Process of Photosynthesis

• Photosynthesis is the process by which chemical energy is transformed from light energy. It gets carried out mostly by plants, while certain prokaryotes are also capable of photosynthesis.

• In plants, a type of organelle called chloroplasts is where photosynthesis takes place in the cell. The higher leaf cells contain a large concentration of chloroplasts since this is the area of the plant that receives the most sunlight.

• There are two stages to the endothermic chemical reactions that occur during photosynthesis.

Stage one (light-dependent stage)

• The light-dependent reaction create ATP and NADPH by converting light energy into chemical energy. The following is a summary of the light-dependent reaction:

• The pigment chlorophyll, which is found in chloroplasts, gives plants their green colour. The pigment chlorophyll absorbs light when it strikes the leaf.

• Water molecules are also divided into hydrogen ions and oxygen by the light. Hydrogen moves to the second stage of the process, while oxygen is expelled from the plant as a waste product.

  • Inputs: water and light

  • Outputs: waste (oxygen) and hydrogen

Stage two (light-independent stage)

• The light-independent reactions reduce carbon dioxide and convert the energy into the chemical bond energy found in carbohydrates like glucose by using the ATP and NADPH from the light-dependent reactions. This is a summary of the light-independent reactions:

• The hydrogen output from the light-dependent stage combines with carbon dioxide to produce glucose.

• Glucose is stored as starch- as soon as the plant requires energy to be broken down and used as fuel for respiration in cells.

• After then, it can be applied for development and maintenance, and can aid in the synthesis of proteins, fats, carbs, and other molecules found in plants.

  • Inputs: Carbon dioxide and hydrogen (from stage one)

  • Outputs: glucose

Equation for photosynthesis

• The fundamental formula of photosynthesis is quite simple. In reality, there are numerous phases in the process that involve intermediate reactants and products.

• Two molecules of GA3P, each with three carbons, combine to form glucose, the main energy source in cells.

• In words, this equation represents the conversion of six molecules of carbon dioxide (CO2) and six molecules of water (H2O), in the presence of light energy, into one molecule of glucose (C6H12O6) and six molecules of oxygen (O2).

Enzymes in photosynthesis

• Enzymes catalyse the chemical reactions involved in photosynthesis. Proteins called enzymes aid in accelerating processes but do not undergo change or exhaustion while doing so they are reusable.

• The substrate is the molecule that an enzyme binds to during a process, and the active site of the enzyme is the location where the substrate binds.

• A substrate molecule attaches itself to an enzyme at its active site during a process, where it is subsequently converted into the final products.

• This is known as the lock and key model of enzyme action because, like different locks that require different keys, each enzyme is unique to a certain type of substrate.

• The rate of an enzyme-catalysed reaction might vary depending on several factors:

  • pH - The ideal pH at which enzymes function is known. The geometry of the active site changes as the pH deviates from this. This indicates that no enzyme-substrate complexes can form because the substrate cannot fit in the active site. This indicates a denatured state of the enzyme and a drop in reaction rate.

  • Temperature - the rate of reaction increases as the temperature rises to the enzyme's optimum. This is a result of the molecules moving more quickly due to their increased kinetic energy. As a result, there can be greater formation of enzyme-substrate complexes and more successful collisions. The geometry of the active site changes and the enzymes become denatured at temperatures far above the optimal range. Due to the inability of enzyme-substrate complexes to form, this lowers the rate of reaction.

  • Concentration of substrate: The rate of reaction rises with increasing substrate concentration grows in a proportionate way. The rate of reaction peaks at high concentrations of the substrate. (stops increasing) when every active site in the enzyme is occupied.

Factors influencing photosynthesis rate

• The limiting factor sets a limit on the rate of photosynthesis. The plant has the least amount of access to this aspect. For instance, because there is relatively little light at night, photosynthesis proceeds at a much slower rate, extremely low, irrespective of temperature and carbon dioxide content.

  • Concentration of carbon dioxide: The rate of photosynthesis rises with an increase in CO2 concentration.

  • Temperature: Enzymes are necessary for photosynthesis to occur. The ideal temperature for photosynthesis is the same as the ideal temperature for these enzymes. This is typically at a temperature of 25°C. Plants photosynthesise at low temperatures, such as those experienced in the winter slowly because there aren't many enzyme-substrate complexes formed because the enzymes have low kinetic energy. These enzymes denature at extremely high temperatures, which also reduces the rate of photosynthesis.

  • Light intensity: The rate of photosynthesis rises with increasing light intensity. According to the inverse square law, light intensity is inversely proportional to the square of the distance between the plant and the light source in this case (𝑰 ∞ 1/𝒅2), where d is the distance and I is the light intensity. Sometimes a high light intensity will cause a plant to heat up past its ideal temperature; nevertheless, at that point, temperature would become the limiting factor and more light intensity would not accelerate photosynthesis.

How do producers obtain the materials they require?

• Many different substances are taken up and released by photosynthetic organisms. For photosynthesis to occur, carbon dioxide and water must be utilised. Mineral ions are also required for the construction of cell structures.

• When plants engage in photosynthesis, oxygen is their primary waste product. The majority of it leaves the plant while a tiny quantity is consumed during respiration.

• Gases such as carbon dioxide and oxygen diffuse throughout the plant. Diffusion is the passive process of molecules moving from the area of high concentration to the area of low concentration.

• Energy is not needed for this. Gases pass through the membranes that surround cells and enter and exit the plant through stomata, which are pores often located on the undersides of leaves.

• Through osmosis, water molecules move. This is a non-energetic process that is comparable to diffusion. A partially permeable membrane allows water molecules to flow from a high concentration area to a low concentration area. Because only specific molecules can travel through it, it is only partially permeable.

• Root hair cells take up mineral ions from the surrounding soil. The concentration of mineral ions in the soil is low, therefore they have to travel up the concentration gradient into the root to reach a high concentration. This process, known as active transport, needs energy.

• Root hair cells have the ideal ability to effectively perform active transport:

  • Their surface area is substantial.

  • They include a lot of mitochondria, which are needed for respiration and the production of energy for active transport. Since they are unable to do photosynthesis below the surface, they are devoid of certain organelles that they do not require, such as chloroplasts.

  • Because there is less distance for molecules to traverse, their thin cell membrane accelerates the rate of diffusion and active transport.

Guard cells and stomata

• The stomata on the underside of the leaf facilitate the diffusion of oxygen and carbon dioxide out of the leaf as well as the entry of water vapour. When there is a restricted water supply, the guard cells cause the stomata to close to minimise water loss.

• Guard cells surround the stomata and can control their opening and closing to limit water loss from the plant. But this also slows down the amount of carbon dioxide that diffuses through the stomata to be used in photosynthesis, which can make carbon dioxide the limiting factor and slow down photosynthesis.

• In order to prevent water loss, plants in warmer climates typically have fewer stomata.

Phloem and Xylem

• Phloem and xylem vessels make up the transport system of plants. These are employed in the movement of molecules from the plant's roots to its stem and leaves and back again.

• Water is moved through plants by the xylem from the roots to the leaves, where transpiration takes place. Dead cells that have been hollowed down and had their ends cut off form the xylem, a tube through which water can travel.

• The phloem is a network of living cells that facilitates the translocation of nutrients and carbohydrates in food.

Transpiration

• The loss of water vapour from the mesophyll cell surface as a result of evaporation is known as transpiration.

• The stomata on the plant then allow the water vapour to go. Transpiration pull—rather than osmosis—draws water molecules up the xylem. Because water molecules are cohesive, they cling to one another.

• This implies that more water is sucked in when the water diffuses out of the stomata and evaporates at the leaf the plant from its roots upward.

• By maintaining cells turgid, this water aids in the maintenance of plant structure. If a plant loses too much water and doesn't replenish it, water moves out of the cells and turgor pressure drops, causing the plant to wilt.

• The plant seals its stomata to stop water vapour from diffusing out in an effort to reduce water loss.

• Environmental elements that restrict the rate of water absorption:

  • Light intensity: High light intensities result in high rates of photosynthesis, which means that stomata are open to allow for the availability of carbon dioxide. Because of this, the rate of transpiration is high, requiring an increase in the rate of water absorption to replace the water that was lost.

  • Air movement: The stomata frequently catch moist air, which lessens the variation in the concentration of water vapour inside and outside the plant. This implies that water is not absorbed at a high rate due to low transpiration. In a similar vein, limited water absorption occurs in humid environments. The leaf absorbs more water when there is a lot of air movement because the moist air is driven away from it.

  • Temperature: High evaporation rates lead to high rates of water absorption at warm temperatures. Furthermore, a high rate of photosynthesis indicates that the stomata will be transparent to enhance transpiration.

Translocation

• Translocation is the movement of sucrose and amino acids through phloem channels. Sources are locations where sucrose and amino acids are made.

• Sinks are areas where they are kept or utilised for development and respiration. Materials are constantly shipped from sink to source using a pressure gradient with water. The leaves create sucrose and amino acids, which are then transferred to the roots for keeping. Afterwards, they are moved to areas where they are utilised for breathing and expansion.

• Within a plant, certain components, like the leaves, can function as a source and a sink as they create chemicals and employ them in metabolic processes.

How are living organisms in an ecosystem interrelated?

• Producer - these are organisms that convert light energy to chemical energy in order to produce their own nutrients. Photosynthetic organisms are the main producers of food and therefore biomass.

• Consumer - an organism which obtains their energy and biomass from feeding on other animals or plants.

• Herbivore - organisms which consume plants.

• Carnivore - organisms which consume animals.

• Decomposer - organisms that are responsible for breaking down decaying organic material (detritus).

• Ecosystem - is made up from all the living organisms and abiotic components (such as soil, rocks and water) in a community. These interact with each other to function as one group.

• Population - comprises organisms of the same species living together in one habitat.

• Community - populations of many various species living together in one ecosystem make up a community.

• Food chain - a diagram which presents the order of energy transfer through feeding in an ecosystem.

• Food web - a diagram that presents how different food chains interact with each other.

• Biomass - the total mass of living things.

• Pyramid of biomass - display the total mass of organisms in each trophic level of a food chain.

• Trophic level - the trophic level of an organism shows its position in the food chain, food web or pyramid of biomass.

Producers

• Producers are organisms in the first stage of the food chain, such as plants and algae. They take compounds from the environment and convert them into small molecules, which can be utilised to create larger molecules and structures.

• In the environment, plants absorb nitrogen and carbon compounds. They then mix these elements with oxygen, hydrogen, and other elements to form a variety of tiny molecules, such as:

  • Sugars: They are composed of carbon, hydrogen, and oxygen.

  • Fatty acids: Made up of oxygen, hydrogen, and carbon.

  • Glycerol: Made up of oxygen, hydrogen, and carbon.

  • Amino acids: nitrogen, oxygen, hydrogen, and carbon are all present.

• These can be utilised to create large molecules such as amino acid chains, create proteins, carbohydrates are made of sugars, and lipids are made from glycerol, fatty acids and phosphate.

Biological Molecule Tests

• Food tests can be used to identify various biological substances found in food samples. Different assays can be employed to identify lipids, proteins, and carbohydrates.

• They entail mixing a food sample with a reagent that, depending on the biological components present, changes colour.

  • Prior to adding the reagent, it could occasionally be required to crush the food or add water to it.

Carbohydrates

• Benedict's Test: used to identify decreasing sugars, including fructose and glucose. Benedict's solution changes from blue to a brick-red precipitate when reducing sugars are present.

• Iodine Test: detects the presence of starch. When iodine is added to a starch-containing solution, it changes color from yellow-brown to blue-black.

Lipids

• Sudan III Test: identifies lipids in a solution accurately. Lipids in the combination produce a noticeable red layer on top of the solution when Sudan III dye is added.

• Emulsion test: when the sample is shaken with water, it forms a hazy, white emulsion that indicates the presence of lipids. If there are lipids, the emulsion lasts for a while.

Proteins

• Biuret Test: mainly determines whether peptide bonds, which are specific to proteins, are present. A solution containing proteins turns violet/purple when it is treated with a diluted solution of copper sulphate and sodium hydroxide.

Consumers

• In order to obtain biomass, organisms known as consumers feed on plants and animals.

• The word "consumer" usually refers to animals, while certain fungus and carnivorous plants are also included in this category. Through food, plants and other animals provide the nitrogen molecules that animals need to survive.

• As these compounds are produced by the breakdown of plant and animal materials, which releases small molecules and compounds that the consumer can absorb and use to construct larger atoms.

Food webs and chains

• A food chain illustrates the sequence in which biomass is transferred between organisms; it does not, however, indicate the quantity of biomass at each level. A food web displays all of the linked food systems in an ecosystem, demonstrating the interdependence of living things.

• Producers are the first link in a food chain because they transform solar light energy into chemical energy.

• Herbivores consume producers in order to obtain nutrients and biomass from the plant. After that, another animal consumes this consumer and absorbs its nutrition.

• Every one of these creatures has a distinct trophic level. A consumer's classification in the food chain determines whether they are considered primary, secondary, tertiary, or quaternary.

• A biomass pyramid that illustrates the quantity of biomass can be used to illustrate this, visible at every level, with producers at the bottom. The procedure for passing biomass between species is one instance of the interdependence among ecological components.

• Because some biomass is lost as waste, the amount of biomass declines between trophic levels:

  • Not all plant and animal materials, such as fur and bones, can be broken down to produce biomass.

  • Biomass is lost by decomposition and excretion.

• Later trophic levels have fewer animals per species because there is insufficient biomass obtained from prey to support a large population, as biomass is lost at each stage.

• For instance, compared to rabbits and deer, which are main consumers, there will be significantly fewer bears and lions, who are further up in the food chain.

• Other variables that limit the size of a population include predation, the quantity of partners available, and competition from other species.

Carbon Cycle

• The majority of molecules in living things are composed of the necessary element carbon. The movement of carbon atoms between the atmosphere and living things is illustrated by the carbon cycle:

1. Carbon dioxide, which makes up around 0.04% of the air, is the form of carbon that is found in the atmosphere.

2. Plants absorb carbon dioxide when they photosynthesise. Here, the carbon is converted into carbon dioxide to other compounds like carbohydrates and proteins.

3. Since feeding involves the passage of these molecules through the food chain, carbon is thus transferred between the trophic levels.

4. When we breathe, we expel carbon dioxide into the atmosphere and return carbon to it and during decomposition.

• In cases when decomposition is not occurring, carbon can become retained in dead organisms. Fossil fuel is created when these organisms get fossilised over thousands of years. Burning this fossil fuel releases a significant amount of carbon dioxide back into the environment.

Water Cycle

1. Water vapour, or gas, is created when water vapour evaporates from bodies of water like lakes and rivers. Additionally, plants release it during transpiration.

2. As it ascends, this water vapour starts to cool. Condensation happens as it cools, converting the vapour back into liquid water and creating clouds.

3. Water falls from clouds as precipitation (rain, snow, hail, etc.) when the cloud becomes too heavy.

4. In order for the cycle to continue, this water is either absorbed by plants and animals or finds its way back to a body of water through runoff.

Decomposition

• Decomposers break down dead organisms to release the nutrients they contain back into the soil. Detritus is the term for dead organic stuff.

• Decomposers are microscopic soil organisms like fungi and bacteria that use extracellular digestion, which is aided by enzymes, to break down debris.

• Enzymes from bacteria and fungi's cells are secreted into extracellular digestion. the soil to decompose organic matter, after which the products are reabsorbed into the cells. It's referred to as "extracellular" since it takes place outside the cells.

• Factors influencing the rate of breakdown include:

  • Temperature: Enzymes are needed by decomposers to process and digest their meal. Warm decomposition rates increase at temperatures that are near to the enzyme's optimal range. Because the enzymes are not active at low temperatures, the rate of degradation is modest.

  • Oxygen:necessary for decomposers to function aerobically and emit carbon dioxide. In regions of breakdown where there is insufficient oxygen, such as landfills and marshes, decomposers use anaerobic processes to break down debris. Because it releases methane, a greenhouse gas with a far greater impact on the environment than carbon dioxide, anaerobic respiration is slower and worse for the ecosystem.

  • Water presence: Because decomposers are living organisms, decomposition in dry soils can proceed slowly because creatures require water to exist. But water fills the air in soils that have been flooded with water spaces, which causes anaerobic breakdown.