DJHGRTER

Cells as Basic Units of Life

• Cells are the basic structural and functional units of all living organisms.
• They are the smallest units of life.
• Organisms are classified into eukaryotic and prokaryotic cells.

Eukaryotic Cells

• Have a defined nucleus enclosed by a membrane.
• Examples include plant and animal cells.
• Contain organelles like the nucleus, mitochondria, and vacuoles.

Prokaryotic Cells

• Lack a nucleus; their genetic material is not enclosed by a membrane.
• Examples include bacteria.

Common Cell Structures

• All cells have a cell membrane, cytoplasm, and nucleus (in eukaryotic cells).

Cell Membrane

• A selectively permeable barrier surrounding the cell.
• Regulates the movement of substances into and out of the cell.
• Composed of lipids and proteins.

Cytoplasm

• The jellylike substance within the cell membrane.
• Contains cytosol (water, salts, and organic molecules) and organelles.

Nucleus

• The control center of eukaryotic cells.
• Contains DNA and regulates cellular activities.
• The nuclear membrane encloses the nucleus and contains pores for material exchange.
• The nucleolus synthesizes ribosomal RNA.

Specialised Cells

• Cells vary in shape, size, and function.
• Nerve cells transmit electrical signals.
• Red blood cells carry oxygen with a biconcave shape for increased surface area.

Organelles and Their Functions

• Mitochondria convert food into usable energy through cellular respiration.
• Vacuoles store nutrients, waste, and maintain turgor pressure in plant cells.

Key Terms and Concepts

• Cytoplasm: Contents within the cell membrane, excluding the nucleus in eukaryotes. Microscope: An instrument for viewing microscopic cells and structures.
• Microscopic: Objects too small to be seen with the naked eye.
• Organelle: Structures within a cell with specific functions.
• Cellular Respiration: Cells convert glucose and oxygen into energy, carbon dioxide, and water.
• DNA: Molecule containing genetic information.
• Selective Permeability: The cell membrane allows some substances to pass while blocking others.

Variations in DNA and Heredity

• Hereditary Traits: Characteristics passed from parents to offspring through DNA.
• Variation: Differences in DNA sequences lead to diversity.

Study of Cells

• Cytology: The scientific study of cells.
• Protoplasm: The living content of a cell, comprising the cytoplasm and nucleus.

Differences Between Plant and Animal Cells

• Plant and animal cells differ significantly due to their roles and functions.

Cell Wall

• Plant cells have a cell wall made of cellulose.
• Provides structural support, protection, and rigidity.
• Protects from mechanical damage and regulates substance entry/ exit.
• Bacterial cell walls contain peptidoglycan, fungal cell walls contain chitin.

Chloroplasts

• Found in plant cells and certain algae.
• Responsible for photosynthesis.
• Contain chlorophyll, which absorbs light energy.
• Thylakoids are membranebound within chloroplasts for light-dependent reactions.
• Stroma is the fluid-filled space for light-independent reactions.

Vacuoles

• Plant cells have large vacuoles.
• Store nutrients, waste, and maintain turgor pressure.
• Animal cells have small, temporary vacuoles.
• Full vacuoles make plant cells turgid.

Additional Differences

• Plant cells have a fixed shape, while animal cells have a flexible shape.
• Plant cells lack centrioles. Animal cells contain centrioles for cell division.
• Plant cells have plasmodesmata for communication between cells, while animal cells have gap junctions.
• Plant cells rarely have lysosomes; vacuoles perform similar functions. Animal cells contain lysosomes for breaking down waste.
• Both cells contain peroxisomes; they have other functions in plant cells, like the glyoxylate cycle.
• Plant cells store energy as starch. Animal cells store energy as glycogen.

Observing Cells Under a Microscope

• Microscopes magnify objects too small to be seen.
• Electron microscopes use electrons for higher magnification.
• Light microscopes use visible light.

Parts of a Light Microscope

• Eyepiece: Magnifies 10x.
• Objective Lenses: Different magnifications (e.g., 4x, 10x, 40x, 100x).
• Stage: Platform for the slide.
• Light Source: Illuminates the specimen.
• Coarse and Fine Focus Knobs: Adjust the focus.
• Diaphragm: Controls light.

Microscope Safety Precautions

• Carry the microscope with two hands.
• Clean lenses with lens paper.
• Use unbroken slides and handle cover slips by the edges.
• Store the microscope with the lowest objective lens in place.

Preparing Specimens for Microscopic Observation

• Wet Mount: Used for living organisms and aquatic samples; involves liquid on the slide.
• Dry Mount: Used for hair, feathers, pollen, or dust; no liquid is used.
• Smear: Used for blood/bodily fluids; sample spread thinly on the slide.
• Staining: Enhances contrast; examples include iodine solution and methylene blue.

Differentiation of Cells in Tissues, Organs, and Systems

• Specialization of cells enables them to fulfill their roles effectively.
• Epithelial cells cover surfaces.
• Muscle cells contract for movement.
• Nerve cells transmit electrical signals.
• Red blood cells transport oxygen and carbon dioxide.

Stem Cells

• Unspecialized cells can differentiate into specialized cells.
• Embryonic stem cells can become any cell type.
• Adult stem cells have limited differentiation potential.

Microscopic vs. Macroscopic Organisms

• Unicellular organisms consist of a single cell (e.g., bacteria).
• Multicellular organisms are composed of many cells (e.g., plants, animals).

Organization of Cells in Multicellular Organisms

• Cells, tissues, organs, and organ systems work together.
• Tissues are groups of similar cells (e.g., muscle tissue).
• Organs are composed of different tissues (e.g., stomach).
• Organ systems are groups of organs (e.g., digestive system).

Example: The Digestive System

• Contains cells: epithelial cells and muscle cells.
• Contains tissues: epithelial tissue and muscle tissue.
• Contains organs: mouth, esophagus, stomach, and intestines.
• The system is the digestive system.

Practical Activity: Observing Cells

• Prepare the microscope and slide.
• Observe the specimen; adjust the light.
• Draw and label observations.

The Digestive System

• Responsible for breaking down food for absorption.

Components of the Digestive System

• Comprises organs forming the alimentary canal: mouth to anus.

Mouth and Esophagus

• Digestion starts in the mouth; saliva breaks down carbohydrates.
• The esophagus moves food to the stomach through peristalsis.

Stomach

• Uses gastric juices and enzymes to digest food.
• Transforms food into chyme through contractions.

Small Intestine

• Most digestion and nutrient absorption occurs here.
• Enzymes from the pancreas and bile from the liver aid digestion.

Large Intestine (Colon)

• Absorbs water and salts from remaining food matter.
• Compacts waste into feces and produces certain vitamins.

Rectum and Anus

• The rectum stores feces; egestion occurs through the anus.

Main Processes in the Digestive System

• Ingestion: Taking food into the body.
• Digestion: Breaking down food mechanically and chemically.
• Absorption: Nutrients absorbed into the bloodstream.
• Egestion: Removal of undigested material.

Health Issues Involving the Digestive System

• Ulcers: Sores on the lining of the digestive system.
• Anorexia Nervosa: Eating disorder with severe food restriction.
• Diarrhea: Frequent, watery stools.
• Liver Cirrhosis: Scar tissue replaces healthy liver tissue.

The Circulatory System

• Transports blood throughout the body.
• Delivers oxygen and nutrients, removes carbon dioxide and waste.
• Regulates body temperature.

Components of the Circulatory System

• Consists of the heart, blood vessels, and blood. Heart
• Pumps blood throughout the body.
• Has four chambers: two atria and two ventricles.

Blood Vessels

• Arteries: Carry oxygenated blood away from the heart.
• Capillaries: Vessels exchanging gases, nutrients, and waste between blood and tissues.
• Veins: Carry deoxygenated blood back to the heart.

Blood

• Composed of plasma, red blood cells, white blood cells, and platelets.
• Transports oxygen, carbon dioxide, nutrients, hormones, and waste.

Main Processes in the Circulatory System

• Pulmonary Circulation: Between the heart and lungs for oxygenation.
• Systemic Circulation: Oxygenated blood to the body, deoxygenated blood back to the heart.

Health Issues Involving the Circulatory System

• High Blood Pressure (Hypertension): Damages blood vessels and organs.
• Heart Attacks (Myocardial Infarction): Blockage of coronary arteries.
• Strokes: Interruption of blood supply to the brain.

The Respiratory System

• Exchanges gases between the body and the environment.
• Supplies oxygen and removes carbon dioxide.

Components of the Respiratory System

• Mouth and Nose: Air entry point; warms, moistens, and filters air.
• Pharynx: Passageway for air and food.
• Trachea (Windpipe): Carries air to the bronchi.
• Bronchi: Lead to the lungs and divide into bronchioles.
• Lungs: Main organs containing alveoli.
• Alveoli: Air sacs surrounded by capillaries for gas exchange.
• Diaphragm: Muscle that helps in breathing.

Main Processes in the Respiratory System

• Breathing (Ventilation): Inhalation and exhalation.
• Gaseous Exchange: Oxygen into the blood, carbon dioxide out.
• Cellular Respiration: Oxygen converts glucose into energy, producing carbon dioxide.

Health Issues Involving the Respiratory System

• Asthma: Inflammation and narrowing of airways.
• Lung Cancer: Often caused by smoking.
• Bronchitis: Inflammation of bronchial tubes.
• Pneumonia: Infection inflaming air sacs.
• Tuberculosis (TB): Infectious disease affecting the lungs.

The Musculoskeletal System

• Enables body movement and supports its structure.

Components of the Musculoskeletal System

• Muscles: Enable movement.
• Bones: Provide support and protection.
• Cartilage: Flexible tissue found in joints etc.
• Tendons: Connect muscles to bones.
• Ligaments: Connect bones at joints.

Main Processes in the Musculoskeletal System

• Locomotion: The ability to move the entire body.
• Movement: Change in shape, direction, position, or size; through muscular contraction.

Health Issues Involving the Musculoskeletal System

• Rickets: Weak bones due to vitamin D, calcium, or phosphate deficiency.
• Arthritis: Joint inflammation and pain.
• Osteoporosis: Brittle and fragile bones.

The Excretory System

• Removes metabolic waste products from the body.

Components of the Excretory System

• Kidneys: Filter blood, producing urine.
• Ureters: Transport urine from kidneys to the bladder.
• Bladder: Stores urine.
• Urethra: Excretes urine from the body.

Main Processes in the Excretory System

• Filtration: Blood filtered in the kidneys.
• Reabsorption: Essential substances reabsorbed into the blood.
• Secretion: Waste products secreted into renal tubules.
• Excretion: Urine excreted through the urethra.

Health Issues Involving the Excretory System

• Kidney Failure: Kidneys lose their ability to filter blood.
• Kidney Stones: Mineral deposits form in the kidneys.
• Bladder Infections (Cystitis): Bacterial infection in the bladder.
• Glomerulonephritis: Inflammation of kidney glomeruli.
• Polycystic Kidney Disease (PKD): Genetic disorder with cyst growth on the kidneys.

The Nervous System

• Transmits nerve impulses between body parts.
• Coordinates actions and sensory information.

Components of the Nervous System

• Nerves: Bundles of neurons transmitting messages.
• Brain: Control center; controls thought, memory, and emotion.
• Spinal Cord: Transmits signals between the brain and the body.
• Sensory Organs: Collect and transmit information from the environment.

Main Processes in the Nervous System

• Sending and Receiving Impulses: Through electrical impulses and neurotransmitters.
• Hearing: Sound converted to electrical signals by hair cells.
• Seeing: Light converted to electrical signals by photoreceptors.
• Feeling: Sensory receptors detect pressure, temperature, and pain.
• Tasting: Taste buds detect flavors.
• Smelling: Olfactory receptors detect airborne chemicals.
• Regulating Body Temperature: Hypothalamus maintains body temperature.

Health Issues Involving the Nervous System

• Trauma and Injuries: Can cause paralysis.
• Stroke: Interrupted blood flow leads to the death of brain cells.
• Degenerative Disorders: Alzheimer's, Parkinson's, Multiple Sclerosis.
• Mental Health Problems: Depression, anxiety, personality disorders.
• Sensory Organ Problems: Deafness, blindness.
• Effects of Drugs and Alcohol: Impair cognitive functions.

The Reproductive System

• Produces sex cells (gametes) for reproduction.

Components of the Reproductive System