Biology Levels of Organization and Characteristics

Study Notes

Levels of Organization

Nonliving: atoms, molecules; Living: cells, tissues, organs, organ systems, organisms.
Organisms exhibit characteristics such as cellular structure, energy requirements, reproduction, homeostasis, organization, and responsiveness.

Molecules of Life

Essential molecules include Sodium ions (Na+) and Water (H2O).
Amino acids can exist as isomers: L-amino acids form proteins; D-amino acids are metabolized.
Only D-glucose is utilized for amino acid synthesis; cellular structures differ between animal and bacterial cells.

Cell Diversity and Structure

Cell specialization occurs, excluding stem cells which can differentiate into any cell type.
Prokaryotic cells lack a nucleus and contain mitochondria, ribosomes, and DNA concentrated in a non-membrane-bound nucleoid.
Eukaryotic cells have a phospholipid bilayer in their plasma membrane, with proteins and carbohydrates allowing selective permeability.

Eukaryotic Organelles

Cytoplasm houses all organelles except the nucleus; it contains cytosol and a cytoskeleton (microfilaments, intermediate filaments, microtubules).
Nucleolus directs RNA synthesis and ribosome formation.
Rough Endoplasmic Reticulum (RER) has ribosomes attached for protein synthesis and modification; Smooth Endoplasmic Reticulum (SER) is involved in carbohydrate and lipid synthesis.
Golgi apparatus functions as the cell's postal service for vesicle reception and packing.
Mitochondria are crucial for energy production, with dysfunction accelerating aging. Replacement can rejuvenate cells.

Oral Cancer and Cell Communication

Crosstalk between organelles is significant in oral cancer and sphingolipid synthesis.
Increased sphingosine-1-phosphate enhances survival of oral cancer cells; its release from the SER results in cancerous signaling.
High levels of ceramide inhibit cancer cell survival, synthesized in the SER to prevent conversion to sphingosine-1-phosphate.

DNA Replication

Occurs during the S-phase, producing two identical DNA replicas.
Nucleotides consist of a phosphate group (5' phosphate), pentose sugar (ribose or 2-deoxyribose), and nitrogenous bases (A, T, C, G, U).
Chargaff's rule states that A pairs with T and G pairs with C.
Replication direction: 5' to 3'; leading strand is synthesized continuously, lagging strand in fragments (Okazaki fragments).
DNA exhibits right-handed helical structure, enhancing stability, and follows a semiconservative model.

DNA Damage and Repair

Damage from chemicals/radiation leads to mutations; defects in repair mechanisms contribute to cancer.
Accumulation of radical oxygen species (ROS) causes DNA damage, with common issues including point mutations and base pair mismatches.
Repair mechanisms include mismatch repair for base pair mismatches, base-excision repair for damaged single-stranded DNA, and nucleotide excision repair for DNA adducts.
Double-strand breaks are repaired through homologous recombination or non-homologous end joining.

Genetic Mutations and Oral Health

Ataxia-Telangiectasia is characterized by dilated blood vessels, enamel hypoplasia, and increased susceptibility to periodontitis.
Bloom Syndrome presents with absent lateral incisors and is linked to defects in DNA repair mechanisms, increasing oral cancer risk.
Werner Syndrome exhibits signs of accelerated aging, including microdontia and xerostomia, affecting oral health.
Cockayne Syndrome leads to dental anomalies and other oral features like thin lips.
Fanconi Anemia is associated with leukoplakia and mucosal abnormalities, increasing the risk of oral infections and dental issues.

Description

Explore the various levels of organization in biology, from atoms and molecules to complex organisms. This quiz covers organism characteristics such as cellular structure, energy requirements, and homeostasis, as well as details about the molecules of life and cell diversity. Test your understanding of these foundational concepts in biology.