Overview
This lecture covers the organization of living things from cells to organ systems, digestion, enzymes, circulatory and respiratory systems, plant organs, and disease concepts.
Organization of Living Things
- Similar cells form tissues, which group into organs that make up organ systems.
- Examples: heart tissue forms the heart (an organ), which is part of the circulatory system.
Digestive System and Enzymes
- The digestive system breaks down food into nutrients using stomach acid, bile (from the liver), and enzymes.
- Bile neutralizes stomach acid and emulsifies fats for faster enzyme activity.
- Enzymes are biological catalysts that speed up the breakdown of large molecules into smaller, absorbable ones.
- Amylase (found in saliva and small intestine) breaks starch into glucose.
- Enzymes are specific; the "lock and key" model explains enzyme-substrate specificity.
- Carbohydrases break down carbohydrates, proteases break down proteins, and lipases break down fats.
- Enzyme activity increases with temperature and pH up to an optimum; too high or too low values cause denaturation.
- Practical tests measure enzyme rates using iodine and spot tiles to determine optimum conditions.
Food Tests
- Iodine turns black with starch.
- Benedict's solution turns orange with sugars.
- Biuret reagent turns purple with proteins.
- Ethanol turns cloudy with lipids.
Respiratory System
- Air enters through trachea → bronchi → bronchioles → alveoli (air sacs).
- Alveoli have large surface area for fast gas exchange.
- Oxygen binds to hemoglobin in red blood cells; COâ‚‚ diffuses into plasma to be exhaled.
Circulatory System
- The heart powers a double circulatory system: blood enters twice per cycle.
- Right side receives deoxygenated blood, sends it to lungs; left side pumps oxygenated blood to body via aorta.
- Arteries carry blood away (thick walls, high pressure), veins return blood (thinner walls, valves), capillaries allow exchange (one cell thick).
- Coronary arteries supply the heart muscle; blockages cause coronary heart disease (CHD).
- Treatments include stents, statins, artificial valves, and pacemakers.
- Blood also contains white blood cells (fight infection) and platelets (clotting).
Disease Concepts
- Non-communicable diseases arise from within (e.g., heart disease, cancer, diabetes) and not pathogens.
- Communicable diseases are caused by pathogens (viruses, bacteria, fungi).
- Carcinogens are substances increasing cancer risk; malignant tumors spread, benign do not.
Plant Organs and Transport
- Leaves perform photosynthesis and transpiration.
- Roots absorb water/minerals; meristem makes new cells.
- Xylem transports water upward (unidirectional); phloem moves sugars up and down (bidirectional).
- Transpiration increased by heat, dryness, wind.
- Nitrate deficiency stunts growth; magnesium deficiency causes chlorosis (leaf yellowing).
- Leaf layers: waxy cuticle (prevents water loss), upper epidermis (light passes), palisade mesophyll (photosynthesis), spongy mesophyll (gas exchange), vascular bundle (xylem/phloem), lower epidermis (with stomata).
Key Terms & Definitions
- Tissue — group of similar cells performing a function.
- Enzyme — biological molecule that speeds up reactions.
- Lock and Key Model — enzyme specificity due to shape matching.
- Bile — substance that emulsifies fats and neutralizes stomach acid.
- Alveoli — lung air sacs where gas exchange occurs.
- Hemoglobin — protein in red blood cells carrying oxygen.
- Stent — tube to keep blood vessels open.
- Statin — medication reducing cholesterol.
- Transpiration — loss of water vapor from plant leaves.
- Chlorosis — yellowing of leaves due to lack of chlorophyll.
- Carcinogen — substance that increases cancer risk.
Action Items / Next Steps
- Review enzyme practical experiment procedure and results interpretation.
- Practice identifying nutrients using food tests.
- Read textbook sections on circulatory and plant transport systems.