Functions of Life (Nutrition and Respiration) PDF

1 Introduction Plants generate food by the process of photosynthesis. They respire too and release CO2. Animals produce energy by obtaining nutrition through the digestion process. Numerous organs are involved in the digestion process. Photosynthesis Photo...

1 Introduction Plants generate food by the process of photosynthesis. They respire too and release CO2. Animals produce energy by obtaining nutrition through the digestion process. Numerous organs are involved in the digestion process. Photosynthesis Photosynthesis is the process by which a photo-autotrophic organism, referred to as the producer, uses light energy to convert carbon dioxide and water into sugars. Carbon dioxide + water →by light energy → Glucose + oxygen Photosynthesis happens in the chlorophyll in the chloroplasts 6CO2 + 6H2O → C6H12O6 + 6O2 The glucose is used by the organism and the oxygen is released, making it available to other organisms. The plant itself might be consumed, providing energy from one trophic level to another. Producer→ primary consumer→ apex predator Internal and external adaptations of leaves Large surface area o More UV light could be absorbed for photosynthesis. o Places where there is excessive sunlight, have reduced leaves, e.g. cactus. Thin leaves o Short distances for the CO2 to travel into the leaves. o Short distances for the O2 to exit the leaves. Chloroplasts o Contain chlorophyll which is the pigment responsible for UV absorption. o Chlorophyll a and b to absorb different light wavelengths. Veins o To transport water to all parts of the leaf. o Glucose generated by photosynthesis to be carried away from the leaves. o Provides the structural strength for the leaf to remain upright Stomata o Openings in the base of the leaf, to provide passageways for the entry of CO2 and the exit of O2. o Provide an opening for water vapour to enter and exit the leaf. Transparent waxy cuticle o Allows light to pass through and reach the palisade cells. o Prevents the loss of too much water vapour. o Protects against foreign intruders. Epidermis o One cell thin to not block the entry of sunlight into the leaf. o Hosts the guard cells which open and close the stomata. Palisade layer o Just below the upper epidermis to be as close to the light as possible. o Full of chloroplasts to absorb as much sunlight as possible. 2  Spongy mesophyll o Contains air sacs just by the stomata openings which provides a space for gaseous exchange and water vapour to enter and exit. o Provides the structural strength of the leaf. Diagrammatic representation of a leaf cross-section. A drawing of a leaf cross-section with the labelling of the different cells and layers, as observed under the microscope. 3 4 Factors affecting photosynthesis Abiotic factors are external factors which are not determined by a living organism and affect living things. E.g. wind, rain, sun and temperature. Abiotic factors might aid photosynthesis or limit it. The compensation point is the point at which the rate of photosynthesis is equal to the respiration rate, so having a net zero oxygen production. o The consumption of oxygen by the plant due to cellular respiration is equal to the rate at which oxygen is produced by photosynthesis. Light intensity. o The higher the intensity, the more UV rays which enter the leaf. o Too much light will scorch the leaves, killing the plant. o The more CO2, the higher the photosynthetic rates. Carbon dioxide levels. o The higher the CO2 levels the more CO2 is available for photosynthesis. Temperature. o Warm temperatures increase the kinetic energy of the enzymes increasing the photosynthetic rates. o Too high temperatures, denature the enzymes and water vapour is lost. How abiotic factors influence photosynthetic rates. Photosynetheiss throughtout the day and rate of respiration to reach the compesnation point later durign the day. 5 Oxygen production experiment Materials Aquatic plant Test tube Water in beaker Sodium hydrogen carbonate Funnel Splint Method 1. Place plant in water with some Sodium hydrogen carbonate (NaHCO3). 2. Place short-stemmed funnel on the plant. 3. Place an inverted test tube full of water and cover the stem of the funnel. 4. After few hours, gas bubbles will form and 5. collect in the test tube. 6. Test the gas in the test tube, by a glowing splint. Results A glowing splinter bursts into the flame shows the presence of oxygen. Precautions The splint should be glowing and not fully lighted in order for it to ignite. The plant needs to be placed in sunlight otherwise no photosynthesis occurs. Limitations Quantitative not quantitative as it only indicates the presence of O2. 6 Nutrition Holozoic nutrition. o Nutrition involving the ingestion of solid organic matter, followed by its internal digestion and absorption. o Holozoic nutrition involves ingesting diverse organic materials, which are then digested, absorbed, assimilated, and egested. o Animals consume large amounts of nutrients for energy through metabolism. o In humans, this process occurs in the alimentary canal, including the mouth, salivary glands, oesophagus, stomach, small intestine (duodenum, ileum), pancreas, liver, gall bladder, and large intestine (colon, rectum, anus). A detailed diagram of the alimentary canal. 1. Digestion The process by which food is broken down into smaller, soluble molecules that can be absorbed by the body, involving both mechanical and chemical processes. 2. Absorption The process by which digested nutrients pass through the lining of the intestines into the bloodstream or lymphatic system for distribution to the body's cells. 3. Assimilation The process by which absorbed nutrients are taken up by cells and used for energy, growth, and repair. 4. Egestion The elimination of indigestible and waste materials from the body, typically through the anus. The alimentary canal. The alimentary canal. o A hollow digestive tract from the mouth to the anus where food is digested, and waste expelled. 7  Glands. o Salivary glands, liver, gall bladder, and pancreas release enzymes and hormones to regulate digestion and nutrient absorption. Hormones. o Hormones from glands coordinate the breakdown and absorption of food. Villi and microvilli. o The small intestine's lining has villi and microvilli to maximize surface area for nutrient absorption. A villus showing the capillary network and lacteal vessel to transport nutrients absorbed through the thin epithelium made of microvilli (left). An image of the villi as observed under the microscope with labelling (right). 8 A labelled drawing of the alimentary canal. 9 10 A labelled drawing of a villus 11 12  Organ Gland Function Breaks down food into smaller components, small enough to be moved Mouth Salivary glands down the oesophagus. Salivary glands produce saliva containing the enzyme salivary amylase, which digests starch Releases gastric juice, including hydrochloric acid (HCl) and enzymes like Stomach Gastric glands pepsin to break down proteins and lipase to break down lipids. The stomach has a mucosal lining to protect against the acid and enzymes. Filters blood and breaks down poisonous chemicals. Produces and secretes Liver Liver glands bile which contains bile salts. Pancreatic Produces the hormone insulin to cause cells in the body to take up glucose. Pancreas glands Glucagon is a hormone to trigger the liver to produce glucose. Contains large surface area equipped with villi to absorb the nutrients Intestinal passing through. Found between the villi and secrete digestive enzyme and Intestines glands mucus. Release Gastrin which is a peptide hormone responsible for gastric mucosal growth, and secretion of hydrochloric acid (HCl) into the stomach. Physical vs chemical digestion Physical. o Breaks food into smaller fragments using physical methods, like chewing by teeth, increasing surface area for enzyme action. Chemical. o Involves enzymes and chemicals that alter the molecular structure of food, breaking it down into molecules small enough for absorption. Process. o Chewing and peristalsis move food through the oesophagus to the stomach, where both physical and chemical digestion continue. Purpose. o Physical digestion prepares food for chemical digestion, which breaks it down into absorbable molecules. Digestive enzymes Salivary juices. o Amylase ▪ Breaks down starch and glycogen into maltose. Gastric juices. o Pepsin ▪ Released as an inactive form called pepsinogen. ▪ When HCl is secreted too, pepsinogen is converted to pepsin. ▪ Pepsin breaks down proteins into amino acids. ▪ HCl kills microbes and triggers pepsin function as it has a pH of 2. Bile. o Bile salts ▪ Found in the bile juice. ▪ Emulsify lipids, meaning that they break down large fat globules into smaller globules. ▪ Bile juice also makes the medium alkaline and activates lipase. Pancreas. o Pancreatic juice ▪ Work due to the alkaline environment created by the bile juice. 13  ▪ Lipase breaks down lipids into the basic components. ▪ Protease breaks down proteins, bacteria and other microbes. ▪ Amylase breaks down starch into maltose. ▪ Trypsin breaks down proteins into amino acids. Produced as an inactivated trypsinogen and becomes trypsin. Enzymes Metabolism. o Chemical reactions break down carbohydrates, lipids, and fats, releasing energy used by the body. Anabolism vs. catabolism. o Anabolism builds large molecules from smaller ones, while catabolism breaks down large molecules into smaller ones by enzymes. Enzymes. o Proteins that speed up chemical reactions without being consumed. Intracellular vs. extracellular enzymes. o Intracellular enzymes work inside cells, extracellular enzymes act outside. Enzyme action o Enzymes act on substrates to produce products, with reactions often being reversible. o Ex: Maltose (substrate)+ enzyme Maltase→ Glucose (product) Carbohydrases work on carbohydrates; lipases work on lipids; proteases work on proteins. Examples of enzymes: o Amylase: Breaks down starch in the mouth; functions at a neutral pH 7. o Pepsin: Breaks down protein in the stomach; functions at an acidic pH 2. o Trypsin: Breaks down protein in the small intestine; functions at an alkaline pH (8). o Catalase: Breaks down hydrogen peroxide (H₂O₂) in potato cells and liver; functions at a neutral pH 7. Properties of enzymes Action-specific o Each enzyme is responsible for one reaction. 14  Denatured by heating o At temperatures higher than 45oC, the enzymes are destroyed. o Heat provides kinetic energy, providing energy to the enzymes causing their rate of reactions to be accelerated. Sensitive to pH. o Appropriate pH conditions enable their activation at the correct time. Work faster in high concentrations. o Enzymes could be used repeatedly without getting destroyed. o The more enzymes present, the more collisions with a substrate. 15  Increase enzymatic activity with an increase in substrate concentration. o The more substrate available, the higher the chance of an enzyme to form a substrate-enzyme complex up till the maximum limit. Sensitive to poisons ▪ Poisons such as cyanide and arsenic block their active sites. Everyday use of enzymes o Change the flavour of food, extract juice from fruit, remove stains. o Biological washing powders. ▪ Contain amylases to digest starch. ▪ Proteases to remove protein from eggs and blood. ▪ Lipases to remove fatty greasy stains. ▪ Advantages Do not require heating and work at neutral pH. Only small amounts needed as enzymes are re-usable. Break down into harmless products so not contaminants. ▪ Disadvantages Some people are allergic to biological powders. Some fabrics like silk will deteriorate. o Lactose. ▪ Sugar in milk and milk products. ▪ People could be lactose intolerant as they do not produce lactase. ▪ Lactase enzymes are added to milk via beads made from lactase bound to alginate gel in calcium chloride, breaking down lactose into glucose and galactose o Pectin breakdown. 16  ▪ In fruit juices, pectin causes the juice to be cloudy and looks unappetizing. By adding pectinase, the juice becomes clear. Cellular respiration Cellular respiration: Combines oxygen with food molecules to produce energy (ATP) and generate CO₂ and H₂O as waste. Catabolic reaction: ATP is released from the breakdown of glucose into smaller molecules. Energy investment: Energy is needed to produce ATP. ATP hydrolysis: ATP is cleaved into ADP and phosphate (Pi) by hydrolysis, requiring water. Energy currency: ATP is known as the energy currency of the cell. The process of respiration, by the production of ATP and the cleaving of ATP into ADP + Pi to release energy. Aerobic and anaerobic respiration Aerobic respiration occurs in the presence of oxygen, anaerobic in the absence of oxygen. Anaerobic Aerobic Reactants Glucose Glucose + oxygen Combustion Incomplete Complete Energy 2 ATP 36-38 ATP Products Animals: Lactic acid CO2 + H2O 17  Yeasts: Ethanol (C2H5OH)+ CO2 Location Cytoplasm Cytoplasm + Mitochondria Alcoholic fermentation (ethanol fermentation) is an anaerobic respiration undertaken by yeasts. Lactic acid fermentation by animals. Alcohol/ ethanol fermentation Lactic acid fermentation 29% efficient 41% efficient Energy 2 ATP 2 ATP By-products Ethanol and CO2 Lactate Occurs Plants Animals Aerobic o Glucose + oxygen -> carbon dioxide + water. C6H12O6 + 6O2 → 6CO2 + 6H2O Anaerobic o Glucose → Lactic acid + energy ▪ C6H12O6 → CH₃CHCOOH + 2 ATP o Glucose → ethanol + carbon dioxide + energy. ▪ C6H12O6 ⟶ 2C2H5OH + 2CO2 + 2ATP. The economic importance of anaerobic respiration o Beer production 1. Barely is boiled to release the sugars and yeast cells added. 2. Yeast cells do not have oxygen available so undergo fermentation producing ethanol and CO2, which makes the drink fizzy. o Bread making 1. Yeast is added to the flour and sugar and water. 2. Yeast ferments the sugar producing CO2. 3. The CO2 causes the dough to rise. o Yogurt production 1. Milk is heated. 2. Bacteria added and left to ferment the milk. 3. Lactose in the milk is converted to lactic acid. 4. The milk contains casein which is a protein that becomes denatured and causes the yogurt to solidify. 18