Life Processes Chapter 6

Life Processes

• The question of what makes something alive is complex, and movement is not always a definite indicator of life.
• Biological molecules are constantly moving, and this molecular movement is necessary for life.

Characteristics of Life Processes

• Maintenance of order and organization of living structures is essential for life.
• Living organisms need to constantly repair and maintain their structures to prevent breakdown.
• This requires energy, which is obtained from outside sources.

Nutrition

• The process of acquiring energy and materials from outside the body is called nutrition.
• Nutrition is essential for maintaining life and for growth and development.
• Autotrophic organisms, such as green plants, make their own food using carbon dioxide and water, releasing oxygen as a byproduct.
• Heterotrophic organisms, such as animals and fungi, obtain their energy by consuming other organisms or organic matter.

Autotrophic Nutrition

• Autotrophs use photosynthesis to convert carbon dioxide and water into carbohydrates and oxygen.
• Photosynthesis occurs in specialized organelles called chloroplasts, which contain chlorophyll.
• Chlorophyll absorbs light energy, which is then used to convert carbon dioxide and water into carbohydrates.

Heterotrophic Nutrition

• Heterotrophs obtain their energy by consuming other organisms or organic matter.
• Different organisms have evolved different strategies for obtaining nutrition, depending on their environment and the availability of food.
• Examples of heterotrophic nutrition include fungi, which break down organic matter outside their bodies, and animals, which ingest whole organisms or organic matter.

Human Nutrition

• The alimentary canal, also known as the digestive system, is a long tube that extends from the mouth to the anus.
• Different regions of the alimentary canal are specialized to perform different functions, such as digestion and absorption of nutrients.
• The process of digestion involves the breakdown of complex molecules into simpler ones that can be absorbed and utilized by the body.

Importance of Nutrition

• Nutrition is essential for maintaining life, growth, and development.
• Without nutrition, living organisms would not be able to maintain their structures, leading to breakdown and death.

Starch and Photosynthesis

• Starch is a complex carbohydrate produced by plants during photosynthesis.
• The presence of starch in plants can be tested using iodine solution, which turns blue-black in the presence of starch.
• Photosynthesis is essential for the production of starch and other organic compounds in plants.

Respiration

• Respiration is the process by which cells generate energy from the breakdown of glucose and other organic molecules.
• In cellular respiration, glucose is broken down into carbon dioxide and water, releasing energy that is used to generate ATP.
• Respiration is essential for the survival of living organisms.### Digestion and Absorption
• The lining of the alimentary canal is soft, so food is wetted to make its passage smooth.
• Saliva, a fluid secreted by the salivary glands, breaks down starch into sugar with the help of an enzyme called salivary amylase.
• The food is mixed thoroughly with saliva and moved around the mouth by the muscular tongue.
• Peristaltic movements in the lining of the canal push the food forward.
• The stomach is a large organ that expands when food enters it, and its muscular walls help mix the food with more digestive juices.

Stomach and Small Intestine

• The stomach releases hydrochloric acid, pepsin, and mucus, which help in digestion.
• Hydrochloric acid creates an acidic medium, which facilitates the action of the enzyme pepsin.
• The mucus protects the inner lining of the stomach from the acid.
• The exit of food from the stomach is regulated by a sphincter muscle, which releases it into the small intestine.
• The small intestine is the longest part of the alimentary canal, where complete digestion of carbohydrates, proteins, and fats takes place.
• The liver and pancreas secrete enzymes to help in digestion.

Absorption and Assimilation

• The walls of the small intestine contain glands that secrete intestinal juice, which finally converts proteins into amino acids, carbohydrates into glucose, and fats into fatty acids and glycerol.
• The digested food is taken up by the walls of the intestine, which has numerous finger-like projections called villi that increase the surface area for absorption.
• The villi are richly supplied with blood vessels that take the absorbed food to each and every cell of the body, where it is utilised for energy, building new tissues, and repairing old tissues.

Respiration

• The energy released during cellular respiration is used to synthesise ATP (adenosine triphosphate), which is used to fuel all other activities in the cell.
• ATP is the energy currency for most cellular processes.
• The process of respiration is used to make an ATP molecule from ADP and inorganic phosphate.
• Endothermic processes in the cell then use this ATP to drive the reactions.

Breathing and Exchange of Gases

• Aerobic organisms need to ensure that there is sufficient intake of oxygen.
• Animals have evolved different organs for the uptake of oxygen from the environment and for getting rid of the carbon dioxide produced.
• Terrestrial animals can breathe the oxygen in the atmosphere, but animals that live in water need to use the oxygen dissolved in water.
• Fishes take in water through their mouths and force it past the gills, where the dissolved oxygen is taken up by blood.
• In human beings, air is taken into the body through the nostrils, and the air passes through the throat and into the lungs.
• The lungs contain an extensive network of blood vessels, and the alveoli provide a surface where the exchange of gases can take place.

Transportation

• Blood transports food, oxygen, and waste materials in our bodies.

• Plasma transports food, carbon dioxide, and nitrogenous wastes in dissolved form.

• Oxygen is carried by the red blood cells, and many other substances like salts are also transported by the blood.

• Haemoglobin is a respiratory pigment that takes up oxygen from the air in the lungs and carries it to tissues which are deficient in oxygen before releasing it.### Our Pump — The Heart

• The heart is a muscular organ, about the size of a fist, that pumps blood throughout the body.

• It has four chambers: left and right atria, and left and right ventricles.

• Oxygen-rich blood from the lungs enters the left atrium, then flows into the left ventricle, and is pumped out to the body.

• Deoxygenated blood from the body enters the right atrium, then flows into the right ventricle, and is pumped to the lungs for oxygenation.

Blood Pressure

• Blood pressure is the force exerted by blood against the walls of blood vessels.
• It is higher in arteries than in veins.
• Systolic pressure occurs when the heart beats, and diastolic pressure occurs when the heart is at rest.
• Normal blood pressure is around 120/80 mmHg.

Tubes — Blood Vessels

• Arteries carry blood away from the heart to the body, and have thick, elastic walls to withstand high pressure.
• Veins collect blood from the body and return it to the heart, and have thinner walls and valves to prevent backflow.
• Capillaries are tiny vessels where exchange of oxygen and nutrients with the body's cells occurs.

Maintenance by Platelets

• Platelets are blood cells that help to plug gaps in damaged blood vessels and prevent blood loss.

Transportation in Plants

• Plants have a system of tubes to transport water, minerals, and sugars.
• Xylem tissue transports water and minerals from roots to leaves.
• Phloem tissue transports sugars and other organic compounds produced by photosynthesis from leaves to other parts of the plant.

Transpiration

• Transpiration is the process of water loss through leaves, which creates suction that pulls water up the xylem.
• It helps to transport water and minerals from roots to leaves.

Excretion in Human Beings

• The excretory system includes the kidneys, ureters, urinary bladder, and urethra.
• Kidneys filter waste products from the blood, and the urine is stored in the urinary bladder until it is released through the urethra.
• Artificial kidneys (hemodialysis) can be used in case of kidney failure.

Excretion Process

• Kidneys filter waste products from the blood, and the urine flows through the ureters to the urinary bladder.
• The urinary bladder stores urine until it is released through the urethra.
• The amount of water reabsorbed by the kidneys depends on the body's need to conserve or eliminate water.