Pointers Ease 1 2024/2025 Biology PDF

POINTERS EASE 1 2024/2025 LO: Outline the need for energy in living organisms, as illustrated by active transport, movement and anabolic reactions, such as DNA replication and protein synthesis. 1. Movement: contraction of muscle cells, transport of vesicle 2. Active transport: sodium pota...

POINTERS EASE 1 2024/2025 LO: Outline the need for energy in living organisms, as illustrated by active transport, movement and anabolic reactions, such as DNA replication and protein synthesis. 1. Movement: contraction of muscle cells, transport of vesicle 2. Active transport: sodium potassium pump, transport of H+ during stomatal opening 3. Molecular synthesis (anabolic process): protein synthesis LO: Describe the features of ATP that make it suitable as the universal energy currency. 1. Easy to hydrolyse 2. releases a useful quantity of energy requiring process in a cell 3. ATP is relatively stable molecule in the range of pH that normally occurs in cells LO: State that ATP is synthesised by: transfer of phosphate in substrate-linked reactions chemiosmosis in membranes of mitochondria and chloroplasts 1. Using energy provided directly by another chemical reaction – called substrate –linked reaction → glycolysis and kreb’s cycle 2. By chemiosmosis, a process that takes place across the inner membranes of mitochondria, using energy released by the movement of hydrogen ions down their concentration gradient. → making ATP during oxidative phosphorylation and light dependent reactions LO: Explain the relative energy values of carbohydrates, lipids and proteins as respiratory substrates. - Different substrate has different amount of Hydrogen - Hydrogen atom play role during chemiosmosis to synthesize ATP. more hydrogen atoms means more energy produced. LO: State where each of the four stages in aerobic respiration occurs in eukaryotic cells. - Glycolysis: Cytoplasm - Link reaction: Matrix of mitochondria - Krebs Cycle: Matrix of mitochondria - Oxidative phosphorylation: Inner membrane of mitochondria (cristae) Eukaryotic cells involve: Protista, Fungi, Plantae, Animalia LO: Outline glycolysis as phosphorylation of glucose and the subsequent splitting of fructose 1,6-bisphosphate (6C) into two triose phosphate molecules (3C), which are then further oxidised to pyruvate (3C), with the production of ATP and reduced NAD. - Site: cytoplasm - Products of Glycolysis for 1 molecule of glucose: 2 reduced NAD (NADH) → ETC 2 Pyruvate → Link reaction 2 ATP (net) → energy LO: Explain that, when oxygen is available, pyruvate enters mitochondria to take part in the link reaction. - When oxygen is available, pyruvate, the product of glycolysis, enters the mitochondria to participate in the link reaction - This process links glycolysis to the Krebs cycle (citric acid cycle) in aerobic respiration. LO: Describe the link reaction, including the role of coenzyme A in the transfer of acetyl (2C) groups. Step: - Site: Matrix of mitochondria - Result of link reaction for 1 1. Pyruvate Transport: After glycolysis, each glucose molecule molecule of glucose: yields two pyruvate molecules, which are transported from the cytoplasm into the matrix of mitochondria. 1. 2 acetyl coA → Krebs cycle 2. Decarboxylation: Inside the mitochondria, pyruvate (a 3-carbon 2. 2 reduced NAD → ETC molecule) undergoes decarboxylation, which means one carbon 3. 2 CO₂ → waste atom is removed in the form of carbon dioxide (CO₂). This leaves a 2-carbon molecule called acetyl group. 3. NADH Production: During the link reaction, NAD+ (nicotinamide adenine dinucleotide) is reduced to form reduced NAD. 4. Formation of Acetyl CoA: The acetyl group is then combined with a molecule called coenzyme A (CoA), forming acetyl coenzyme A (acetyl CoA). LO: Outline the Krebs cycle. Site: matrix of mitochondria Result of Krebs cycle for 1 molecule of glucose: 1. 6 reduced NAD → ETC 2. 2 reduced FAD → ETC 3. 2 ATP → Energy 4. 4 CO₂ → waste LO: Describe the role of NAD and FAD in transferring hydrogen to carriers in the inner mitochondrial membrane. - NAD and FAD play key roles in transferring hydrogen atoms (protons and electrons) from metabolic reactions to the electron transport chain in the inner mitochondrial membrane. By doing so, they facilitate the production of ATP through oxidative phosphorylation. LO: Explain what happens during oxidative phosphorylation. LO: Outline respiration in anaerobic conditions in mammals (lactate fermentation) and in yeast cells (ethanol fermentation). Lactate fermentation in mammals: - site: cytoplasm - result for 1 molecule glucose: 2 ATP and lactate - lactate can be converted into pyruvate if oxygen is available. LO: Outline respiration in anaerobic conditions in mammals (lactate fermentation) and in yeast cells (ethanol fermentation). Ethanol fermentation yeast: - site: cytoplasm - result for 1 molecule glucose: 2 ATP, ethanol, and CO2 (Ethanal) LO: Explain why the energy yield from respiration in aerobic conditions is much greater than the energy yield from respiration in anaerobic conditions. - anaerobic respiration produces far less ATP because it relying only on glycolysis, produce only 2 ATP - if oxygen is not available link reaction, krebs cycle, and ETC will shut down because no NAD regenerated LO: Describe and carry out investigations using redox indicators, including DCPIP and methylene blue, to determine the effects of temperature and substrate concentration on the rate of respiration of yeast. - The principle of using redox indicators like DCPIP and methylene blue in investigations of respiration in yeast relies on their ability to change color as they undergo reduction. - During cellular respiration, yeast cells metabolize substrates (such as glucose), transferring electrons to these redox indicators as part of the process of ATP production. The reduction of these indicators allows researchers to monitor the rate of respiration indirectly by observing the color change. - DCPIP and methylene blue are redox indicators that change color when they are reduced. When these indicators are reduced by the electrons released during yeast respiration, they become colorless. - The faster the rate of respiration, the quicker the color change occurs. - The time it takes for the indicator to turn from blue to colorless is used as a measure of the respiration rate. - Temperature: The rate of respiration will increase with temperature until an optimal point, after which enzyme denaturation decreases respiration. - Substrate concentration: As substrate concentration increases, the respiration rate will increase until it reaches saturation, where all enzyme active sites are occupied. LO: Explain that energy transferred as ATP and reduced NADP from the light-dependent stage is used during the light-independent stage (Calvin cycle) of photosynthesis to produce complex organic molecules. LO: State that within a chloroplast, the thylakoids, which occur in stacks called grana, are the site of the light-dependent stage and the stroma is the site of the light-independent stage. - Thylakoids are the individual disc-like membranes where light dependent reaction takes place → place for light dependent reactions - Granum: stack of thylakoid - Grana: stacks of thylakoid - Stroma: liquid material found throughout the cavity of the chloroplast → place for calvin cycle LO: Describe the role of chloroplast pigments in light absorption in thylakoids. - Chlorophylls (Chlorophyll a and b): Chlorophyll a absorbs light mainly in the blue-violet and red regions of the light spectrum, while chlorophyll b extends the range of light absorption by capturing more blue and orange light. - Carotenoids: These accessory pigments, like beta-carotene, absorb light in the blue and green regions, which chlorophyll cannot effectively capture. - Energy Transfer: Once the pigments absorb light, the energy excites electrons LO: Describe and use chromatography to separate and identify chloroplast pigments. - A higher Rf means the pigment travels farther up the chromatography paper - A higher Rf generally indicates that the pigment is more soluble in the solvent - A higher Rf means the pigment is more non-polar - A lower Rf means the pigment travels a shorter distance. - A lower Rf suggests the pigment is less soluble in the mobile phase. - A lower Rf The pigment is more polar LO: State that cyclic photophosphorylation and non-cyclic photophosphorylation occur during the light-dependent stage of photosynthesis. - Non-cyclic photophosphorylation involves the flow of electrons passing through both Photosystem II and Photosystem I, resulting in the production of ATP, NADPH, and the release of oxygen (through photolysis). - Cyclic photophosphorylation involves only Photosystem I, where electrons are cycled back to the reaction center, leading to the production of ATP without the generation of NADPH or oxygen. LO: Explain that in cyclic photophosphorylation: only photosystem I (PSI) is involved, photoactivation of chlorophyll occurs, ATP is synthesised. - Light energy is absorbed by chlorophyll molecules in Photosystem I. This energy excites electrons to a higher energy level, a process known as photoactivation. - The excited electrons are passed from the reaction center of PSI to an electron transport chain consisting of a series of carrier molecules. Unlike non-cyclic photophosphorylation, these electrons do not move on to reduce NADP⁺; instead, they are cycled back to PSI. - As the electrons flow through the electron transport chain, they release energy. This energy is used to pump protons (H⁺) across the thylakoid membrane, creating a proton gradient. - The proton gradient drives ATP synthesis by ATP synthase, a process called chemiosmosis. However, no NADPH or oxygen is produced in cyclic photophosphorylation. LO: Explain what happens in non-cyclic photophosphorylation LO: Explain what happens during photophosphorylation. - Light energy is absorbed by chlorophyll and other pigments in the photosystems (Photosystem I and/or Photosystem II), exciting electrons to a higher energy level (a process called photoactivation). - The excited electrons are transferred through an electron transport chain. As electrons pass through a series of electron carriers, they release energy. - The released energy is used to pump protons (H⁺) from the stroma into the thylakoid lumen, creating a proton gradient (higher concentration of protons inside the thylakoid lumen than in the stroma). - Protons flow back into the stroma through ATP synthase, an enzyme embedded in the thylakoid membrane. As the protons pass through ATP synthase, the enzyme uses the energy from the proton flow to convert ADP and inorganic phosphate (Pi) into ATP. - reduction of NADP become NADPH LO: Outline what happens in the three main stages of the Calvin cycle. LO: State that Calvin cycle intermediates are used to produce other molecules, limited to GP to produce some amino acids and TP to produce carbohydrates, lipids and amino acids. In the Calvin cycle, intermediates are used to produce other essential molecules: - GP (glycerate-3-phosphate) is used to produce some amino acids. - TP (triose phosphate) is used to produce carbohydrates, lipids, and amino acids. LO: State that light intensity, carbon dioxide concentration and temperature are examples of limiting factors of photosynthesis. - A limiting factor in photosynthesis is a condition or resource that, when in short supply, restricts the rate of photosynthesis, even if other factors are present at optimal levels. In photosynthesis, common limiting factors include light intensity, carbon dioxide concentration, and temperature. - In low light intensities, the limiting factor is light intensity - In high light intensity, the limiting factor can be carbon dioxide concentration or temperature. LO: Explain the effects of changes in light intensity, carbon dioxide concentration and temperature on the rate of photosynthesis. - Light Intensity: Increasing light boosts photosynthesis until other factors limit it. - CO₂ Concentration: Higher CO₂ levels enhance photosynthesis until a maximum rate is reached. - Temperature: Increasing temperature speeds up photosynthesis up to an optimum level, beyond which the rate declines due to enzyme denaturation. LO: Describe and carry out investigations using whole plants, including aquatic plants, to determine the effects of light intensity, carbon dioxide concentration and temperature on the rate of photosynthesis. 1. Light Intensity: The rate of photosynthesis (oxygen bubbles per minute) will increase as light intensity increases up to a certain point. Beyond that, the rate levels off because light is no longer the limiting factor. 2. Carbon Dioxide Concentration: As CO₂ concentration increases, the rate of photosynthesis will increase until it plateaus at higher concentrations when carbon dioxide is no longer limiting. 3. Temperature: The rate of photosynthesis will increase with temperature up to an optimum temperature (around 25-35°C for most plants), after which the rate will start to decrease as enzymes involved in photosynthesis begin to denature at higher temperatures. - increasing distance between lamp and apparatus will decrease light intensity - increasing bicarbonate will increase carbon dioxide concentration - put ice cube will decrease temperature, boiling the water will increase temperature LO: Explain what is meant by homeostasis and the importance of homeostasis in mammals. - Homeostasis is the maintenance of a relatively constant internal environment for the cells within the body. - Homeostasis controls the composition of the blood, which controls the composition of the tissue fluid. - Temperature, pH, water potential and glucose concentration of the tissue fluid affect cells. LO: Explain the principles of homeostasis in terms of internal and external stimuli, receptors, coordination systems, effectors and negative feedback. - Stimuli are changes in the internal or external environment that can disrupt the balance of homeostasis. - Internal stimuli: These are changes within the body, such as changes in blood glucose levels or body temperature. - External stimuli: These come from outside the body, like changes in ambient temperature or oxygen availability. - Receptors are specialized cells or proteins that detect changes (stimuli) in the environment and send signals to a control center. - Nervous system: Provides rapid responses by sending electrical signals to effectors. - Endocrine system: Provides slower but longer-lasting responses by releasing hormones (chemical signals) into the bloodstream. - Effectors are organs, tissues, or cells that carry out the response to restore the internal balance. Effectors include muscles, glands, or any structure that directly adjusts the condition - Negative feedback is the key mechanism that restores homeostasis. In this system, any deviation from the normal condition triggers a response that opposes or negates the initial change. LO: State that urea is produced in the liver from the deamination of excess amino acids. LO: Describe the structure of the human kidney. LO: Identify, in diagrams, photomicrographs and electron micrographs, the parts of a nephron and its associated blood vessels and structures. LO: Describe and explain the formation of urine in the nephron. - In ultrafiltration, small molecules of blood like water, urea, glucose, amino acids and salts are filtered out of blood into the bowman’s capsule forming filtrate. - The holes in the capillary endothelium and the gaps between the podocytes make it relatively easy for substances dissolved in the blood plasma to pass from the blood into the capsule. - However, the basement membrane stops large protein molecules from getting through. Any protein molecule with a relative molecular mass over about 69000 cannot pass through the basement membrane and so cannot escape from the glomerular capillaries - The high rate of filtration is mostly because of the high blood pressure in glomerulus as a result of efferent arterioles being narrower than the afferent arterioles. - In selective reabsorption, useful molecules are taken back into blood from the filtrate. - Selective reabsorption mostly happens in the proximal convoluted tubule. In this step, useful molecules like glucose and amino acids plus most of water are reabsorbed into blood. - Loop of Henle and collecting ducts work together for reabsorption of water and some salts(Na, Cl and K) according to body needs. - The function of these loops of Henle is to create a very high concentration of sodium and chloride ions in the tissue fluid in the medulla. This is partly achieved by active transport by the cells of the thick region of the ascending limb of each loop. LO: Describe the roles of the hypothalamus, posterior pituitary gland, antidiuretic hormone (ADH), aquaporins and collecting ducts in osmoregulation. - Osmoregulation is the control of the water potential of the body fluids. - The hypothalamus is the control center for osmoregulation. It contains osmoreceptors that detect changes in the water potential (concentration of solutes) of the blood. - When the blood becomes too concentrated (i.e., low water potential), the hypothalamus senses this and triggers the release of ADH from the posterior pituitary gland. If the blood is too diluted, it inhibits ADH release. - The posterior pituitary gland stores and releases ADH - ADH plays a central role in controlling the amount of water reabsorbed by the kidneys. - When blood water levels are low (dehydration), ADH increases the permeability of the collecting ducts in the kidneys to water by promoting the insertion of aquaporins (water channels) into the membrane. - This allows more water to be reabsorbed from the urine back into the bloodstream, resulting in more concentrated urine and less water loss. - Aquaporins are specialized proteins that form channels in the membranes of cells, allowing water molecules to pass through. - In the presence of ADH, aquaporins are inserted into the membranes of the cells lining the collecting ducts of the kidney, enabling water to be reabsorbed more effectively. - Without ADH, aquaporins are not inserted, and the collecting ducts remain impermeable to water, causing more water to be excreted in the urine. - The collecting ducts are part of the nephron in the kidney where water reabsorption occurs. LO: Explain how negative feedback control mechanisms regulate blood glucose concentration, with reference to the effects of insulin on muscle cells and liver cells and the effect of glucagon on liver cells.  - effects of insulin: 1. increase the number of GLUT4 on the surface membrane of liver and muscle 2. increasing absorption of glucose from blood 3. stimulates activation of glucokinase enzyme: Glucokinase phosphorylates glucose so that it cannot go out of the cell 4. stimulates activation glycogen synthase enzymes to add excess glucose molecules to glycogen. - effects of glucagon (only on liver cell): 1. Activates glycogen phosphorylase to breakdown glycogen into glucose 2. stimulates gluconeogenesis - glycogenesis: Synthesis of glycogen by adding glucose - glycogenolysis: Breaking down of glycogen to glucose - gluconeogenesis: formation of glucose from amino acids, fatty acids, glycerol, lactate and pyruvate in the liver LO: Explain the principles of operation of test strips and biosensors for measuring the concentration of glucose in blood and urine, with reference to glucose oxidase and peroxidase enzymes - Test strips for glucose contain glucose oxidase and peroxidase enzymes immobilised on a pad. - Glucose biosensor contains immobilised glucose oxidase, which produces hydrogen peroxide(H2O2). Oxidation of H2O2 at an electrode causes electron flow proportional to the glucose concentration. LO: Explain that stomata respond to changes in environmental conditions by opening and closing and that regulation of stomatal aperture balances the need for carbon dioxide uptake by diffusion with the need to minimise water loss by transpiration. LO: Explain that stomata have daily rhythms of opening and closing - Stomata generally open in the morning, coinciding with the onset of light. This allows for the uptake of carbon dioxide (CO₂), which is needed for photosynthesis - As light levels decrease toward the evening or in the absence of light, stomata close to conserve water. The guard cells lose potassium ions and water, causing them to become flaccid and leading to the closing of the stomatal pores. LO: Describe the structure and function of guard cells and explain the mechanism by which they open and close stomata. LO: Describe the role of abscisic acid in the closure of stomata during times of water stress, including the role of calcium ions as a second messenger. Abscisic acid (ABA) is a plant stress hormone stimulating closing of stomata. If a plant is subjected to difficult environmental conditions, such as very high temperatures or much reduced water supplies, then it responds by secreting ABA. Role of ABA: - inhibits proton pump and lead to accumulation of H+ inside the guard cells, this condition stimulates K+ to move out from guard cells - activates Ca2+ as second messenger, Ca2+ will open the gate for negative ions to move out from guard cells and triggers more K+ diffuse out from guard cells GOOD LUCK FOR YOUR EASE 1