Biology Chapter: Cells and Genetics

The Fundamental Unit of Life

• The cell is the basic structural and functional unit of all living organisms.
• Cells are the building blocks of life and perform all the functions required for life.
• There are two basic types of cells: prokaryotes (lack a nucleus and other membrane-bound organelles) and eukaryotes (have a nucleus and other membrane-bound organelles).

A Chromosome

• A chromosome is a thread-like structure located inside the nucleus of animal and plant cells.
• Each chromosome carries DNA, which contains the genetic information for the organism.
• Chromosomes are essential for cell division and inheritance, ensuring that each new cell receives a complete set of genetic instructions.
• Chromosomes are made up of two identical copies called sister chromatids, joined together at a constricted region called the centromere.

Nucleic Acids

• Nucleic acids are large biomolecules that carry genetic information.
• Deoxyribonucleic acid (DNA) plays a central role in cellular processes, including the storage and transfer of genetic information.
• DNA is a double-stranded helix, with each strand composed of a chain of nucleotides.
• Ribonucleic acid (RNA) is a single-stranded molecule involved in protein synthesis.
• DNA and RNA work together to ensure the correct sequence of amino acids in proteins.

Preparing Temporary Stained Slide of Cheek Cells

• The preparation of a temporary stained slide of cheek cells is a common laboratory technique used to visualize the nucleus and cytoplasm of eukaryotic cells.
• Methylene blue is a stain that helps to visualize the nucleus of the cheek cells because it binds to acidic molecules in the nucleus, making it more visible under a microscope.

Cytoplasm

• Cytoplasm is the gel-like substance that fills the cell and contains all the organelles.
• It serves as the medium for many important cellular processes, such as metabolism, protein synthesis, and cell division.
• Cytoplasm contains two main components: cytosol and cell organelles.
• Cytosol is the fluid portion of the cytoplasm, containing water, ions, enzymes, and other dissolved molecules.
• Cell organelles are specialized structures within the cytoplasm that perform specific functions.
• Organelles can be either membrane-bound or membrane-less.

Cell Organelles and Inclusions

• Cell organelles help to maintain the cell's structure, carry out essential functions, and produce energy.
• Organelles are classified based on their membranes:
  • Double membrane-bound: mitochondria, plastids (in plant cells), and the nucleus
  • Single membrane-bound: endoplasmic reticulum, Golgi apparatus, lysosomes, and vacuoles
  • Membrane-less: ribosomes.