Cell_division

Lecture Notes on Cell Division

Equation: 6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂
Process: Takes place in chloroplasts, where sunlight is captured by chlorophyll, promoting the conversion of water and carbon dioxide into glucose and oxygen.
Oxidation and Reduction: In photosynthesis, carbon dioxide is reduced to glucose, providing energy that sustains the plant and those who consume it.

Equation: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy (ATP)
Process: Occurs in mitochondria, where glucose is oxidized to produce ATP, the energy currency of the cell, along with carbon dioxide and water as byproducts.
Oxidation and Reduction: Glucose is oxidized to carbon dioxide, releasing energy utilized in various cellular processes.

Photosynthesis:
- Location: Thylakoid membranes of chloroplasts
- Source of Electrons: Water molecules split to release electrons, contributing to ATP and NADPH formation.
Respiration:
- Location: Inner mitochondrial membrane
- Source of Electrons: Electrons are derived from glucose breakdown during glycolysis and the citric acid cycle.
Purpose: Both ETCs involve a series of redox reactions that create a proton gradient, enabling ATP synthesis through chemiosmosis.

Prokaryotic cells lack a nucleus and other organelles, typically smaller than eukaryotic cells.

Process:
1. DNA replication: The circular DNA molecule replicates, creating two identical copies.
2. Cell growth: The cell enlarges, and cytoplasm increases to accommodate two DNA molecules.
3. Final division: The cell membrane pinches inwards, forming two daughter cells.
Result: Two genetically identical daughter cells with no genetic diversity.
Asexual Reproduction: Involves one parent leading to identical offspring; this leads to increased evolutionary adaptability in prokaryotes due to shorter generation times.

Mitosis:
- Produces two genetically identical diploid cells for growth and tissue repair.
Meiosis:
- Produces gametes (sperm and egg cells) with half the chromosome number, ensuring genetic diversity through recombination, critical for evolution.

Interphase (G1, S, G2):
- G1 (Gap 1): The cell grows and synthesizes proteins.
- S (Synthesis): DNA is replicated, resulting in duplicated chromosomes.
- G2 (Gap 2): Further growth and preparation for mitosis.
Mitosis (M Phase): The actual process of cell division.

G1 phase length varies: Eg: Skin cells divide rapidly (24 hours), while liver cells divide slowly (around 1 year).

Prophase: Chromosomes condense, nuclear envelope breaks down, and mitotic spindle forms.
Prometaphase: Spindle fibers attach to chromosomes, and the nuclear envelope fully disappears.
Metaphase: Chromosomes align at the metaphase plate, ensuring proper segregation.
Anaphase: Sister chromatids are pulled apart to opposite poles of the cell by spindle fibers.
Telophase: Nuclear envelopes reform around two sets of chromosomes, and the chromosomes begin to decondense.

In Animal Cells: A cleavage furrow forms to physically separate cells.
In Plant Cells: A cell plate forms to develop a new cell wall, allowing the cell to divide.

Chromosomes: Humans have 23 pairs (46 total), diploid (2n) cells, essential for genetic information storage.
Sister Chromatids: Duplicated chromosomes that are genetically identical, connected at the centromere.
Homologous Chromosomes: Chromosomes that are similar but may carry different alleles, crucial for genetic variation.

G1 Checkpoint: Evaluates if conditions are favorable for division (nutrients, size).
G2 Checkpoint: Checks if all DNA is replicated and verifies for damage before proceeding.
M Checkpoint: Ensures all chromosomes are properly attached to the spindle, preventing improper segregation.

Control progression through the cell cycle by regulating key transitions.
Cyclins: Proteins whose levels fluctuate throughout the cell cycle; they activate CDKs at specific phases.
CDKs: Enzymes that, when bound to cyclins, phosphorylate target proteins to drive the cell cycle forward.

Apoptosis: Programmed cell death, which recycles cell components and is critical for development (e.g., removing webbing in fingers).
Necrosis: Uncontrolled cell death often due to injury, resulting in inflammation and damage to surrounding cells.

For visual learners, understanding processes with diagrams is beneficial for grasping complex ideas such as mitosis and meiosis. Further activities like lab exercises will solidify understanding and retention of cell division processes.