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

Virus Characteristics

Viruses are unique pathogens, not classified as living organisms. A virus particle, a submicroscopic infectious agent, has a single nucleic acid type (DNA or RNA) within a protein coat called the viral capsid, forming the nucleocapsid.

Some viruses have a lipid-protein envelope. The capsid's protein organization determines the virus's shape, usually helical or polyhedral. Viruses are genetic elements in transit, switching between extracellular and intracellular states.

Extracellular Phase (Virion)

In the extracellular phase, the virion is metabolically inert. It carries viral genetic material from one cell to another.

Intracellular Phase

Inside a cell, the virus replicates, using the cell's machinery to synthesize new viral... Continue reading "Virus Structure, Classification, and Replication Cycles" »

Understanding Human Sexuality

Human sexuality encompasses three fundamental aspects:

• Biological: The physiological and anatomical differences between sexes.
• Spiritual: The emotional and relational dimensions of sexuality.
• Socio-cultural: How society and culture shape sexual norms and behaviors.

Biological Foundations of Sex

The differentiation between the two sexes begins at the cellular level. In a zygote, if the 23rd pair of chromosomes has the characteristics XY, the individual is male; if XX, the individual is female. From that moment, primary sexual characteristics (reproductive organs) begin to form. At puberty, secondary sexual characteristics develop due to hormone production, leading to changes in body shape, voice tone, and hair growth.... Continue reading "Human Sexuality: Biology, Reproduction, and Health" »

1. Bacterial Antibodies

Which individual component of a bacterium should be injected into rabbits to generate effective antibodies against subsequent exposure to the same bacteria?
c. Bacterial chromosome DNA fragments

2. Lymphocytes

The lymphocyte, a type of leukocyte, is characterized by:
II. Providing long-term or short-term immunity to the body

3. Acquired Immunity

Acquired immunity, whether natural or artificial, is achieved by:
I. Suffering from an illness
II. Vaccination with an attenuated microbe
III. Administration of antibodies produced by another source

4. Natural Immunity

The term "natural immunity" refers to:
I. Immunity that develops during an individual's life as a result of the body's response to a pathogen
II. Immunity that is activated

**Functions of the Cell**

• Nutrition: Through nutrition, cells obtain the energy they need to create and maintain their structures and perform other vital functions. The molecules from which they obtain materials and energy are nutrients such as water, minerals, oxygen, and organic molecules.
• Relationship: By using this function, cells perceive physical and chemical changes that occur in the environment that surrounds them.
• Reproduction: Using this function, cells originate and divide into new cells.

**Types of Cells**

• Prokaryotes: They are characterized by a lower degree of complexity and a smaller number of organelles. These are single-celled organisms.
• Eukaryotes: They are characterized by a complex organization with many different compartments

Core Biological Concepts: Nucleic Acids and Genetics

Nucleic Acids: Composition and Structure

Biomolecules such as Nucleic Acids are critical for living organisms. They are composed of carbon, hydrogen, nitrogen, phosphorus, and oxygen. They are also called polynucleotides because they are formed by the joining of subunits called nucleotides. Each nucleotide is made of:

• A sugar (with 5 carbon atoms)
• A molecule of phosphoric acid
• A nitrogenous base

DNA Structure and Function

DNA (Deoxyribonucleic Acid) is a macromolecule consisting of two long chains of nucleotides, known as complementary strands, shaped like a double helix. The structure maintains its stability due to the nitrogenous bases, which are located in the center of the helix and joined by... Continue reading "DNA, Genetics, and Key Medical Diagnostic Techniques" »

Stages of Embryonic Development

A key feature that differentiates living things from non-living things is the ability to reproduce. Reproduction occurs through cell division. In more complex organisms, this includes sexual and asexual reproduction. The essential phenomenon is mitosis in plants and animals. Sexual reproduction involves meiosis, the process of gamete formation, or specialized cells for reproduction, with the participation of individuals of different sexes. Genetic and hormonal events, along with synchronization mechanisms, ensure the release of gametes for successful fertilization. This is followed by a series of events that characterize successive development and differentiation, transforming the egg or zygote into an adult individual.... Continue reading "Embryonic Development: Stages, Fertilization, and Processes" »

Eradication of Diseases Worldwide

If we tried to reach all the world, including countries that are not even developed, we could eradicate diseases.

The Relationship Between Diseases and Microorganisms

Pasteur established for the first time the relationship between certain diseases and the presence of microorganisms in the patient, but the mere observation of microorganisms with the disease does not guarantee that it will cause it.

Ebola Virus: A Highly Contagious Disease

The Ebola virus is the cause of Ebola viral hemorrhagic fever, an infectious, highly contagious, and very severe condition that affects both animals and humans. The virus is transmitted by direct contact with infected bodily fluids such as blood, saliva, sweat, urine, or vomit.... Continue reading "Understanding Common Infectious Diseases and the Immune System" »

The Lamarckian Theory of Evolution

Jean-Baptiste Lamarck set out a detailed conception of the theory of evolution and its mechanisms. The Lamarckian theory, which can be synthesized in the expressions: "evolution creates the organ" or "environmental influence," can be summarized as follows:

1. The environment, where living things develop, is subject to change, disrupting life within the system and the needs of the organisms inhabiting that environment.
2. Changes in environmental needs produce changes in behavior, developed to meet new necessities.
3. In turn, behavioral change requires changes in the anatomical or physiological structure of living organisms.

The Darwinian Theory of Evolution

The reason Charles Darwin's name is associated with the idea of... Continue reading "Evolutionary Theories: Lamarck vs. Darwin and Genetic Basis" »

Genetic Diseases: Hereditary or Not?

No, a genetic disease can be inherited or acquired. A genetic disorder occurs when a normal gene or chromosome undergoes changes, preventing it from performing its normal function. If these changes affect all body cells, the genetic disease is hereditary. For example, most cancers and certain viral diseases like AIDS are not inherited.

Understanding Prenatal Diagnosis

Prenatal diagnosis involves the early detection of genetic diseases in utero. Amniocentesis and Chorionic Villus Sampling (CVS) are common methods of prenatal diagnosis.

What is Amniocentesis?

Amniocentesis is a prenatal diagnostic procedure that involves taking a sample of amniotic fluid, which contains fetal cells in suspension, using a hypodermic... Continue reading "Essential Concepts in Genetics and Molecular Biology" »

Sweat

Sweat glands are located in the skin, opening to the epidermis through pores. These glands are mainly concentrated in areas like the forehead, armpits, palms, and soles of the feet. Each gland consists of a thin tube called a glomerulus, which extracts fluid from blood capillaries. This fluid contains compounds like urea and water, similar to urine but more dilute. From the glomerulus, sweat travels through channels to the pores and is released as droplets.

Regulating Urine Concentration

Urine concentration depends on the permeability of the collecting tubules, regulated by the antidiuretic hormone vasopressin. Increased osmotic pressure stimulates vasopressin secretion, increasing the permeability of the collecting tubules. This leads... Continue reading "Understanding Sweat, Urine, and Osmoregulation" »