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

DNA and Chromosomes

DNA is the biomolecule that contains genetic information to make proteins in the cell.

The chromosomes are composed of chromatin (DNA + protein).

Before cell division the DNA is duplicated. Each chromosome is formed by two chromatids joined together.

Karyotype and Genome

Karyotype: chromosome set ordered by pairs. Humans have 23 pairs.

Genome: the complete set of genes.

Genes and Genetic Information

A gene is a segment of DNA containing information to produce a given necessary protein. Genes together make up the genome.

Cell Cycle and Division

Cellular division is the process by which a cell is divided into two daughter cells.

Interphase

Interphase is the stage of growth: the cell increases in size, the cytoplasm grows, and routine... Continue reading "DNA, Chromosomes, Mitosis & Meiosis — Genetics Fundamentals" »

Waste Products

Non-Nitrogenous Products

These include CO2, H2O, mineral salts, and bile pigments. CO2 is removed by respiration. H2O is eliminated through the excretory apparatus and perspiration. Minerals are excreted in urine and sweat, and bile pigments pass out through the digestive system in the feces.

Nitrogenous Products

These are highly toxic compounds eliminated in various forms, such as ammonia, uric acid, and urea. They are categorized into three groups based on the primary excretion product:

• Ammoniotelics: The excretion product is ammonia. Due to its high toxicity, only organisms with abundant water supply can excrete nitrogen this way.
• Uricotelics: The excretion product is uric acid, which is ejected in crystal form. Its toxicity is

Biological Functions of Proteins

Structural Function

Proteins are essential components of plasma membranes, working alongside phospholipids and cholesterol. There are two main types of membrane proteins: peripheral proteins, located on the exterior or interior surfaces, and integral proteins, which are housed within the phospholipid bilayer.

Why is the water molecule a dipole? It is because electrons are closer to the more electronegative oxygen atom, resulting in positive and negative charges for hydrogen and oxygen respectively.

Enzymatic Function

Enzymes are globular proteins that catalyze metabolic reactions. A catalyst is a substance that accelerates chemical reactions. In our organism, only enzymes can perform this function. While chemical... Continue reading "Biological Functions of Proteins and DNA Replication" »

The Small Intestine: Structure and Function

Structure

It is divided into three parts: the Duodenum, Jejunum, and Ileum. The small intestine represents the largest portion of the digestive tube. Its length varies with the type of feed: it is longer in herbivores and shorter in carnivores.

Function

Its primary function is to perform most of the chemical digestion and absorption of nutrients. For this, it requires that the secretions discharged by the pancreas, liver, and intestinal glands are mixed with chyme through sawing motions and peristaltic waves. After this mixture, chyme becomes chyle, consisting of H₂O, mineral salts, monosaccharides, and amino acids, which are absorbed by the intestinal mucosa to be incorporated into the circulatory... Continue reading "Human Digestive System: Stomach and Intestine Functions" »

The Circulatory System: Blood and Its Components

Composition of Blood

Blood is a red liquid that constantly circulates through blood vessels. It transports cells, nutrients, and oxygen, while collecting carbon dioxide and other waste products that must be expelled. Blood is formed by plasma and blood cells.

• Plasma: Transports nutrients and supports the blood cells.
• Blood Cells:
  • Red Blood Cells (Erythrocytes): Responsible for oxygen transport.
  • White Blood Cells (Leukocytes): Including neutrophils, monocytes, and lymphocytes, crucial for the immune system.
  • Platelets (Thrombocytes): Essential for blood clotting.

Blood Vessels

Blood vessels form a network of channels that distributes blood throughout the body, comprising three main types:

• Arteries: Carry

Central Nervous System (CNS) Components and Protection

The Central Nervous System (CNS) is composed of the brain and spinal cord. It is protected by membrane layers, called the meninges, and bone structures: the skull (for the brain) and the vertebrae (for the spinal cord).

Major CNS Structures Housed in the Cranium

The brain structure housed in the cranium includes the Cerebrum, Cerebellum, and Medulla.

The Cerebrum Structure and Function

The Cerebrum is divided into two hemispheres. Its surface features include protrusions called gyri and depressions called sulci or fissures. The cerebral cortex is the outer part, made up of gray matter that receives information from sense organs, produces response orders, and stores and processes information.... Continue reading "Understanding the Central and Peripheral Nervous Systems" »

The Human Circulatory System

The circulatory system is responsible for distributing food and oxygen around the body and collecting waste products from cells. It consists of blood, the heart, and blood vessels (arteries, veins, and capillaries).

Blood Tissue and Its Components

Blood is a tissue formed by a liquid, plasma, and a set of cells: red blood cells, white blood cells, and platelets.

• Plasma: Composed of 90% water and dissolved substances such as nutrients, salts, waste products, hormones, etc.
• Red Blood Cells (RBC): Responsible for transporting oxygen.
• White Blood Cells: Responsible for phagocytizing microbes and producing antibodies.
• Platelets: Essential for blood clotting.

Heart Anatomy and the Cardiac Cycle

The heart muscle contracts to empty... Continue reading "Human Circulatory and Lymphatic System Functions" »

Key Components of the Immune System

Immune Cells

The immune system relies on various specialized cells to identify and eliminate pathogens:

• Neutrophils: These are phagocytic cells (microphages) that can pass through blood vessel walls in a process called diapedesis.
• Monocytes: These cells can collaborate with macrophages and lymphocytes in immune reactions.
• Lymphocytes: A crucial category of white blood cells, central to the specific immune response.
• Basophils: Contain histamine granules, which, when released, dilate blood vessels and increase capillary permeability.
• Eosinophils: Capable of performing both phagocytosis and diapedesis.

Immune Protein Molecules

Immune protein molecules are synthesized by certain immune cells and are essential for defending... Continue reading "The Body's Defense: Immune Cells, Proteins, and Responses" »

Levels of Biological Organization

The human body is organized into several levels of complexity:

• Atoms: These are chemical elements that form living beings, such as Carbon, Hydrogen, and Oxygen.
• Molecules: These are the components from which cells build their own structures, including Proteins, Carbohydrates, and Lipids.
• Cell: The basic unit of structure and functioning within the human body.
• Tissue: A set of cells that specialize and associate to accomplish a specific function.
• Body (Organ): These are formed by different tissues and are assigned a specific function.
• Apparatus or System: A partnership or relationship of organs working together to perform a vital role.

Key Components and Parts of the Cell

The cell contains various organelles and structures... Continue reading "Human Biological Organization and Cellular Anatomy" »

Biological Foundations

Photosynthesis: Energy Capture

Photosynthesis is a vital process that enables plants to convert light energy into chemical energy. This fundamental process, crucial for life, relies on the presence of leaves and pigments to capture solar energy.

Cellular Structures & Nutrient Transport

Unicellular vs. Multicellular Organisms

Unicellular organisms are in direct contact with their external environment. In contrast, multicellular organisms do not have all their cells in direct contact with the outside world, facing challenges in spreading nutrients across individual cells.

Therefore, multicellular organisms require internal transport systems (like 'pipes' or circulatory systems) to distribute nutrients to all cells not in... Continue reading "Biological Foundations and Wastewater Treatment Essentials" »