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" »

Female Reproductive Anatomy

The Uterus

The uterus is a pear-shaped organ, inverted. Its walls are formed by a muscular layer lined by an epithelial layer, the uterine lining or endometrium.

The Vagina

The vagina is an elastic conduit connected to the uterus.

Sperm and Spermatogenesis

Sperm Structure

Sperm cells are tiny, highly specialized cells. The front portion, known as the head, contains the nucleus with the parental genetic material. They also have a long thread called the flagellum (or scourge).

Formation of Sperm

Sperm are formed within the testes in small tubes called seminiferous tubules. Each testis contains many seminiferous tubules inside.

Ovules and Oogenesis

Ovules (Egg Cells)

Ovules are large cells containing hereditary information and... Continue reading "Human Reproduction: Gamete Formation and Fetal Development" »

The Mouth Cavity and Pharynx

The mouth cavity contains the teeth and tongue. Dentition is made up of hard parts embedded in the jaw and covered by dental enamel. The tongue is a powerful muscle that contains taste receptors. The pharynx is a cavity common to both the digestive and respiratory systems.

The Esophagus and Stomach

The esophagus is a muscular conduit that connects the pharynx to the stomach. Regarding the digestive tract, the stomach is a widening of the tract that binds to the esophagus through a valve called the pylorus.

The Small and Large Intestines

The Small Intestine

The small intestine is a tube bending over 6 meters in many loops. It is divided into three regions: the duodenum, the jejunum, and the ileum.

The Large Intestine

The... Continue reading "The Biological Process of Digestion" »

Noncyclic Phosphorylation

The arrangement of the pigment-protein complexes, Photosystems I and II, both electron carriers in the electronic transport chains and ATP synthase enzymes, is necessary to maintain a specific spatial arrangement in the thylakoid membrane, which enables ATP synthesis. The mechanism of ATP synthesis is nearly identical to that of the mitochondria; it depends on the existence of the ATP synthase enzyme complex on the stromal face of the thylakoid membrane. Proton pumping into the thylakoid, performed by several protein complexes of the light phase, generates a proton-motive force gradient necessary for synthesis. In the chloroplast, it is known that each ATP synthesis catalyzed by the stromal portion F1 is associated... Continue reading "Mechanisms of Photophosphorylation in Chloroplasts" »

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" »

Circulatory System: Blood and Lymph

The circulatory system is responsible for distributing food (nutrients) and oxygen throughout the body. Blood, lymph — HCH-HCH.

Circulatory Blood

Circulatory blood (a tissue of cells suspended in a liquid medium) includes several components:

Plasma

Plasma: acellular liquid (about 90% water) containing dissolved substances, including:

• Nutrients: glucose, amino acids, lipids, water and minerals — transported from the digestive tract to the rest of the body;
• Waste products: transported from cells to the excretory organs (e.g., urea), excess salts and carbon dioxide;
• Hormones: carried from producing glands to the organs where they are used;
• Other substances dissolved in plasma.

Red Blood Cells / Erythrocytes

Red blood

Biological Contaminants in Indoor Environments

Biological contaminants are living or once-living organisms that can negatively affect indoor air quality and human health. Key types include:

• Bacteria: Carried by people, animals, soil, and plant debris.
• Viruses: Primarily transmitted by people and animals.
• Moulds: Grow on water-damaged materials or wet surfaces.
• Pollens: Originate from plants.
• Animal Dander: Sources include household pets.
• Saliva: Mainly from cats and rabbits.
• Dust Mites: Thrive in damp, warm environments.
• Insects and Pests: Including ants, cockroaches, mice, and rats.

Humans as Sources of Indoor Contamination

Human activities significantly contribute to indoor biological contamination:

• During sneezing, between 4,000 and 40,000 small drops

Carbohydrates: Primary Energy Source

Carbohydrates are chemical compounds of oxygen, carbon, and hydrogen, synthesized by plants through the action of solar energy. Sugars are found in bread, grains, fruits, and vegetables.

They serve as the first major energy substrate, providing between 50% and 60% of the total energy necessary for movement and basic functions. They are also essential to feed the brain.

Fats (Lipids)

Fats (lipids) consist of hydrogen, oxygen, and carbon that form a chain, categorized as saturated or unsaturated fatty acids.

Sources of Fats

• Saturated Fats: Meat, eggs, and dairy.
• Unsaturated Fats: Olive oil or sunflower oil.

Fats are indispensable; they serve as an energy source, help regulate body temperature (Tª), and transport... Continue reading "Essential Nutrients: Macronutrients, Vitamins, and Diet" »