Cells terms bio level 2

$G_1$ phase

The stage of interphase in which the cell grows, synthesizes new proteins, and produces organelles.

S phase

The stage of interphase where DNA replication occurs, resulting in duplicated chromosomes each composed of two sister chromatids.

$G_2$ phase

The final stage of interphase where the cell inspects replicated DNA for copying errors and prepares structures required for division.

Primary stages of the cell cycle

Interphase (growth and replication) followed by cell division (mitosis and cytokinesis).

Distribution of time in the cell cycle

A cell spends the vast majority of its life in interphase, while cell division occupies only a brief period at the end.

Structural shape of DNA

A double helix composed of two antiparallel strands held together by complementary base pairs.

Components of the DNA backbone

Alternating sugar (deoxyribose) and phosphate groups.

Nitrogenous base pairing forces in DNA

Hydrogen bonds formed between complementary base pairs (adenine with thymine, cytosine with guanine).

Antiparallel (DNA)

The arrangement in which the two complementary strands of the double helix run parallel to one another but in opposite directions.

Semiconservative replication

The method of DNA replication where each newly synthesized double helix retains one intact strand from the original parent molecule and one newly formed strand.

Purpose of DNA replication prior to division

To ensure that both resulting daughter cells receive a complete and identical copy of genetic material.

Four main steps of DNA replication

1. Unwind: Enzymes untwist the double helix and break hydrogen bonds between base pairs.
2. Expose: Strands separate, exposing bases to serve as templates.
3. Pair: Free nucleotides align with their complementary exposed bases.
4. Join: Nucleotides bond together, forming two identical DNA double helices.

Mitosis

The process of nuclear division that yields two genetically identical daughter nuclei.

Light-dependent phase of photosynthesis

• Location: Grana (thylakoids)
• Inputs: Light energy and water ($H_2O$)
• Outputs: Oxygen ($O_2$), ATP, and NADPH
• Key Event: Photolysis (splitting of water molecules)

Light-independent phase (Calvin cycle)

• Location: Stroma
• Inputs: Carbon dioxide ($CO_2$), ATP, and NADPH
• Outputs: Glucose
• Key Event: Carbon fixation