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

Protein Definition

A protein consists of amino acids linked together. Each amino acid has a central carbon atom attached to an amino group (-NH2), a carboxyl group (-COOH), a hydrogen atom, and a variable radical group (side chain).

Protein Classification

Proteins can be classified based on their composition:

• Holoprotein: Composed solely of amino acids.
• Heteroprotein: Composed of amino acids along with other non-amino acid molecules (prosthetic groups).

Amino Acids

Amino acids are organic compounds characterized by having both a carboxyl group (-COOH) and an amino group (-NH2). They are typically solid, crystalline substances with high melting points, soluble in water, and possess optical activity. Their chemical behavior is amphoteric, meaning they... Continue reading "Protein Essentials: Structure, Properties, and Functions" »

Non-Infectious Diseases

Cardiovascular Diseases

Cardiovascular diseases affect the heart and blood vessels, and their incidence is higher in adults and the elderly.

• Atherosclerosis: An enlargement of the walls of the arteries due to the deposition of cholesterol, platelets, and fibrous tissue. The arteries can become calcified and hardened, resulting in a loss of elasticity.
• Thrombus: A blood clot that occurs in an artery or vein, leading to its obstruction (thrombosis). When the clot forms in a vein, it can be released and easily move to another place (embolism).
• Aneurysm: A weakening of the arterial wall, which promotes dilation of the artery. This can rupture and form a hemorrhage.
• Stroke: Interruption of blood supply to the brain.
• Coronary Artery

Emerging and Reemerging Diseases

Emerging diseases are caused by previously unknown germs. These germs may have been hidden or have mutated. An example is Ebola.

Reemerging diseases are those that reappeared after a period of decline. Examples include cholera, tuberculosis, dengue, and malaria.

Outbreaks and Spread

An epidemic outbreak is the rapid spread of an infectious disease affecting many people in a limited area and time.

A pandemic is an epidemic affecting many parts of the world.

Key Concepts

A syndrome refers to the complex and variable damage caused by infectious agents.

A reservoir is an animal that harbors infectious agents transmissible to humans, such as rodents.

A vector is an animal that transmits germs to a healthy person, such as... Continue reading "Infectious Diseases: Emergence, Spread, and Immunity" »

Male Reproductive System Components

Sperm Production and Testicular Hormones

Spermatogonial: Embryonic cell producing sperm.

Testosterone: A hormone produced by the testis; its function is the development and maintenance of male sexual characteristics.

Hormones Synthesized by the Testis: Testosterone acts on the maturation of testicular germ cells.

Luteinizing Hormone (LH): Stimulates the secretion of testosterone by the Leydig cells.

Follicle-Stimulating Hormone (FSH): Stimulates the Sertoli cells.

Epididymis and Vas Deferens Function

Epididymal Function: Allows the passage of spermatozoa and facilitates their maturation.

Role of the Vas Deferens: Its function is to allow sperm to leave the epididymis and transport them to the ejaculatory duct.

Male

Stages of Childbirth

Expulsion (Second Stage of Labor)

The fetus is pushed outward by uterine contractions and by the force exerted by the mother pushing her diaphragm. This stage usually lasts about 15 to 30 minutes. It concludes when the baby is born and takes its first breath.

Placental Delivery (Third Stage of Labor)

Between 5 to 15 minutes after the baby's birth, the placenta is expelled, along with the remaining uterine lining.

Childbirth Complications

Inadequate Dilation of the Cervix and Vagina

To alleviate this problem, the mother may be given the hormone oxytocin, which causes uterine contractions and cervical dilation.

Umbilical Cord Clamping

If the umbilical cord is compressed, the blood flow between the mother and fetus is cut off. If this... Continue reading "Human Reproduction: Conception, Childbirth, and Family Planning" »

Essential Health Concepts

Public health encompasses the activities and services aimed at promoting, protecting, and restoring the health of populations.

The Immune System

The immune system is a complex network of organs, cells, and molecules that defends the body against infectious agents and abnormal cells, including cancerous cells.

Diagnosis

Diagnosis is the process of identifying a disease and determining its primary cause.

Chemotherapy

Chemotherapy involves the use of chemical drugs to combat disease.

Disinfectants and Antiseptics

• Disinfectants: Substances used to destroy microorganisms on objects.
• Antiseptics: Substances used to eliminate microorganisms that colonize tissues, such as skin.

Antibiotics

Antibiotics are chemicals that destroy or inhibit... Continue reading "Essential Health Concepts: Public Health, Immunity, and Treatments" »

Thin Filament Structure

The thin filament is composed of three types of proteins:

• Actin: Forms helical rolls.
• Troponin: Binds to actin and tropomyosin. It is formed by three subunits:
  • C: Calcium-binding unit.
  • I: Calcium-inhibiting unit.
  • T: Troponin-tropomyosin union unit.
• Tropomyosin: Covers the active binding sites on actin for myosin.

Muscle Adaptation Mechanisms

Hypertrophy

An increase in the size of muscle fibers, therefore increasing muscle size.

Hyperplasia

An increase in the number of muscle fibers, not their size. This has been observed in animals like cats.

Atrophy

A reduction in the size of the muscle. It is typically caused by lack of muscle use and protein loss.

Autogenic Inhibition Explained

Autogenic inhibition is a reflex that causes muscles... Continue reading "Muscle Function, Adaptation & Energy Systems" »

The environment is everything that surrounds us. It can therefore be an urban environment or, more broadly, a natural environment. It is generated by the natural world and influenced by humans. This applies to both transformed and non-transformed environments.

What is Ecology?

The science that studies ecosystems is **ecology** (from Greek: *oikos* 'house' + *logos* 'study'), meaning the study of the 'living house' or ecosystems. Ecologists seek to explain phenomena that occur in the environment.

Earth's Spheres and Ecosystems

On Earth, there are several layers: the atmosphere, hydrosphere, and lithosphere. There are broader terms that encompass the Earth as a whole: the biosphere, ecosphere, and ecosystem.

• Biosphere

  The part of the planet that contains

Mendel's Experiments with Pea Plants

Mendelian genetics refers to the laws of inheritance discovered by Gregor Mendel through his work with pea plants. He studied specific characters, including:

• Seed color (Yellow vs. Green)
• Seed surface (Smooth vs. Wrinkled - implied, though not explicitly stated in the original text)

In his first cross, Mendel bred purebred yellow-seeded plants with purebred green-seeded plants. The resulting first filial generation (F1) consisted of 100% plants with yellow seeds.

Conclusions from Initial Crosses

• Each individual carries two hereditary factors (now called alleles) for each character, one inherited from each parent.
• In an individual carrying alleles for both yellow and green seeds, the yellow allele dominates over