S7 4P Biology ATP Synthesis 2022-2023 PDF

S7 4P Biology 2022-2023 Introduction & Topic 1 – 7.1.1 ATP Synthesis Mr David McGregor.  Introduction To The Year. This Year, you will need… Notebook (Ideally Lined Paper, that can be taken out of the notebook) Pens & Pencils – Varying colours. Assessments in blue or black. A folder, lik...

S7 4P Biology 2022-2023 Introduction & Topic 1 – 7.1.1 ATP Synthesis Mr David McGregor.  Introduction To The Year. This Year, you will need… Notebook (Ideally Lined Paper, that can be taken out of the notebook) Pens & Pencils – Varying colours. Assessments in blue or black. A folder, like the one below to store & organise your notes. BYOD – you will have plenty of opportunities to use them throughout the year. Highlighters. Information Booklets. (Diagram) Class Expectations & Behaviour… You are in S7. Syllabus & Timings (If Available) Use the syllabus to help guide your revision for summative assessments & especially for the BAC.  S7 4P Biology – Topic 1. 7.1.1 ATP Synthesis Photosynthesis Focus Weekly Homework on Carousel. – It can be done on your phone quickly & easily, no excuse! For this topic you will have the following assessments; Summative Test Schematic/Explanatory Poster Lab Report (Small)  Lesson 1 – Reviewing Cells & ATP 1. TPS – Name every organelle you recognise in the below images. 2. Explain what ATP is. 3. Extension: What does each organelle do? Learning Objectives Be able to recall the structure of animal & plant cells Be able to explain the function of most organelles Be able to describe the structure and function of the chloroplast Be able to explain what ATP is, and how it is utilised. Organelle Found In Function Nucleus RER & SER Golgi Apparatus Vesicles/lysosomes Centrioles Ribosomes Cell Membrane Cell Wall Chloroplast Mitochondria Permanent Vacuole Organelle Found In Function Nucleus Eukaryotic House the DNA. Allow for DNA replication & protein synthesis initial stages. RER & SER Eukaryotic Part of the protein synthesis process. Golgi Apparatus Eukaryotic Part of the protein synthesis process. Vesicles/lysosomes Eukaryotic Transporting materials/transporting lysozymes to break down structures. Centrioles Eukaryotic Structural chemicals that allow for cell division. Ribosomes All (80s & 60s) Key component in protein synthesis. (Translation!) Cell Membrane All Border of the cell. Allows for movement of select molecules. Cell Wall Varies. Plant, some prokaryotes, fungi. Border of the cell. Prevents cell lysis, provides extra support. Chloroplast Varies. Generally plants, but some Site of photosynthesis! prokaryotes. Mitochondria All eukaryotic cells & some protists. Site of aerobic respiration. Permanent Vacuole Varies. Plant Cells. Cellular storage.  What is ATP and why do we need it? ATP stands for… Adenosine Triphosphate. ATP is the “universal energy currency” in life. When a short burst of energy is needed for a reaction (e.g opening/closing a gated protein channel) then the third phosphate can be broken, releasing the stored energy in the bond. This converts ATP into ADP (diphosphate) and an inorganic phosphate. ATP is produced in many ways, although the method of adding ADP to P i remains the same. How can ATP be produced? Chemiosmosis. This takes place in both respiration & photosynthesis, and will be the focus of this topic. The method & numbers through which chemiosmosis take place are slightly different, and we will have a review lesson towards the end comparing the two.  Lesson 2 – Chloroplasts & Photosynthesis Task - Write definitions for the following keywords: Photosynthesis Chlorophyll Autotroph Reduction Fixation Challenge: Is photosynthesis an endothermic or exothermic reaction, how can you tell? Modes of Nutrition: 1. Autotrophic: synthesis of organic molecules from inorganic molecules using an energy source. * Photoautotroph’s: uses light energy e.g. plants, some bacteria, some algae. * Chemoautotroph’s: uses energy from chemical reactions e.g. nitrifying bacteria in soil – get their energy from oxidizing ammonia to nitrate or nitrite to nitrate. 2. Heterotrophic: ingesting and digesting complex organic molecules, releasing the chemical potential energy stored in them. The simple soluble molecules are synthesized to form complex molecules such as lipids, proteins and nucleic acids.. What is the equation for photosynthesis? Light Carbon dioxide + Water Glucose + Oxygen Chlorophyll 6CO2 + 6H2O C6H12O6 + 6O2 Why is photosynthesis described as a transduction reaction? Is photosynthesis as simple as the equation seems? So how does photosynthesis work? light O2 Absorbed by 2H2O 4H (CH2O) + H2O chlorophyll CO2 carbohydrate Light- Light- dependent independent reactions reactions Challenge: How does respiration fit into this? When do plants respire? Challenge: How do autotrophs and heterotrophs differ in this? What is the relationship between respiration and photosynthesis? Challenge: How do the rates of these reactions vary over a day? CHLOROPLAST STRUCTURE Thylakoids (membranes) (site of Light reaction) Lipid globule Stroma (site of Light granum independent reaction) lamella envelope Chloroplast starch grain (inner + outer DNA membrane)  Structure to Function: Chloroplast 1. The many grana (stacks of thylakoid membranes), provide a large surface area for photosynthetic pigments – maximising light absorption. 2. Several different photosynthetic pigments are embedded in the membranes – each absorbs energy from certain wavelengths of light – this broadens the range of light that can be used in photosynthesis. 3. The pigments are embedded in the thylakoids in discrete units of organization called photosystems – these are held together by proteins in the grana. 4. Grana are surrounded by the stroma – so the products of the LDS, which are needed by the LIS can easily pass in to the stroma. 5. Chloroplasts can make some of the proteins needed for photosynthesis using the chloroplast DNA and ribosomes.  Photosynthetic Pigments In order for light energy to be used by living systems, it must be first ABSORBED. A substance that absorbs light is known as a PIGMENT. The photosynthetic pigments are contained within funnel-shaped structures called photosystems. These photosystems are found within thylakoid membranes.  There are a few different photosynthetic pigments – each absorbs a range of wavelengths in the visible region and has its own distinct peak of absorption. Other wavelengths are reflected. Only chlorophyll a is directly involved with pss – all others are accessory pigments that broaden the range of wavelengths of light absorbed. They transfer the energy to chlorophyll a  Chlorophyll Chlorophyll a is the most abundant ¾ of all the chlorophyll Chlorophyll b is an accessory pigment – not directly involved in pss.  Porphyrin ring – stable ring shaped molecule around which electrons are free to migrate This allows chlorophyll to “capture” the energy of sunlight Carotenoids Not directly involved in the light dependent reaction They absorb light wavelengths not well absorbed by chlorophylls and pass on the energy Carotene (orange) and xanthophyll (yellow) are the main carotenoid pigments Chloroplast Pigments Chlorophyll absorbs light from the visible part of the EM spectrum It is made up of a number of different pigments: - Chlorophyll a  absorbs RBV - Chlorophyll b  absorbs RBV - Carotenoids  absorbs BV  The light absorption pattern of a pigment is known as the absorption spectrum of that substance Absorption Spectra of the Different Photosynthetic Pigments  An action spectra is a graph showing the rate of photosynthesis plotted against the wavelength of light. Action Spectrum  Pigment absorbs light Electrons are temporarily boosted to a high energy level (excited state) As these electrons return to ground level, the energy has 2 fates: 1) Resonance Energy Transfer (chlorophyll a, b and other accessory pigments) 2) high energy electron transferred to an electron acceptor, which then passes through an electron transport chain. (chlorophyll a) Question Chlorophyll, being green, doesn’t absorb green light. What would be a ‘better’ colour for chlorophyll, which would allow it to absorb light of all wavelengths? Can you suggest a major disadvantage of this colour? (2 marks) Black would be a ‘better’ light absorbing colour. (1) Although it would be more likely to overheat (1). Questions To Practice… Cambridge International A & AS Biology Book. Questions on pg 311-312 1a) Explain why an action spectrum can be determined for isolated chloroplasts but not for isolated synthetic pigments. 1bi) Reviewing the action spectrum, which wavelength of light produces the highest rate of photosynthesis? 1bii) Suggest why the leaf used to produce this action spectrum appears green. Lesson 3 – The Light Dependent Reactions  New Key Terms! What do you think they mean? Photolysis Photoionisation Photophosphorylation Cyclic phosphorylation & non-cyclic (or acyclic) photophosphorylation. Photoexcitation LDR LIR Learning Outcomes; Be able to define key terms on the previous slide Be able to describe the process of non-cyclic photophosphorylation Be able to explain why photolysis is integral to plant survival Light Dependent Reactions This is the primary focus (along with chemiosmosis) for your syllabus. Strictly speaking, you do not need to know the detailed overview of the light independent reaction (otherwise known as the calvin cycle,) however it would be useful for context & for the higher marks to go through it. I suggest that you investigate the calvin cycle after this lesson, and ask questions. I am happy to go through the calvin cycle during a lunchtime if requested by the class. Light-dependent reaction Non-Cyclic Photophosphorylation. The details… You can follow along with the biology factsheet – I recommend you annotate your factsheet with information from the following slides, or make notes directly using this resource &  Light-dependent reaction Energy reaching the reaction centre (of a photosystem) raises an electron in the primary chlorophyll molecule to a higher energy level. This excited electron is then emitted by the chlorophyll (i.e. the chlorophyll is oxidised) and taken up by an electron acceptor or carrier molecule: Light energy Chlorophyll Chlorophyll+ + e- Electron passed to acceptor Light-dependent reaction light Energy passed through energy level pigment Decreasing molecules by resonance transfer Chlorophyll a in e- (electron passed to reaction centre acceptor molecule) Light-dependent reaction This is effectively the point where light energy is converted into chemical energy. The light has raised the energy level of the electron enough to make the chlorophyll able to donate the electron to the acceptor (this would not happen with the ‘unexcited’ electron). So, the chlorophyll has become a very strong reducing agent. Light-dependent reaction Because of their role, the accessory pigments are often described as acting as an ‘antenna complex’ for light. In the photosystems, photons of light are not emitted by one pigment molecule and absorbed by another. Instead the energy is transferred by a physical process called resonance transfer. Light-dependent reaction Eventually most of the energy is passed to the reaction centre, which loses an electron. The energy level of the pigments decreases as they get nearer to the reaction centre, which ensures a favourable energy gradient, transferring the energy in the direction of the reaction centre. It is like a funnel with accessory pigments at the top and reaction centre at the neck. Light-dependent reaction The electron acceptor is therefore reduced by the gaining of an electron from the reaction centre. The electron is then passed along a series of electron carriers. So it moves from one carrier to the next, each carrier becomes reduced and then reoxidised in a series of redox reactions. Light-dependent reaction Each carrier in the sequence has a lower energy level than the preceding one, so that as the electrons are passed along, enough energy is released to synthesise ATP from ADP and inorganic phosphate. The process is ‘driven’ by light energy rather than chemical energy, so it known as photophosphorylation. Light-dependent reaction Both P680 (PSII) and P700 (PSI) lose ‘excited’ electrons in this way, leaving the primary pigments of the photosystems oxidised. In order for photosynthesis to continue, they must be reduced again by replacement of the missing electrons. Video Recap! If you feel confident, then have a go at the questions on page 313 & 314. (Question 4 will be a challenge right now…) If you’re not so confident yet, then watch the first half of this video… https://www.youtube.com/watch?v=sQK3Yr4Sc_k Photolysis. We have been looking at Non-Cyclic Photophosphorylation, why do this? Brief Comparison to Cyclic.. Lesson 4 – Light Dependent Summary  Assessment! Produce an A3 Poster explaining the light dependent stage of photosynthesis. You must include: A diagram showing the LDR of photosynthesis. A diagram & explanation of photolysis, including why it is important. A diagram & explanation of cyclic & non-cyclic photophosphorylation, explaining why each step is important & useful. For the highest two grades… Look ahead to the calvin cycle & chemiosmosis and explain why the products of the LDR are important. Focusing on the thylakoid membrane explain how chemiosmosis helps further rounds of photosynthesis. Lesson 5 – Chemiosmosis In The Chloroplast After the LDR produces some ATP & some reduced NADP (or NADPH, Or NADPH+H) the light independent stage takes place, also known as the Calvin Cycle. Look at the image below, explain what is taking place.  The LIR, or Calvin Cycle, produces more ATP, NADPH, & glucose. (Which is then converted to sucrose.) We are going to focus on the production of NADPH.  Chemiosmosis During chemiosmosis, the free energy from the series of redox reactions that make up the electron transport chain is used to pump hydrogen ions (protons) across the membrane. The uneven distribution of H+ ions across the membrane establishes both concentration and electrical gradients (thus, an electrochemical gradient) owing to the hydrogen ions' positive charge and their aggregation on one side of the membrane.  Chemiosmosis is used to generate 90% of the ATP made during aerobic glucose catabolism. The production of ATP using the process of chemiosmosis in mitochondria is called oxidative phosphorylation. It is also the method used in the light reactions of photosynthesis to harness the energy of sunlight in the process of photophosphorylation. The overall result of these reactions is the production of ATP from the energy of the electrons removed from hydrogen atoms. These atoms were originally part of a glucose molecule. At the end of the pathway, the electrons are used to reduce an oxygen molecule to oxygen ions. The extra electrons on the oxygen attract hydrogen ions (protons) from the surrounding medium and water is formed. Activity! Review your understanding with the chemiosmosis hand out, ask questions if you’re unsure! Task – explain what is happening at each of the numbered stages on the diagram below.  Mixed Up answers 1.The electrons reduce the carrier molecule NADP along with the hydrogen ions from the photolysis of water. 2.Electrons in the magnesium atom of chlorophyll a (primary pigment) of PSII are excited to a higher energy level (photoionisation) 3.Electron transport chain, a series of redox reactions which results in the photophosphorylation of ADP and Pi to ATP. 4.Photons hit the photosystems and the energy is passed down to the reaction centre by resonance transfer (photoexcitation) 5.Electrons in the magnesium atom of chlorophyll a (primary pigment) of PSI are excited to a higher energy level (photoionisation) Correct answers 1.Photons hit the photosystems and the energy is passed down to the reaction centre by resonance transfer (photoexcitation) (4) 2.Electrons in the magnesium atom of chlorophyll a (primary pigment) of PSII are excited to a higher energy level (photoionisation) (2) 3.Photolysis of water replaces the electrons lost from PSII and produces oxygen as a waste product (6) 4.Electron transport chain, a series of redox reactions which results in the photophosphorylation of ADP and Pi to ATP. (3) 5.Electrons in the magnesium atom of chlorophyll a (primary pigment) of PSI are excited to a higher energy level (photoionisation) (5) 6.The electrons reduce the carrier molecule NADP along with the hydrogen ions from the photolysis Lesson 6 -The Calvin Cycle The purpose of the calvin cycle is to produce glucose. & it can be broken down into 3 stages. Fixation (Where CO2 is attached to a molecule) Reduction (Where the molecule is reduced) Regeneration (Where the molecule returns to its original form, and releases a glucose precursor)