PLANT SCIENCE 184

Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings

PowerPoint® Lecture Slides for Essential Biology, Second Edition & Essential Biology with Physiology

Neil Campbell, Jane Reece, and Eric Simon

Presentation prepared by Chris C. Romero

PLANT SCIENCE 184PLANT SCIENCE 184

Cellular Respiration: Harvesting Chemical Energy


• Bacteria are used to produce yogurt, sour cream, pepperoni, and cheese

• Both carbon monoxide and cyanide kill by disrupting cellular respiration


• All the energy in all the food you eat can be traced back to sunlight

• If you exercise too hard, your muscles shut down from a lack of oxygen


• When you exercise

BIOLOGY AND SOCIETY: FEELING THE “BURN”

– Muscles need energy in order to perform work

– Your cells use oxygen to release energy from the sugar glucose


• Aerobic metabolism

– When enough oxygen reaches cells to support energy needs

• Anaerobic metabolism

– When the demand for oxygen outstrips the body’s ability to deliver it


• Anaerobic metabolism

– Without enough oxygen, muscle cells break down glucose to produce lactic acid

– Lactic acid is associated with the “burn” associated with heavy exercise

– If too much lactic acid builds up, your muscles give out


• Physical conditioning allows your body to adapt to increased activity

– The body can increase its ability to deliver oxygen to muscles

• Long-distance runners wait until the final sprint to exceed their aerobic capacity

Figure 6.1


ENERGY FLOW AND CHEMICAL CYCLING IN THE BIOSPHERE

• Fuel molecules in food represent solar energy

– Energy stored in food can be traced back to the sun

• Animals depend on plants to convert solar energy to chemical energy

– This chemical energy is in the form of sugars and other organic molecules


• Photosynthesis

Producers and Consumers

– Light energy from the sun powers a chemical process that makes organic molecules

– This process occurs in the leaves of terrestrial plants


• Autotrophs

– “Self-feeders”

– Plants and other organisms that make all their own organic matter from inorganic nutrients

• Heterotrophs

– “Other-feeders”

– Humans and other animals that cannot make organic molecules from inorganic ones


• Producers

– Biologists refer to plants and other autotrophs as the producers in an ecosystem

• Consumers

– Heterotrophs are consumers, because they eat plants or other animals

Figure 6.2


• The ingredients for photosynthesis are carbon dioxide and water

– CO2 is obtained from the air by a plant’s leaves

– H2O is obtained from the damp soil by a plant’s roots

• Chloroplasts rearrange the atoms of these ingredients to produce sugars (glucose) and other organic molecules

– Oxygen gas is a by-product of photosynthesis

Chemical Cycling Between Photosynthesis and Cellular Respiration


• Both plants and animals perform cellular respiration

– Cellular respiration is a chemical process that harvests energy from organic molecules

– Cellular respiration occurs in mitochondria

• The waste products of cellular respiration, CO2 and H2O, are used in photosynthesis


Figure 6.3

Sunlightenergy

Ecosystem

Photosynthesis(in chloroplasts)

Glucose

Oxygen

Carbon dioxide

Cellular respiration(in mitochondria)

Water

for cellular work

Heat energy


• Cellular respiration

CELLULAR RESPIRATION: AEROBIC HARVEST OF FOOD ENERGY

– The main way that chemical energy is harvested from food and converted to ATP

– This is an aerobic process—it requires oxygen


• Cellular respiration and breathing are closely related

– Cellular respiration requires a cell to exchange gases with its surroundings

– Breathing exchanges these gases between the blood and outside air

The Relationship Between Cellular Respiration and Breathing


Figure 6.4

Breathing

Lungs

Musclecells

Cellularrespiration


• A common fuel molecule for cellular respiration is glucose

– This is the overall equation for what happens to glucose during cellular respiration

The Overall Equation for Cellular Respiration

Unnumbered Figure 6.1

Glucose Oxygen Carbondioxide

Water Energy


• During cellular respiration, hydrogen and its bonding electrons change partners

– Hydrogen and its electrons go from sugar to oxygen, forming water

The Role of Oxygen in Cellular Respiration


• Chemical reactions that transfer electrons from one substance to another are called oxidation-reduction reactions

Redox Reactions

– Redox reactions for short


• The loss of electrons during a redox reaction is called oxidation

• The acceptance of electrons during a redox reaction is called reduction


Unnumbered Figure 6.2

[Oxygen gains electrons (and hydrogens)]

Oxidation[Glucose loses electrons (and hydrogens)]

Glucose Oxygen Carbondioxide

Water

Reduction


•RS IS NECESSARY IN ALL LIVING CELLS.

•PLANTS ARE WELL KNOWN FOR PS, BUT THEY MUST ALSO REPIRE IN ORDER TO

SURVIVE.

• PS - OCCURS ONLY IN PLANT CELLS CONTAINING CHLOROPHYLL DURING THE DAYLIGHT HOURS.

•RS - OCCURS IN ALL OF A PLANT’S LIVING CELLS 24 -7.


PLANTS NEED ENERGY TO PERFORM MANY ESSENTIAL FUNCTIONS OF LIFE:

GROWTH,

REPAIR,

NUTRIENT MOVEMENT,

REPRODUCTION, &

NUTRIENT TRANSPORT.

WHY IS RS NECESSARY?


• Cellular respiration is an example of a metabolic pathway

– A series of chemical reactions in cells –building or degradation process

• All of the reactions involved in cellular respiration can be grouped into three main stages

– Glycolysis

– The Krebs cycle

– Electron transport

– * WHAT IS METABOLISM?

The *Metabolic Pathway of Cellular Respiration


A Road Map for Cellular Respiration

Cytosol

Mitochondrion

High-energyelectronscarriedby NADH

High-energyelectrons carriedmainly byNADH

Glycolysis

Glucose2

Pyruvicacid

KrebsCycle

ElectronTransport

Figure 6.7


Glycolysis


• Glycolysis breaks a six-carbon glucose into two three-carbon molecules

– These molecules then donate high energy electrons to NAD+, forming NADH

• A molecule of glucose is split into two molecules of pyruvic acid

Stage 1: Glycolysis


Figure 6.8

Glucose

2 Pyruvic acid


Krebs Cycle


Stage 2: The Krebs Cycle

• The Krebs cycle completes the breakdown of sugar


• In the Krebs cycle, pyruvic acid from glycolysis is first “prepped” into a usable form, Acetyl-CoA

Figure 6.10

CoA

1

2

3Pyruvic

acid

Aceticacid

Coenzyme A

Acetyl-CoA(acetyl-coenzyme A)

CO2


• The Krebs cycle extracts the energy of sugar by breaking the acetic acid molecules all the way down to CO2

– The cycle uses some of this energy to make ATP

– The cycle also forms NADH and FADH2


Figure 6.11

Input

Acetic acid

ADP

3 NAD

FAD

KrebsCycle

Output

2 CO2

1 2

3

4

5

6


Electron Transport


Stage 3: Electron Transport

• Electron transport releases the energy your cells need to make the most of their ATP


• The molecules of electron transport chains are built into the inner membranes of mitochondria

– The chain functions as a chemical machine that uses energy released by the “fall” of electrons to pump hydrogen ions across the inner mitochondrial membrane

– These ions store potential energy


Figure 6.12

Proteincomplex

Electroncarrier

Innermitochondrialmembrane

Electronflow

Electron transport chain ATP synthase


The Versatility of Cellular Respiration

• Cellular respiration can “burn” other kinds of molecules besides glucose

– Diverse types of carbohydrates

– Fats

– Proteins


Figure 6.13

Food

Polysaccharides Fats Proteins

Sugars Glycerol Fatty acids Amino acids

Amino groups

Glycolysis Acetyl-CoA

KrebsCycle Electron

Transport


Adding Up the ATP from Cellular Respiration

Figure 6.14

Cytosol

Mitochondrion

Glycolysis

Glucose2

Pyruvicacid

2Acetyl-

CoA

KrebsCycle Electron

Transport

bydirectsynthesis

by directsynthesis

byATPsynthase

Maximumper

glucose:


FERMENTATION: ANAEROBIC HARVEST OF FOOD ENERGY

• Some of your cells can actually work for short periods without oxygen

– For example, muscle cells can produce ATP under anaerobic conditions

• Fermentation

– The anaerobic harvest of food energy


• Human muscle cells can make ATP with and without oxygen

– They have enough ATP to support activities such as quick sprinting for about 5 seconds

– A secondary supply of energy (creatine phosphate) can keep muscle cells going for another 10 seconds

– To keep running, your muscles must generate ATP by the anaerobic process of fermentation

Fermentation in Human Muscle Cells


• Glycolysis is the metabolic pathway that provides ATP during fermentation

– Pyruvic acid is reduced by NADH, producing NAD+, which keeps glycolysis going

– In human muscle cells, lactic acid is a by-product


Figure 6.15a

2 ADP+ 2

Glycolysis

Glucose

2 NAD

2 Pyruvicacid

+ 2 H

2 NAD

2 Lacticacid

(a) Lactic acid fermentation


• Various types of microorganisms perform fermentation

– Yeast cells carry out a slightly different type of fermentation pathway

– This pathway produces CO2 and ethyl alcohol

Fermentation in Microorganisms


Figure 6.15b

2 ADP+ 2

2 ATPGlycolysis

Glucose

2 NAD

2 Pyruvicacid

2 CO2 released

+ 2 H

2 NAD

2 Ethylalcohol

(b) Alcoholic fermentation


• The food industry uses yeast to produce various food products

Figure 6.16


• Ancient bacteria probably used glycolysis to make ATP long before oxygen was present in Earth’s atmosphere

EVOLUTION CONNECTION:LIFE ON AN ANAEROBIC EARTH

– Glycolysis is a metabolic heirloom from the earliest cells that continues to function today in the harvest of food energy


SUMMARY OF KEY CONCEPTS

• Chemical Cycling Between Photosynthesis and Cellular Respiration

Visual Summary 6.1

Sunlight

Heat

PhotosynthesisCellular

respiration


• The Overall Equation for Cellular Respiration

Visual Summary 6.2

Oxidation:Glucose loses electrons(and hydrogens)

Glucose Carbon dioxide

Electrons(and hydrogens) Energy

Oxygen

Reduction:Oxygen gainselectrons (andhydrogens)


• The Metabolic Pathway of Cellular Respiration

Visual Summary 6.3

Glucose Oxygen Water Energy

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PLANT SCIENCE 184