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

The Human Heart: Anatomy and Function

The heart is an organ about the size of a fist, located in the center of the chest, slightly to the left. It is comprised of two atria and two ventricles. Blood enters the atria through the veins and is driven out of the ventricles through the arteries. The heart has valves that force the blood to circulate in one direction.

The Heartbeat

The beating of the heart is the most noticeable manifestation of its activity. The frequency with which the heart beats varies according to the body's needs. Every heartbeat follows a set of phenomena that constitute a cardiac cycle:

• Atrial systole: The atria contract and push blood into the ventricles.
• Ventricular systole: The ventricles contract, and blood leaves through

Cellular Nutrition and Energy Transformation

Cellular nutrition is the set of processes by which cells incorporate and transform matter and energy from their environment. This function includes the exchange of substances through the membrane, the chemical transformations of molecules, and the excretion of waste products. Nutrition builds new structures or repairs existing ones, providing the energy required for all cellular activities.

Transport Without Membrane Deformation

Substances are exchanged in two primary ways. In transport without membrane deformation, gases like oxygen and small molecules like water pass through the membrane via simple diffusion. This is the movement of particles from an area of higher concentration to an area of lower... Continue reading "Cellular Nutrition and Membrane Transport Mechanisms" »

Understanding Biological Reproduction

Reproduction is the fundamental process by which living descendants arise, similar to themselves. This process guarantees the survival of the species by transmitting genetic information.

Asexual Reproduction

Asexual reproduction involves a single parent and creates identical copies of itself. Gametes are not needed. Descendants arise from the division of the organism or one of its cells.

Key Types of Asexual Reproduction

• Bipartition: Cell division into two identical cells (e.g., bacteria and protozoa).
• Sporulation: Successive divisions of the nucleus. Each new nucleus and cytoplasm is enveloped by a membrane, forming a spore that gives rise to a new individual (e.g., fungi, algae, mosses, ferns).
• Gemmation (Budding)

Genetic Engineering: Understanding the Building Blocks

Genetic engineering relies on our knowledge of the genetic code, gene regulation mechanisms, transcription, translation, and reduction. Automated sequencing techniques, restriction enzymes, and a set of other tools allow us to split and join DNA fragments. These fragments, when combined with other macromolecular carrier DNA, enable the transfer of genetic information between organisms. These are called recombinant DNA molecules.

Key Processes in Genetic Engineering

• DNA Transformation: A cell undergoes a genetic change resulting from the entry of a foreign DNA molecule into its core.
• Transduction: The process of transferring genetic information (e.g., in bacteria) without direct contact, often

Endocrine System

We are formed by a series of glands, whose main characteristic is the production of substances called hormones. These hormones, usually discharged into the blood, perform a variety of functions. They regulate the growth, development, and function of many tissues and coordinate the body's metabolic processes. The most important function is to maintain homeostasis. Some of these glands are:

Hypophysis

A small gland housed at the base of the skull in the center of the sphenoid bone (sella turcica). It produces growth hormone and antidiuretic hormone.

Thyroid

A gland in the neck, at the height of the first tracheal rings. It regulates the growth and maturation of tissues.

Parathyroid

There are four glands located in the back of the thyroid.... Continue reading "Endocrine and Urinary Systems: Functions and Anatomy" »

Genetic Fingerprint

Genetic fingerprinting is a technique capable of distinguishing and identifying individuals through individual peculiarities in their own DNA.

Mutations

Mutations are alterations in the genetic information of cells that may occur spontaneously in any cell of a living being. Their consequences can be negative, neutral, or harmless, but also advantageous or beneficial.

Gene Mutations

Gene mutations are mutations affecting the nucleotides of DNA.

Chromosomal or Genomic Mutations

Chromosomal or genomic mutations affect chromosome number or structure. They are due to errors in the processes of meiosis. When they affect the whole chromosome, it is called genomics.

Biotechnology

Biotechnology consists of a set of techniques or processes... Continue reading "Genetic Fingerprinting, Mutations, and Biotechnology" »

Proteins: Composition and Structure

Proteins consist of carbon (C), hydrogen (H), oxygen (O), and nitrogen (N), and may also contain sulfur (S), phosphorus (P), iron (Fe), magnesium (Mg), and copper (Cu). Proteins are made up of smaller molecules called amino acids, which are linked by peptide bonds.

Amino Acids and Their Properties

Amino acids with uncharged polar side chains are hydrophilic and are usually found on the outside of the cell. Nonpolar side chains tend to aggregate in the interior.

Peptide Bonds and Polypeptides

Amino acids are commonly attached through amide links, called peptide bonds. The union of multiple amino acids results in a peptide. A peptide with fewer than 10 amino acids is called an oligopeptide, and if it contains more... Continue reading "Understanding Proteins: Structure, Properties, and Classification" »

1. The Blood Circulatory System

Blood Vessels and Heart

1.1 Composition of Blood

Blood is a reddish liquid composed of:

• Plasma: Constitutes 55% of the blood. It is a yellowish liquid consisting of water, mineral salts, proteins, glucose, etc.
• Blood Cells: Constitute 45% of the blood.

Blood Cells:

• Red Blood Cells (or Erythrocytes/Hamaties): Transport oxygen ($\text{O}_2$). They contain hemoglobin.
• White Blood Cells (or Leukocytes): Defend the body.
• Platelets (or Thrombocytes): Prevent bleeding.

1.3 Functions of Blood

• Transporting nutrients (via red blood cells).
• Transporting gases.
• Controlling bleeding (via platelets).
• Distributing body heat.

2. Diseases

Anemia

• Symptoms: Paleness, tiredness, spots on nails, nosebleeds.
• Grounds: Lack of iron, resulting in insufficient

Lysosomes, Peroxisomes, and Vacuoles

These are all membrane-bound organelles.

Structure and Function of Lysosomes

Lysosomes are organelles containing enzymes that degrade all types of biological polymers. They are acid hydrolases and act as a cellular digestive system, breaking down material captured from outside the cell. When a cell incorporates material via endocytosis, it forms a phagosome. A primary lysosome then fuses with this to form a secondary lysosome, or phagolysosome, where enzymes break down substances for cellular use. When material to be digested comes from within the cell, the process is called autophagy. This forms an autophagosome, which fuses with a primary lysosome for digestion.

Structure and Function of Peroxisomes

Peroxisomes... Continue reading "Cellular Organelles: Lysosomes, Peroxisomes, Vacuoles, and Mitochondria" »

Anabolism: The Constructive Phase of Metabolism

Anabolism is the constructive phase of metabolism. It is the set of metabolic pathways whose objective is to obtain more or less complex organic molecules, sharply reduced, from simpler and relatively oxidized ones. Therefore, these are chemical reduction processes.

Features of Anabolic Pathways

• As we have said, they are basically chemical reduction processes.
• Reactions are strongly endergonic (energy is needed), for which they use the energy released in catabolic reactions as ATP, NADH, and NADPH.
• The anabolic pathways for the synthesis of molecules are different from the catabolic ones, although they often share reversible reactions close to equilibrium. There is always some different way on each