• The active site is the region on the enzyme where

the substrate binds.

• Induced fit of a substrate brings chemical groups

of the active site into positions that enhance their

ability to catalyze the reaction.


Substrate

Active site

Enzyme Enzyme-substrate complex

(b) (a)

Substrates

Enzyme

Products are released.

Products

Substrates are converted to products.

Active site can lower EA and speed up a reaction.

Substrates held in active site by weak interactions, such as hydrogen bonds and ionic bonds.

Substrates enter active site; enzyme

changes shape such that its active site

enfolds the substrates (induced fit).

Active site is

available for two new

substrate molecules.

Enzyme-substrate complex

5

3

2

1

6

4


Cofactors and coenzymes affect enzyme function. http://highered.mcgraw-hill.com/sites/0070960526/student_view0/chapter6/animations.html

• Cofactors are small molecules that bind either

permanently or reversibly with enzymes and are

necessary for enzyme function.

• They may be inorganic, such as various metal ions, or

organic molecules called coenzymes.

• The interaction between enzymes and their cofactors

relates to a structural change that alters the activity

rate of the enzyme.

• The enzyme may only become active when all the

appropriate cofactors or coenzymes are present and

bind to the appropriate sites on the enzyme.

http://highered.mcgraw-hill.com/sites/0070960526/student_view0/chapter6/animations.html




Cofactors and Coenzymes



Other molecules and the environment in which the enzyme acts can enhance or inhibit enzyme activity.

• Molecules can bind reversibly or irreversibly to the

active or allosteric sites, changing the activity of

the enzyme.

• Enzyme inhibitors selectively disrupt the action of

enzymes.

– Competitive inhibitors compete with the

substrate for the active site of the enzyme.

– Noncompetitive inhibitors bind to a part of the

enzyme separate from the active site and change

the shape of the enzyme, thus impeding it’s action.

(b) Competitive Inhibition: Mimics the substrate and competes for the active site

(c) Noncompetitive Inhibition: Binds to the enzyme at a location away from the active site,

but alters the shape of the enzyme so that the active site is no longer fully functional.


Regulation of Enzyme Activity Helps Control Metabolism http://bcs.whfreeman.com/thelifewire/content/chp06/0602002.html

• Chemical chaos would result if a cell’s metabolic

pathways were not tightly regulated.

• A cell does this by switching on or off the genes

that encode specific enzymes or by regulating the

activity of enzymes.

• Allosteric regulation may either inhibit or

stimulate an enzyme’s activity.

• Allosteric regulation occurs when a regulatory

molecule binds to a protein at one site and affects

the protein’s function at another site.


http://bcs.whfreeman.com/thelifewire/content/chp06/0602002.html

(a) Allosteric activators and inhibitors

Inhibitor Non- functional active site

Stabilized inactive form

Inactive form

Oscillation

Activator

Active form Stabilized active form

Regulatory site (one of four)

Allosteric enzyme with four subunits

Active site (one of four)


• Cooperativity is a form of allosteric regulation that can

amplify enzyme activity.

• In cooperativity, binding by a substrate to one active site

stabilizes favorable conformational changes at all other

subunits.


Cooperativity

Intermediate C

Feedback inhibition

Isoleucine used up by cell

Enzyme 1 (threonine deaminase)

End product

(isoleucine)

Enzyme 5

Intermediate D

Intermediate B

Intermediate A

Enzyme 4

Enzyme 2

Enzyme 3

Initial substrate (threonine)

Threonine in active site

Active site available

Active site of enzyme 1 no longer binds threonine; pathway is switched off.

Isoleucine binds to allosteric site


The change in function of an enzyme can be interpreted from data regarding the concentrations of product of substrate as a function of time.

• These representations demonstrate the

relationship between an enzyme’s activity, the

disappearance of substrate, and/or the presence

of a competitive inhibitor.

• An enzyme’s activity can be affected by:

– General environmental factors, such as

temperature, salinity and pH.

– Chemicals that specifically influence the

enzyme.

– http://www.sumanasinc.com/webcontent/animations/content/protei

nstructure.html

http://www.sumanasinc.com/webcontent/animations/content/proteinstructure.html

http://www.sumanasinc.com/webcontent/animations/content/proteinstructure.html

Ra

te o

f re

ac

tio

n

Optimal temperature for enzyme of thermophilic

(heat-tolerant) bacteria

Optimal temperature for typical human enzyme

(a) Optimal temperature for two enzymes

(b) Optimal pH for two enzymes

Rate

of

rea

cti

on

Optimal pH for pepsin (stomach enzyme)

Optimal pH for trypsin (intestinal enzyme)

Temperature (ºC)

pH

5 4 3 2 1 0 6 7 8 9 10

0 20 40 80 60 100



Biology

Eighth Edition









Cooperative interactions within organisms promote

Efficiency in the use of energy and matter.


Essential Knowledge 4.B.2: Cooperative interactions within

organisms promote efficiency in the use of energy and matter.


– (4.18) The student is able to use representations

and models to analyze how cooperative

interactions within organisms promote efficiency in

the use of energy and matter.


Organisms have areas or compartments that perform a subset of functions related to energy and matter, and these parts contribute to the whole.


At the cellular level, the plasma membrane, cytoplasm and, for eukaryotes, the organelles contribute to the overall specialization and functioning of the cell.

• “The Whole is Greater than the Sum of its Parts”:

– Cells rely on the integration of structures and organelles in order

to function.

– CELLULAR FUNCTIONS ARISE FROM CELLULAR ORDER –

the cell is a living unit greater than the sum of its parts!!!


Within multicellular organisms, specialization of organs contributes to the overall functioning of the organism.

• Illustrative examples include:

– Exchange of Gases: lungs, trachea, bronchi,

diaphragm

– Digestion of Food: mouth, esophagus, stomach,

small intestine, colon, rectum, anus

– Excretion of Wastes: kidneys, ureters, bladder,

urethra

• For each system, consider the overall function of

the system and how the organs are specialized to

support that function.


Interactions in Unicellular Communities

• Interactions among cells of a population of

unicellular organisms can be similar to those of

multicellular organisms, and these interactions

lead to increased efficiency and utilization of

energy and matter.

• Illustrative examples include:

– Bacterial community in the rumen of animals


Bacterial Communities in the Rumen of Animals



Biology

Eighth Edition









Interactions between and within populations influence

patterns of species distribution and abundance.


Essential Knowledge 4.B.3: Interactions between and within

populations influence patters of species distribution and abundance.


– (4.19) The student is able to use data analysis to

refine observations and measurements regarding

the effect of population interactions on patterns of

species distribution and abundance.


Interactions between and within populations influence patterns of species distribution and abundance.

• Competition, parasitism, predation, mutualism and

commensalism can affect population dynamics.

• Relationships among interacting populations can be

characterized by positive and negative effects, and can be

modeled mathematically (predator/prey, invasive species).

• Many complex symbiotic relationships exist in an ecosystem,

and feedback control mechanisms play a role in the functioning

of the system.

• Read Articles:

– Population Interactions & Community Structure

– Community Structure & Interspecific Interactions


A population of organisms has properties that are different from those of the individuals that make up the population.

• The cooperation and competition between

individuals contributes to these different

properties.

biology - carnes ap bio · form inactive form oscillation ... enzyme 4 enzyme 2 enzyme 3 initial...

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