Notes, abstracts, papers, exams and problems of Biology

Polymerase Chain Reaction (PCR)

Continuous replication is a fragment of DNA containing a gene or genes of our interest. In this way, we obtain a large number of copies that make it possible to study without worrying about the amount of the sample.

At first, it was a cumbersome technique. Due to the different temperatures used during the process, some of them very high, we were forced to replace the polymerase at each change in temperature. This problem was solved by the DNA polymerase of a thermophilic bacterium: Thermus aquaticus (Taq polymerase).

The method is deceptively simple and involves replication in a medium rich in triphosphate nucleotides, the DNA strand of interest, to which we add small pieces of RNA and Taq polymerase.

A cyclic temperature

Human Digestive and Circulatory Systems

Nutrition is the process by which a living being obtains the matter and energy needed to sustain life.

Components of Digestive Function:

• Taste: Involves eating food, breaking it down, and transporting it.
• Reduce: Food is broken down into simple molecules that cells can use.
• Absorb: Simple molecules are absorbed and passed into the bloodstream for circulation to all body tissues.
• Remove: Undigestible remains are eliminated.

Digestive Tract Components:

The Pharynx

A short part of the digestive tract, also part of the respiratory system, extending from the oral cavity to the top of the esophagus.

The Esophagus

The conduit between the pharynx and the stomach.

The Stomach

An enlarged, bag-shaped part of the digestive tube,... Continue reading "Human Digestive and Circulatory Systems: Functions and Components" »

The Digestive Process

There are three phases in food processing: digestion, absorption, and the expulsion of waste. The movement of food through the digestive tract is known as peristaltic movements. These consist of the narrowing of the tube through the contraction of the muscles of the walls. The muscles contract successively.

Digestion

Types of Digestion

• Mechanical digestion consists of cutting, crushing, moving, and diluting foods.
• Chemical digestion is done through the action of various substances, which attack the foods and bring about chemical changes.

Stages of Food Digestion

• Digestion in the mouth is a result of mastication and salivation. Mastication cuts and crushes the food. Saliva is a liquid produced by the salivary glands in the mouth.

Stress and the Nervous System

In alarming situations, the nervous and hormonal systems trigger a series of processes that provoke reactions such as increased heart rate, elevated blood pressure, and heightened tension. This tension typically subsides when the alarming situation ends. However, if the situation persists, it can lead to anxiety, distress, depression, and insomnia.

To reduce these effects, consider the following:

• Adequate sleep
• Regular exercise
• Balanced diet
• Avoid consumption of tranquilizers, drugs, and sleep aids

Hormonal Coordination: The Endocrine System

The endocrine system is a set of glands formed by specialized cells that secrete hormones. Glands are classified as:

• Endocrine: Release hormones into the bloodstream.
• Exocrine: Discharge

Genetics

Core Concepts

Genetics is the study of biology that focuses on genes and biological inheritance related to characteristics.

Chromosomes are components that appear as cylindrical or rod-shaped bodies during cell division: mitosis and meiosis.

Genetic engineering involves manufacturing techniques.

The world lives thanks to bacteria and other antibiotic substances they produce. These products prevent the growth of bacteria and fungi.

Cellular Biology and Cloning

Stem cells and blastocysts are cells in the body with no specialized function. They can multiply while maintaining that state and can be transformed into over 200 cell types in an adult individual. They are fundamental.

Cloning:

• Therapeutic cloning: Obtaining stem cells to regenerate tissues

Infectious Diseases: Stages and Characteristics

Infectious diseases manifest through various symptoms, including fever, malaise, and fatigue. These diseases typically progress through three stages:

1. Incubation Period: The time between the pathogen's entry and the appearance of the first symptoms. During this period, the pathogen multiplies. The incubation period varies depending on the disease.
2. Development Period: Characteristic symptoms appear.
3. Convalescence: The body recovers from the disease.

Medical Terminology and Definitions

Symptoms, Signs, and Treatments

Symptom: A subjective experience reported by a patient, perceived as abnormal and potentially caused by a disease.

Sign: An objective, observable indication of a disease or health impairment.... Continue reading "Understanding Infectious Diseases, Symptoms, and Treatments" »

Photosynthesis: Key Reactions and Processes

Oxygen Release in Photosynthesis: Oxygen is released during the light-dependent reactions of photosynthesis, specifically when water molecules are split (photolysis).

Organelles Involved: The organelles represented are the mitochondria and chloroplast. Photosynthesis occurs in the chloroplast, and cellular respiration occurs in the mitochondria.

Oxygen as a Waste Product: Oxygen (O2) is produced as a byproduct during photosynthesis and is consumed during cellular respiration.

Anabolic and Catabolic Processes: Photosynthesis is an anabolic process (building complex molecules), while cellular respiration is a catabolic process (breaking down complex molecules).

Photosystems: Structure and Location

Photosystems... Continue reading "Photosynthesis: Key Reactions and Processes Explained" »

Endocrine, Exocrine, and Mixed Glands

The endocrine system is composed of glands that secrete hormones. Hormones are chemical messengers that travel through the blood and exert specific actions on certain organs, known as target organs.

• Endocrine glands discharge hormones directly into the bloodstream.
• Exocrine glands discharge substances onto the body's surface through excretory ducts.
• Mixed glands combine the features of both endocrine and exocrine glands.

Endocrine System Functions

Hormones are key regulators of metabolism, reactions, and responses to states of alarm.

Endocrine Gland Characteristics

• Lack excretory ducts
• Generally small in size
• Act in small doses
• Can be formed as independent bodies, arranged in clusters, or within other organs

Pituitary

The Small Intestine

The small intestine is about 6 meters long. In the duodenum, two liquids are added to continue digestion: pancreatic juice and bile. Pancreatic juice contains enzymes such as lipases, proteases, and carbohydrase (e.g., amylase).

Enzyme Breakdown

Each enzyme breaks down food in the following way:

• Protein -> protease -> amino acids
• Lipid -> lipase -> fatty acids and glycerol
• Carbohydrate -> carbohydrase -> sugar

Bile's Role in Digestion

Bile is made in the liver, stored in the gallbladder, and delivered to the small intestine via the bile duct. Bile neutralizes the acid which was added to the food in the stomach because it is alkaline. This provides the optimal pH for enzymes in the small intestine to work. Bile... Continue reading "Small and Large Intestine: Digestion and Absorption" »

Homeostasis and the Respiratory System

Homeostasis refers to the actions performed by the body to maintain a stable internal environment. The respiratory system plays a crucial role in this process.

Key Components of the Respiratory System

• Mucus: Contains water and lysozyme, an enzyme that kills bacteria.
• Trachea: A tube that carries air into the lungs, branching into bronchi and bronchioles.
• Diaphragm: A muscle that separates the chest from the abdominal cavity.
• Ribs: Protect the lungs, which have a spongy structure.

The trachea, bronchi, and bronchioles share similar anatomical characteristics. The trachea is horseshoe-shaped and located behind the liver.

Functions of the Respiratory System

• Gas exchange: The primary function, involving the intake