Cell Biology: Cellular Reproduction and Size

Study Notes

Cellular reproduction is the process by which cells grow and divide.
A life cycle is a sequence of growth and development stages an organism goes through in its lifetime.

Cell size is influenced by several factors.
Surface area is the area covered by the plasma membrane. The plasma membrane is where nutrients enter and waste products leave the cell.
Volume is the space taken up by the inner contents of the cell.
As a cell gets larger, the ratio of surface area to volume decreases.
Cells with a higher surface area-to-volume ratio can sustain themselves more easily. This is because nutrients can easily reach the organelles and waste products can easily exit the cell
The need to keep a high surface area-to-volume ratio limits cell size.

1 meter (m) is equal to 10 decimeters (dm), 100 centimeters (cm), 1,000 millimeters (mm), 1,000,000 micrometers (µm), 1,000,000,000 nanometers (nm), and 1,000,000,000,000 picometers (pm).
1 mm is equal to 1000 microns.
1 inch is equal to 25400 microns.

Chromatin is the relaxed form of DNA.
Chromosomes are condensed structures that contain DNA. They are visible during mitosis.
Chromosomes are passed from generation to generation.
Eukaryotic DNA is organized into chromosomes.
Phosphate groups in DNA create a negative charge, attracting positively charged histone proteins and creating nucleosomes.
Nucleosomes group together to form chromatin fibers, which supercoil to make up chromosomes.

Cells reproduce through a cycle of growth and division, called the cell cycle.
Interphase is the stage where the cell grows, develops into a mature, functional cell, duplicates DNA, and prepares for division.
Interphase is divided into three stages: Gap 1 (G₁), Synthesis (S), and Gap 2 (G₂).
Gap 1 (G₁): cells grow, carrying out normal cellular functions, and preparing to replicate DNA.
Synthesis (S): Copying DNA to prepare for cell division.
Gap 2 (G₂): Preparing for the division of the nucleus.
Mitosis is the stage of the cell cycle where the nucleus and nuclear material divide. It separates the replicated genetic material and prepares to split the cell into two.
In multicellular organisms, mitosis increases the number of cells in young, growing organisms and helps organisms replace damaged cells.
Mitosis helps maintain chromosome numbers in organisms that reproduce asexually.