LIFE PROCESSES
Comprehensive Biology Class Notes
WRITTEN BY HUZAYFA PRIVATE TUITION
1. DEFINITION OF LIFE PROCESSES
Life Processes are the fundamental maintenance activities performed by living organisms to sustain life, repair tissues,
and prevent damage to their cellular structure.
The core life processes include Nutrition, Respiration, Transportation, and Excretion.
2. NUTRITION & MODES OF NUTRITION
Nutrition is the process of intake of nutrients (carbohydrates, proteins, fats, vitamins, minerals) and their utilization by an
organism.
Modes of Nutrition
• Autotrophic Nutrition: Organisms synthesize their own organic food from simple inorganic raw materials (CO , H O)
2 2
using sunlight.
Example: Green plants, autotrophic bacteria.
• Heterotrophic Nutrition: Organisms cannot synthesize their own food and depend on autotrophs directly or indirectly.
◦ Holozoic: Intake of solid complex organic food, digested internally (e.g., Humans, Amoeba).
◦ Saprophytic: Feeding on dead and decaying organic matter by secreting digestive enzymes externally (e.g.,
Fungi, Yeast).
◦ Parasitic: Deriving nourishment from a host organism without killing it directly (e.g., Cuscuta, tapeworms, lice).
3. PHOTOSYNTHESIS
Photosynthesis is the autotrophic process by which green plants convert light energy into chemical energy to synthesize
glucose using carbon dioxide and water in the presence of chlorophyll.
6CO2 + 12H2O —— Sunlight / Chlorophyll ——> C6H12O6 + 6O2 + 6H2O
Main Events in Photosynthesis
1. Absorption of light energy by chlorophyll.
2. Conversion of light energy to chemical energy and splitting of water molecules (H O) into hydrogen and oxygen.
2
3. Reduction of carbon dioxide (CO ) to carbohydrates (glucose).
2
4. STOMATA: STRUCTURE & FUNCTION
Structure: Stomata are microscopic pores present on the surface of leaves. Each pore is bounded by a pair of kidney-
shaped guard cells containing chloroplasts.
Written by Huzayfa Private Tuition Page 1 of 5
, FIGURE 1: STRUCTURE AND MECHANISM OF OPEN AND CLOSED STOMATA
OPEN STOMA (Turgid) CLOSED STOMA (Flaccid)
Guard Cell
Stomatal Pore
Pore Closed (Prevents Water Loss)
Mechanism of Opening & Closing:
• When guard cells absorb water, they swell, become turgid, and curve outward, causing the stomatal pore to open.
• When guard cells lose water, they shrink, become flaccid, and the stomatal pore closes.
Functions:
1. Massive gas exchange (CO and O ) during photosynthesis and respiration.
2 2
2. Loss of excess water in the form of water vapor through transpiration.
5. HUMAN DIGESTIVE SYSTEM
Mouth → Pharynx → Oesophagus → Stomach → Small Intestine → Large Intestine → Anus
Digestive Enzymes & Organs
Organ Enzyme / Fluid Function
Mouth Salivary Amylase Breaks down starch into simple sugars (maltose).
Stomach Pepsin, HCl, Mucus HCl: Kills bacteria, provides acidic pH (1.5-2.0).
Pepsin: Digests proteins into peptones.
Mucus: Protects stomach wall from HCl.
Liver Bile Juice Emulsifies large fat globules into small globules; makes
medium alkaline for pancreatic enzymes.
Pancreas Trypsin, Lipase, Pancreatic Trypsin: Digests proteins.
Amylase Lipase: Breaks down emulsified fats.
Amylase: Digests remaining carbohydrates.
Small Intestine Intestinal Enzymes Final digestion:
• Proteins → Amino acids
• Carbohydrates → Glucose
• Fats → Fatty acids + Glycerol
Note: The inner lining of the small intestine has finger-like projections called Villi that increase the surface area for
maximum nutrient absorption into the bloodstream.
Written by Huzayfa Private Tuition Page 2 of 5
Comprehensive Biology Class Notes
WRITTEN BY HUZAYFA PRIVATE TUITION
1. DEFINITION OF LIFE PROCESSES
Life Processes are the fundamental maintenance activities performed by living organisms to sustain life, repair tissues,
and prevent damage to their cellular structure.
The core life processes include Nutrition, Respiration, Transportation, and Excretion.
2. NUTRITION & MODES OF NUTRITION
Nutrition is the process of intake of nutrients (carbohydrates, proteins, fats, vitamins, minerals) and their utilization by an
organism.
Modes of Nutrition
• Autotrophic Nutrition: Organisms synthesize their own organic food from simple inorganic raw materials (CO , H O)
2 2
using sunlight.
Example: Green plants, autotrophic bacteria.
• Heterotrophic Nutrition: Organisms cannot synthesize their own food and depend on autotrophs directly or indirectly.
◦ Holozoic: Intake of solid complex organic food, digested internally (e.g., Humans, Amoeba).
◦ Saprophytic: Feeding on dead and decaying organic matter by secreting digestive enzymes externally (e.g.,
Fungi, Yeast).
◦ Parasitic: Deriving nourishment from a host organism without killing it directly (e.g., Cuscuta, tapeworms, lice).
3. PHOTOSYNTHESIS
Photosynthesis is the autotrophic process by which green plants convert light energy into chemical energy to synthesize
glucose using carbon dioxide and water in the presence of chlorophyll.
6CO2 + 12H2O —— Sunlight / Chlorophyll ——> C6H12O6 + 6O2 + 6H2O
Main Events in Photosynthesis
1. Absorption of light energy by chlorophyll.
2. Conversion of light energy to chemical energy and splitting of water molecules (H O) into hydrogen and oxygen.
2
3. Reduction of carbon dioxide (CO ) to carbohydrates (glucose).
2
4. STOMATA: STRUCTURE & FUNCTION
Structure: Stomata are microscopic pores present on the surface of leaves. Each pore is bounded by a pair of kidney-
shaped guard cells containing chloroplasts.
Written by Huzayfa Private Tuition Page 1 of 5
, FIGURE 1: STRUCTURE AND MECHANISM OF OPEN AND CLOSED STOMATA
OPEN STOMA (Turgid) CLOSED STOMA (Flaccid)
Guard Cell
Stomatal Pore
Pore Closed (Prevents Water Loss)
Mechanism of Opening & Closing:
• When guard cells absorb water, they swell, become turgid, and curve outward, causing the stomatal pore to open.
• When guard cells lose water, they shrink, become flaccid, and the stomatal pore closes.
Functions:
1. Massive gas exchange (CO and O ) during photosynthesis and respiration.
2 2
2. Loss of excess water in the form of water vapor through transpiration.
5. HUMAN DIGESTIVE SYSTEM
Mouth → Pharynx → Oesophagus → Stomach → Small Intestine → Large Intestine → Anus
Digestive Enzymes & Organs
Organ Enzyme / Fluid Function
Mouth Salivary Amylase Breaks down starch into simple sugars (maltose).
Stomach Pepsin, HCl, Mucus HCl: Kills bacteria, provides acidic pH (1.5-2.0).
Pepsin: Digests proteins into peptones.
Mucus: Protects stomach wall from HCl.
Liver Bile Juice Emulsifies large fat globules into small globules; makes
medium alkaline for pancreatic enzymes.
Pancreas Trypsin, Lipase, Pancreatic Trypsin: Digests proteins.
Amylase Lipase: Breaks down emulsified fats.
Amylase: Digests remaining carbohydrates.
Small Intestine Intestinal Enzymes Final digestion:
• Proteins → Amino acids
• Carbohydrates → Glucose
• Fats → Fatty acids + Glycerol
Note: The inner lining of the small intestine has finger-like projections called Villi that increase the surface area for
maximum nutrient absorption into the bloodstream.
Written by Huzayfa Private Tuition Page 2 of 5
