Notes, abstracts, papers, exams and problems of Biology

Microbiology: The Science of Microorganisms

Microbiology, derived from the Greek words mikros ("small"), bios ("life"), and logos ("study"), is the scientific discipline dedicated to the study of microorganisms. These are living things too small to be seen with the naked eye. Microorganisms, often called germs, were discovered over 300 years ago. Their only common characteristic is their small size.

Microscopy depends on factors such as contrast, resolution, and magnification.

Taxonomy involves the study of nomenclature, classification, and identification of microorganisms.

Factors Influencing Microbial Growth

The number and types of microorganisms in an environment depend on factors like humidity, heat, nutrient availability, aeration, and pH.

• Soil

Plant Anatomy: Roots, Stems, and Leaves

Root Structure

The root has a simple structure with no central bone. It contains vascular tissue in the phloem and wood beams, along with fundamental bark tissue. The endodermis clearly demarcates these areas. Two meristems are present: the cambium, which forms a ring of dividing cells between the phloem and wood, and the phellogen, which develops in the cortical parenchyma. The phellogen produces corky tissue layers for protection and cortical parenchyma internally.

Stem Structure

Stem structure differs between dicotyledonous and monocotyledonous plants. In dicots, vascular tissue forms a cylinder with the xylem inside and phloem outside. Fundamental tissue is located between the epidermis and vascular tissue... Continue reading "Plant Root, Stem, and Leaf Anatomy: Structure and Function" »

Reproduction of Human Beings

It is comprised of the following processes:

• The production of gametes: In specialized reproductive organs.
• Fertilization: Is the union of two gametes within the female reproductive system, forming a single cell, the zygote.
• Zygote development: Inside the female reproductive system.
• Birth: A fully formed baby is born.

Development to Sexual Maturity

Changes from infancy to sexual maturity:

• Primary sexual characters: Are present at birth. These are the sexual organs: the penis in boys, and the vulva and excretory system in girls.
• Secondary sexual characters (Puberty):
  • In children: Deep voice, beard, pubic and underarm hair, increased bone and muscle mass.
  • In girls: High voice, growth of breasts and hips, and pubic and underarm

Siphonaptera (Fleas)

Fleas have three pairs of legs, a segmented body, and are 0.5 to 4 mm in size. They can jump 33 times their size. Ctenidia are hairs on their body. The female spermatheca is where the eggs are stored. They have a complete or holometabolous life cycle. The adult lays eggs, and in three weeks, the larvae emerge. In 9-15 days, the pupa stage is reached, and then the adult. Males and females feed on blood. The larvae feed on the feces of the adult fleas. The pupa is covered with earth and is motionless until the temperature changes.

• Pulex irritans (Human flea)
• Ctenocephalides canis (Dog flea)
• Ctenocephalides felis (Cat flea)
• Xenopsylla cheopis (Rat flea)
• Tunga penetrans: The female introduces itself inside the skin, producing a wound

Electron Transport Chain

Cytochrome P-450 - NADH cytochrome reductase: This enzyme facilitates the hydroxylation of many substrates. Therefore, it is important in the synthesis of steroid hormones and detoxification processes. Cytochrome b5 - cytochrome b5 reductase NADF4: These endoplasmic reticulum (ER) membrane proteins exhibit asymmetry, with one face oriented towards the hyaloplasm and the other towards the lumen. Carbohydrates are attached to lipids and proteins facing the luminal side.

Synthesis of Exportable Proteins (Rough Endoplasmic Reticulum)

The cell synthesizes proteins that either remain within the cell or are exported to other locations. These locations can be extracellular, as products of secretion, or intracellular. Protein synthesis... Continue reading "Endoplasmic Reticulum: Protein and Lipid Synthesis" »

The Respiratory System: How Air Enters Your Body

Air entry is performed through the nostrils and reaches the nasal cavity, where it is warmed. The nasal wall is full of blood vessels. The nostrils open into the pharynx, an organ common to the respiratory and digestive tracts. The inferior pharynx communicates with the larynx, allowing air to enter the trachea.

In the larynx, a cartilaginous lamina, the epiglottis, closes to prevent food from entering the respiratory tract. The larynx, in addition to serving as an air passage, is also a vocal apparatus. Inside the larynx, the vocal cords vibrate as air passes over them, allowing us to produce sounds.

The trachea is lined with a mucous membrane rich in glands that trap dust particles. The walls... Continue reading "Respiratory System and Urine Formation: A Comprehensive Look" »

Asexual Reproduction

Asexual reproduction involves a single individual or vegetative parts giving rise to new organisms through mitosis. These offspring are genetically identical and are considered clones. There are several types:

• Bipartition: Organisms divide through a typical mitosis process, resulting in two new individuals of the same size.
• Budding: Daughter cells are formed of different sizes. During mitosis, a bud forms on the parent body, and one of the nuclei migrates to it. When the bud separates, it forms two cells, one larger than the other.
• Multiple Division: Multiple daughter cells are formed. The nucleus of the stem cell divides repeatedly by mitosis, forming a multi-core structure. The cytoplasm is shared, and each core is surrounded

Background

Medical History

• Morbid background
• Chronic respiratory diseases (presence or absence)
• Thoracic surgery history
• Injuries

Reproductive History

• Relevant for therapeutic and diagnostic decisions
• Reproductive age
• Contraceptive methods
• Catamenial regimen

Habits

• Crucial for diagnosis
• Snuff: type, frequency, duration, mode, passive exposure
• Pack-years (e.g., 1 pack/day for 1 year = 1 pack-year)
• Alcohol consumption
• Animal breeding (mammals, birds)
• Biomass fuel use

Drug Use History

• Impact on diagnosis and treatment
• Effects on bronchial kinetics
• Effects on lung morphology
• Influence on respiratory comorbidities

• ACE inhibitors
• Beta-blockers (e.g., propranolol)
• Antineoplastics (e.g., bleomycin, doxorubicin)
• Antiarrhythmics (e.g., amiodarone)
• Nitrofurantoin, methotrexate
• Calcium,

DNA Structure and Function

DNA is a large molecule formed by the union of simpler molecules called nucleotides. The nucleotides correspond to the links of a long chain and consist of:

• A molecule of phosphoric acid
• A carbohydrate called deoxyribose
• A nitrogenous base (adenine (A), guanine (G), cytosine (C), or thymine (T))

The DNA sequence is the order of DNA nucleotides. Each DNA molecule is composed of two long chains of nucleotides coiled up in a double helix. The two strands are chemically complementary. This is because the nitrogenous bases are joined and locked inside the double helix, with specific pairings: (A = T), (T = A), (C = G), and (G = C).

DNA Replication

The DNA molecule is the only molecule in living beings that can make an exact copy... Continue reading "DNA Structure, Replication, and Biotechnology" »

The Human Digestive System

The digestive process begins in the **mouth**. The first processes are chewing, conducted by teeth (*incisors, canines, molars, and premolars*), and salivation, managed by a muscular organ called the tongue. The **tongue** moves food during chewing and contains **taste buds** for sensing flavor. During salivation, food is broken down by teeth and moistened by **saliva**, a watery secretion produced by the **salivary glands**. Saliva production can be triggered by the sight or smell of food. Saliva contains **mucin**, which gives it viscosity, and enzymes such as **salivary amylase** and **lingual lipase** (which hydrolyzes milk fat).

The ground food and saliva form the **bolus**, which is pushed into the **esophagus*... Continue reading "Human Digestive and Respiratory Systems: A Detailed Look" »