Notes, summaries, assignments, exams, and exercises for Biology for Baccalaureate

Understanding Immune System Components

Lymphoid Organs: Sites of Immune Activity

Lymphoid organs are specialized sites where immune system cells concentrate and function. They are classified into two main types:

• Primary Lymphoid Organs: These are the sites where lymphocytes mature. Stem cell precursors originate in the bone marrow. T lymphocytes mature in the thymus, while B lymphocytes mature in the bone marrow (or the Bursa of Fabricius in birds).
• Secondary Lymphoid Organs: These are the locations where mature lymphocytes accumulate, encounter antigens, and initiate adaptive immune responses. Examples include the spleen (which filters blood), lymph nodes (which filter lymph), and various lymphoepithelial structures (like tonsils and Peyer's patches)

Plant Tissue Systems

Plant tissues are responsible for growth and structure. They are broadly classified into meristematic and definitive tissues.

Meristematic Tissues

Meristematic tissues are responsible for plant growth. The cells are small, polyhedral in form, with thin walls and abundant small vacuoles initially.

• Apical Meristems: Responsible for primary growth in length of the plant. They are located at the ends of the root and stem.
• Lateral Meristems: Responsible for growth in girth or secondary growth. They are distributed throughout the plant. They produce vascular cambium (conducting tissue) and cork cambium (which gives rise to suber or cork).

Definitive Tissues (Fundamental Tissue System)

Definitive tissues are specialized and typically...

Fundamentals of Amino Acids and Protein Structure

Defining Amino Acids (AA)

Amino acids (AA) are organic compounds characterized by the presence of both an amino group (-NH₂) and a carboxyl group (-COOH). There are 20 standard amino acids. We cannot metabolize the essential amino acids, meaning they must be obtained through the diet.

Classification of Amino Acid Side Chains

Amino acids are classified based on the properties of their side chain (R group):

• Nonpolar (Hydrophobic): R group is hydrophobic and typically located on the exterior in aqueous environments.
• Polar Ionizable: R group is polar and located internally.
• Polar Acids: R group contains an additional carboxyl group, located internally.
• Polar Basic: R group contains an additional amino

Genetics

Core Concepts

Genetics is the study of biology that focuses on genes and biological inheritance related to characteristics.

Chromosomes are components that appear as cylindrical or rod-shaped bodies during cell division: mitosis and meiosis.

Genetic engineering involves manufacturing techniques.

The world lives thanks to bacteria and other antibiotic substances they produce. These products prevent the growth of bacteria and fungi.

Cellular Biology and Cloning

Stem cells and blastocysts are cells in the body with no specialized function. They can multiply while maintaining that state and can be transformed into over 200 cell types in an adult individual. They are fundamental.

Cloning:

• Therapeutic cloning: Obtaining stem cells to regenerate tissues

Protein Structure Levels and Denaturation

Tertiary Structure

Tertiary Structure: Disposition that takes the structure in the secondary space, resulting in the final three-dimensional arrangement. The tertiary structure dictates the protein's function, so any changes in this layout can lead to a loss of biological activity. This structure arises from the union of specific areas of the chain. These unions are formed through links between the side chains (R groups) of the amino acids (AAs). It is maintained by hydrogen bridges, disulfide bonds, and Van der Waals forces.

Quaternary Structure

Quaternary Structure: This structure is present in proteins made up of a number of chains or subunits. The Quaternary Structure is the arrangement of protein subunits...

Photosynthesis

Photosynthesis is the process by which some cells can capture light energy from the sun and transform it into chemical energy. This process is carried out by plants, green or red algae, and some bacteria. Its purpose is to synthesize organic matter from inorganic matter (CO₂, H₂O, mineral salts) using light energy and releasing molecular oxygen into the atmosphere during the process.

In eukaryotic cells, it occurs in chloroplasts in two phases:

• Light Phase

  This occurs in the thylakoid membrane of chloroplasts, driven by chlorophyll. It captures light energy from the sun and converts it into chemical energy in the form of energy-rich ATP and a molecule with great reducing power, NADPH. The photolysis of water liberates O₂.

• Dark Phase

Tumors

In normal tissues, cells divide to replace old or damaged cells. This balance can be disrupted, leading to tumor formation. Tumors are defined as a mass of disorganized tissue. Most tumors are benign, meaning they grow locally and do not spread.

Malignant Tumors: Cancer

Cancer is a malignant tumor whose cells can spread from the initial tumor site to other parts of the body. These cells have two key characteristics:

1. Invasiveness: Ability to penetrate and spread through adjacent tissues.
2. Metastasis: Capacity to enter the blood and lymph systems, travel to other parts of the body, and form secondary tumors.

Cancer Treatment

• Surgery: Removal of the tumor mass.
• Radiotherapy: Use of radiation to shrink cancer cells.
• Chemotherapy: Administration of

Genetic Engineering: Understanding the Building Blocks

Genetic engineering relies on our knowledge of the genetic code, gene regulation mechanisms, transcription, translation, and reduction. Automated sequencing techniques, restriction enzymes, and a set of other tools allow us to split and join DNA fragments. These fragments, when combined with other macromolecular carrier DNA, enable the transfer of genetic information between organisms. These are called recombinant DNA molecules.

Key Processes in Genetic Engineering

• DNA Transformation: A cell undergoes a genetic change resulting from the entry of a foreign DNA molecule into its core.
• Transduction: The process of transferring genetic information (e.g., in bacteria) without direct contact, often

Defining Health and Disease

Health is typically defined as the state where the body's organs and systems are functioning correctly. When an alteration occurs in one or more of these systems, disrupting their function, a disorder known as disease arises. A disease manifests through a series of bodily changes or abnormalities called symptoms.

Classifying Disease Types

Diseases can be categorized based on their causes:

• Infectious Diseases: Caused by microorganisms such as viruses, some bacteria, fungi, and protozoa.
• Environmental Diseases: Resulting from components of the physical environment, such as extreme heat or cold, air pollution, radiation, etc.
• Toxic Diseases: Originating from breathing or ingesting certain toxic substances, like carbon monoxide

Clinical Characteristics of Polymyositis

Myopathic Weakness

Myopathic weakness evolves over weeks to months, typically sparing the facial and eye muscles. It presents as difficulty in:

• climbing steps
• rising from a chair
• lifting objects
• combing hair

Disease Onset

Typically occurs above the age of 18 years.

Features the Patient Does Not Have

The following features are not characteristic of polymyositis in the typical presentation:

• Rash (characteristic of dermatomyositis)
• Family history of neuromuscular diseases
• Exposure to myotoxic drugs, especially penicillamine²⁶, zidovudine²⁷, and (rarely) statins^28,29
• Endocrine disease (hypothyroidism, hyperthyroidism, hypoparathyroidism, hypercortisolism)

Excluded Conditions

• Neurogenic disease (excluded by electromyography