The Three Components of Cell Theory:
All living organisms are composed of one or more cells.
The cell is the basic unit of life.
All cells arise from pre-existing cells.
What are organelles?
Small specialized structures within a cell that perform specific functions.
Prokaryotic Cells vs. Eukaryotic Cells:
Prokaryotic Cells: No nucleus (e.g., bacteria).
Eukaryotic Cells: Have a nucleus and organelles (e.g., animal and plant cells).
Structure & Function of the Nucleus:
Contains genetic material (DNA) and controls cell activities.
Surrounded by the nuclear envelope with nuclear pores.
Contains nucleolus, which makes ribosomes.
What is DNA?
The molecule that carries genetic information, determining traits and controlling cell functions.
Structure of DNA:
Double helix (twisted ladder shape).
Sugar-phosphate backbone (sides) and paired nitrogenous bases (steps/rungs).
Base pair rule: A-T, C-G.
What is a nucleotide?
The building block of DNA, made of:
A sugar (deoxyribose)
A phosphate group
A nitrogenous base (A, T, C, G)
Different Forms of DNA:
Uncoiled double helix (when not dividing).
Chromatin (loose DNA in the nucleus).
Chromosomes (condensed DNA for cell division).
Karyotype:
A picture of chromosomes used to check for genetic disorders.
Human Chromosomes:
46 chromosomes (23 pairs).
Somatic (body) cells: 46 chromosomes.
Sex cells (gametes): 23 chromosomes.
Genes & Proteins:
Genes: Segments of DNA that code for proteins.
Proteins: Perform essential functions (e.g., enzymes, hormones, transport proteins).
Purpose of Cell Division:
Growth, repair, and reproduction.
DNA Replication (S phase of Interphase):
Three Main Steps:
Unwinding: Enzyme helicase unzips DNA.
Base Pairing: DNA polymerase adds new bases.
Two Identical DNA Strands: Semi-conservative process.
Interphase:
G1 Phase: Cell growth, normal functions.
S Phase: DNA replication.
G2 Phase: Prepares for mitosis.
Mitosis (PMAT):
Prophase: Chromosomes condense, spindle fibers form, nucleus disappears.
Metaphase: Chromosomes line up at the equator.
Anaphase: Sister chromatids separate.
Telophase: Two nuclei form in one cell.
Cytokinesis:
Splitting of cytoplasm to form two identical daughter cells.
Checkpoints & Cancer:
Checkpoints ensure proper cell division.
Cancer results from uncontrolled cell division.
Asexual Reproduction Examples (5.2):
Binary Fission (bacteria), Budding (yeast), Fragmentation, Vegetative Reproduction, Artificial Cloning.
Diploid vs. Haploid:
Diploid (2n): Full set of chromosomes (46 in humans).
Haploid (n): Half the chromosomes (23 in gametes).
Meiosis Counterbalances Fertilization:
Meiosis creates haploid gametes â Fertilization restores diploid number.
Meiosis I:
Homologous chromosomes separate.
Meiosis II:
Sister chromatids separate.
Produces four genetically unique gamete cells.
Spermatogenesis vs. Oogenesis:
Spermatogenesis (male) â 4 sperm cells.
Oogenesis (female) â 1 egg cell + 3 polar bodies.
Genetic Variation Factors:
Crossing Over (Prophase I)
Independent Assortment (Metaphase I)
Random Fertilization
First Trimester: Formation of organs, heart starts beating.
Second Trimester: Growth, movement felt.
Third Trimester: Final development, fat storage.