Notes, abstracts, papers, exams and problems of 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" »

1. Inorganic Chemical Compounds in Cellular Reactions

Electrolytes are inorganic chemical compounds necessary for cellular reactions.

2. Collecting Tube Reabsorption

Chloride reabsorption in the collecting tube: 1%

3. Urinary Potassium Excretion

Urinary excretion of potassium: 15%

4. Medullary Osmotic Gradient

The countercurrent multiplier mechanism in the loop of Henle creates the medullary osmotic gradient.

5. Urine Acidification

Urine acidification occurs in the collecting tube.

6. Hormonal Control of Blood Pressure

Renin converts angiotensin I in the hormonal control of blood pressure.

7. Glomerular Filtration

Capillary hydrostatic and colloid osmotic pressures determine glomerular filtration volume.

8. Smooth Muscle in Digestive Tract

Longitudinal and... Continue reading "Renal and Digestive Physiology: Cellular Processes and Regulation" »

DNA Replication: A Detailed Explanation

DNA replication is a fundamental process in all living organisms. It ensures the accurate duplication of the genome before cell division. This process involves several key steps and enzymes.

1. Unwinding the DNA Helix

The first step involves unwinding and opening the DNA helix. This process, also known as DNA despiralization, separates the two DNA strands. Specific enzymes, including helicases, attach to the DNA strands and unwind them. Topoisomerases prevent the formation of knots during this unwinding process.

Replication begins at specific points of origin. In prokaryotes, there is typically one point of origin, while eukaryotes have multiple origins due to their larger DNA content. Helicases break the... Continue reading "Understanding DNA Replication: A Comprehensive Look" »

Protozoa

Features:

• Microscopic and eukaryotic unicellular organisms.
• Exhibit movement.
• Aquatic, living in aquatic or terrestrial environments.
• Some are free-living; others are parasites.
• Reproduction may be sexual or asexual.

Classification:

• Mastigophora (Flagellates): Possess flagella for locomotion.
• Rhizopods (Sarcodina): Move via pseudopods, extensions of the cytoplasm.
• Ciliophora (Ciliates): Move using cilia.
• Apicomplexa (Sporozoa): Have a complex life cycle; all are parasites.
• Suctoria: Have cilia in their juvenile phase and tentacles in adulthood.

Locomotion: Move by extending cytoplasm externally (pseudopods), into which the rest of the cytoplasm flows.

Nutrition: Engulf organic particles via pseudopods, forming a digestive vacuole. Enzymes digest... Continue reading "Protozoa, Bryophytes, Gymnosperms, and Angiosperms: A Comparison" »

Meiosis: Diploid to Haploid Cell Division

Meiosis is a specialized cell division mechanism that produces haploid daughter cells (n) with distinct genetic combinations from a single diploid cell (2n). It involves two consecutive divisions: Meiosis I (the first meiotic division) and Meiosis II (the second meiotic division).

Essentially, Meiosis transforms one diploid cell (2n), which has already duplicated its genetic material, into four genetically different haploid cells (n) through these two divisions. Without meiosis, gametes would retain the same chromosome number as somatic cells. Consequently, after each fertilization event, the resulting zygote would have double the necessary chromosomes. This highlights the crucial role of meiosis in maintaining... Continue reading "Meiosis Explained: Diploid to Haploid Cell Division Process" »

Mutations

Mutations: Sudden alterations in genetic material may go unnoticed or be a source of genetic variation. Mutations occurring in gametes are transmitted to offspring.

Types of Mutations:

1. Gene or Point Mutations:

   These replace one base pair with another. This can halt protein synthesis or cause the synthesis of a different protein.

2. Chromosome Mutations:

   These involve the loss (deletion) or duplication of a chromosome. They also include variations in the distribution of chromosome segments, such as translocation, where segments move to another chromosome.

3. Genomic Mutations:

   These include euploidies, which affect the entire set of chromosomes, leading to haploid (n) or polyploid (3n or 4n) conditions, often seen in plants. Aneuploidies involve

Cellular Biology

Synthesis of Cell Theory

• Each living organism is made up of one or more cells (structural unit).
• The smallest living organisms are single cells, and cells are structural units of multicellular organisms.
• All cells come from preexisting cells (the source drive).

Forms of bacteria:

• Bacilli
• Coccobacilli
• Vibrio
• Spirochetes / Spirilla

Prokaryotic and Eukaryotic Cells

Prokaryotic Cells: Are those that have no internal membranes or an organized nucleus (bacteria).

Eukaryotic Cells: They have internal membranes and an organized nucleus.

Difference Between Animal and Plant Cells

Plasma membrane: Structure that separates the intracellular from the extracellular... Continue reading "Cellular Biology: Prokaryotic and Eukaryotic Cells" »