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

Fundamentals of Biological Molecules and Bonds

Essential Elements and Molecular Formation

The primary elements that form biological molecules are often summarized by the acronym CHOMPS (Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus, Sulfur). Carbon (C) is highly versatile, forming the backbone of organic compounds.

Monomers, Polymers, and Reactions

• Monomers: The smallest units of organic compounds.
• Polymers: Large molecules formed by repeating monomer units (M + M = Polymer + H₂O).
• Polymerization: The process of forming polymers.
• Dehydration Synthesis: A reaction where monomers join to form a polymer, releasing a water molecule (H₂O).
• Hydrolysis: A reaction that breaks down a polymer by adding a water molecule.

Chemical Bonds and Essential Elements

Molecules... Continue reading "Essential Biomolecules: Structure, Function, and Chemical Bonds" »

Cellular Respiration: Definition and Function

Respiration is the fundamental process in which glucose, oxygen, and fatty acids are transformed inside the cell into water, carbon dioxide, and energy (ATP). The primary goal is to convert glucose and oxygen into usable energy.

• It happens inside the cells, specifically within the mitochondria.
• Mitochondria are often described as the site of the "burning of food."
• Oxygen is essential to combine with glucose to facilitate this energy transformation.

Understanding Metabolic Rate (MR)

The Metabolic Rate (MR) is an average measure of the amount of energy that a person needs daily. The MR is typically higher in an active person compared to a sedentary individual.

Energy is required constantly, even while sleeping,... Continue reading "Cellular Respiration and the Mechanics of Human Breathing" »

Cancer Treatment Modalities

The basis of cancer treatment lies in the elimination of tumors through surgery, chemotherapy, immunotherapy, and radiotherapy.

Chemotherapy

Chemotherapy is anticarcinogenic. Certain drugs act directly on DNA, such as oxaliplatin, anthracyclines, and cyclophosphamide. Others, like taxanes and vinblastine, interact with mitotic spindle formation. Common side effects can include hair loss or effects on leukocytes.

Immunotherapy

Immunotherapy is based on the stimulation of the immune system to trigger a response against tumors. Approaches include the use of interferon alpha, which can reduce tumor growth; vaccines using antigens present in cancer cells to stimulate immune defense; and monoclonal antibodies.

Radiotherapy

Radiotherapy... Continue reading "Cancer Treatment Methods and Surgical Procedures" »

Economic Entomology

It refers to the study of all aspects of insects that are related in a way or another with human activity involving the economic, ecological and social.

Ecology of Insects

Species: A group of individuals who share common characteristics, can interbreed and produce fertile offspring under natural conditions.

Population: Group of organisms of the same species that occupy a certain space at a given time.

Community: A group of populations of several species of plants or animals that share a certain time regardless.

Ecosystem: Habitat where biotic and abiotic factors interact to exchange energy and matter in a continuous cycle.

Agroecosystem: Artificial system manipulated by man but stable in nature.

Ecological Niche: Resources that... Continue reading "Economic Entomology: Insect Ecology and Pest Management" »

Cerebral and Basilar Arteries

The carotid artery supplies 80% of the oxygen to the cerebral hemispheres. The two internal carotid arteries branch into the middle cerebral arteries, which provide 60% of the brain's oxygen supply. The anterior communicating artery connects the right and left middle cerebral arteries.

Two vertebral arteries (left and right) ascend along the spinal cord and merge at the base of the skull to form the basilar artery. This artery supplies the medulla, pons, and other brainstem structures.

Circle of Willis

1. Frontal lobes
2. Temporal lobes
3. Middle cerebral artery (right and left)
4. Anterior cerebral artery
5. Posterior cerebral artery
6. Basilar artery
7. Vertebral arteries (right and left)
8. Spinal cord
9. Internal carotid artery
10. Anterior communicating

Cytokinesis

Cytokinesis begins in anaphase and continues through telophase.

• In animals: The process involves strangling the cytoplasm. Segmentation is a linear division, resulting in the formation of a contractile ring formed by actin filaments.
• In plants: The cell wall prevents segmentation. This is done by forming a new wall inside the cell. This new wall is formed at the equator by the association of Golgi apparatus vesicles and microtubules, and it is called a phragmoplast. It extends laterally to reach the cell wall.

Types of Cell Division

1. Bipartition

   Division of the cell. Two daughter cells originate, equal in size. The process involves karyokinesis and cytokinesis, with its variant being strangulation.

2. Multiple Fission

   Divisions of the cell.

Understanding Key Health Concepts

1 - Life expectancy is the average number of years a person born in a particular country in a specific year is expected to live, assuming mortality rates remain constant.

2 - According to the WHO, health can be defined as: "A state of complete physical, mental, and social well-being, and not merely the absence of disease or infirmity."

3 - CVD stands for cardiovascular diseases, which affect the heart or blood vessels.

4 - Myocardial infarction, a type of coronary heart disease (CHD), results in the death of myocardial tissue and permanent damage to the heart muscle. Angina pectoris occurs when a partial blockage reduces blood flow to an area of the heart, causing pain but not irreversible damage. Heart attacks... Continue reading "Understanding Key Health Concepts: A Concise Overview" »

Viral Morphology

The morphology of the virion capsid is defined by its composition of multiple copies of a single protein or several different proteins, each encoded by a viral gene. A capsid, along with the nucleic acid it contains, is called a nucleocapsid. Virions exhibit two primary types of symmetry: helical and icosahedral.

Symmetry Types

Helical Symmetry

This is a helical protein structure with RNA or DNA protected inside it.

Icosahedral Symmetry

An icosahedral virus is a polyhedron composed of 20 identical, equilateral triangular faces.

In some viruses, the nucleocapsid is coated by an outer shell, or envelope, which is a fragment of the host cell's plasma membrane acquired as the virus emerges through a process called budding.

Complex Structures

Some... Continue reading "The Fundamentals of Virus Morphology and Replication" »

Staphylococcus

• Easily develops antimicrobial resistance
• Gram-positive cocci
• Catalase-positive
• Facultative anaerobes
• Not demanding in their nutritional requirements
• Grow in normal media
• Some pathogenic species are generally opportunistic pathogens, commensals
• Important in animal and human infections

Natural Habitat

Widespread in nature; found on human and animal skin, surfaces of objects, air, soil, water, and milk.

S. aureus

Main pathogen associated with infections; colonizes nasal passages and pharynx.

S. epidermidis

Produces skin lesions, wound infections; microbiota found in the skin, respiratory tract, and gastrointestinal tract.

S. saprophyticus

Associated with urinary tract infections.

Immunogens

• Polysaccharide A (specific for S. aureus)
  • Antiphagocytic
  • Antiplatelet
  • Activator

Forensic Aspects of Asphyxia

Carotid Artery Occlusion

Loss of consciousness typically occurs within 10-15 seconds of complete occlusion of the carotid arteries. This timeframe allows for the implementation of restraint mechanisms.

Differential Diagnosis at the Scene

Differential diagnosis is crucial and is made at the scene, considering:

• The victim's clothing state.
• Presence of extracervical lesions indicative of control or struggle.
• Severity of neck injuries.

The diagnosis of accidental etiology is based on a meticulous examination of the scene. A high blood alcohol level may explain the victim's low resistance or the possibility of accidental strangulation.

Forensic Pathology of Submersion (Drowning)

Definition and Types of Submersion

Death or pathological... Continue reading "Forensic Pathology: Asphyxia and Drowning Investigations" »