Notes, summaries, assignments, exams, and problems for Biology

Proteins: Composition and Structure

Proteins consist of carbon (C), hydrogen (H), oxygen (O), and nitrogen (N), and may also contain sulfur (S), phosphorus (P), iron (Fe), magnesium (Mg), and copper (Cu). Proteins are made up of smaller molecules called amino acids, which are linked by peptide bonds.

Amino Acids and Their Properties

Amino acids with uncharged polar side chains are hydrophilic and are usually found on the outside of the cell. Nonpolar side chains tend to aggregate in the interior.

Peptide Bonds and Polypeptides

Amino acids are commonly attached through amide links, called peptide bonds. The union of multiple amino acids results in a peptide. A peptide with fewer than 10 amino acids is called an oligopeptide, and if it contains more... Continue reading "Understanding Proteins: Structure, Properties, and Classification" »

Lysosomes, Peroxisomes, and Vacuoles

These are all membrane-bound organelles.

Structure and Function of Lysosomes

Lysosomes are organelles containing enzymes that degrade all types of biological polymers. They are acid hydrolases and act as a cellular digestive system, breaking down material captured from outside the cell. When a cell incorporates material via endocytosis, it forms a phagosome. A primary lysosome then fuses with this to form a secondary lysosome, or phagolysosome, where enzymes break down substances for cellular use. When material to be digested comes from within the cell, the process is called autophagy. This forms an autophagosome, which fuses with a primary lysosome for digestion.

Structure and Function of Peroxisomes

Peroxisomes... Continue reading "Cellular Organelles: Lysosomes, Peroxisomes, Vacuoles, and Mitochondria" »

Anabolism: The Constructive Phase of Metabolism

Anabolism is the constructive phase of metabolism. It is the set of metabolic pathways whose objective is to obtain more or less complex organic molecules, sharply reduced, from simpler and relatively oxidized ones. Therefore, these are chemical reduction processes.

Features of Anabolic Pathways

• As we have said, they are basically chemical reduction processes.
• Reactions are strongly endergonic (energy is needed), for which they use the energy released in catabolic reactions as ATP, NADH, and NADPH.
• The anabolic pathways for the synthesis of molecules are different from the catabolic ones, although they often share reversible reactions close to equilibrium. There is always some different way on each

Medical and Demographic Notes: Part 1

Social Sciences Definitions

Demographics

Population sciences studying their geographical distribution.

Statistics

Science where knowledge of a phenomenon is based on measurement results.

Economy

Studies the ways in which individuals and society use obtained resources and services.

Psychology

Science that studies psychic functions in normal and abnormal aspects.

Digestive System Facts

Digestion

The splitting of complex food materials.

Pylorus Statement (Evaluation)

FALSE: The pylorus is the passage that allows food from the esophagus to the stomach.

Small Intestine Components (Evaluation)

FALSE: The duodenum, jejunum, and appendix are located in the small intestine. (Note: Duodenum and jejunum are parts of the small intestine;

Phonetics and Phonology Basics

Phonetics Defined

Phonetics deals with the material or substance of sound. When we make a sound, it is made with a number, a tone, an intensity...

Physical Qualities of Sound

• Tone: High-intensity musical quality, related to articulatory energy.
• Quantity: Term related to time or duration.
• Resonance: Depends on the volume and sounding board, namely, the oral cavity.

Sounds originate in the speech apparatus. Syllables are also studied in phonetics because they are also sound units. Our sound system consists of 19 consonants and 5 vowels. There are more letters than phonemes because a phoneme may represent several letters.

Phonology Defined

Phonology deals with the study of the characteristics that are relevant in each sound... Continue reading "Phonetics and Phonology Fundamentals" »

Cellular Foundations of Life

Cell Theory Principles

The Cell Theory was set forth in 1860. According to this theory:

• All living things are composed of cells.
• Cells are the basic units that constitute the structural and functional basis of life.
• Every cell comes from another existing cell through cell division.

Plasma Membrane Function

The plasma membrane encloses the cell, provides structural integrity, and facilitates the exchange of substances with the external environment.

Cytoplasm: Cell's Internal Environment

The cytoplasm is the space between the plasma membrane and the nucleus. It contains various structures and other organelles, such as the cytoskeleton.

The Cell Nucleus: Control Center

The nucleus is the area of the cell bounded by the nuclear... Continue reading "Fundamentals of Biology: Cells, Tissues, Systems & Diagnostics" »

Type I Hypersensitivity Reactions: Immediate Allergic Responses

These are the most common type of allergic reactions. They are mediated by Immunoglobulin E (IgE) antibodies, which are primarily located on mast cells found in various tissues throughout the body. The reaction between an antibody (Ab) and an antigen (Ag), also known as an allergen in this context, triggers a cascade of responses that can sometimes lead to tissue damage.

Phases of Type I Hypersensitivity

Type I hypersensitivity reactions occur in two distinct phases:

• Immediate Phase: Mediated primarily by histamine, leading to rapid symptoms.
• Late-Phase Reaction: Mediated by other compounds such as Leukotriene C₄ (LTC₄) and Prostaglandin D₂ (PGD₂), which have similar inflammatory effects

Animal Tissues

Epithelial Tissue

Epithelial tissue consists of sheets of densely packed and connected cells that cover internal and external body surfaces.

Simple Epithelia

Simple epithelia are formed by a single layer of cells that can be:

• Flattened, like the endothelial walls of capillaries and the lining of blood vessels, which protect yet allow the exchange of substances.
• Polyhedral (cubic and cylindrical), such as the epithelial lining inside the intestine. Their cells possess microvilli or fingerings on the surface that faces the lumen of the tube.

Stratified Epithelia

Stratified epithelia consist of several layers of cells. Cells in the deepest layer are constantly dividing, and new cells push the older ones upward. The most superficial cells,... Continue reading "Animal Tissues: Epithelial, Muscle, and Nervous Tissues Explained" »

Biotope: The Foundation of Ecosystems

The biotope refers to the main components that determine the presence of living organisms: the medium and environmental (physical and chemical) factors.

The Medium

The medium is the place where living organisms reside and interact within an ecosystem, maintaining constant exchanges of matter and energy. Broadly speaking, we can distinguish two primary types of media:

• Terrestrial Medium: Located on the surface of continents, characterized by direct contact with the atmosphere.
• Aquatic Medium: Consists of water and is characteristic of aquatic ecosystems.

Abiotic Environmental Factors

Abiotic environmental factors encompass all physical and chemical conditions of the biotope. This set of external conditions significantly... Continue reading "Ecosystem Components: Biotope & Biocoenosis Explained" »

Vision Development in Infants

The visual system is designed to capture light effects. The apparatus of global vision allows us to perceive images based on the amount of light reflected. Light enters through the cornea, passes through the pupil to the lens, and is then sent to the retina.

Developmental Milestones

• Newborn: Distinguishes between light and dark (chiaroscuro).
• 1 Month: Can stare at a large object.
• 2 Months: Can accommodate and converge their vision.
• 3 Months: Can follow a moving object by turning their head.
• 4 Months: Has a vertical and horizontal visual field of 180 degrees.
• 6 Months: Acquires eye-hand coordination.
• 8 Months: Examines objects with more detail.
• 12 Months: Acquires adult-like visual acuity.

Vision Disorders

Refractive Errors

• Myopia