Life and Physical Sciences Review

Biological Organization

• Biological systems are structured across various levels integral to understanding life processes.
• Basic Units of Life: Cells are the fundamental unit of life, which may be unicellular (bacteria) or multicellular (humans).
• Hierarchy of Biological Organization:
  • Cells
  • Tissues: Formed when multiple cells work together (e.g., cardiac muscle tissue).
  • Organs: Composed of tissues that work together (e.g., heart, lungs, kidneys).
  • Organ Systems: Groups of organs that work together (e.g., digestive system).
  • Organisms: The result when all organ systems interconnect.

Cell Theory

• Cells are the most fundamental unit of life.
• All living beings are composed of cells.
• Cells arise from pre-existing cells.

Types of Cells

• Prokaryotes:

  • Lack a nucleus and membrane-bound organelles (e.g., bacteria).

• Eukaryotes:

  • Have a nucleus and membrane-bound organelles (e.g., plants, animals, fungi).

Organelles and Their Functions

• Cell Membrane: Selectively permeable membrane that regulates passage of materials, maintaining homeostasis.
• Cytoplasm: Jelly-like substance that contains organelles.
• Cytoskeleton: Provides structural support and aids in cellular movement.
• Ribosomes: Sites of protein synthesis, found in both prokaryotes and eukaryotes.
• Nucleus: Control center of eukaryotic cells containing DNA.
• Endoplasmic Reticulum (ER):
  • Rough ER: Studded with ribosomes, involved in protein synthesis.
  • Smooth ER: Lacks ribosomes, functions in lipid synthesis and detoxification.
• Golgi Apparatus: Packages and distributes proteins and molecules.
• Mitochondria: Powerhouse of the cell, generates ATP through cellular respiration.
• Chloroplasts: Only in plant cells, responsible for photosynthesis.
• Lysosomes: Digests cellular debris, waste, and unwanted materials.
• Vacuoles: Storage of nutrients and waste products, important in plant growth.

Mitosis vs. Meiosis

Mitosis:

• Produces two genetically identical diploid cells.
• Key phases: Prophase, Metaphase, Anaphase, and Telophase (PMAT).

Meiosis:

• Produces four genetically unique haploid cells (gametes).
• Involves two rounds of PMAT (Meiosis I and Meiosis II).
• Includes processes such as crossing over during Prophase I for genetic variation.

Genetics

• Genes: Segments of DNA that dictate traits.
• Alleles: Variants of a gene (dominant or recessive).
• Punnett Squares: Used for predicting genetic outcomes of crosses.

Macromolecules

1. Carbohydrates

• Monomer: Monosaccharides (e.g., glucose).
• Energy source for cells, forms structural components in cell walls (e.g., cellulose in plants).

2. Lipids

• No true monomer; composed mainly of glycerol and fatty acids.
• Functions: Long-term energy storage, insulation, cell membranes (phospholipids).

3. Proteins

• Monomer: Amino acids.
• Functions: Structural components in tissues, enzymes, hormones, immune system components.

4. Nucleic Acids

• Monomer: Nucleotides.
• Types: DNA and RNA, function in genetic information storage and transmission.

Infectious Agents

• Pathogenic: Agents that cause disease; can be viruses, bacteria, fungi, or protozoa.
• Virulence: The degree of pathogenicity.

Viruses:

• Non-living entities, require a host cell to replicate.
• Transmission through respiratory droplets, direct contact, or by vectors (e.g., mosquitoes).

Bacteria:

• Living cells classified as prokaryotes.
• Can be harmful (e.g., pathogenic bacteria) or beneficial (e.g., gut microbiota).

Fungi:

• Eukaryotic organisms, possess cell walls made of chitin.
• Can cause superficial infections or serious systemic infections in immunocompromised individuals.

Protozoa:

• Unicellular eukaryotic organisms, can cause diseases such as malaria and giardiasis.

Modes of Transmission

• Direct Transmission: Person-to-person contact or droplets.
• Indirect Transmission: Through intermediate objects (fomites) or vectors.

Microscopy

• Light Microscope: Uses light for imaging.
• Electron Microscope: Uses electron beams for detailed imaging of small organisms.
• Types include Transmission Electron Microscope (TEM) for internal structures and Scanning Electron Microscope (SEM) for external surfaces.

Practice Questions

• In hierarchy of biological organization, the correct order is: Cells -> Tissues -> Organs -> Organ Systems -> Organisms.
• Correct answer for ribosome function: Assembling proteins using mRNA.
• In genetics, the monomer of carbohydrates is monosaccharide.
• Fungi have cell walls made of chitin, distinguishing them from plants that have cellulose.

Note: Practice problem solving with Punnett squares to aid in genetics understanding.