Plant Transport and Energetics PDF

Bioenergetics LOs: 1. Define autotrophic and heterotrophic nutrition Autotrophs Heterotrophs - Make their own organic matter from - Cannot make organic molecules from inorganic nutrients through anabolic inorganic on...

Bioenergetics LOs: 1. Define autotrophic and heterotrophic nutrition Autotrophs Heterotrophs - Make their own organic matter from - Cannot make organic molecules from inorganic nutrients through anabolic inorganic ones reactions - Producers because ecosystems - Consumers because they eat other depend upon them for food organisms to obtain energy from food through catabolic reaction - Photosynthesis - Cellular respiration - Anabolic pathways consume energy to build complex molecules from simpler ones - e.g. chloroplast >>> photosynthesis - small to big - Catabolic pathways release energy by breaking down complex molecules into simpler compounds - e.g. mitochondria >>> cellular respiration - big to small - Energy released by catabolic pathways is used to drive anabolic pathways 2. Briefly explain why most forms of life are completely dependent on photosynthesis Photosynthesis: - Converts energy from the sun into chemical energy, which is needed by other organisms - Removes carbon dioxide from the atmosphere - Produces oxygen needed for respiration by other organisms - Contributes to the energy stored in fossil fuels Nutrition and Transport in flowering plants LOs: 1. Identify the cellular and tissue structure of a dicotyledonous leaf, as seen in transverse section using the light microscope and describe the significance of these features in terms of their functions Cellular structure Feature Function Concept/ Ultimate goal Stomata present in the - Open in the presence of light Gaseous exchange epidermal layers - Allows CO2 to diffuse in - Allows O2 to diffuse out of leaf Guard cells control size of - Stomata opens as a result of stomata* turgid guard cells - Stomata closes when water leaves the guard cells (flaccid) Interconnecting system of - Allow rapid diffusion of CO2 air spaces in the spongy and O2 into and out of mesophyll mesophyll cells Chloroplasts containing - Absorbs energy from light Photosynthesis chlorophyll in all - Transfers it to chemical stores mesophyll cells of energy in glucose molecules More chloroplasts in upper - More light can be absorbed palisade tissue near the upper leaf surface Waxy cuticle on upper and - Reduces water loss through lower epidermis evaporation from the leaf - Transparent for light to enter the leaf Veins containing xylem - Xylem transports water and Transport of and phloem situated close mineral salts to mesophyll nutrients to mesophyll cells cells - Phloem transports sucrose away from the leaf Special structures Leaf hair Limits air movement near stomata Succulent leaf Stores water Sunken stomata To trap water vapour to reduce water vapour concentration gradient Thick cuticle To prevent evaporation of water from the ell *Stomata opens: - Light triggers active uptake of potassium ions by guard cells from nearby cells - Lowers water potential of guard cells and water enters by osmosis - Uneven thickness of cell walls of guard cells result in cells bowing with water intake, guard cells are turgid, opening pore of stoma *Stomata closes: - Water leaves guard cells by diffusion of potassium ions out of guard cells - Increases water potential of guard cells and water leaves by osmosis - Guard cells become flaccid and stoma closes *Stoma is the space in between stomata, guard cells are in the stomata, stomata is the 2 structures Structure of a leaf of a Dicotyledonous Plant (e.g. sunflowers, mung beans) Upper and lower epidermis - Both made up of a single layer of closely-packed cells that protect the inner parts of the leaf - Epidermal cells do not contain chloroplasts - Only exception are guard cells Palisade mesophyll - Contain the largest number of chloroplasts in the leaf and are the main sites of photosynthesis - Elongated and cylindrical in shape - Closely packed side by side Spongy mesophyll - Spongy mesophyll cells carry out photosynthesis but contain fewer chloroplasts than palisade mesophyll cells - Irregular in shape, loosely packed and covered with a thin film of moisture - The large spaces in between the spongy mesophyll cells are known as intercellular air spaces - They allow gases such as oxygen and carbon dioxide to diffuse quickly throughout the entire leaf Guard cells - A pair of guard cells controls the opening and closing of each stoma - When the stomata are closed, gaseous exchange and the release of water vapour into the atmosphere cannot occur  - Unlike the lower epidermal cells, guard cells contain chloroplasts and are able to carry out photosynthesis Stoma - Stomata are microscopic openings found mainly in the lower epidermis that allow the leaf to carry out gaseous exchange - Allow water vapour to leave the leaf - Each stoma is surrounded by a pair of guard cells Cuticle - Outermost layer of a leaf - Transparent to let light pass through it and reach the plant cells on the inside of the leaf - Waterproof to prevent water from leaving the leaf too quickly, giving leaves a waxy texture Vascular bundle - Consists of the xylem and phloem - Xylem vessels are hollow tubes made up of many dead cells that transport water and dissolved mineral ions from the roots to the leaves - The walls of xylem vessels are strengthened by lignin, allowing the xylem to provide mechanical support for the plant External structures Features Function Lamina (leaf blade) - Wide blade means the leaf has more surface area for light absorption for photosynthesis - Thin blade means it has a shorter distance for carbon dioxide to diffuse easily into the mesophyll cells/ easier for light to penetrate leaf to reach the photosynthetic cells Petiole (leaf stalk) - Hold leaf upwards to absorb light for photosynthesis Network of veins - Consists of xylem and phloem Leaf arrangement - Arranged in a regular pattern around the stem - Don’t overlap each other - Increased surface area for light absorption for photosynthesis 2. Describe how carbon dioxide reaches mesophyll cells in a leaf  a) CO2 diffuses into the leaf through the stomata b) It dissolves in the water around the cells c) It then diffuses into the cells 3. Identify the positions of and explain the functions of xylem vessels and phloem (sieve tube elements and companion cells) in sections of an herbaceous dicotyledonous leaf, stem and root, under the light microscope Vessel Xylem Phloem Function - F1: Transport water and Transport sucrose and amino mineral salts up from the acids from the leaves to other roots parts of the plant - F2: Strengthen the walls, prevents vessels from collapsing - When bundled together, xylem vessels provide mechanical support to plant Contained Water Water and sucrose and substances amino acids - Sucrose and amino acids has to be dissolved in water to be transported - Transportation of water is not key Adaptations - Long hollow tube made up of - A column of sieve dead cells tube cells/elements - For F1 forms a long sieve - Tube does not have cross tube walls or cytoplasm - The sieve plates, - Enables water to which are ‘cross-walls’ move easily through between the cells lumen for F1 have many minute - Lignin on the inner walls pores to ensure rapid - For F2 flow of manufactured food such as sucrose and amino acids through sieve tubes - Companion cell of each sieve tube cell load sugars from mesophyll cells into sieve tube via active transport - Companion cells have many mitochondria to provide the energy needed for active transport End walls Completely broken down Partially broken down Direction of flow Unidirectional — Upwards Bidirectional — Up and downwards Process by which Transpiration Translocation substances are moved P is the sieve tube, Q is the companion cell *of dicot stem  4. Define the term translocation and illustrate the process through translocation studies Translocation: The transport of food (mainly sucrose) in the phloem tissue - Produce of photosynthesis are translocated via the phloem from production sites in green leaves to parts (known as sinks) where they are utilised, such as seeds, fruits, roots and new leaves. Pathway travelled: - The sucrose molecule moves from the mesophyll cells in the leaf to the phloem in a vascular bundle of the leaf. This is followed by movement to the phloem in a vascular bundle of the fruits, and finally to the cells of the fruit Impact of scoring on translocation - Interrupts translocation - Sugars synthesized by photosynthesis in the leaves are only transported as sucrose to one area for stage 5. Explain how the structure of a root hair cell is suited for its function of water and ion uptake Adaptations Structure of root hair cell Functions Has a long and narrow - High surface area to volume ratio extension - Increases rate of absorption of water and mineral salts by the root hair cell  Has a cell membrane - Prevents the cell sap, which contains sugars, amino acids and salts, from leaking out. - Ensures it has a lower water potential than the soil solution - Water enters root hair by osmosis Has numerous mitochondria - Aerobic respiration in the mitochondria releases energy for the active transport of ions into the cell How root hairs absorb ions or mineral salts By diffusion By active transport - When concentration of ions in the soil - When concentration of ions in the soil solution is higher than that in the root solution is lower than that in the root hair cell sap hair cell sap - Ions diffuse in accordance to the - Ions are absorbed against the concentration gradient concentration gradient - Energy of process comes from cellular respiration in the root hair cell Transpiration pull Concept behind: Capillary action is the ability of a liquid to flow through narrow spaces without any assistance and even against gravity. It occurs when the adhesive forces between the liquid and the walls of the space are stronger than the cohesive forces between the liquid molecules. - Adhesive forces are attractive forces between molecules of the same substance - Cohesive forces are attractive forces between molecules of different substances Plants make use of this concept to help water to move up the narrow xylem vessels of plants. 1. While water is taken into plants through their roots, it is also evaporating through the stomata of the leaves 2. The loss of water vapour through the stomata is known as transpiration 3. As transpiration occurs, a suction force is created, drawing water up from the roots to the leaves. This force is called transpiration pull. Transpiration 1. Water evaporates from the mesophyll cells and forms a thin film of moisture over the cell surfaces 2. Water evaporates from the thin film of moisture and then moves into the intercellular air spaces 3. Water vapour accumulates in the intercellular air spaces near the stomata and diffuses out through the stomata via transpiration to the drier atmosphere. Effect of rainy days on transpiration rate 1. During rainy days, the humidity in the air is high which means the concentration of water vapour in the atmosphere is high, which decreases the water vapour gradient between the air and the inside of leaves in a plant  2. As a result, water vapour in the intercellular spaces in the spongy mesophyll layer diffuses out of the leaf into the air through the stomata at a lower rate 3. Thus, the plant loses less water and the transpiration rate of the plant decreases Additional content: Wilting - Occurs when the rate of transpiration is higher than the rate of absorption of water by the roots - Turgor pressure in the leaf mesophyll cells helps to support the leaf and keep it firm - Enables it to spread out widely and to absorb light for photosynthesis Advantages Disadvantages Reduction in rate of transpiration Close of stomata reduced amount of CO2 - Reduction in leaf surface area entering the leaf exposed to light - CO2 becomes a limiting factor - Reduced exposed of stomata to - Decrease in rate of photosynthesis atmosphere - Reduced rate of water loss through Folding of leaf reduces surface area exposed stomata to light - Excessive loss of water causes guard - Decrease in rate of photosynthesis cells to become flaccid and stomata to close Photosynthesis LOs: 1. State that: Chlorophyll absorbs light energy and converts it into chemical energy for the formation of carbohydrates and their subsequent uses. 2. State the equation, in words and symbols, for photosynthesis - Conditions needed: light, CO2, chlorophyll, suitable temperature, water  - Products of the light independent stage are used to drive reactions in light independent stage to produce sugars 3. Outline how light energy is harnessed and converted into chemical energy during the light-dependent reactions of photosynthesis Light dependent stage (within photosystems on grana): a) Light energy absorbed by chloroplast pigments is used in photolysis of water molecule (splitting of water by light), formation of NADPH (reducing power) & ATP i) Photochemical step b) Oxygen is released as a by-product c) Largely unaffected by temperature 4. outline the role of Calvin cycle/ light independent reactions in photosynthesis for synthesis of sugar Light independent stage/ Calvin cycle (within stroma): a) Stage 1 — Carbon Fixation - CO2 diffuses into the stroma, combines with ribulose bisphosphate (RuBP; 5-Carbon sugar) - Done in the presence of RuBisCO (ribulose bisphosphate carboxylase/oxygenase; CO2- fixing enzyme) - Product: Glycerate-3-Phosphate (GP; 6-Carbon sugar)  b) Stage 2 — Reduction - Glycerate-3-Phosphate is reduced to triose phosphate (TP; 3-Carbon sugar) by NADPH and ATP from light dependent stage - Done by energy from ATP and hydrogen from NADPH (oxidation of NADPH to NADP) - Obtained from light dependent stage - From triose phosphate, carbohydrates (other sugars and starch, sucrose for translocation), lipids and amino acids can be synthesized - Means all these other nutrients can be made by using triose phosphate c) Stage 3 — Regeneration of ribulose bisphosphate - RuBP is regenerated using energy from adenosine triphosphate (ATP), so that more CO2 can be fixed Calvin Cycle: - makes use of enzyme-catalyzed reactions - dependent upon continuous supply of NADPH and ATP from light dependent stage - Highly temperature sensitive - Can take place in absence of/ under low light in stroma of chloroplasts Possibilities of what happens to glucose formed during photosynthesis: - Used immediately - For cellular respiration to provide energy for cellular activities  - To form cellulose cell walls - Converted to starch and stored temporarily - In darkness, photosynthesis stops and starch is converted by enzymes back to glucose - Converted to sucrose and transported away to be stored - Converted to amino acids to form proteins - For synthesis of new protoplasm in leaves - Becomes fats - For storage - Used in cellular respiration - For synthesis of new protoplasm 5. Investigate and discuss the effects of varying light intensity, carbon dioxide concentration and temperature on the rate of photosynthesis (e.g. in submerged aquatic plant) Temperature: - An increase gives molecules more kinetic energy causing substrates to collide with active sites more frequently, increasing the rate of photosynthesis - As temperature approaches the optimum, the enzymes begin to denature (active site changes to become non-functional), causing the rate of photosynthesis to increase more slowly and eventually peak - After the optimum temperature, enzymes denature rapidly causing a fast decrease in the rate of photosynthesis as temperature increases further  6. Discuss light intensity, carbon dioxide concentration and temperature as limiting factors on the rate of photosynthesis - A limiting factor is a factor that affects the rate of a reaction. The rate cannot increase unless the value of the limiting factor is increased. - Within a certain range, when a limiting factor is increased, the rate of photosynthesis will increase. - However, up to a certain point, the rate of photosynthesis would not increase further as it will no longer be a limiting factor. At that point, other factors would be the limiting factors. Light intensity CO2 concentration Temperature Light is needed for CO2 is needed for carbon A suitable temperature is light-dependent reactions to fixation to occur during the needed for photosynthetic occur on the thylakoids of light independent reactions of enzymes such as RuBisCO  chloroplasts photosynthesis to function Background info. Photosynthesis - Photosynthesis is a chemical process by which green plants produce carbohydrates from carbon dioxide and water in the presence of light. - Chlorophyll, a green pigment found in the chloroplast of plant cells, is required for this process to occur. - Chlorophyll gives plants their green colouration. - Photosynthesis takes place mainly in the leaves of plants - The xylem transports water and dissolved mineral ions from the roots to the leaves of plants. The phloem transports sucrose and amino acids from the leaves to other parts of the plant. Note: Sucrose and amino acids are dissolved in water to be transported in the phloem. However, the transport of water is not the main function of the phloem. The sieve tube, made up of many sieve tube elements, is relatively hollow. It contains only cytoplasm. Sieve plates, which have pores within them, are found in between sieve tube elements. Each sieve tube element is accompanied by a companion cell. Companion cells contain a nucleus and many mitochondria. Through the process of respiration, these cells release the energy required for the the active transport of sucrose and amino acids. Evaporation of water from the leaves removes water from the xylem vessels. This results in a suction force which pulls water up the xylem vessels. This suction force due to transpiration is called transpiration pull. It is the main force that draws water and mineral salts up the plant. The stream of water up the plant is called transpiration stream. As transpiration occurs mainly through the stomata, it is linked to gas exchange between the plant and the environment. During photosynthesis, the plant releases oxygen as waste while simultaneously absorbing carbon dioxide. There is a concentration gradient between the environment in the leaf and the air around it as water vapour is more concentrated in the intercellular air spaces. Water vapour diffuses out of the leaf through the stomata. Transpiration does not occur when the stomata are closed. Guard cells control whether the stomata is open or closed. Transpiration pull draws water and mineral salts from the roots to the stem and leaves. 2. Evaporation of water from the cells in the leaves removes latent heat of vaporisation. This cools the plant. 3. Water transported to the leaves can be used for photosynthesis; to keep the cells turgid; and to replace water lost from the cells. Dry mass: without water molecules Monomer (glucose) makes starch, cellulose and lignin (complex carbohydrate) and sucrose Soil water contains Mg2+, NO3-, Ca2+, NH4+, forms the nitrogen in the amino group and has amino acids, polypeptides Monocotyledonous - pandan leaf suction force, negative liquid pressure in xylem vessel sieve tube element, cells have end walls with perforations and has a 2 way flow source of ‘food’ (product of P.S, like glucose): photosynthetic organs (mainly green leaves) that contain chlorophyll stems that are green have chlorophyll sinks: non-photosynthetic organs like roots pushing force for 2 way flow The light-dependent stage of photosynthesis is a photochemical step that occurs at the photosystems in the grana of the chloroplast in the presence of light. Stroma is between 2nd and 3rd membrane (thylakoid), ATP creation is here Granum is 1 stacks of thylakoids, grana is plural Blue and red light is absorbed by membrane, causing water to split (½ O2 [which is O but it’s unstable] and 2H), hydrogen carried by transporter to stroma where light independent stage takes place - Formation of NADPH (reducing power) and ATP Photolysis: Splitting of water by light Compounds - Ribulose Bisphosphate (RuBP) - Glycerate-3-phosphate (GP) - Triose Phosphate (TP) - Adenosine Triphosphate (ATP) Carbon Fixation RuBP is a 5 carbon compound, carbon dioxide is a 1 carbon compound, together, they form a compound (6 carbon compounds and 2 Phosphate compounds) when both RuBP and CO2 bind in the active site of the Rubisco (Ribulose biphosphate carboxylase oxygenase; CO2 fixing enzyme) enzyme. It then splits into 2, each with its own phosphate, forming 3-Phosphoglycerate (3P). Reduction ATP (from light-dependent stage) gives out its terminal phosphate (i.e covalent bond breaks off) so now you have 1 3-Bisphosphoglycerate compound, introduce H+ and be reduced (because hydrogen ions are gained) to 6 G3P, 1 of the G3P (GP) is reduced to 2 TP by hydrogen from NADPH (oxidation of NADPH to NADP) and ATP to form glucose and other organic compounds (lipids, carbohydrates, amino acids etc.) Regeneration of RuBP The other 5 of the G3P use ATP to reform to 3 RuBP compounds with the newly entered 3 CO2, forming 18 carbon compounds, in turn, 3 RuBP. Cycle repeats. Stages of Location Input/ Reactant Output/ Product Processes involved Photosynthesis Light Grana - Sunlight - ATP - Photoactivation Dependent - ADP - Oxygen - when lights Stage - Inorganic - NADPH shine on the phosphate chlorophyll, - Water electrons - NADP are activated  - Photolysis of water - when water splits in the presence of light Light Stroma - ATP - ADP - Carbon fixation Independent - CO2 - NADP - Reduction Stage - NADPH - Glucose - Regeneration of RuBP Glucose is converted to sucrose Glucose forms fats Nitrates come from soil water 6CO2 +12 H2O → C6H12O6 + 6O2 + 12H2O Redox: - Oxidation: gains oxygen/ loses hydrogen/ loses electrons/ increase in oxidation state (Fe 2+ —> Fe 3+ + e-) - Reduction: everything is opposite of oxidation (i.e. loses oxygen/ gains hydrogen/ gains electrons/ decrease in oxidation state Factors affecting rate of photosynthesis - Asymmetry for graph of temperature affecting rate of photosynthesis - Water availability and chlorophyll is a given for the occurrence of photosynthesis so it’s not included as a factor - All graphs should start at (0,0) - If it’s on slope, x-axis variable is limiting factor, but if it’s on the horizontal line, another factor is the limiting factor (e..g temperature) - If there’s too much of the x-axis variable, it might go down to 0 - White light is the best since it has both blue and red light included - Rate of a process = D.V/ Time taken - Described by fast, normal, slow - Limiting Factor is a factor that can affect the rate of a process such that when the magnitude of this factor is increased, the rate of the process will also increase - Carbon dioxide concentration can change through greenhouse (can go beyond usual) - If 2 variables are different, you cannot compare them, it's not a fair test Respiration - Release energy/ Provide energy, not produce energy  - Increased breathing to obtain oxygen - Increased heart rate to supply oxygen - Demand of energy >>> supply and energy by just aerobic respiration - Aerobic (needs oxygen) - Involves the breakdown of glucose in the presence of oxygen - Produces carbon dioxide and water as waste products - Generates large amount of energy in the form of ATP - Location of process: mitochondria - Anaerobic respiration (can occur in absence of oxygen) - Involves the breakdown of glucose in the absence of oxygen - Occurs in muscle cells during vigorous activity - Generates relatively small amount of energy - Glucose (C6H12O6, 6C compound) to lactic acid (3C-compound) - 1 molecule to 2 molecules Cytosol + organelle Glucose → ethanol + carbon dioxide + release a small amount of energy - CO2 expands upon heating When continuous muscle contraction occurs: - Aerobic respiration alone is not fast enough to supply the increase in energy demand - Anaerobic respiration takes place to meet the increased energy demand