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" »

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

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" »

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" »

Protective Tissues

Epidermal Tissue

This outermost layer covers roots, herbaceous stems, and leaves. It consists of a single layer of living cells without chlorophyll, tightly arranged without spaces. The outer cell wall is covered with a cuticle, a waterproof layer made of cutin and waxes. In aerial parts, the epidermis protects stems and leaves, regulates perspiration, and facilitates gas exchange. In roots, it protects and aids water and salt absorption through root hairs. Trichomes, also present in the epidermis, provide additional protection.

Cork Tissue (Suber)

This tissue replaces the epidermal tissue in older plant parts. It comprises multiple layers of dead cells coated with suberin, making it highly waterproof. Due to cell activity, the... Continue reading "Plant Tissues and Their Functions" »

The Double Helix of DNA

Deoxyribonucleic acid (DNA) is a molecule composed of simpler molecules: a pentose sugar called deoxyribose, phosphoric acid, and four nitrogenous bases: adenine (A), thymine (T), guanine (G), and cytosine (C).

DNA is formed by two antiparallel strands of DNA. This double chain is held together by hydrogen bonds that are established between their nucleobases. This forms the characteristic double helix structure of DNA.

Its function is to carry the genetic information encoded in a living organism and it has the ability to replicate itself.

DNA Replication

The information contained in DNA encodes all the bases, the basic pattern of inheritance of each species. It contains all the information that needs to be transmitted intact... Continue reading "DNA and RNA: Structure, Replication, and Mendel's Laws" »

Fixism vs. Evolutionism

To understand our present and future, it is crucial to know our origins. One key concept in this understanding is evolution, the theory that the universe and life are products of development, change, and adaptation, leading to the diversity of species. This stands in contrast to Fixism.

Fixism is a conception of living beings encompassing various theories. In our culture, the most widespread is the one that follows the Genesis narrative of the Bible. Proposed by George Cuvier, this theory posits that all species are independent and remain unchanged over time.

Lamarckism

This theory, proposed by Lamarck, applies primarily to animals and represents the first comprehensive theory of biological evolution. Lamarck's theory is... Continue reading "Evolutionary Theories: From Fixism to Neo-Darwinism" »

Toxins

• Toxins:

• Main Routes of Transmission of Infectious Diseases and Examples

In any infectious disease, a pathogen must pass from a healthy host to another to become a new host. Transmission can occur through:

• Transmission by direct contact: injuries, sexually, via parental (mother to fetus). Examples: