Biology: Cells, Osmosis, and Stem Cells

Prokaryotes and Eukaryotes

• Prokaryotes are single-celled organisms (like bacteria) without a nucleus or membrane-bound organelles.
• Eukaryotes are organisms with cells containing a nucleus and membrane-bound organelles (like plants, animals, and fungi).

Osmosis and Diffusion

• Diffusion: Particles move from high concentration to low concentration.
• Osmosis: Water moves across a membrane.
• Cell membranes are semipermeable (some things can pass).
• Hypertonic: Solution with more solutes outside the cell than inside; water moves out, cell shrinks.
• Hypotonic: Solution with fewer solutes outside the cell than inside; water moves in, cell swells (or bursts).
• Isotonic: Solution with the same solute concentration inside and outside the cell; water moves in and out equally, cell size stays the same.

Stem Cells

• Stem cells are unspecialized cells that divide and differentiate into specialized cell types.
• Types include embryonic (can become any cell type) and adult (limited to specific cells).
• Importance: Used to study diseases, develop treatments, and regenerate damaged tissues (e.g., cancer treatment).

Cancer

• Cancer occurs when cells grow and divide uncontrollably due to mutations.
• Causes include inherited factors, aging, and harmful substances (e.g., smoking, UV light).
• Cancer cell traits: Uncontrolled growth, immune system avoidance, spreading, and tissue damage.
• Types of Tumors:
  • Metastatic: Spread to other areas.
  • Benign: Stay in one area.
  • Malignant: Mass of cells interfering with normal functions of neighboring cells; may destroy surrounding tissues.

Detecting and Screening Cancer

• Methods include medical imaging (MRI and CT scans).
• ABCDE rule for detecting skin cancer:
  • Asymmetry: One half doesn't match the other.
  • Border: Irregular, blurred, or notched edges.
  • Color: Uneven colors (black, brown, red, white, blue).
  • Diameter: Larger than 6mm (pencil eraser size).
  • Evolving: Changes in size, shape, or color.

Treatments for Cancer

• Surgery: Removing tumors (drawback: large/inaccessible tumors).
• Chemotherapy: Drugs that kill fast-growing cells (drawback: tissue damage).
• Radiation: Damages cancer cell DNA.
• Biophotonics: Uses lasers to target cells.

Animal and Plant Cell Differences

• Similarities: Both have a cell membrane, cytoplasm, nucleus, mitochondria, and ribosomes. Both undergo mitosis, and cellular respiration
• Animal Cells: No cell wall, no chloroplasts, small or no vacuole, round shape.
• Plant Cells: Cell wall for support and structure, chloroplasts for photosynthesis, large central vacuole, rectangular shape.

Mitosis Stages

• Interphase: DNA replicates; cell lives its life cycle
• Prophase: Chromosomes condense, nuclear envelope breaks down, spindle fibers form.
• Metaphase: Chromosomes align in the cell's middle, spindle fibers attach.
• Anaphase: Sister chromatids separate and move to opposite poles.
• Telophase: Chromosomes unravel, new nuclear membranes form around each set.
• Cytokinesis: Cytoplasm divides; animal cells pinch, plant cells form a cell plate.

Enzymes and Digestive System

• Amylase: Found in saliva; breaks down carbohydrates.
• Pepsin: Found in stomach; breaks down proteins.
• Trypsin: Found in small intestine; continues protein breakdown.
• Lipase: Found in small intestine; breaks down fats/lipids.

Digestion Process

• Chemical Digestion: Enzymes break down food.
• Mechanical Digestion: Physical breakdown of food (e.g., teeth, stomach churning).

Human Organ Systems

• Digestive System:*
  • Mouth (chewing, amylase), Esophagus (transport), Stomach (mechanical and chemical digestion), Small Intestine (nutrient absorption), Large Intestine (water absorption, waste).
  • Accessory organs (liver and gallbladder) support digestion without touching food.
• Circulatory System:*
  • Functions: Delivers oxygen and nutrients, removes wastes, transports hormones, regulates temperature.
  • Essential parts: Heart (pump), blood (fluid), blood vessels (arteries, veins, capillaries).
  • Blood components: Plasma (water, dissolved substances), Red Blood Cells (oxygen transport), White Blood Cells (immunity), Platelets (clotting).
• Respiratory System:*
  • Path of air: Nose/Mouth (entry), Trachea (airway), Bronchi (branches), Bronchioles (smaller branches), Alveoli (gas exchange), Diaphragm (breathing muscle).
• Musculoskeletal System:*
  • Bones: Support, protection, mineral storage, blood cell production.
  • Ligaments: Connect bones at joints, provide stability.
  • Cartilage: Smooth surface at joints, reduces friction.
  • Tendons: Connect muscles to bones, enable movement.
  • Muscles: Contract to move bones, work in pairs.
• Nervous System:*
  • Central Nervous System (CNS): Brain, spinal cord; processes information, coordinates responses.
  • Peripheral Nervous System (PNS): Nerves connecting CNS to body control muscles, carries sensory info, regulates involuntary actions.
  • Neurons: Transmit electrical signals, some have myelin for faster signal transmission.
  • Sensory Receptors: Detect light, temperature, chemicals, pressure, pain.
  • Spinal Cord: Relay station for reflexes and communication brain-body.

Short Answer - Multiple Organ Systems

• Lungs (respiratory): Alveoli increase surface area for gas exchange.
• Small Intestine (digestive): Villi and microvilli increase nutrient absorption surface area.
• Capillaries (circulatory): Extensive network maximizes gas, nutrient, and waste exchange with tissues.
• Skin (integumentary): Large surface area for temperature regulation and environmental sensing.
• Brain (nervous): Folds (gyri and sulci) increase surface area for neuronal processing/control.

Systems Working Together

• Respiratory and Circulatory Systems: Work in tandem to transport oxygen to cells, and remove carbon dioxide.
• Musculoskeletal and Nervous Systems: Coordinate movement and body functions.
• Digestive and Circulatory Systems: Break down food and transport nutrients.

Gas Exchange in Lungs

• Alveoli in lungs facilitate diffusion of oxygen into blood and carbon dioxide out of blood.

Respiratory System Issues

• Tuberculosis (TB): Infectious Lung disease
• Lung Cancer: Often caused by smoking and is preventable.
• Vaping: Harms lungs, long-term effects still being studied.
• COVID-19: Virus impacting breathing.

Nervous System Issues

• Concussion: Brain injury.
• Multiple Sclerosis: Immune system damages myelin.
• Paralysis: Severe spinal cord damage.

Heart and Blood Flow

• Blood movement: Pulmonary (lungs) and Systemic (body) loops.
• Path summary: Oxygenated blood leaves heart via arteries, deoxygenated returns via veins. Capillaries facilitate gas and nutrient transfer.
• Key Blood Vessels: Superior/Inferior Vena Cava, Pulmonary Veins and arteries, Aorta

Climate Change

• Greenhouse gases: Trap heat in atmosphere, leading to warming, causing problems with global warming. (e.g. Carbon dioxide, Methane)
• Climate change: Long-term changes in weather patterns (e.g., temperature, rainfall, storms).
• Global warming: Overall increase in Earth's average temperature.
• Climate vs. Weather: Climate is long-term weather averages, weather is day-to-day conditions.
• Evidence of global warming: Increasing CO2 levels, melting glaciers, rising sea levels, and more extreme weather.

Carbon Dioxide (CO2)

• A greenhouse gas, naturally occurring but increased by human activities.
• CO2 levels have risen dramatically since the Industrial Revolution, due to activities like burning fossil fuels and deforestation.
• Present levels are the highest in over 800,000 years. Increased CO2 means more trapped heat, which has significant impact on the planet:

Climate Change Effects

• Examples of effects, including reduced agricultural productivity due to irregular and less rainfall, increased drought risk for agriculture and animals, and increase in heat waves, causing health problems.