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ENZYME Factors That Affect Enzyme Activity - Enzymes are proteins that play a crucial Several factors can influence how well enzymes role in speeding up biochemical work. These include: reactions in the body....

ENZYME Factors That Affect Enzyme Activity - Enzymes are proteins that play a crucial Several factors can influence how well enzymes role in speeding up biochemical work. These include: reactions in the body. Without enzymes, many reactions that are necessary for Temperature: Enzymes work best at a life would occur too slowly to sustain specific temperature range. In humans, life. enzymes typically function best at body - Enzymes are biological catalysts, temperature (around 37°C). Too high or meaning they increase the rate of too low temperatures can reduce enzyme chemical reactions without being activity. High temperatures can even consumed in the process. Each enzyme denature (destroy) enzymes, rendering is specific to a particular reaction or type them ineffective. of reaction. Enzymes lower the pH Levels: Every enzyme has an activation energy required for a reaction optimal pH level. For instance, stomach to occur, allowing biological processes enzymes like pepsin work best in acidic to happen more quickly and efficiently. conditions, while enzymes in the small intestine prefer a more alkaline Example environment. Substrate Concentration: As substrate Enzymes in the stomach, such as pepsin, help concentration increases, enzyme activity break down proteins into smaller peptides, also increases—up to a point. Once all which the body can absorb. Without enzymes, the enzyme molecules are bound to digesting food would be a much slower and less substrates, the reaction rate levels off, efficient process. because the enzyme is saturated. TWO MODEL OF ENZYME Enzyme Inhibitors Lock and Key Model - In this model, the Enzyme inhibitors are substances that can slow enzyme's active site is perfectly shaped for the down or stop enzyme activity. There are two substrate, much like a key fits into a lock. This main types of inhibitors: model suggests that enzymes are very specific and only work with substrates that fit their active 1. Competitive Inhibitors: These site exactly. molecules resemble the enzyme's substrate and compete for the active site. Induced fit Model - This model suggests that If the inhibitor binds to the active site, while the active site of the enzyme may not the substrate cannot, and the reaction is initially be a perfect fit for the substrate, it can slowed down or blocked. change shape slightly to accommodate the 2. Non-competitive Inhibitors: These substrate. Once the substrate binds, the enzyme inhibitors bind to a different part of the molds itself around the substrate, enabling the enzyme, changing the shape of the reaction to proceed. active site so the substrate can no longer fit. This type of inhibition is harder to overcome, as it doesn’t depend on the concentration of the substrate. Why Enzymes Are Important Enzymes are essential for life because they allow cells to carry out complex chemical reactions quickly and efficiently. They are involved in processes such as digestion, respiration, DNA replication, and metabolism. Without enzymes, life processes would slow down or stop altogether ATP And ADP Cycle ATP provides energy to cells through a cycle where its phosphate bonds are broken, releasing energy. This converts ATP to ADP plus a phosphate. ADP is then recycled back to ATP by adding a phosphate group, using the same amount of energy released originally. The ATP-ADP cycle transfers chemical energy in cells by breaking and reforming ATP's phosphate bonds. ATP - adenosine triphosphate supplies energy to the cell. ( most important biological of the cell) atp composed of 3 parts. 1. A Nitrogenous base ( Adenine) 2. A sugar ( Ribosome) 3. Three phosphate groups bonded by high energy bonds ADP - adenosine diphosphate is the spent molecule of atp. - Has two phosphate groups and a lot less energy. Binding site NON COMPETITIVE INHIBITOR - Amino acid residues that function to - These inhibitors bind to a different bind or accommodate the substrate part of the enzyme, changing the molecule. shape of the active site so the substrate can no longer fit. This type Catalytic site of inhibition is harder to overcome, as it doesn’t depend on the - Amino acid residues in the active concentration of the substrate. site serve to speed up or catalyze the reaction once binding has Photosynthesis and the Role of occurred. Pigments SUBSTRATE - Pigments are organic molecules that selectively absorb light of specific - A molecule that the reaction of which wavelengths. Plants have is catalyzed by the enzymes. photosynthetic pigments built in the - Each enzyme is specific to a thylakoid membranes of their substrate. chloroplasts. PRODUCT 1. Chlorophyll A The most common and most important photosynthetic pigment in - Once the enzyme and substrate are plants, algae, some protists, and bound to each other and the reaction cyanobacteria. This pigment absorbs violet, has occurred, a product is then blue, and red light, and reflects mainly produced by the enzyme. green, so most plants appear green to us. It participates directly in the light reactions ENZYMES AS CATALYSTS during photosynthesis, particularly an important player in the light-harvesting - Catalysis is the speeding up of complex of chloroplasts. reaction rates that are specific to the type of substrate and enzyme 2. Chlorophyll B This pigment absorbs involved. mainly blue and orange light but reflects olive green. Chlorophyll b does not COMPETITIVE INHIBITOR participate directly in light reactions, although it conveys absorbed energy to - These molecules resemble the chlorophyll a to work in the light reactions. enzyme's substrate and compete for the active site. If the inhibitor binds 3. Carotenoids Chloroplasts also contain to the active site, the substrate pigments called carotenoids, which are cannot, and the reaction is slowed various shades of red, yellow, and down or blocked. orange-green light. These colors are common in leaves during the season of fall. These yellow-orange hues of longer-lasting carotenoids appear once the chlorophyll breaks down reactions. This pigment is also important in LIGHT-DEPENDENT REACTION photoprotection. Carotenoids absorb and Light capture: Pigments like chlorophyll dissipate excess light energy that would absorb light energy, propelling electrons in otherwise damage the chlorophyll or interact photosystems. with oxygen to form reactive oxidative ATP generation: The released electrons molecules that can damage the cell. create a flow that drives ATP synthesis, storing chemical energy. 4. Anthocyanins are pigments found in the NADPH production: Another stream of vacuoles of plant cells, responsible for a electrons generates NADPH, an energy and wide range of colors, including red, purple, electron carrier molecule. and blue, depending on the pH of the plant Oxygen release: The water molecule splits, tissue. These pigments are water-soluble releasing oxygen crucial for the atmosphere and are most commonly seen in flowers, and respiration. fruits, and autumn leaves. Unlike chlorophyll and carotenoids, anthocyanins are not LIGHT-INDEPENDENT REACTION directly involved in photosynthesis. CO2 capture: The enzyme RuBisCO fixes Anthocyanins play a critical role in carbon dioxide (CO2) into organic protecting plants from environmental compounds in the Calvin cycle. stresses. One of their key functions is Sugar formation: The resulting molecules photoprotection, helping to reduce damage convert into sugars, utilizing ATP and caused by excessive light. Anthocyanins act NADPH from the light-dependent phase. as a "sunscreen" by absorbing harmful RuBisCO regeneration: Molecules blue-green and UV light, preventing these enabling CO2 capture regenerate, ensuring high-energy wavelengths from damaging cycle continuity. the plant tissues. This protective function is Readying for new cycles: The cycle especially important under conditions of persists, creating sugars and regenerating high light intensity or when plants molecules for CO2 fixation in future experience environmental stress such as iterations. drought, cold, or nutrient deficiency. Importance 5. Phycobilins play a crucial role in the Vital energy source: Photosynthesis photosynthetic processes of aquatic converts sunlight into chemical energy, organisms, especially those living in deeper nourishing plants and initiating food webs waters where light penetration is limited. on Earth. These pigments are highly efficient at Oxygen production: Photosynthetic capturing light in the orange, red, and green organisms release oxygen as a byproduct, regions of the light spectrum—wavelengths sustaining the respiration of most living that penetrate deeper into the water than beings and enriching the atmosphere with other colors of light, such as blue and violet. this gas. By absorbing these lower-energy Climate regulation: Photosynthesis wavelengths, phycobilins allow absorbs carbon dioxide, aiding in climate cyanobacteria and red algae to change control and maintaining the balance photosynthesize in environments where of the greenhouse effect. light is scarce. Photosynthesis converts solar energy to chemical energy autotrophs occurs in the chloroplasts Steps in the Light-Dependent Reactions next stage of photosynthesis, as it carries of Photosynthesis the energy needed for the Calvin cycle. 1.Photon Absorption (Photoexcitation) Calvin Cycle ( Light Independent ) Chlorophyll and other pigments in The enzyme-mediated reactions of the Photosystem II (PSII) absorb light. This light Calvin-Benson cycle , or simply the Calvin Energy excites electrons in the chlorophyll, cycle , ultimately produce glucose in the setting off a series of reactions. fluid-filled stroma of chloroplasts. These reactions are light-independent because 2. Water Splitting (Photolysis) energy from photons is not directly required To replace the excited electrons lost from for the chemical reactions to proceed. PSII, water molecules (H2O) are split. This Instead, they run on the ATP and NADPH process produces hydrogen ions (H+), molecules generated from light dependent electrons, and oxygen (O2) as a byproduct. reactions. The most important input to the The oxygen is released into the Calvin cycle is the carbon dioxide that atmosphere. comes from the atmosphere via the stomata of leaves. In this process, the 3. Electron Transport Chain (ETC) starting material, alongside the carbon The excited electrons are transferred to a dioxide, is a five-carbon sugar called the series of proteins known as the electron ribulose 1,5-bisphosphate or simply ribulose transport chain. As the electrons move bisphosphate (RuBP) , which is also along this chain, they lose energy, which is regenerated for use in the succeeding used to pump H+ ions into the thylakoid rounds of the Calvin cycle. lumen, creating a gradient. Three main phases of the Calvin cycle 4. ATP Synthesis (Chemiosmosis) The build-up of H+ ions in the thylakoid Fixation lumen creates a proton gradient. As H+ ions The process of incorporating carbon atoms from an inorganic source into an organic flow back into the stroma through a protein molecule is called carbon fixation. During complex called ATP synthase, this the carbon fixation of the Calvin cycle the movement drives the conversion of ADP enzyme RuBisCo (or ribulose bisphosphate and inorganic phosphate (Pi) into ATP. This carboxylase) catalyzes the reaction process is known as chemiosmosis. between the carbon dioxide and the five-carbon sugar RuBP. This process 5. Photosystem I (PSI) Activation results in the formation of an unstable six-carbon molecule, which spontaneously The electrons from the electron transport splits into two three-carbon organic acids, chain are passed to Photosystem I (PSI). the 3-phosphoglycerate or 3-PGA, which Here, they are re-energized by absorbing continue in the cycle. more light, giving them another boost. Reduction 6. NADPH Production During the reduction phase (as shown in Finally, the energized electrons from PSI Phase 2 of Figure 1) two chemical reactions are transferred to NADP+, reducing it to use energy from ATP and electrons NADPH. This molecule is essential for the donated from NADPH to reduce molecules of 3-PGA into energy-rich three-carbon sugars, the glyceraldehyde 3-phosphate liver normally stores it in the form of (G3P). This stage is called the reduction glycogen. The liver can store the excess reaction phase because it involves the glucose from the blood with the help of gain of electrons from the NADPH. The insulin produced by pancreas. Insulin resulting ADP and NADP + molecules also affects the ability of cells to absorb return to light-dependent reactions for them glucose, to be used in cellular to be reenergized. respiration, from the blood. Glucose is Regeneration a high-energy molecule that needs to To complete the Calvin cycle, RuBP must be broken down through the process of be regenerated. In this phase, for every cellular respiration. Cellular respiration three carbon dioxide molecules fixed, one uses oxygen molecules and releases G3P molecule leaves the cycle as a carbon dioxide as one of its product. This molecule contributes to the by-products. formation of the carbohydrate molecule, This is the reason why humans and animals which is commonly known as glucose. During the regeneration stage , a series of need to breathe in oxygen and expel carbon chemical reactions utilize energy from ATP dioxide. It is the opposite of photosynthesis to rearrange the atoms in the remaining five which requires carbon dioxide to start the G3P molecules (total of 15 carbon atoms) process and releases oxygen as its into three molecules of RuBP (likewise, a by-product. Cellular respiration can happen total of 15 carbon atoms). This process in two conditions—with or without oxygen. enables the cycle to replenish RuBP for the Aerobic respiration is the process of succeeding carbon fixation reactions. producing energy that uses oxygen while anaerobic respiration is the process that Products of Calvin Cycle does not use oxygen. It takes six carbon dioxide molecules to produce the hexose glucose. During the The Role of Mitochondria in Cellular Calvin cycle, there is one G3P molecule Respiration that leaves the cycle as a product for every The mitochondria are the major sites of three carbon dioxide fixed. For every three energy production. Energy is produced molecules of carbon dioxide fixed and through a process of cellular respiration and reduced to G3P, six ATPs and six NADPH the mitochondria play a vital role in this. The were used. An addition of three ATPs is number of mitochondria varies in each cell needed during the regeneration of RuBP. A depending on the activities carried out by total of six carbon dioxide molecules are the cell. If the cell carries out numerous needed to produce one molecule of six-carbon glucose (C 6 H 12 O 6 ) ; thus, activities, like the muscle cells, it may multiplying with the ATP and NADPH contain thousands of mitochondria. If cells requirements means that a total of 18 ATP like the fat cells do not need energy to and 12 NADPH molecules are needed. function, they may only contain a few mitochondria. The structures of mitochondria help it to efficiently function during cellular respiration. Cellular Respiration Mitochondria has an outer membrane, an Glucose is the primary source of inner membrane that folds into cristae, energy in humans. The body uses the intermembrane space, and a matrix space. available glucose to produce energy. In The intermembrane space is responsible for the excess of glucose in the blood, the holding the protons that are pumped out of oxygen indirectly. Pyruvate from the matrix. glycolysis is first converted to acetyl-CoA, a 2-carbon molecule The mitochondrial matrix is where ATP that enters the cycle. Through a synthesis and Krebs cycle happen. series of enzyme-driven reactions, Furthermore, the inner membrane of the acetyl-CoA is broken down mitochondria contains the proteins involved completely, releasing carbon atoms in the electron transport chain as well as the as carbon dioxide (CO₂). In the ATP synthase. Cristae, on the other hand, process, the cycle generates are folds of the inner membrane which high-energy molecules: 3 NADH, 1 increase the surface area for ATP FADH₂ (another electron carrier), production. and 1 ATP for each acetyl-CoA, amounting to a total of 2 ATP per Glycolysis glucose molecule. These electron - occurs in the cytoplasm and can carriers (NADH and FADH₂) are happen in an anaerobic crucial for the final stage. The environment, meaning it can still cycle’s location in the mitochondrial proceed in the process. During matrix allows it to interact directly glycolysis, one molecule of glucose with the ETC and is essential for (a 6-carbon sugar) is broken down cells to fully oxidize glucose, into two molecules of pyruvate, each capturing as much energy as containing 3 carbons. This process possible in the form of ATP. releases a small amount of energy, resulting in a net gain of 2 ATP Electron transport chain (ETC) molecules per glucose and - takes place in the inner membrane producing 2 molecules of NADH, an of the mitochondria and is directly electron carrier that will later dependent on oxygen. Here, NADH contribute to ATP production. and FADH₂, produced in the earlier - Glycolysis happens in the stages, release their electrons into a cytoplasm because it’s a relatively chain of proteins embedded in the simple process that doesn’t need inner mitochondrial membrane. As oxygen or the specialized electrons pass through the chain, machinery found in mitochondria. It they release energy, which is used provides quick energy, which is to pump protons (H⁺ ions) across the essential when oxygen isn’t readily membrane, creating a gradient. This available or when cells need a rapid gradient drives ATP synthesis as ATP boost. The pyruvate and NADH protons flow back through ATP produced in glycolysis are then synthase, a protein that generates transported into the mitochondria, ATP. where they enter the next stage if - Oxygen is essential here, acting oxygen is available. as the final electron acceptor at the end of the chain, where it Citric acid cycle (or Krebs cycle) combines with electrons and - occurs in the mitochondrial matrix, protons to form water. This process the innermost part of the generates the majority of ATP in mitochondria, and is aerobic, cellular respiration, producing about depending on the presence of  34 ATP molecules per glucose. The ETC’s location in the inner membrane maximizes efficiency, enabling the cell to harness the full energy potential of glucose by generating large amounts of ATP. Glycolysis provides a rapid ATP supply, the citric acid cycle captures electrons for the ETC, and the ETC maximizes ATP production in the presence of oxygen, making cellular respiration highly efficient.