ASSIGMENT DISCUSSION
chu98
Mader_Essentials_7e_LecturePPT_Ch06_ACCESS.pptxChapter 6
Energy for Life
Essentials of Biology
SEVENTH EDITION
Sylvia S. Mader Michael Windelspecht
© McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC.
Because learning changes everything.®
6.1 Overview of Photosynthesis
Photosynthesis
Transforms solar energy into chemical energy of carbohydrates
Plants, algae, and cyanobacteria
Producers—feed themselves and all of the consumers (most other living organisms on Earth)
2
© McGraw Hill LLC
Figure 6.1 Photosynthetic Organisms
(kelp): Chuck Davis/The Image Bank/Getty Images; (diatoms): ©Ed Reschke; (Euglena): M I (Spike) Walker/Alamy Stock Photo; (sunflower): Hammond HSN/Design Pics; (mosses): Steven P. Lynch; (cyanobacteria): John Hardy, University of Washington - Stevens Point Department of Biology
3
© McGraw Hill LLC
Figure 6.2 Leaves and Photosynthesis
Plants as photosynthesizers
Green portions carry on photosynthesis.
Carbon dioxide enters leaves through stomata.
Roots absorb water.
C O2 and H2O diffuse into mesophyll cells and then into chloroplasts.
Access the text alternative for slide images.
(mesophyll cell): Dr. David Furness, Keele University/Science Source; (chloroplast): Omikron/Science Source
4
© McGraw Hill LLC
Chloroplast
Chloroplast:
Double membrane surrounds stroma.
Third membrane forms thylakoids.
Grana—stacks
Thylakoid space
Chlorophyll and other pigments reside within thylakoid membrane.
Pigments absorb solar energy.
Carbon dioxide will be reduced in the stroma into carbohydrates.
Glucose is the chief organic energy source for most organisms.
5
© McGraw Hill LLC
The Photosynthetic Process 1
The photosynthetic process:
Begins with the end products of cellular respiration—C O2 and H2O
Hydrogen atoms removed from water are added to carbon dioxide.
Solar energy is required.
Oxygen is a by-product of the oxidation of water.
End product is CH2O or glucose C6H12O6.
© McGraw Hill LLC
The Photosynthetic Process 2
Two sets of reactions
Light reactions
Occur in thylakoid membrane
Chlorophyll absorbs solar energy and energizes electrons.
Water is oxidized, releasing electrons, hydrogen ions, and oxygen.
ATP produced in electron transport chain
NADP⁺ → N A D P H
Calvin cycle reactions
Occur in stroma
C O2 taken up
ATP and N A D P H used to reduce C O2 to a carbohydrate.
7
© McGraw Hill LLC
Figure 6.4 The Photosynthetic Process
© McGraw Hill LLC
6.2 The Light Reactions—Harvesting Energy
Pigments absorb solar energy.
Solar energy can be described in terms of its wavelength and energy content.
Visible light contains various wavelengths.
Shorter wavelengths contain more energy.
Longer wavelengths contain less energy.
Less than half of the solar radiation reaching the Earth hits the surface.
Vision and photosynthesis are adapted to use the most prevalent wavelengths (visible light).
9
© McGraw Hill LLC
Wavelengths and Pigments
Figure 6.5 The electromagnetic spectrum.
Figure 6.6 Photosynthetic pigments and photosynthesis.
© McGraw Hill LLC
Photosynthetic Pigments
Photosynthetic pigments:
Most photosynthesizing cells have chlorophylls and carotenoids.
Both chlorophyll a and b absorb violet, blue, and red wavelengths better than other colors.
Because green is reflected, leaves appear green.
Accessory pigments, such as carotenoids, appear yellow or orange because they reflect those colors—they absorb light in the violet-blue-green range.
Accessory pigments become noticeable in fall when chlorophyll breaks down.
11
© McGraw Hill LLC
Figure 6.7 Leaf Colors 1
Chlorophylls absorb violet, blue, and red wavelengths best.
Leaves looks green because they reflect green light.
Chlorophylls cover up accessory pigments, which are more visible in autumn.
Access the text alternative for slide images.
(White Birch Forest): Exactostock/SuperStock
12
© McGraw Hill LLC
Figure 6.7 Leaf Colors 2
Carotenoids absorb violet, blue, green.
But reflect yellow-orange
Leaf looks yellow-orange.
When chlorophylls are no longer produced, we see the other pigments.
Access the text alternative for slide images.
(Silver Birch Forest): Ron Crabtree/Digital Vision/Getty Images
13
© McGraw Hill LLC
The Light Reactions: Capturing Solar Energy
Electron pathway of the light reactions
Capture sun’s energy and stores in the form of a hydrogen ion (H⁺) gradient
Gradient used to produce ATP
N A D P H is also produced
14
© McGraw Hill LLC
Figure 6.8 The Light Reactions of Photosynthesis
© McGraw Hill LLC
The Light Reactions 1
Two photosystems used
Named for order discovered
Consist of pigment complex (contains chlorophyll and carotenoids) and an electron acceptor
Complex serves as antenna for gathering solar energy and passing it to the reaction center (chlorophyll a molecule).
16
© McGraw Hill LLC
The Light Reactions 2
Photosystem II
Absorption of solar energy energizes electrons.
Electrons escape to electron acceptor molecule.
Sent through electron transport chain
Replacement electrons obtained by splitting water
Releases oxygen gas as waste product
Electron transport chain
Series of carriers pass electrons along, releasing energy
Energy stored in the form of H⁺ gradient
Will be used to make ATP
Photosystem 1
Absorption of solar energy energizes electrons.
Electrons captured by another electron acceptor molecule.
Electrons and a hydrogen passed to NADP⁺ to become N A D P H.
Replacement electrons come from electron transport chain.
17
© McGraw Hill LLC
The Electron Transport Chain 1
Organization of thylakoid membrane
PS II, PS1, and the electron transport system are located within the thylakoid membrane.
Promotes efficient transfer of electrons
ATP synthase complex also here
ATP production
Thylakoid space is a reservoir for H⁺
Each time water is split, 2 H⁺ remain in thylakoid space.
Energy from electrons transferred between carriers used to pump more H⁺ from the stroma into the thylakoid space
Establishes H⁺ gradient = large amount of potential energy
18
© McGraw Hill LLC
The Electron Transport Chain 2
H⁺ gradient is used to produce ATP
The H⁺ flow down concentration gradient
Pass through ATP synthase complex
Energy release allows for production of ATP
Captures released energy
NADP⁺ is a coenzyme that accepts electrons and a H⁺ to become N A D P H.
19
© McGraw Hill LLC
Figure 6.9 The Electron Transport Chain 1
© McGraw Hill LLC
Figure 6.9 The Electron Transport Chain 2
© McGraw Hill LLC
6.3 The Calvin Cycle Reactions—Making Sugars
Powered by ATP and N A D P H generated by light reactions
Occurs in stroma of chloroplasts
End product is glucose C6H12O6.
Three steps
Carbon dioxide fixation
Carbon dioxide reduction
Regeneration of first substrate (RuBP)
22
© McGraw Hill LLC
Fixation of Carbon Dioxide
Fixation of carbon dioxide:
C O2 from the atmosphere attached to RuBP by RuBP carboxylase (rubisco)
6-carbon molecule split into two 3-carbon molecules.
23
© McGraw Hill LLC
Reduction of Carbon Dioxide
Reduction of carbon dioxide:
Uses N A D P H (for electrons) and some ATP (for energy) from light reactions
Forms G3P, which can become glucose
24
© McGraw Hill LLC
Regeneration of RuBP
Regeneration of RuBP:
1 G3P can be made into glucose or other organic molecules.
5 G3P used to reform RuBP (5-carbon molecule)
Utilizes ATP from light reactions
25
© McGraw Hill LLC
Figure 6.10 The Calvin Cycle Reactions, C O2 Fixation
© McGraw Hill LLC
Figure 6.10 The Calvin Cycle Reactions, C O2 Reduction
The Calvin cycle is divided into three portions: C O2 fixation, C O2 reduction, and regeneration of RuBP. Because five G3P are needed to re-form three RuBP, it takes three turns of the cycle to achieve a net gain of one G3P. Two G3P molecules are needed to form glucose.
Access the text alternative for slide images.
27
© McGraw Hill LLC
Figure 6.10 The Calvin Cycle Reactions, Regeneration of RuBP
© McGraw Hill LLC
Figure 6.11 The Uses of G3P
Fate of G3P
Plants and algae can make any molecule they need from G3P.
Form amino acids, fatty acid, and glycerol
Form glucose for energy needs
Form sucrose for transport through plant
Form starch for storage
Form cellulose for cell walls
© McGraw Hill LLC
6.4 Variations in Photosynthesis
Plants are adapted to the light and rainfall conditions of their environment.
C3 Photosynthesis
When light and rainfall are moderate:
Use C3 photosynthesis – C3 plant – C3 compound formed first after C O2 fixation
30
© McGraw Hill LLC
Figure 6.12 Carbon Dioxide Fixation in C3 Plants
© McGraw Hill LLC
Variations in Photosynthesis, C4 Photosynthesis
When weather is hot and dry, preventing water loss is critical.
Closing stomata to limit water loss also limits C O2 intake and allows O2 buildup.
Some types of plants use C4 photosynthesis – C4 plant – where a C4 compound formed first after C O2 fixation.
32
© McGraw Hill LLC
Comparing C3 and C4 Photosynthesis
C4 photosynthesis
Anatomy of C4 plant different from C3 plant
C3 plant has mesophyll cells arranged in parallel rows.
Calvin cycle and light reactions both occur here.
C4 plant has layered arrangement around leaf veins.
Chloroplasts in mesophyll cells fix C O2 only, shield bundle sheath cells from buildup of O2
Chloroplasts in bundle sheath cells carry out Calvin cycle only.
Partitioning of pathways in space
33
© McGraw Hill LLC
Figure 6.13 Comparison of C3 and C4 Plant Anatomy
© McGraw Hill LLC
Comparing C3 and C4 Plants
C3 plants carry out both reactions in the mesophyll cell.
Advantage in moderate conditions
C4 plants partition reactions
Allows stomata to stay closed (conserving water) while avoiding oxygen exposure to rubisco
Advantage in hot, dry weather
35
© McGraw Hill LLC
Figure 6.14 Carbon Dioxide Fixation in C4 Plants
© McGraw Hill LLC
C A M Photosynthesis
C A M photosynthesis:
Crassulacean-acid metabolism
Most succulents in a desert environment
Partitioning in time
During the night, C A M plants open stomata when it is cooler.
Use C3 molecules to fix C O2 forming C4 molecules
Store C4 molecules in vacuoles
During the day, keep stomata closed to avoid water loss
Release stored C O2 when N A D P H and ATP available from light reaction
37
© McGraw Hill LLC
Figure 6.15 Carbon Dioxide Fixation in a C A M Plant
© McGraw Hill LLC
Evolutionary Trends
Evolutionary trends:
C4 plants most likely evolved in, and are adapted to, areas of high light, high temperature, and limited rainfall.
More sensitive to cold—C3 plants do better than C4 plants below 25°C
Over 20% of total annual plant growth is conducted by these plants despite only 4% of plant species being C4 plants.
Of the 18 most problematic weed plants on the planet, 14 are C4 plants.
C A M plants compete well with C3 or C4 when the environment is extremely arid.
C A M is quite widespread.
39
© McGraw Hill LLC
End of Main Content
© McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC.
Because learning changes everything.®
www.mheducation.com
40
Accessibility Content: Text Alternatives for Images
41
© McGraw Hill LLC
Figure 6.2 Leaves and Photosynthesis - Text Alternative
Return to parent-slide containing images.
The cross-section of a leaf part shows an upper cuticle, a chain of rectangular cells of the upper epidermis, layers of mesophyll cells consisting of chloroplasts, and a circular vascular bundle. The vascular bundle appears in the cut part of the leaf vein. A chain of rectangular cells of the lower epidermis is present at the lower side with a circular opening of stomata for absorbing carbon dioxide and releasing oxygen.
An enlarged view of a mesophyll cell shows several chloroplasts stacked inside a membrane.
An enlarged view of chloroplast shows the outer covering with a stack of disc-like structures labeled granum, and the fluid surrounding granum labeled stroma. Each disc-shaped component of the granum is labeled as thylakoid.
The micrograph of chloroplast shows dark green regions on roughly rectangular structures labeled granum and longitudinal and lateral blank spaces labeled stroma.
Return to parent-slide containing images.
42
© McGraw Hill LLC
The Photosynthetic Process 1 - Text Alternative
Return to parent-slide containing images.
a. Reaction shows that H two O plus C O two yields C H two O plus O two, or water reacts with carbon dioxide in presence of solar energy forming end products of carbohydrate and oxygen. Carbon dioxide undergoes reduction through the gain of electrons and forms carbohydrates. Water undergoes oxidation through the loss of electrons and forms oxygen.
Return to parent-slide containing images.
43
© McGraw Hill LLC
Figure 6.4 The Photosynthetic Process - Text Alternative
Return to parent-slide containing images.
The process takes place inside the chloroplast. The thylakoid membranes absorb the solar energy and water for the light reactions and produce oxygen. The ADP to ATP conversion and the NADP superscript positive to N A D P H conversion also take place inside the thylakoid. The Calvin’s cycle inside the chloroplast converts ATP to ADP and N A D P H to NADP superscript positive. It utilizes the C O2 and produces CH2O (carbohydrate).
Return to parent-slide containing images.
44
© McGraw Hill LLC
Wavelengths and Pigments - Text Alternative
Return to parent-slide containing images.
Figure 6.5: Wavelength and energy are represented with arrows, showing that as wavelength increases, energy decreases. The electromagnetic spectrum shows a continuum of 7 electromagnetic waves including gamma rays, X-rays, UV rays, infrared rays, micro-waves, and radio waves. The visible light spectrum, which lies between ultraviolet light and infrared light is expanded to show specific wavelengths marked as 380, 500, 600, and 750 nanometers each for different colors.
Figure 6.6: The horizontal axis represents wavelengths in nanometers ranging from 380 to 750. The vertical axis shows relative absorption ranging from low through high.
The line curve representing chlorophyll a has two distinct peaks, one in the range of violet to blue-violet light at around 400 nanometers and another in the range of red-orange light at around 700 nanometers. The line curve representing chlorophyll b has two peaks as well, one in the blue range at about 450 nanometers and one in the orange range at around 650 to 700 nanometers. The line curve of carotenoid has two distinct peaks in the blue-to-blue-green range, both between 400 and 500 nanometers.
Note: All data is approximate.
Return to parent-slide containing images.
45
© McGraw Hill LLC
Figure 6.7 Leaf Colors 1 - Text Alternative
Return to parent-slide containing images.
Green colored leaves are caused due to: Warm weather; more daylight hours, Much chlorophyll is produced, Leaf absorbs all colors of light but green. Hence we see reflected green light.
Return to parent-slide containing images.
46
© McGraw Hill LLC
Figure 6.7 Leaf Colors 2 - Text Alternative
Return to parent-slide containing images.
Yellow colored leaves are caused due to: Cool weather; fewer daylight hours, Little chlorophyll is produced, Leaf absorbs all colors but yellow to orange. We see reflected yellow to orange light.
Return to parent-slide containing images.
47
© McGraw Hill LLC
Figure 6.8 The Light Reactions of Photosynthesis - Text Alternative
Return to parent-slide containing images.
The photosynthesis process takes place inside the chloroplast. The thylakoid membranes absorb the solar energy and water for the light reactions and produce oxygen. The ADP to ATP conversion and the NADP superscript positive to N A D P H conversion also take place inside the thylakoid. The Calvin’s cycle inside the chloroplast converts ATP to ADP and N A D P H to NADP superscript positive. It utilizes the C O2 and produces CH2O (carbohydrate). The light reactions are as follows: water splits into two hydrogen molecules and half oxygen molecule while emitting an electron. It enters the pigment complex along with the solar energy. The electron from the pigment complex enters the electron acceptor, it enters the electron transport chain to PS1. ADP and P combine to form ATP. Electron from PS1 reaches electron acceptor and converts NADP positive and H positive to N A D P H. The ATP and N A D P H released enter the Calvin’s cycle.
Return to parent-slide containing images.
48
© McGraw Hill LLC
Figure 6.9 The Electron Transport Chain 1 - Text Alternative
Return to parent-slide containing images.
The photosynthetic reactions are as follows: In thylakoid space, the water splits into two hydrogen ions and half oxygen. The exited electron obtained from the splitting of water reaches photosystem two (PS 2) which is attached to the thylakoid membrane. Further, photosystem two traps solar energy and releases energized electron which is transferred to an electron transport chain The newly de-energized electrons from Photosystem two are taken up by Photosystem one (PS 1). Photosystem one also traps solar energy and releases an energized electron and passes it to NADP superscript positive, which then combines with H to form N A D P H. The hydrogen ion received from the splitting of water in thylakoid space and the electron transport chain transfers to the stroma through the protein complex ATP synthase. The ATP (adenosine triphosphate) formed from ADP (adenosine diphosphate) (ADP) and phosphate (P) and N A D P H are utilized by Calvin cycle reactions inside stroma.
Return to parent-slide containing images.
49
© McGraw Hill LLC
Figure 6.9 The Electron Transport Chain 2 - Text Alternative
Return to parent-slide containing images.
The photosynthetic reactions are as follows: In thylakoid space, the water splits into two hydrogen ions and half oxygen. The exited electron obtained from the splitting of water reaches photosystem two (PS II) which is attached to the thylakoid membrane. Further, photosystem two traps solar energy and releases energized electron which is transferred to an electron transport chain The newly de-energized electrons from Photosystem two are taken up by Photosystem one (PS I). A label reads, hydrogen is pumped from the stroma to the thylakoid space. Photosystem one also traps solar energy and releases an energized electron and passes it to NADP superscript positive, which then combines with H to form N A D P H. The hydrogen ion received from the splitting of water in thylakoid space and the electron transport chain transfers to the stroma through the protein complex ATP synthase. The other label reads, hydrogens flow back out into stroma through ATP synthase complex. The ATP (adenosine triphosphate) formed from ADP (adenosine diphosphate) (ADP) and phosphate (P) and N A D P H are utilized by Calvin cycle reactions inside stroma.
Return to parent-slide containing images.
50
© McGraw Hill LLC
Figure 6.10 The Calvin Cycle Reactions, C O2 Fixation - Text Alternative
Return to parent-slide containing images.
Key molecules of the Calvin Cycle are:
R u B P: ribulose-1,5-bisphosphate.
3PG: 3-phosphoglycerate.
BPG: 1,3-bisphosphoglycerate.
G3P: glyceraldehyde 3-phosphate.
Return to parent-slide containing images.
51
© McGraw Hill LLC
Figure 6.10 The Calvin Cycle Reactions, C O2 Reduction - Text Alternative
Return to parent-slide containing images.
At the end of the second stage, six molecules of glyceraldehyde-3-phosphate show the net gain of one glyceraldehyde-3-phosphate yielding glucose and other organic molecules.
Key molecules of the Calvin Cycle are:
R u B P: ribulose-1,5-bisphosphate.
3PG: 3-phosphoglycerate.
BPG: 1,3-bisphosphoglycerate.
G3P: glyceraldehyde 3-phosphate.
Return to parent-slide containing images.
52
© McGraw Hill LLC
Figure 6.10 The Calvin Cycle Reactions, Regeneration of RuBP - Text Alternative
Return to parent-slide containing images.
At left, in the chloroplast, solar energy is absorbed by the thylakoid membrane, where light reactions take place converting water into oxygen and producing N A D P H and ATP. These N A D P H and ATP are used by Calvin cycle reactions that occur inside the stroma. During the Calvin cycle, carbon dioxide gets converted into CH2O (carbohydrate). It also produces ADP with phosphate and NADP positive, which is again utilized in light reactions.
Three carbon dioxide molecules enter the Calvin cycle forming three hexose (glucose) molecules acting as intermediate. In carbon dioxide reduction, three hexose (glucose) molecules are transformed to six molecules of 3-phosphoglycerate which further gives six molecules of 1,3-bisphosphoglycerate. Here, six ATP received from light reaction converts to six ADP plus six phosphates. Further, six molecules of 1,3-bisphosphoglycerate on the conversion of six N A D P H into six NADP positive gives six molecules of glyceraldehyde-3-phosphate showing a net gain of one molecule of glyceraldehyde-3-phosphate, that yields glucose and other organic molecules. In the regeneration of ribulose-1,5-bisphosphate, three ATP received from light reactions convert into three ADP plus three phosphates, forming three molecules of ribulose-1,5-bisphosphate. Further, the carbon dioxide fixation occurs and the cycle continues.
Return to parent-slide containing images.
53
© McGraw Hill LLC
Figure 6.11 The Uses of G3P - Text Alternative
Return to parent-slide containing images.
G3P leads to amino acids, glycerol, fatty acids, and glucose phosphate. Glucose phosphate leads to starch, sucrose, and cellulose.
Return to parent-slide containing images.
54
© McGraw Hill LLC
Figure 6.12 Carbon Dioxide Fixation in C3 Plants - Text Alternative
Return to parent-slide containing images.
The Calvin cycle representation in the C3 plant, geranium shows the conversion of Carbon Dioxide into carbon three (C3) with the help of ribulose-1, 5-bisphosphate (RUBP) enzyme in the mesophyll cell, which further converts into glycerol 3-phosphate during the day.
Return to parent-slide containing images.
55
© McGraw Hill LLC
Figure 6.13 Comparison of C3 and C4 Plant Anatomy - Text Alternative
Return to parent-slide containing images.
The cross-section labeled C3 plant shows that the mesophyll cells are arranged in parallel layers containing vascular bundles with bundle sheath cells surrounding the vein. The bottom layer of the epidermis shows a stomatal opening between the epidermis cells.
The cross-section labeled C4 Plant shows that the mesophyll cells are arranged concentrically around the circular vascular bundles containing bundle sheath cells. The bottom layer of the epidermis shows a stomatal opening between the epidermis cells.
Return to parent-slide containing images.
56
© McGraw Hill LLC
Figure 6.14 Carbon Dioxide Fixation in C4 Plants - Text Alternative
Return to parent-slide containing images.
The Calvin cycle representation in C4 plant, corn shows the conversion of Carbon Dioxide into carbon four (C4) in the mesophyll cell, which converts into carbon dioxide in the bundle sheath cell, further converting into glycerol 3-phosphate during the day.
Return to parent-slide containing images.
57
© McGraw Hill LLC
Figure 6.15 Carbon Dioxide Fixation in a C A M Plant - Text Alternative
Return to parent-slide containing images.
The Calvin cycle representation in C A M plant pineapple shows the conversion of Carbon Dioxide into carbon four (C4) during the night, which converts into carbon dioxide, further converting into glycerol 3-phosphate during the day.
Return to parent-slide containing images.
58
© McGraw Hill LLC
