Microscopy, Scientific Measurement, Cell Anatomy & Division

🔸 Cell Membrane

• Structure: Phospholipid bilayer with embedded proteins

• Function: Controls what enters and exits the cell (selective permeability); communication via receptors

🔸 Cytoplasm

• Structure: Jelly-like fluid (cytosol) + organelles

• Function: Site of many metabolic reactions; supports organelles

🔸 Nucleus

• Structure: Surrounded by nuclear envelope with pores; contains chromatin and nucleolus

• Function: Control center; stores DNA; coordinates cell activities like growth, metabolism, protein synthesis, and reproduction

🔸 Nucleolus

• Structure: Dense structure inside the nucleus

• Function: Produces ribosomes

🔸 Ribosomes

• Structure: Small particles made of RNA and proteins; free-floating or attached to rough ER

• Function: Protein synthesis

🔸 Rough Endoplasmic Reticulum (RER)

• Structure: Network of membranes with ribosomes attached

• Function: Modifies and transports proteins made by ribosomes

🔸 Smooth Endoplasmic Reticulum (SER)

• Structure: Network of membranes without ribosomes

• Function: Synthesizes lipids and steroids; detoxifies drugs

🔸 Golgi Apparatus

• Structure: Stack of flattened membranes

• Function: Modifies, packages, and ships proteins and lipids

🔸 Mitochondria

• Structure: Double membrane; inner membrane folded into cristae

• Function: Produces ATP (energy) through cellular respiration; "powerhouse of the cell"

🔸 Lysosomes

• Structure: Membrane-bound vesicles containing digestive enzymes

• Function: Break down waste, damaged organelles, and cellular debris

🔸 Centrioles (in animal cells)

• Structure: Cylindrical structures made of microtubules

• Function: Organize spindle fibers for mitosis

🔸 Cytoskeleton

• Structure: Network of protein filaments (microfilaments, microtubules)

• Function: Maintains cell shape, assists in movement, transports materials within the cell

🔹 Objective 2: Understand Somatic Cell Division – Mitosis and Cytokinesis

🔸 Somatic Cells

• Definition: All body cells except reproductive (gametes)

• Division: Undergo mitosis

🔸 Purpose of Mitosis

• Growth

• Repair of damaged tissues

• Replacement of old cells

• Asexual reproduction (in some organisms)

🔸 Cell Cycle Phases

1. Interphase (Not part of mitosis, but preparation)

• G1 phase: Cell grows, performs normal functions

• S phase: DNA is replicated

• G2 phase: Final preparations for division

🔸 Mitosis Stages (PMAT)

1. Prophase

• Chromatin condenses into visible chromosomes (sister chromatids joined by centromere)

• Nuclear envelope breaks down

• Spindle fibers begin to form from centrioles

2. Metaphase

• Chromosomes align in the center (metaphase plate)

• Spindle fibers attach to centromeres

3. Anaphase

• Sister chromatids pulled apart to opposite poles of the cell

• Each chromatid is now considered an individual chromosome

4. Telophase

• Chromosomes begin to uncoil back into chromatin

• Nuclear envelope re-forms around each set of chromosomes

• Spindle fibers disappear

🔸 Cytokinesis

• Definition: Division of the cytoplasm into two daughter cells

• In animal cells: Cleavage furrow forms and pinches cell in two

• In plant cells: Cell plate forms (due to rigid cell wall)

🔸 End Result of Mitosis + Cytokinesis

• Two genetically identical diploid daughter cells

• Same number of chromosomes as the original (parent) cell

🔹 Somatic Cell Division

Q: What is mitosis?
A: Division of the nucleus to create two identical daughter cells.

Q: What is cytokinesis?
A: Division of the cytoplasm after mitosis.

Q: List the 4 phases of mitosis in order.
A: Prophase, Metaphase, Anaphase, Telophase.

Q: What happens in prophase?
A: Chromosomes condense, spindle forms, nuclear envelope breaks down.

Q: What happens in metaphase?
A: Chromosomes line up in the middle of the cell.

Q: What happens in anaphase?
A: Sister chromatids are pulled apart to opposite sides.

Q: What happens in telophase?
A: Nuclear envelope reforms, chromosomes decondense.

1. Basic SI Units (Metric System)

2. Common Prefixes

3. Tools Used in Measurement

4. Accuracy vs. Precision

• Accuracy = How close a measurement is to the true value.

• Precision = How consistent repeated measurements are.

5. Significant Figures (Sig Figs)

Used to show precision in measurements.

• All non-zero digits are significant.

• Zeros between digits are significant.

• Leading zeros are not significant.

• Trailing zeros after a decimal are significant.

Example:

• 0.00450 → 3 sig figs

• 4500 → 2 sig figs (unless written as 4.50 × 10³)

6. Scientific Notation

Used for very large or small numbers.

Format: a × 10ⁿ

• 5,000 = 5.0 × 10³

• 0.00042 = 4.2 × 10⁻⁴

7. Conversions

Use dimensional analysis to convert between units.