Life Processes Chapter 5

Life Processes

• Life processes are essential to maintain life and include nutrition, respiration, transportation, and excretion.
• These processes are necessary to maintain a state of order in the body and to grow and develop.

What are Life Processes?

• Life processes are the maintenance functions of living organisms that go on even when they are not doing anything particular.
• These processes are necessary to prevent damage and break-down, and energy is needed for them.
• The energy comes from outside the body of the individual organism, and there must be a process to transfer a source of energy from outside to the inside.

Nutrition

• Nutrition is the process by which living organisms obtain energy and materials from outside.
• Autotrophs, such as green plants and some bacteria, use simple food materials obtained from inorganic sources, such as carbon dioxide and water.
• Heterotrophs, such as animals and fungi, utilise complex substances that have to be broken down into simpler ones before they can be used.
• Bio-catalysts called enzymes are used to break down complex substances into simpler ones.

Autotrophic Nutrition

• Autotrophic nutrition is the process by which autotrophs take in substances from the outside and convert them into stored forms of energy.
• Photosynthesis is the process by which autotrophs take in carbon dioxide and water and convert them into carbohydrates in the presence of sunlight and chlorophyll.
• Chlorophyll is essential for photosynthesis, and it absorbs light energy.
• The energy from light is used to convert carbon dioxide and water into carbohydrates and oxygen.

Heterotrophic Nutrition

• Heterotrophic nutrition is the process by which heterotrophs obtain energy and materials from outside.
• Heterotrophs can be classified into different categories based on how they obtain their food, such as herbivores, carnivores, omnivores, and parasites.
• Heterotrophs use different strategies to obtain their food, such as breaking down food material outside the body and then absorbing it, or taking in whole material and breaking it down inside their bodies.

How do Organisms obtain their Nutrition?

• The way organisms obtain their nutrition differs, and the digestive system is different in various organisms.
• In single-celled organisms, the food may be taken in by the entire surface.
• In multicellular organisms, different parts become specialised to perform different functions.

Nutrition in Human Beings

• The alimentary canal is a long tube that extends from the mouth to the anus.
• The alimentary canal has different parts that are specialised to perform different functions.
• Saliva contains an enzyme called salivary amylase that breaks down starch into simple sugar.
• The stomach is a large organ that expands when food enters it, and the muscular walls of the stomach help in mixing the food thoroughly with more digestive juices.
• Peristaltic movements occur all along the gut to move the food in a regulated manner along the digestive tube.### Digestion Process
• Gastric glands in the stomach wall release hydrochloric acid, pepsin (protein-digesting enzyme), and mucus to facilitate digestion
  • Hydrochloric acid creates an acidic medium for pepsin to act
  • Mucus protects the inner lining of the stomach from acid under normal conditions
• Food exits the stomach through a sphincter muscle, which releases it in small amounts into the small intestine
• Small intestine is the longest part of the alimentary canal, fitted into a compact space due to extensive coiling
  • Length of small intestine varies in animals depending on their diet (e.g., herbivores have longer small intestines to digest cellulose)

Digestion in the Small Intestine

• Small intestine is the site of complete digestion of carbohydrates, proteins, and fats
• Receives secretions from the liver and pancreas for digestion
  • Bile juice from the liver makes food alkaline for pancreatic enzymes to act
  • Bile salts break down fats into smaller globules, increasing enzyme efficiency (similar to soap's emulsifying action on dirt)
• Pancreatic juice contains enzymes like trypsin for protein digestion and lipase for fat breakdown
• Intestinal juice from the walls of the small intestine converts proteins to amino acids, complex carbohydrates to glucose, and fats to fatty acids and glycerol

Absorption in the Small Intestine

• Digested food is absorbed through the walls of the small intestine
• Inner lining of the small intestine has numerous finger-like projections (villi) that increase surface area for absorption
• Villi are richly supplied with blood vessels that take absorbed food to every cell in the body

Respiration

• Energy from food is used by cells to provide energy for various life processes
• Diverse organisms use different pathways to break down glucose:
  • Aerobic respiration (with oxygen): glucose → carbon dioxide + water + energy (ATP)
  • Anaerobic respiration (without oxygen): glucose → ethanol + carbon dioxide (in yeast) or lactic acid (in muscles)

ATP and Energy

• ATP (adenosine triphosphate) is the energy currency for most cellular processes
• Energy released during respiration is used to synthesize ATP from ADP and inorganic phosphate
• ATP is broken down to release energy that drives endothermic reactions in the cell

Breathing and Exchange of Gases

• Terrestrial animals need to ensure sufficient oxygen intake
• Plants exchange gases through stomata and have large intercellular spaces for diffusion
• Animals have evolved different organs for oxygen uptake and carbon dioxide removal (e.g., lungs, gills)
• Rate of breathing in aquatic organisms is much faster than in terrestrial organisms due to low oxygen levels in water

Human Respiratory System

• Air is taken into the body through nostrils, filtered, and passed through the throat and lungs
• Lungs have an extensive network of blood vessels and contain alveoli (balloon-like structures) for gas exchange
• Alveoli provide a large surface area for oxygen absorption and carbon dioxide release
• Haemoglobin in red blood corpuscles has a high affinity for oxygen and carries it to tissues

Transportation in Human Beings

• Blood transports food, oxygen, and waste materials in the body
• Plasma transports food, carbon dioxide, and nitrogenous wastes in dissolved form
• Oxygen is carried by red blood corpuscles
• Heart is a muscular organ that pumps blood around the body### The Heart and Blood Vessels
• The heart has different chambers to prevent oxygen-rich blood from mixing with carbon dioxide-rich blood.
• The oxygen-rich blood from the lungs comes to the left atrium, which then contracts and transfers the blood to the left ventricle.
• The left ventricle then pumps the blood out to the body.
• Deoxygenated blood from the body comes to the right atrium, which then contracts and transfers the blood to the right ventricle.
• The right ventricle then pumps the blood to the lungs for oxygenation.
• Valves in the heart ensure that blood does not flow backwards when the atria or ventricles contract.

Blood Pressure

• Blood pressure is the force exerted by blood against the walls of blood vessels.
• Systolic pressure is the pressure of blood inside the artery during ventricular contraction, while diastolic pressure is the pressure during ventricular relaxation.
• Normal blood pressure is around 120 mmHg (systolic) and 80 mmHg (diastolic).
• High blood pressure, also known as hypertension, can lead to the rupture of an artery and internal bleeding.

Blood Vessels

• Arteries are thick-walled vessels that carry blood away from the heart to various organs.
• Veins are thinner-walled vessels that collect blood from different organs and bring it back to the heart.
• Capillaries are the smallest vessels, with walls that are one-cell thick, where exchange of materials between blood and surrounding cells takes place.
• Platelets help to clot blood and plug leaks in the blood vessels.

Lymph

• Lymph is a fluid that helps to transport nutrients and oxygen to cells and remove waste products.
• Lymph is similar to plasma but contains less protein.
• Lymph vessels drain into larger veins and finally open into the bloodstream.

Transportation in Plants

• Plants have a system of transportation that moves energy stores from leaves to other parts of the plant.
• The xylem transports water and minerals from the soil to the leaves.
• The phloem transports products of photosynthesis from the leaves to other parts of the plant.
• Transpiration is the process of water loss from the plant through evaporation, which helps to create a suction force that pulls water up from the roots.

Excretion

• Excretion is the process of removing waste products from the body.
• In humans, the excretory system includes the kidneys, ureters, urinary bladder, and urethra.
• Kidneys filter out waste products from the blood, which are then removed from the body through urine.
• Artificial kidneys can be used in cases of kidney failure to remove waste products from the blood through dialysis.