Chapter 1: The Nature and Variety of Living Organisms

Characteristics of Living Organisms:

● MRS GREN: Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion,

Nutrition.
● Living organisms have cellular structures and are organized into cells, tissues, organs,
and systems.

Cell Types:

● Prokaryotic Cells: Lack a nucleus (e.g., bacteria).

● Eukaryotic Cells: Contain a nucleus (e.g., plants, animals, fungi).

Variety of Organisms:

● Plants: Multicellular, perform photosynthesis, cell walls made of cellulose.

● Animals: Multicellular, no photosynthesis, no cell walls.
● Fungi: Multicellular (e.g., mushrooms) or unicellular (e.g., yeast); feed by saprotrophic
nutrition.
● Bacteria: Unicellular; some carry out photosynthesis, others are pathogens.
● Protoctists: Microscopic, some have features of plants or animals.
● Viruses: Non-living, parasitic; consist of genetic material (DNA/RNA) and protein coat.

Chapter 2: Structure and Function of Living Organisms

Cell Structure:

● Animal Cells: Nucleus, cytoplasm, cell membrane, mitochondria, ribosomes.

● Plant Cells: Have all animal cell components + chloroplasts, large vacuole, cell wall.
● Specialized Cells: Adapted for functions, e.g., red blood cells (oxygen transport), root
hair cells (water absorption).

Movement of Substances:

● Diffusion: Passive movement of molecules from high to low concentration.

● Osmosis: Movement of water through a semi-permeable membrane from high water
potential to low water potential.
● Active Transport: Movement against a concentration gradient, requires energy.

Chapter 3: Biological Molecules

Carbohydrates:
 ● Monosaccharides (glucose), disaccharides (maltose), polysaccharides (starch,
glycogen).
● Test: Benedict’s solution (brick-red for reducing sugars).

Proteins:

● Composed of amino acids; vital for growth, repair, enzymes.

● Test: Biuret reagent (purple color indicates proteins).

Lipids:

● Composed of glycerol and fatty acids; provide energy and insulation.

● Test: Ethanol emulsion test (cloudy white).

Enzymes:

● Biological catalysts that speed up reactions, affected by:

○ Temperature: Too high = denatured.
○ pH: Extremes can denature enzymes.
○ Substrate concentration: Increases rate until saturation.

Chapter 6: Gas Exchange

Humans:

● Lungs: Alveoli provide large surface area for gas exchange.

● Breathing Mechanism:
○ Inhalation: Diaphragm contracts, air drawn in.
○ Exhalation: Diaphragm relaxes, air pushed out.

Plants:

● Stomata regulate gas exchange (CO₂ in, O₂ out during photosynthesis; O₂ in during
respiration).
● Guard cells control stomatal opening.

Chapter 7: Transport
Plants:

● Xylem: Transports water/minerals from roots to leaves.

● Phloem: Transports sugars and amino acids.
● Transpiration: Loss of water vapor through leaves; affected by temperature, humidity,
wind.

Nutrition in Mammals
Nutrition is the process by which living organisms obtain and process food
to provide energy and materials needed for growth, repair, and
reproduction. Mammals, being heterotrophic organisms, require organic
substances like carbohydrates, proteins, fats, vitamins, and minerals from
their environment. These are essential for maintaining health and function.

The Digestive System of Mammals

The digestive system of mammals is complex and specialized to process a variety of foods. Its
function is to break down food, absorb nutrients, and eliminate undigested materials. The
process of digestion is mechanical and chemical, involving both physical breakdown and
enzymatic reactions.

Main Parts of the Digestive System:

1. Mouth:
○ Teeth: Mammals have different types of teeth, each adapted for specific
functions in food processing.
■ Incisors: For cutting food.
■ Canines: For tearing food (especially meat).
■ Molars: For grinding and crushing food.
○ Salivary Glands: These produce saliva, which moistens food and contains
amylase enzyme, starting the digestion of starch into maltose.
2. Esophagus:
○ A muscular tube connecting the mouth to the stomach.
○ Peristalsis: A wave-like muscle contraction that moves food down the
esophagus to the stomach.
3. Stomach:
○ Mechanical Digestion: Churning action of the stomach muscles mixes food with
digestive juices.
○ Chemical Digestion: The stomach produces gastric juices, including:
■ Hydrochloric acid (HCl): Acidifies the stomach environment, aiding in
enzyme function and killing harmful microorganisms.
■ Pepsin: An enzyme that breaks down proteins into shorter polypeptides.
■ Rennin: In young mammals, it helps curdle milk proteins.
○ Mucus: Protects the stomach lining from the acidic environment.
4. Small Intestine:
○ The primary site of digestion and absorption.
○ Divided into three sections:
■ Duodenum: Receives bile from the liver and pancreatic juices from the
pancreas. These help digest fats, proteins, and carbohydrates.
■ Jejunum and Ileum: Main areas of absorption, where nutrients pass
through the walls of the intestine into the bloodstream.
○ Villi: Tiny finger-like projections in the lining of the small intestine that increase
surface area for absorption.
○ Microvilli: Even smaller projections on the epithelial cells of the villi, further
increasing surface area.
5. Liver:
 ○ Bile Production: The liver produces bile, which is stored in the gall bladder and
released into the duodenum to emulsify fats (break down large fat droplets into
smaller ones), increasing the surface area for enzyme action.
○ Detoxification: The liver removes toxins, alcohol, and drugs from the blood.
○ Glycogen Storage: It stores excess glucose as glycogen and releases it into the
bloodstream when blood glucose levels are low.
6. Pancreas:
○ Exocrine Function: The pancreas secretes digestive enzymes into the small
intestine. These include:
■ Amylase: Breaks down carbohydrates into sugars.
■ Lipase: Breaks down fats into fatty acids and glycerol.
■ Protease: Breaks down proteins into amino acids.
○ Endocrine Function: The pancreas also secretes hormones like insulin and
glucagon, which regulate blood glucose levels.
7. Large Intestine:
○ Water Absorption: The large intestine absorbs water from the undigested food,
converting it into semi-solid feces.
○ Bacterial Digestion: Beneficial bacteria in the large intestine help break down
certain indigestible substances, releasing gases and producing vitamins B and
K.
○ Feces Formation: Undigested food, bacteria, and water form feces, which is
stored in the rectum before being expelled through the anus.
8. Rectum and Anus:
○ The rectum stores feces until they are ready to be expelled.
○ Egestion is the process of eliminating undigested food and waste through the
anus.

Digestive Enzymes and Their Functions

● Amylase: Breaks down starch (polysaccharides) into maltose (disaccharide). It is
produced in the mouth and pancreas.
● Protease (Pepsin): Breaks down proteins into peptides and amino acids. Pepsin is
secreted by the stomach.
● Lipase: Breaks down lipids (fats) into fatty acids and glycerol. Secreted by the
pancreas.
● Sucrase: Breaks down sucrose into glucose and fructose. Secreted by the small
intestine.

Absorption of Nutrients
● Villi in the small intestine are lined with epithelial cells that have tiny microvilli,
increasing the surface area for absorption.
● Nutrient Absorption:
○ Glucose and Amino Acids: Transported via active transport into the blood
capillaries of the villi.
 ○ Fatty Acids and Glycerol: Absorbed into lymphatic vessels (lacteals) before
entering the bloodstream.

The Role of Bile

● Bile is produced in the liver, stored in the gallbladder, and released into the duodenum
when fat is present.
○ Emulsification of Fats: Bile salts break large fat droplets into smaller droplets,
increasing the surface area for lipase action.
○ Neutralization: Bile also neutralizes the acidic chyme entering the small intestine
from the stomach, creating an optimal pH for enzyme function.

Types of Nutrition in Mammals

1. Ingestion: The intake of food through the mouth.
2. Digestion: The breakdown of food into simpler molecules (mechanical and chemical
digestion).
3. Absorption: The process of nutrients being absorbed through the walls of the small
intestine into the bloodstream or lymphatic system.
4. Assimilation: The incorporation of absorbed nutrients into body tissues, where they are
used for growth, repair, and energy production.
5. Egestion: The elimination of undigested food and waste products as feces.

Balanced Diet
A balanced diet is essential for good health. It provides all the necessary nutrients in the correct
proportions.

● Carbohydrates: Primary source of energy.

● Proteins: Used for growth, tissue repair, and enzyme production.
● Fats: Provide energy, store fat-soluble vitamins, and insulate the body.
● Vitamins and Minerals: Essential for various biochemical processes and maintaining
health.
● Water: Vital for chemical reactions, temperature regulation, and nutrient transport.

Deficiency Diseases in Mammals

Malnutrition or lack of essential nutrients can lead to deficiency diseases:

1. Proteins: Kwashiorkor (characterized by edema, stunted growth, and immune system

weakness).
2. Carbohydrates: Marasmus (extreme weight loss and muscle wasting).
3. Fats: Deficiency can lead to energy loss, dry skin, and poor growth.
4. Vitamins:
○ Vitamin A: Deficiency causes night blindness and weak immune function.
○ Vitamin C: Lack of vitamin C leads to scurvy (gum disease, fatigue).
○ Vitamin D: Rickets in children (weak bones) and osteomalacia in adults.
5. Minerals:
○ Iron: Leads to anemia, where the body lacks sufficient red blood cells.
○ Calcium: Leads to weak bones and teeth (osteoporosis).