Cell Transport

BIOLOGYCONCEPTS & CONNECTIONS

Fourth Edition

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Neil A. Campbell • Jane B. Reece • Lawrence G. Mitchell • Martha R. Taylor

From PowerPoint® Lectures for Biology: Concepts & Connections

CHAPTER 5The Working Cell

Modules 5.1 – 5.4


• Fireflies use light, instead of chemical signals, to send signals to potential mates

• Females can also use light flashes to attract males of other firefly species — as meals, not mates

Cool “Fires” Attract Mates and Meals


• The light comes from a set of chemical reactions, the luciferin-luciferase system• Fireflies make light energy from chemical energy

• Life is dependent on energy conversions


• Living cells are compartmentalized by membranes

• Membranes are sites where chemical reactions can occur in an orderly manner

• Living cells process energy by means of enzyme-controlled chemical reactions

ENERGY AND THE CELL


• Energy is defined as the capacity to do work

• All organisms require energy to stay alive

• Energy makes change possible

5.1 Energy is the capacity to perform work


• Kinetic energy is energy that is actually doing work

• Potential energy is stored energy

Figure 5.1A

Figure 5.1B


• First law of thermodynamics

• Energy can be changed from one form to another

– However, energy cannot be created or destroyed

5.2 Two laws govern energy conversion

Figure 5.2A


• Second law of thermodynamics

• Energy changes are not 100% efficient

– Energy conversions increase disorder, or entropy

– Some energy is always lost as heat

Figure 5.2B


• Cells carry out thousands of chemical reactions

– The sum of these reactions constitutes cellular metabolism

5.3 Chemical reactions either store or release energy


• There are two types of chemical reactions:– Endergonic reactions absorb energy and

yield products rich in potential energy

Figure 5.3A

Reactants

Po

ten

tia

l en

erg

y o

f m

ole

cule

s Products

Amount of energy INPUT


– Exergonic reactions release energy and yield products that contain less potential energy than their reactants

Figure 5.3B

Reactants

Po

ten

tia

l en

erg

y o

f m

ole

cule

s

Products

Amount of energy OUTPUT


• In cellular respiration, some energy is stored in ATP molecules

• ATP powers nearly all forms of cellular work

• ATP molecules are the key to energy coupling

5.4 ATP shuttles chemical energy within the cell


• When the bond joining a phosphate group to the rest of an ATP molecule is broken by hydrolysis, the reaction supplies energy for cellular work

Figure 5.4A

Phosphategroups

Adenine

Ribose

Adenosine triphosphate

Hydrolysis

Adenosine diphosphate(ADP)

Energy


• How ATP powers cellular work

Figure 5.4B

Reactants

Po

ten

tia

l en

erg

y o

f m

ole

cule

s

Products

Protein Work


• The ATP cycle

Figure 5.4C

Energy from exergonic reactions

Deh

yd

rati

on

syn

thes

is

Hyd

roly

sis

Energy for endergonic reactions

Cell Transport

Education

Transcript of Cell Transport