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

Levels of organization refer to the different degrees of complexity in organized matter.

• Subatomic level: Particles that make up atoms (protons, neutrons, electrons).
• Atomic level: Formed by atoms; the smallest constituents of matter that retain their properties.
• Molecular level: Molecules resulting from the binding of different atoms. There are two types:
  • Inorganic: Found in non-living or dead material (water and mineral salts).
  • Organic: Found only in living matter, usually polymers, chains formed by the union of a similar type of monomer molecules.
• Cellular level: The first level with life.
• Tissue level: Groups of cells with the same function and similar structure.
• Organ level: Different tissues are grouped for a particular function.
• System level:

Mitochondria: Structure and Function

In mitochondria is where cellular respiration occurs (specifically the Krebs cycle, beta-oxidation, electron transport, and oxidative phosphorylation), whose ultimate objective is to obtain energy in the form of ATP. Mitochondria also generate precursors of the major anabolic routes.

The mitochondria are structured as follows: a double membrane formed by an external and an internal membrane, which delimits two different compartments: the intermembrane space and the mitochondrial matrix.

The Outer Mitochondrial Membrane

The outer mitochondrial membrane is in continuous contact with the cytosol. It contains numerous proteins that regulate trade in chemicals with it, including channel proteins (porins) that form... Continue reading "Mitochondrial Structure and Function in Cellular Respiration" »

The Central Nervous System: Brain and Spinal Cord

The Central Nervous System (CNS), comprising the brain and spinal cord, receives information to process and control bodily functions.

The Brain

Located within the braincase, the brain is divided into two hemispheres. Its outermost part, the gray matter, has convolutions (gyri) and grooves (sulci). This area receives information and develops responses. The innermost zone is white matter.

The Cerebellum

Situated below the brain, the cerebellum is also divided into two hemispheres and features convolutions. It coordinates movements such as walking and maintains balance.

The Medulla Oblongata (Bulb)

This vital part links the encephalon with the spinal cord. It controls automatic bodily functions, including... Continue reading "Understanding the Nervous System: Components and Health" »

Forest Ecosystems: A Comprehensive Look

Forest: A natural ground dominated by trees. Vegetation: Various species of plants with 3 strata: arboreal, shrubby, and herbaceous. Conditions: Light, heat. Virosta: Composition of residue that accumulates sun.

Plant Types

• Bryophytes (moss, liverwort)
• Pteridophytes (fern, horsetail)
• Spermatophytes (seed plants)

Gymnosperms (not enclosed seeds). Angiosperms (enclosed seeds). Vegetation Zones: Forest (arboreal), thicket (tall shrub), springs (low shrub), meadow (herbaceous).

Revolt: Perennial, deciduous. Mineral salts (active absorption via PX transport - against gradient, sometimes with gradient). Concentration: Hypotonic (-), isotonic (=), hypertonic (+).

Osmosis and Photosynthesis

Osmosis: Process of water absorption... Continue reading "Understanding Forest Ecosystems: Flora, Soil, and Life Cycles" »

Understanding Health & Disease

Health initiatives are often geared toward reducing exposure to various factors that are carcinogens, such as alcohol, tobacco, and diet. Recent years have spawned a new area of scientific knowledge: epigenetics, which studies the influence of the environment on gene expression.

Mental Health Conditions

Some diseases of the nervous system are due to malfunctioning neurons or injuries provoked by varied causes, such as high blood pressure, strokes, or lack of blood supply. The most important mental health challenges include:

• Depression

  Characterized by deep sadness and an incapacity to lead a normal life.

• Schizophrenia

  A disease that can present from adolescence, provoking serious personality disorders and disconnecting

Biological Organization: From Subatomic to Organismal Levels

Matter is organized into different degrees of complexity, forming the hierarchical structure of life. These levels include:

• Subatomic Level: Particles that make up atoms (e.g., protons, neutrons, electrons).
• Atomic Level: Formed by individual atoms (e.g., carbon, oxygen, hydrogen).
• Molecular Level: Resulting from the linkage of different atoms. Molecules can be inorganic (e.g., water, salts) or organic (e.g., proteins, carbohydrates, lipids, nucleic acids), with organic molecules being fundamental to living material.
• Cellular Level: The first level of life; the smallest unit capable of independent existence.
• Tissue Level: A network of specialized cells with the same function and origin.

Understanding Cells: The Basic Units of Life

Fundamental Biological Units

• Cell: The structural and functional unit of all living beings. Cells originate from pre-existing cells.
• Abiotic (Non-Living Components): Subatomic particles, atoms, molecules, macromolecules, supramolecular complexes, and organelles.
• Biotic (Living Components): Cellular level, tissues, organs, organ systems, individuals, populations, communities, ecosystems, and the ecosphere.

Prokaryotic Cells: Simple Cellular Organization

Prokaryotic cells lack a true nucleus and other membrane-bound organelles.

• Cell Wall: A rigid and strong protective layer formed by polysaccharides and proteins.
• Plasma Membrane: Located inside the cell wall, it controls the entry and exit of substances.
• Bacterial

Interaction

Interaction is the set of processes through which a living being obtains information from the environment, takes decisions, controls its actions, and coordinates the functioning of the body itself.

Obtaining Information

There are various mechanisms responsible for obtaining information from the exterior and the interior of the body. These mechanisms are called receptors.

Analysis of the Information and Elaboration of a Response

This process is carried out by the nervous system and the endocrine system. The elaborated response is an order that is transmitted to the organs via different procedures.

Execution of a Response

The effectors, which are the organs responsible for carrying out a response, are as varied as the possible responses... Continue reading "Interaction: Obtaining, Analyzing, and Executing Responses in Living Beings" »

Types of Illness

• Physical Diseases: Caused by injury, infection, or degenerative processes in the body. They are classified into infectious and non-infectious diseases.
• Mental Illness: Provoked by a malfunction of the brain.
• Social Ills: Caused by the existence of a social environment with serious violent, economic, or educational deprivation.

Health vs. Illness

• Health: A state of complete physical, mental, and social well-being.
• Illness: The state in which a person's health is disturbed.

Violence as a Social Disease

Violence is a terrible social disease that kills many people every year. It is a disease that is incubated in childhood.

Viruses

Viruses are not living creatures but protein capsules containing DNA or RNA that is injected into a cell.

Infectious

DNA Replication: Semiconservative Process

DNA replication is a semiconservative process. It begins at replication origins, forming "bubbles."

Key Enzymes and Proteins in DNA Replication

• Helicases: Unwind the DNA double helix, moving in opposite directions from the origin.
• Topoisomerases: Act ahead of the replication fork to relieve supercoiling that arises from unwinding.
• SSB Proteins (Single-Strand Binding Proteins): Bind to and stabilize the separated single DNA strands, preventing them from re-annealing.

DNA synthesis always proceeds in the 5' to 3' direction, leading to two distinct modes of synthesis:

Continuous Synthesis (Leading Strand)

On the leading strand, synthesis is continuous. An RNA primase (a type of RNA polymerase) synthesizes a short... Continue reading "DNA Replication and RNA Transcription Processes" »