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

HIV and AIDS: An Introduction

AIDS (Acquired Immunodeficiency Syndrome) is caused by infection with the retrovirus HIV. This virus attacks and destroys T4 lymphocytes and macrophages. Affected individuals have a depressed immune system, which can lead to certain types of cancers.

Development of the Disease

HIV is found in the blood and other bodily fluids of infected persons. Transmission to a healthy person can occur through various routes. These include contaminated blood transfusions and sexual intercourse between an infected and healthy individual.

Once HIV enters the blood of a new host, it joins T cells and penetrates inside. There, a large number of viruses are created, ultimately destroying the infected cell.

AIDS: Treatment and Prevention

There... Continue reading "HIV and AIDS: Understanding the Disease and Prevention" »

Aquatic Respiration: Understanding Gills

Gills are highly effective respiratory structures adapted for life in water. They are laminar expansions formed by the filiform body wall of an animal. If these expansions project outside the body, they are called external gills. If they are housed inside a cavity that communicates with the outside, they are called internal gills.

External Gills: Simpler Respiratory Structures

External gills are evolutionarily the oldest, formed by expansions of the body surface. They occur in some mollusks, insects, and aquatic larvae of amphibians and crustaceans. However, they present several disadvantages:

• They are vulnerable to predators.
• They are easily injured.
• They can make movement difficult.
• Animals possessing these

Food Chains and Trophic Levels

Living beings require material and energy, obtained from nutrients in food, to perform vital functions such as nutrition, relationships, and reproduction. Living things are classified into three groups or trophic levels:

• Producers: These are autotrophic organisms that produce organic matter from inorganic substances. Most are photosynthetic, using sunlight to convert water, mineral salts from the soil, and carbon dioxide from the atmosphere into organic material. This level is formed by plants, algae, and certain bacteria.
• Consumers: These are heterotrophic organisms that feed on organic matter from other living beings. Consumers are categorized into types:
  • Primary Consumers: They feed on producers. Herbivores are

Advanced Medical Imaging Techniques

• Computed Tomography (CT) Scans

  Computed Tomography (CT) allows for the visualization of body parts in very fine, successive cross-sections, revealing even the smallest details. The apparatus uses an X-ray tube and detectors that analyze the fraction of X-rays absorbed by tissues. Soft tissues absorb less radiation than hard tissues, allowing for differentiation.

• Magnetic Resonance Imaging (MRI)

  Magnetic Resonance Imaging (MRI) uses a powerful magnet to generate a magnetic field, which is absorbed by hydrogen atoms in the body. By changing the magnetic field, these atoms return to their original state, emitting signals that are detected and computed by a computer to generate detailed images. MRI can produce images

The First Cells: Cell Evolution

All organisms that currently inhabit the Earth are related because they come from ancestral cells that emerged more than 3,800 million years ago as a result of a slow evolutionary process of organic molecules accumulated in the primeval oceans. It is believed that the decisive moment in the origin of cells was the appearance of a biological membrane.

• The membrane separated the external environment from the internal environment, which favored the existence of a rudimentary metabolism that enabled the ancestral cells to get energy (via nutrition) and use it to reproduce and respond to environmental changes.

Because they originated in a sea of organic molecules, the first cells were probably anaerobic fermentative

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

Physical Assessment of a Patient with Cancer

Skin

• Inspection: Color, integrity, turgor, humidity, temperature.
• Check for: Injuries (type, size, and location), purpura, petechiae, edema, and appearance of nails.

Head and Neck

• Inspect: Face (asymmetry), eyes, mouth, trachea, maxillary sinuses.
• Palpation: Thyroid.

Thorax

• Inspection: Breathing movements and rate.
• Palpation, percussion, auscultation: Tone, intensity, and duration of breath sounds.

Breasts and Armpits

• Inspection and palpation.

Cardiovascular

• Inspection: Tremors and palpitations in the chest.
• Auscultation, palpation, blood pressure.

Musculoskeletal

• Inspection: Hair distribution, abnormal masses or lesions, asymmetries, nodules.
• Palpation: Painful masses, joint range of motion.

Neurologic

• Presence of

Types of Transplants

• Autotransplant: Donor and recipient are the same patient. Used for tissues or organs such as skin portions or bone.
• Isotransplant: Donor and recipient are identical twins. No rejection occurs.
• Xenotransplant: Donor and recipient are distinct species (e.g., using pig heart valves in humans). There is a risk of rejection.
• Allogeneic Transplant: Donor and recipient are of the same species but genetically different. This is the most common type, and there is a risk of rejection.

Immune Rejection Problems

Our immune system distinguishes self from foreign. If it locates foreign tissue, it attempts to destroy it. This is of great importance when dealing with viruses and bacteria, but it also applies to donor tissue. It is crucial that... Continue reading "Medical Transplants and Regenerative Medicine" »

Nutrition: Function and Importance Nutrition includes all processes to get the materials of development and the energy we need to live like .--- La Nutricion: Nutrition is a long process. One step is to take food. Function in the 4 processes involved Nutrition: Circulation - the digestive process, respiration, and excretion Feeding and Nutrients To live, we need the nutrients that food contains. The main groups are carbohydrates, fats, proteins, water, vitamins, and minerals - A diet is complete when it contains all types of nutrients. A balanced diet is when it gives us the necessary amount of each nutrient.

Functions of Muscle Tissue

• Production of body movements
• Stabilization of posture
• Volume regulation of the body
• Movement of chemicals in the body
• Production of heat

Properties of Muscle Tissue

• Electrical excitability
• Contractility
• Extensibility
• Elasticity

Types of Muscle Tissue

There are three types of muscle tissue: striated skeletal, striated cardiac, and smooth.

• Striated skeletal muscle: Called skeletal because the function of these muscles is to move the bones; it often works on a voluntary basis.
• Heart muscle (myocardium): Is located in the heart and is part of its wall. Its movement is involuntary.
• Smooth muscle: Is part of the walls of blood vessels, airways, and some guts. Almost always, this type of muscle movement is involuntary.

Structure of Striated