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

Cellular Digestion: Monomers, Polymers, and Enzymes

Cells may absorb simple molecules (monomers). Monomers are scarce in nature. Typically, there are large molecules (polymers), where hundreds or thousands of simple molecules are joined together, forming foods. Digestion is a process where digestive enzymes break down the bonds between monomers, releasing free monomers. Digestive enzymes are specific to each polymer.

For example, amylase breaks down the links between glucose molecules in starch. Lipase separates fatty acids from glycerol in fats. Proteases break the links between amino acids in proteins, releasing them. The digestive system is essentially a tube. Food undergoes a series of transformations during its journey.

These actions are... Continue reading "Cellular Digestion: Monomers, Polymers, and Digestive Enzymes" »

Regulation of Gene Expression

Cells do not continuously synthesize proteins, which could result in metabolic chaos. There must be a regulation. Jacob and Monod devised a model for gene regulation in bacteria called Operon. An operon is a set of genes on the chromosome, fairly close together, that encode proteins involved in related metabolic processes. In each operon, there are two classes of genes:

• Structural genes

  (z, A) that code for the synthesis of proteins in a given process.

• Regulator gene

  (I) that codes for the synthesis of a repressor protein, which controls the expression of structural genes.

There are also two regions close to these genes whose base sequences influence regulation:

• The promoter (P)

  Next to the structural genes, this is the

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

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" »

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

Medical and Demographic Notes: Part 1

Social Sciences Definitions

Demographics

Population sciences studying their geographical distribution.

Statistics

Science where knowledge of a phenomenon is based on measurement results.

Economy

Studies the ways in which individuals and society use obtained resources and services.

Psychology

Science that studies psychic functions in normal and abnormal aspects.

Digestive System Facts

Digestion

The splitting of complex food materials.

Pylorus Statement (Evaluation)

FALSE: The pylorus is the passage that allows food from the esophagus to the stomach.

Small Intestine Components (Evaluation)

FALSE: The duodenum, jejunum, and appendix are located in the small intestine. (Note: Duodenum and jejunum are parts of the small intestine;