Overview
This lecture covers the structure and function of tissues, organs, organ systems, and key processes such as digestion, respiration, circulation, plant transport, and diseases.
Tissues, Organs, and Organ Systems
- Similar cells form tissues; tissues form organs; organs group into organ systems.
- The circulatory and digestive systems are examples of organ systems.
Human Digestion and Enzymes
- The digestive system breaks down food into nutrients using stomach acid, bile, and enzymes.
- Bile, made in the liver and stored in the gallbladder, neutralizes acid and emulsifies fats.
- Enzymes are biological catalysts that break down large molecules for absorption.
- Amylase breaks down starch into glucose; found in saliva and the small intestine.
- Enzymes are specific and work via a lock and key model with substrates.
- Enzyme activity rates increase with temperature and pH to an optimum, then denature if too extreme.
- Practical: Test enzyme activity by mixing with substrates, timing breakdown, and plotting results.
Food Tests
- Iodine turns black with starch.
- Benedict’s solution turns orange with sugars.
- Biuret’s reagent turns purple with proteins.
- Cold ethanol goes cloudy with lipids.
Respiratory and Circulatory Systems
- Breathing brings oxygen for respiration; air moves from trachea to alveoli for gas exchange.
- Oxygen binds to hemoglobin in red blood cells and circulates to body cells.
- Carbon dioxide produced by respiration is carried in blood plasma and exhaled.
- The heart pumps blood in a double circulatory system; right side to lungs, left to body.
- Arteries carry blood away from the heart (oxygenated except pulmonary artery); veins carry blood back (deoxygenated except pulmonary vein).
- Capillaries are one cell thick for fast diffusion.
- Coronary arteries supply the heart muscle; blockages cause coronary heart disease (CHD).
Heart Disease and Treatments
- Stents keep blood vessels open; statins lower cholesterol and reduce fatty buildup.
- Faulty heart valves can be replaced artificially.
- Blood transports white blood cells, platelets, and plasma.
Communicable and Non-communicable Diseases
- Non-communicable diseases originate from within (e.g., CVD, cancer, autoimmune diseases).
- Communicable diseases are caused by pathogens (viruses, bacteria, fungi).
- Risk factors: poor diet, smoking, alcohol.
- Carcinogens increase cancer risk; cancer is uncontrolled cell division.
Plant Structure and Transport
- Leaves conduct photosynthesis and transpiration (water loss).
- Xylem transports water upward (unidirectional); phloem moves food up and down (bidirectional).
- Transpiration increases with temperature, lower humidity, and wind.
- Lack of nitrates stunts growth; magnesium deficiency causes chlorosis (yellow leaves).
- Leaf structure: waxy cuticle, upper epidermis, palisade mesophyll (photosynthesis), spongy mesophyll (gas exchange), vascular bundles (xylem/phloem), lower epidermis with stomata controlled by guard cells.
Key Terms & Definitions
- Tissue — group of similar cells with a specific function.
- Organ — structure composed of different tissues performing a function.
- Enzyme — protein catalyst that speeds up chemical reactions.
- Bile — digestive fluid that neutralizes acid and emulsifies fats.
- Lock and Key Model — enzyme specificity model where substrate fits enzyme's active site.
- Stent — tube inserted into blood vessels to keep them open.
- Statin — drug that lowers cholesterol.
- Carcinogen — agent increasing cancer risk.
- Transpiration — evaporation of water from plant leaves.
- Chlorosis — yellowing of leaves due to lack of chlorophyll.
- Stomata — pores in leaves for gas exchange.
Action Items / Next Steps
- Review enzyme practical steps and results interpretation.
- Memorize the key food tests and their outcomes.
- Study the structure and function of leaf layers and plant transport systems.