copyright © 2003 pearson education, inc. publishing as benjamin cummings fireflies use light to...

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

• Fireflies use light to signal to potential mates

• attract males of other species — as meals

Cool “Fires” Attract Mates and Meals

• luciferin-luciferase system

• What is energy? Why do we need it?

• How do chemical reactions use or produce energy?

• How does ATP transfer energy?

• How do enzymes affect rates of chemical reactions?

Energy and cells

•Energy is the capacity to perform work


Chemical energy is due to the arrangement of atoms in molecules

Rearrangement of atoms will either store or release energy

chemical reaction = rearrangement of atoms


– 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

Energy content of commonchemicals (foods)

Energy used in activities


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

• ATP powers nearly all forms of cellular work

• ATP is key to energy coupling

ATP shuttles chemical energy within the cell


• This reaction supplies energy for cellular work:

Figure 5.4A

Phosphategroups

Adenine

Ribose

Adenosine triphosphate

Hydrolysis

Adenosine diphosphate(ADP)

Energy

How is ATP’s chemical energy used to do work in a

cell?


• For a chemical reaction to begin, reactants must absorb some energy

– energy of activation (EA) = energy barrier

Enzymes lower energy barriers

How do enzymes work?


• enzymes can decrease the energy barrier

EA barrier

Reactants

1 Products 2

En

zym

eFigure 5.5A


Enzyme(sucrase)

Activesite

1

2

3

Substrate(sucrose)

Enzyme available with empty active site

Substrate binds to

enzyme with induced fit

Substrate is converted to

products

4

Products are released

Glucose Fructose

• enzyme is unchanged and can repeat the process

Figure 5.6

A specific enzyme catalyzes each cellular reaction


• Enzyme activity is influenced by

– temperature

– salt concentration

– pH

• Reaction rate is affected by amount of substrate

• Allosteric regulation by other factors

The cellular environment affects enzyme activity


•Some enzymes require nonprotein cofactors

Ex. zinc, iron

coenzymes = cofactors that are organic molecules

Ex. vitamins

A. Cellular respiration

1.Glycolysis

1.Kreb cycle

1.Electron transport chain

B. Fermentation


• Cellular respiration breaks down glucose molecules and banks their energy in ATP

– uses O2 and releases CO2 and H2O

Glucose Oxygen gas

Carbon dioxide

Water Energy


• Glucose gives up energy as it is oxidized

oxidation = loss of H

Oxygen is reduced (gains H)

Loss of hydrogen atoms

Glucose

Gain of hydrogen atoms

Energy

Figure 6.4

Redox reactions are linked oxidations and reductions


• An overview of cellular respiration

Figure 6.8

High-energy electrons carried by NADH

GLYCOLYSIS

Glucose Pyruvicacid

KREBSCYCLE

ELECTRONTRANSPORT CHAIN

AND CHEMIOSMOSIS

MitochondrionCytoplasmic

fluid


Glycolysis harvests chemical energy by oxidizing glucose to pyruvic acid

Figure 6.9A

Glucose Pyruvicacid


• Each pyruvic acid molecule is broken down to form CO2 and a two-carbon acetyl group, which enters the Kreb cycle

Pyruvic acid is chemically groomed for the Kreb cycle

Figure 6.10

Pyruvicacid

CO2

Acetyl CoA(acetyl coenzyme A)


• enzymes strip away electrons and H+ from each acetyl group, generating many NADH and FADH2 molecules

The Krebs cycle completes the oxidation of organic fuel

Figure 6.11A

Acetyl CoA

KREBSCYCLE

2CO2


Steps in the Electron Transport System

Figure 3.28


• Electron Transport System and chemiosmosis in the mitochondrion

Figure 6.12

Intermembranespace

Innermitochondrialmembrane

Mitochondrialmatrix

Proteincomplex

Electroncarrier

Electronflow

ELECTRON TRANSPORT CHAIN ATP SYNTHASE

cell

innermembrane

outermembrane

mitochondrion

glycolysis

Krebscycle

outermembrane

innermembrane

electrontransportchain

inner compartment

H2O

O2

H+

e-

outer compartment

H+

H+H +

H+

H+

H +

H +H +


Certain poisons interrupt critical events in cellular respiration

Figure 6.13

Rotenone Cyanide,carbon monoxide

Oligomycin

ELECTRON TRANSPORT CHAIN ATP SYNTHASE


• An overview of cellular respiration

Figure 6.8

High-energy electrons carried by NADH

GLYCOLYSIS

Glucose Pyruvicacid

KREBSCYCLE


AND CHEMIOSMOSIS

MitochondrionCytoplasmic

fluid


• Without oxygen, cells can use glycolysis alone to produce small amounts of ATP

– But a cell must replenish NAD+

Fermentation is an anaerobic alternative to aerobic respiration

Glucose Pyruvicacid


• In alcoholic fermentation, pyruvic acid is converted to CO2 and ethanol– This recycles NAD+ to keep glycolysis working

GLYCOLYSIS

2 Pyruvicacid

released

2 EthanolGlucose

Figure 6.15C

FERMENTATION


• In lactic acid fermentation, pyruvic acid is converted to lactic acid– NAD+ is recycled

• Produces cheese and yogurt

GLYCOLYSIS

2 Pyruvicacid

2 Lactic acidGlucose

Figure 6.15B


• Polysaccharides monosaccharides glucose for glycolysis

• Proteins amino acids Krebs cycle

• Fats acetyl-Co A Krebs cycle

Cells use many kinds of organic molecules as fuel for cellular respiration


• Pathways of molecular breakdown

Figure 6.16

Food, such as peanuts

Polysaccharides Fats Proteins

Sugars Glycerol Fatty acids Amino acids

Amino groups

Glucose G3PPyruvic

acid

GLYCOLYSIS

AcetylCoA

KREBSCYCLE


AND CHEMIOSMOSIS


• cells need raw materials for growth and repair

– Some directly from food

– Others made from intermediates in glycolysis and the Krebs cycle

• Biosynthesis uses ATP (endergonic)

Food molecules provide raw materials for biosynthesis


• Biosynthesis of macromolecules from intermediates in cellular respiration

Figure 6.17

ATP needed todrive biosynthesis

PolysaccharidesFatsProteins

KREBSCYCLE

AcetylCoA

Pyruvicacid G3P Glucose

GLUCOSE SYNTHESIS

Aminogroups

Amino acids Fatty acids Glycerol Sugars

Cells, tissues, organisms

copyright © 2003 pearson education, inc. publishing as benjamin cummings fireflies use light to...

Documents

energy output slide

energy input slide

energy energy of activation

potential energy figure

atps chemical energy

reaction supplies energy

atp transfer energy

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