Lecture Notes: Experiment Highlights and Concepts
Experiment 1: Cell and Membrane Mechanisms
Cell Structure
- Fundamental unit of life.
- Contains protoplasm divided into nucleus and cytoplasm.
- Plasma membrane (cell membrane): provides strength, shape, protection, regulates nutrient transfer.
- Processes of regulation:
- Diffusion: Movement from higher to lower concentration.
- Osmosis: Movement of water to balance solute concentration.
- Osmotic terms:
- Hypertonic: High solute concentration outside, cell shrinks.
- Hypotonic: Low solute concentration outside, cell swells.
- Dialysis: Solute diffusion across a permeable membrane.
- Surface Tension: Cohesion force on liquid surface.
Experiment Procedures
- Cell Observation: Use microscope to examine and sketch animal and plant cells.
- Dialysis: Test diffusion of chloride ions and starch across cellophane membrane.
- Osmosis: Measure weight change in potato slices in different saline solutions.
- Diffusion: Time color change in potassium permanganate solution.
- Surface Tension: Observe differences in emulsion formation with and without soap.
Results and Discussion
- Differences between plant and animal cells identified.
- Dialysis showed chloride ions pass membrane, starch doesn't.
- Osmosis affected potato slice weights depending on solution concentration.
- Diffusion time was consistent across trials.
- Soap affects surface tension and emulsification.
Experiment 2: Water and pH
Importance of Water
- Essential for life, biochemical reactions, and cellular processes.
- Influences enzyme activity and protein structure via pH.
pH Scale
- Measures hydrogen ion concentration.
- pH impacts biological functions and is tightly regulated.
- Buffers: Maintain stable pH by neutralizing added acids/bases.
- Composed of weak acid/base and its conjugate.
Lab Results
- Various solutions tested for pH with paper and meter.
- Distilled water pH affected by CO2 absorption.
Solution Reactions to NaOH
- Distilled water and NaAc showed large pH increases.
- Acetate buffer showed minimal pH change against NaOH and HCl.
Key Questions
- Need for boiling distilled water before pH testing.
- Factors affecting buffer capacity: concentration, ratio, pH range.
Experiment 3: Proteins and Amino Acids
Protein Structure
- Comprised of amino acids linked by peptide bonds.
- Functions include enzyme catalysis, oxygen transport, and structural roles.
Protein Reactions
- Denaturation: Breakdown of protein structure by heat, acids, or alcohol.
- Color Tests: Detect specific amino acids or proteins:
- Biuret Test: Detects peptide bonds.
- Ninhydrin Test: Identifies amino acids/amines.
- Xanthoproteic Test: Aromatic amino acids.
- Millon's Test: Tyrosine detection.
- Sakaguchi Test: Arginine detection.
- Lead Acetate Test: Sulfur-containing amino acids.
Lab Applications
- Use of heat and alcohol for microorganism control.
- Heavy metal poisoning treatment with egg white.
Experiment 4: Milk Casein
Milk Proteins
- Caseins (80%), whey proteins, and minor proteins.
- Casein micelles responsible for milk's white color.
- Micelles stabilized by charge repulsion, affected by pH changes.
Isoelectric Point (IEP)
- pH at which casein is least soluble and precipitates.
Biuret and Xanthoproteic Test on Casein
- Detected presence of proteins and aromatic amino acids.
Experiment 5: Amino Acid Separation
Paper Chromatography
- Separates amino acids based on polarity.
- Rf Value: Indicates compound movement through chromatography medium.
- More polar substances have lower Rf values, less polar have higher values.
Lab Results
- Analysis of amino acids like lysine, glutamic acid, and MSG.
Key Concepts
- Influence of polarity on chromatography and protein structure.
- Factors affecting Rf value: stationary phase, temperature, solvent concentration.
This comprehensive summary of the experiments and concepts provides a detailed understanding of cellular processes, water chemistry, protein functions, milk composition, and chromatographic separation of amino acids for academic and laboratory applications.