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BIOLOGYBASICSUNIT3BIOLOGYWORKBOOK

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This workbook is a product of: Biology Teachers Workshop Deer Park Vic 3023 First edition 2014 Second edition 2016 © Biology Teachers Workshop ISBN 978-0-9942148-1-2 Reproduction and communication All rights reserved. No part of this publication may be recorded, reproduced, stored in a retrieval system or transmitted in any form or by any means such as emailing, scanning or photocopying without prior permission of the authors. Disclaimer Every effort has been made to trace and acknowledge copyright. All contributions by others than the authors have been acknowledged at the end of the text. The authors would welcome any information from individuals or organisations who believe that they own copyright to any material contained within this book.


INDEX Information about this work book 3

Assessment information 4

Assumed knowledge from previous studies 5

Advice regarding writing skills 6

Area of study One: How do cells maintain life?

Chapter 1: Plasma membranes 22

Chapter 2: Nucleic acids and proteins 29

Chapter 3: Gene structure and regulation 48

Chapter 4: Structure and regulation of biochemical pathways 64

Chapter 5: Photosynthesis 78

Chapter 6: Cellular respiration 82

Chapter 8: Cellular respiration 90

AREA OF STUDY TWO: How do cells communicate Chapter 9: Cellular signals 100

Chapter 10: Responding to antigens 118

Chapter 11: Immunity 137

Acknowledgements 152


CHAPTER 5: PHOTOSYNTHESIS

Key Knowledge The purpose of photosynthesis Chloroplasts as the site of photosynthesis, an overview of their structure and evidence of their bacterial origins Inputs and outputs of the light dependent and light independent (Calvin cycle) stages of photosynthesis in C3 plants (details of the biochemical pathway mechanisms are not required) Factors that affect the rate of photosynthesis, including light, temperature and carbon dioxide concentration.

PHOTOSYNTHESIS

Photosynthesis is the biochemical process by which plants absorb light energy and use this energy to convert carbon dioxide and water into glucose and oxygen (technically water is also a product of photosynthesis as well as an input). Photosynthesis takes place in the chloroplasts of plant cells, and occurs in two separate stages; the light dependent stage and the light independent stage. Each of these stages occurs in a specific location within the chloroplast. The light dependent stage occurs in the grana and is catalysed by chlorophyll, which absorbs light, enabling the photolysis of water into hydrogen ions, high-energy electrons and oxygen gas. The electrons are passed along a chain of molecules, known as the electron transport chain. When an electron comes into contact with a molecule in the chain, energy is released. This is ultimately used to phosphorylate ADP and inorganic phosphate, producing ATP. A carrier molecule, NADP, accepts electrons and protons and becomes NADPH, which transports the hydrogen ions to the stroma. The light independent stage occurs in the stroma. This series of reactions is known as the Calvin-Benson cycle and requires inputs of carbon dioxide gas, hydrogen ions and ATP in order to produce sugar molecules. Question 1 Write a balanced equation for the process of photosynthesis.

Question 2 Photosynthesis occurs in two stages. Identify both of these stages.


Question 3 In simple terms, the light dependent reactions are responsible for energy capture. What does this mean?

Question 4 In simple terms the light independent reactions are responsible for carbon fixation. What does this mean?

CHLOROPLASTS

Chloroplasts are organelles located in the leaf cells of many plants. They are responsible for carrying out the process of photosynthesis, the reaction by which plants produce their organic nutrients. Chloroplasts have a range of structures that facilitate their ability to carry out the reactions associated with photosynthesis. These include:

• A folded inner membrane that joins to form stacks of flattened discs called grana. • The green pigment, chlorophyll. • Chloroplast DNA • Ribosomes • Internal fluid known as stroma

Figure 5.1: An internal view of a chloroplast.


Question 5 Use the information from figure 5.1 to assist you to answer the following questions.

a. Identify which stage of photosynthesis occurs in the grana and which occurs in the stroma.

b. Explain how the organisation of the thylakoid discs that make up the grana facilitates

the function carried out by these discs.

ENDOSYMBIOTIC THEORY

Endosymbiotic theory states that chloroplasts were actually once primitive bacterial cells that were then taken up by larger host cells. The two cells then developed a symbiotic relationship with each other. Over a long period of time chloroplasts became increasingly specialised and were eventually unable to live outside of the host cell. Question 6 Based on the information provide in image 5.1, identify three components of a chloroplast that could be used as evidence to support endosymbiotic theory.

Question 7 Chloroplasts contain DNA, RNA and ribosomes. Explain why their presence is important to the process of photosynthesis.


INPUTS AND OUTPUTS OF THE LIGHT DEPENDENT AND LIGHT INDEPENDENT STAGES OF PHOTOSYNTHESIS

Figure 5.2 represents an overview of the process of photosynthesis divided into the two main stages. The direction that the arrows are pointing indicates whether a factor is an input or an output of each stage.

Figure 5.2: An overview of photosynthesis Question 8 Use the information from figure 5.2 to answer the following questions.

a. Identify the inputs of the light dependent stage.

b. Identify the outputs of the light dependent stage.

c. Briefly explain what occurs during the light dependent stage.

Light dependent reactions occur in the grana

Light independent reactions occur in the stroma

H2O Light O2

CO2

ATP NADPH ADP + Pi NADP+

C6H12O6


d. Identify what happens to each of the outputs of the light dependent stage.

e. What term is used to describe molecules such as NADPH?

f. Describe the role that NADPH plays in photosynthesis. What is the importance of this

role?

g. Identify the process responsible for the production of ATP during the light dependent

stage.

h. Identify the inputs of the light independent stage.

i. Identify the outputs of the light independent stage.

j. Identify what happens to each of the outputs of the light independent stage.


Question 9 Complete the summary table relating to the two stages of photosynthesis. Identify whether a substance is produced, used or plays no role in that stage. Information regarding ATP has already been completed as an example.

COMPOUND LIGHT DEPENDENT STAGE LIGHT INDEPENDENT STAGE ATP Produced Used

Carbon dioxide

Glucose

NADP

NADPH

Oxygen

Water

FACTORS AFFECTING THE RATE OF PHOTOSYNTHESIS The main factors that affect the rate of photosynthesis are light intensity, carbon dioxide concentration and temperature. Other factors, such as chlorophyll concentration and the wavelength of light may also affect the rate of the reaction. Generally one factor has a greater impact on the reaction rate until it becomes limiting.

CARBON DIOXIDE CONCENTRATION Carbon dioxide is a reactant for photosynthesis so altering the concentration of carbon dioxide will alter the rate of photosynthesis. If the concentration of carbon dioxide increases then the rate at which carbon is incorporated into the carbohydrate product of the light dependent stage also increases.

Figure 5.3: The effect of carbon dioxide concentration on the rate of photosynthesis.


Question 10 a. Use the information provided in figure 5.3 to describe what happens to the rate of

photosynthesis as the concentration of carbon dioxide increases.

b. Explain why the rate of photosynthesis changes as described in question 9a.

LIGHT INTENSITY

As light intensity increases the number of photons of light falling onto leaves also increases. This increases the number of chlorophyll molecules that are activated resulting in an increase in the production of ATP and NADPH.

Figure 5.4: The effect of light intensity on the rate of photosynthesis.

Question 11

a. Use the information provided in figure 5.4 to describe what happens to the rate of photosynthesis as light intensity increases.


b. Explain why the rate of photosynthesis changes as described in question 10a.

TEMPERATURE

The temperature will affect the thermal motion of the substances involved. The light independent reactions are catalysed by enzymes. These enzymes have optimal temperatures and their activity will be affected by temperature like all other enzymes. In addition to this, in high temperatures, stomata will close to reduce water loss, limiting the amount of carbon dioxide available and slowing photosynthesis.

Figure 5.5: The effect of temperature on the rate of photosynthesis. Question 12 Explain why the rate of photosynthesis initially increases as temperature increases and then subsequently decreases.


LIMITING FACTORS All of the factors that affect the rate of photosynthesis also act as limiting factors, with the rate of photosynthesis being limited by the factor which is in the shortest supply. As an example if there is no light then photosynthesis will not occur even if carbon dioxide is present and temperature is at an appropriate level. As light intensity increases, the rate of photosynthesis will also increase as long as all of the other factors are present at an appropriate level, however, eventually one of the other factors will become limiting. Question 13 An experiment was conducted to show how the light intensity, temperature and carbon dioxide concentration all affect the rate of photosynthesis. The results are shown in figure 5.6.

Figure 5.6: The effect of light intensity, temperature and carbon dioxide concentration on

the rate of photosynthesis. Based on the information provided, does carbon dioxide concentration or temperature have the greater effect on the rate of photosynthesis? Provide a reason to support your answer.

CHLOROPHYLL CONCENTRATION Chlorophyll is necessary for the light stage of photosynthesis. If it is present in a low concentration then the rate of photosynthesis will be low.


LIGHT WAVELENGTH The quality of light affects photosynthesis. If the chlorophyll is green; then the red and blue wavelengths of light are best absorbed by the chloroplasts and increase the reaction rate. Green light is reflected by the leaves and decreases the rate, so less light energy is absorbed causing the rate of photosynthesis to decrease. Question 14 A classic experiment was conducted in order to determine if the wavelength of light affects the rate of photosynthesis. It involved placing a piece of algae into a watery environment with different sections of the algal filament exposed to varied colours (wavelengths) of light as shown in figure 5.7. Aerobic bacteria were then added to the water and their positions were observed and recorded.

Figure 5.7: The effect that the wavelength of light has on the rate of photosynthesis

Why are the aerobic bacteria present in high numbers around the algae exposed to light in the 400 to 500 and 600 to 700nm regions? Refer to the rate of photosynthesis and products of photosynthesis in your answer.


Question 15 A series of experiments were run in which specimens of Elodea (a water plant) were placed into test tubes containing water, provided with sufficient carbon dioxide and exposed to an appropriate light intensity. The colour of light that the plant was exposed to was varied using coloured filters. Bubbles were observed to be released from the leaves of the plant. The number of bubbles produced by the plant over a period of 30 seconds was observed and recorded in the table below. Run Carbon dioxide concentration Light Intensity Filter Bubble count

1 5 units 5 units White 17 2 5 units 5 units Blue 14 3 5 units 5 units Green 4 4 5 units 5 units Red 11

a. What substance was most likely to be contained in the bubbles produced by the plant?

Provide a reason to support your answer.

b. Explain why production of this substance can be as a means of establishing the rate of

photosynthesis.

c. Explain why the bubble count was highest when the plant was supplied with white

light.

d. Were the results for the other wavelengths of light as expected? Provide a reason to

support your answer.


e. The following graph shows the absorption spectrum of chlorophyll.

Consider the information in this graph and the experimental results shown on the previous page. Are these two pieces of information consistent with each other? Provide a reason to support your answer.

KEY TERMS

Carrier Chloroplast Grana Light independent stage Light dependent stage NADP Stroma Thylakoid discs

REVISION SKILLS AND KNOWLEDGE

Identify the balanced equation for photosynthesis Understand the structure and function of the chloroplasts Identify the two stages of photosynthesis and locate where each stage occurs. Identify the inputs and outputs of each the two stages of photosynthesis Identify and explain what happens to the inputs and outputs of each stage of photosynthesis

Understand the role played by NADP/NADPH in the light independent stage Be able to link information regarding photosynthesis and cellular respiration Identify the factors that will affect the rate of photosynthesis. Explain how light intensity, the wavelength of light, environmental temperature and carbon dioxide concentration will affect the rate of photosynthesis

Identify and discuss the evidence that supports the theory that chloroplasts have a bacterial origin

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