Recording-2025-02-19T16:39:08

Cells

• Definition: Basic unit of life; all living organisms are composed of cells.

Types of Microscopes

• Light Microscope: Can view cells and nuclei but lacks the clarity to see subcellular structures.

• Electron Microscope: Offers higher resolving power and resolution, revealing details of organelles.

• Magnification Calculation:

  • Formula: Magnification = Image Size / Object Size

  • Rearrangement: Actual Cell Size = Image Size / Magnification

Types of Cells

• Eukaryotic Cells:

  • Have a nucleus that contains DNA.

  • Examples: Plant and animal cells.

• Prokaryotic Cells:

  • Lack a nucleus; DNA is in the form of a plasmid.

Cell Structures

• Cell Membrane: Semi-permeable barrier that controls the entry and exit of substances.

• Cell Wall: Present in plant cells and bacteria, made of cellulose, providing structural support.

• Cytoplasm: Liquid medium where chemical reactions occur.

• Mitochondria: Powerhouse of the cell where respiration occurs and energy is released.

• Ribosomes: Sites of protein synthesis.

• Chloroplasts (in plant cells): Contain chlorophyll, site of photosynthesis.

• Vacuole: Permanent in plant cells, stores sap.

Cell Division

• Mitosis: Process by which new cells are produced for growth and repair.

  • Stages include duplication of genetic material, separation of chromosomes, and formation of two identical nuclei.

• Diploid vs. Haploid Cells:

  • Diploid Cells: Eukaryotic cells with 23 pairs of chromosomes (46 total).

  • Haploid Cells: Gametes with just one set of 23 chromosomes.

Specialization of Cells

• Cells develop specific functions based on their roles:

  • Examples: Nerve cells, muscle cells, root hair cells.

• Stem Cells: Unspecialized cells that can differentiate into various types; found in embryos and in adult bone marrow.

• Cloning Uses: Potential to produce stem cells for medical treatments, raising ethical considerations.

Transport Mechanisms

• Diffusion: Movement of molecules from high to low concentration; passive process that requires no energy.

• Osmosis: Special type of diffusion referring specifically to water movement across a semi-permeable membrane.

  • Example: If glucose concentration is higher outside the cell, water moves out, resulting in decreased cell mass.

• Active Transport: Energy-requiring process to move substances against their concentration gradient (e.g., mineral ions into root hair cells).

Organ Systems

• Cells form tissues, tissues form organs, and organs interconnect to create organ systems (e.g., circulatory system).

• Digestive System: Converts food into usable nutrients.

  • Stomach acid, bile, and enzymes work together to digest food.

  • Enzymes: Catalysts that speed up reactions, specific to their substrates.

Enzymatic Activity

• Enzymes:

  • Types include carbohydrases (starch to sugar), proteases (proteins to amino acids), and lipases (fats to glycerol and fatty acids).

  • Function based on the 'lock and key' model where the shape of the substrate must match the active site.

• Factors Affecting Enzymes:

  • Temperature and pH can affect enzyme activity, with extremes causing denaturation.

Nutrient Testing

• Food Tests:

  • Iodine for starch (turns black), Benedict's solution for sugars (turns orange), Biuret reagent for proteins (turns purple), ethanol for lipids (turns cloudy).

Respiratory System

• Breathing vs. Respiration:

  • Breathing provides oxygen for cellular respiration occurring in cells.

• Pathway of Air:

  • Air travels from trachea to bronchi, bronchioles, and alveoli, where gas exchange occurs.

  • Oxygen binds to hemoglobin in red blood cells for transport throughout the body.

Circulatory System

• Heart:

  • Double circulatory system with oxygenated and deoxygenated blood flow.

  • Blood enters heart via vena cava into right atrium, passes through right ventricle to lungs, then returns oxygenated to left atrium and ventricle and out via aorta.

• Blood Vessels:

  • Arteries (thick walls, transport away from heart) and veins (thinner walls, transport to heart with valves to prevent backflow).

• Coronary Heart Disease (CHD): Caused by blockages in coronary arteries; treated with stents or statins.

Diseases

• Non-communicable Diseases: Conditions like cardiovascular disease caused by internal factors or lifestyle choices.

• Communicable Diseases: Caused by pathogens (viruses, bacteria, fungi, protists).

Immune Response

• Immune System Functions:

  • Lymphocytes: Produce antibodies to neutralize pathogens and create immunity.

  • Phagocytes: Ingest and destroy pathogens.

• Vaccines: Introduce a harmless version of a pathogen to stimulate an immune response without causing disease.

• Antibiotics: Target bacteria, ineffective against viruses; resistance is a growing concern.

Photosynthesis

• Process: Conversion of carbon dioxide and water into glucose using light energy.

• Factors Slowing Photosynthesis: Temperature, light intensity, and CO2 concentration can limit rates.

• Practical Investigation: Measure oxygen production in submerged pondweed to assess photosynthesis rates.

Respiration

• Aerobic vs. Anaerobic:

  • Aerobic respiration occurs using oxygen, producing lactic acid or ethanol in anaerobic conditions (e.g., fermentation in yeast).

• Importance of oxygen debt in muscular fatigue and recovery post-exercise.

Metabolism

• Definition: All reactions in a cell/organism, including respiration, nutrient synthesis, and waste production.