Chapter 5: Life Processes

• Chapter 5 explores the essential processes that sustain life.
• The chapter outlines how living organisms maintain themselves, acquire nutrients, respire, transport substances, and excrete waste.

Telling Alive from Not Alive

• Living beings can be identified by movements like running, chewing, or shouting.
• Breathing and growth are other indicators of life.
• Visible movement is insufficient to define life; molecular movement is necessary.
• Viruses lack molecular movement until they infect a cell, leading to debate about their living status.
• Living organisms are well-organized structures that require constant maintenance and repair at the molecular level to counteract environmental effects.

Life Processes

• Life processes are the maintenance functions performed by living organisms, like repairing damage, which requires energy.
• Energy for maintenance comes from outside the body through the process of nutrition.
• Growth necessitates additional raw materials from external sources.
• Carbon-based molecules are the primary source of food for life on Earth, guiding nutritional processes.
• Organisms break down energy sources into a uniform source for molecular movements, using oxidizing-reducing reactions.
• Respiration involves acquiring oxygen to break down food for cellular needs.

Complexity and Organization

• Single-celled organisms don't need specific organs for nutrient intake or waste removal because their entire surface interacts with the environment.
• Multicellular organisms need specialized tissues for food and oxygen uptake, which requires a transportation system.
• Excretion removes harmful by-products from chemical reactions via specialized excretory tissues.

Nutrition

• Nutrition is essential for supplying the energy needed for bodily activities, growth, development, protein synthesis, and the maintenance of order.
• Food serves as the source of energy and materials for living organisms.
• Autotrophs use simple, inorganic food material like carbon dioxide and water.
• Green plants and some bacteria are autotrophs.
• Heterotrophs utilize complex substances broken down by enzymes, depending on autotrophs for survival.

Autotrophic Nutrition

• Photosynthesis fulfills autotrophic organisms' carbon and energy needs.
• Autotrophs take in carbon dioxide and water from the environment and convert them into carbohydrates using sunlight and chlorophyll.
• Carbohydrates provide energy, and excess carbohydrates are stored as starch as an energy reserve.
• Energy derived from food is stored as glycogen in our bodies, similar to plants storing starch.

Photosynthesis Process

• The overall chemical reaction for photosynthesis is: 6CO2 + 12H2O → C6H12O6 + 6O2 + 6H2O.
• Chlorophyll absorbs light energy.
• Light energy converts to chemical energy, splitting water molecules into hydrogen and oxygen.
• Carbon dioxide reduces to carbohydrates.
• Desert plants take up carbon dioxide at night, using energy absorbed during the day.
• Chloroplasts, containing chlorophyll, are cell organelles essential for photosynthesis.

Carbon Dioxide Intake

• Stomata are tiny pores on leaf surfaces that facilitate gaseous exchange for photosynthesis.
• Gas exchange also occurs across stems, roots, and leaves.
• Stomata close when carbon dioxide is not needed for photosynthesis to prevent water loss.
• Guard cells regulate the opening and closing of stomatal pores via water flow.

Raw Materials for Autotrophs

• Water is absorbed by plant roots from the soil.
• Terrestrial plants gather water via the roots from the soil.
• Nitrogen, phosphorus, iron, and magnesium are also taken up from the soil.
• Nitrogen is essential for protein synthesis, absorbed as inorganic nitrates or nitrites, or organic compounds from atmospheric nitrogen-fixing bacteria.

Heterotrophic Nutrition

• Organisms adapt their nutrition based on food availability and how they obtain it.
• Some organisms break down food outside the body before absorbing it, e.g., fungi.
• Others ingest whole food and break it down internally.
• Some derive nutrition from plants or animals without killing them, i.e., parasitic nutrition used by ticks, lice, leeches, and tape-worms.

Obtaining Nutrition

• The digestive system differs based on the food and how it is obtained.
• Single-celled organisms may take in food through the entire surface.
• Amoeba uses temporary extensions called pseudopodia to engulf food.
• Paramoecium has a definite shape and moves food to a specific spot using cilia.

Nutrition in Human Beings

• The alimentary canal is a long tube from the mouth to the anus.
• Various regions of the alimentary canal perform specialized functions.
• Food is crushed by teeth into small particles making way for the stomach.
• Saliva, secreted by the salivary glands, wets the food for smooth passage-aiding for biological enzyme function.
• Salivary amylase enzyme breaks down starch into simple sugars.
• The muscular tongue mixes food with saliva during chewing.

Digestion and the Gut

• The food moves along the digestive tube in a regulated manner, which is aided by canal muscles which contract rhythmically.
• The stomach expands when food enters, where its muscular walls help mix food with digestive juices.
• Gastric glands in its walls secrete mucus , hydrochloric acid, and pepsin.
• Pepsin breaks down proteins.
• Hydrochloric acid creates an acidic medium for pepsin action and protects the stomach lining.
• A sphincter muscle regulates food exit from the stomach into the small intestine.
• The small intestine completely digests carbohydrates, proteins, and fats with liver and pancreas secretions.
• Bile juice from the liver makes the food alkaline and acts on fats, breaking them into smaller globules (emulsification).
• Pancreatic juice contains trypsin (digests proteins) and lipase (breaks down emulsified fats).
• Intestinal juice, secreted by the small intestine walls, further converts proteins to amino acids, carbohydrates to glucose, and fats to fatty acids and glycerol.
• Villi, finger-like projections on the inner lining, increase the surface area for absorption.
• Blood vessels transport absorbed food to cells for energy, tissue building, and repair.

Large Intestine

• The unabsorbed food proceeds to the large intestine, which absorbs more water from the unused source.
• The residue is expelled via the anus, controlled by the anal sphincter.
• Dental caries or tooth decay soften enamel and dentine via bacteria producing acids from sugars which form dental plaque covering enamel.

Respiration

• Nutrition creates cellular energy and materials used in diverse life processes.
• Organisms extract energy in different ways when breaking down glucose.
• Some use oxygen, others use alternative pathways.
• The first step involves breaking down glucose into pyruvate, which takes place in the cytoplasm.
• Pyruvate then converts to ethanol and carbon dioxide (fermentation) in yeast or into lactic acid in muscle cells during oxygen deficiency.

Aerobic and Anaerobic Respiration

• Aerobic respiration refers to the break-down of pyruvate with oxygen which occurs in the mitochondria.
• This yields three molecules of carbon dioxide and water.
• Aerobic respiration releases more energy than anaerobic respiration.
• Lactic acid build-up causes cramps.

Energy Currency

• ATP is the energy currency for cellular processes.
• Aerobic organisms require sufficient oxygen intake.
• Plants exchange gases through stomata and intercellular spaces which aids to keep them in contact with air.
• Animals have evolved diverse organs to uptake oxygen and release carbon dioxide.
• Terrestrial animals breathe atmospheric oxygen.
• Aquatic animals use dissolved oxygen like that of fish, which force water via gills.

Human Respiratory System

• Humans take in air through nostrils, which is filtered by fine hairs and mucus.
• This air passes through the throat and into the lungs.
• Cartilage rings in the throat prevent collapse.
• Within the lungs, air passages divide into smaller tubes ending in alveoli, which enable gas exchange.
• Alveoli walls have blood vessels.
• Breathing involves lifting ribs and flattening the diaphragm, causing air to be sucked into the lungs.
• Blood carries carbon dioxide for release into alveoli and takes up oxygen for transport.
• Lungs retain a residual volume of air to maintain sufficient absorption and release.
• Hemoglobin, a respiratory pigment in red blood corpuscles, carries oxygen due to strong affinity; likewise, it is more soluble in water than carbon dioxide.

Transportation

• Lymph, or tissue fluid, transports substances.
• Plasma, proteins, and blood cells escape into intercellular spaces through capillary pores, forming lymph.
• It carries digested fat from the intestine and drains excess fluid from extracellular space.

Transportation in Plants

• Plants take in CO2 and use photosynthesis to store energy in leaves.
• Soil provides essential raw materials like nitrogen and phosphorus
• Roots absorb substances with the soil contact.
• Distances between soil and leaves require transportation systems.
• Plants can live with dead cells and plants can utilize relatively slow transport stems.
• Plant transport systems move energy from leaves and raw materials from roots.
• Xylem aids water and mineral transport.
• Phloem aids photosynthesis product transport.

Water and Ion Transportation

• Interconnected xylem vessels and tracheids transport water throughout the plant to contact soil with actively take ions.
• Ions create an electric potential difference between root and soil and cause the water to flow.
• Water moves into root xylem, creating an upward-moving column.

Transpiration

• Transpiration refers to the loss of water in the form of air.
• Transpiration helps in water and mineral absorption.
• Transpirations aid in upward movement, and temperature regulation.
• Transpiration is more important in the day, since stomatas are open.

Metabolic Transportation

• Products of metabolic processes, in particular photosynthesis, are moved by leaves where they are formed .
• This transport of soluble products is called translocation.
• Translocation is carried out by vascular tissue (phloem) with amino acids and other substances.
• Unlike xylem transport, pholem transport utilizes energy.
• Material (sucrose) transfers to the pholem with ATP.
• Osmotic pressure from tissue is increased when water enters, which causes pholem to move the substance to the plant tissue.

Excretion

• Organisms remove gaseous wastes from photosynthesis or respiration.
• Nitrogenous and harmful materials need to be removed though.
• The removal of harmful metabolic wastes is called excretion.
• In unicellular organisms they diffuse waste from body to water.
• Multicellular ones use specific or specialised organs.

Human Excretion

• A pair of kidneys is housed in the abdomen for excretion.
• They are joined to a pair of ureters, a urinary bladder, and finally a urethra.
• Urine, a liquid for waste product removal, removes, nitrogenous waste, like urea or uric acid.
• Kidneys filter waste products from blood.
• The filtering units in the kidneys is called are very thin walled capillary clusters in the kidney.
• These are usually associated with a Bowman's capsule.
• Substances are selectively re-absorbed and travel to the tube.

Wastes

• Wastes travel from kidneys with the ureters to the bladder.
• Kidney failures have a solution of artificial kidney, where blood is ran through a dialysis, a semi-permeable tubing and tank with dialysis fluid.
• Then the purified blood is pumped back into the patent like that of the kidney function.

Excretion in Plants

• Plants use different strategies, sometimes wasteful ones.
• Oxygen can be seen as waste from photosynthesis.
• Plants deal with oxygen via gas exchange.
• Excess water is removed by transpiration.
• Plants consist of dead cells for their tissues and waste.
• Waste products can be stored in cellular vacuoles or the leaves.
• Wastes can be stored as gums or reisins.
• Plants excrete waste into the soil.