Notes, abstracts, papers, exams and problems of Biology

Interaction and Homeostasis

Interaction includes a series of processes whose object is to adapt the body to changing conditions in the internal and external environment. It connects and coordinates the different parts of our body so that they work together.

Homeostasis is the process that maintains the body's stability when there are changes in the internal environment. This process works as a feedback device, meaning that when a variation is detected in a particular element, a series of mechanisms in the body start up to make the variation return to its normal state.

Systems Participating in the Interaction Process

• Sensory Organs: Capture the stimulus, which is transformed into a nerve impulse and transmitted to the nervous system.
• Nervous System:

Steroid Hormones

Steroid hormones are a type of hormone consisting of four rings made of carbon atoms. They are derived from cholesterol and have three primary modes of action:

• Binding to membrane receptors
• Binding to and activating proteins in the cytoplasm
• Acting on receptors linked to chromosomes

Sex Hormones

Gonadal steroid hormones are produced by the gonads, which include the ovaries and testes. These hormones include:

• Androgens (e.g., testosterone, dihydrotestosterone)
• Estrogens
• Progesterone

It is important to note that gonads can produce both types of hormones, with the aromatase enzyme mediating conversions between them.

Organizing Effects of Sex Hormones

Organizing effects refer to the hormonal effects on the brain and genitals that occur during... Continue reading "Steroid and Sex Hormones: Organizing and Activating Effects" »

Saturated Fats

Carbon atoms fully saturated with hydrogen atoms. (meats, animal fats, lard, whole milk, butter, cheese, ice cream, coconut oil, palm oil)

Trans Fatty Acids

Solidified fat forms by adding hydrogen to MUFA and PUFA to increase shelf life

Osteoporosis

Condition of softening, deterioration, or loss of bone mineral density that leads to disability, bone fractures, and even death from medical complications

Protein

Classification for nutrients consisting of complex organic compounds containing nitrogen and forms by combinations of amino acids; the main substances used in the body to build and repair tissues

Amino Acids

Chemical compounds that contain nitrogen, carbon, hydrogen and oxygen; the basic building blocks the body uses to build different... Continue reading "Understanding Nutrition: Fats, Proteins, Vitamins, and Minerals" »

1. The Circulatory System

The circulatory system carries substances via the blood, which circulates through the blood vessels and is pumped by the heart.

1.1 Blood

Human blood is a thick, red liquid composed of plasma and blood cells.

Types of Blood Cells:

• Red Blood Cells: Small cells without a nucleus. They are the most numerous in the body and contain iron. This protein helps transport oxygen and carbon dioxide.
• White Blood Cells: Larger and less numerous. They defend our bodies against pathogens and tumor cells.
• Platelets: Are not true cells, but pieces of cytoplasm. They help our bodies to clot.

The Functions of Blood:

• Transport Substances: Transport nutrients and waste substances.
• Regulates Body Temperature: Maintain body temperature by distributing

Nerve Impulse

A stimulus occurs, sensory receptors detect the stimulus, sensory neurons receive the information and transmit it to the central nervous system (CNS). The CNS receives the information and a response is decided. Motor neurons transmit the response to the effectors, which carry out the response. The response is given through motor responses carried out by muscles and secretory responses carried out by glands.

Nervous System

The nervous system receives and transmits information rapidly through electrical impulses. Information is transmitted through sensory neurons and processed in the CNS.

Endocrine System

The endocrine system consists of glands that secrete hormones. These hormones are carried in the blood to the cells of the target... Continue reading "Understanding the Nervous and Endocrine Systems" »

Nucleic Acid Structure and Function

• Nucleoside: A part of a nucleotide made up of one sugar (ribose or deoxyribose) and one nitrogenous base (pyrimidine or purine) joined together by N-glycosidic bonds.
• Nucleotide: Simple molecules that form large molecules called nucleic acids. It is formed by a nitrogenous base, sugar, and three phosphate groups.
• Chromatin: Bundles of DNA and proteins; the normal state of the genetic material during interphase.
• Chromosome: Structures formed by the condensation of chromatin that appear when the cell is about to divide.
• Centromere: A bond that joins two sister chromatids; it's where the microtubules are attached to the chromosome during the division process.
• Telomere: The end of the arms of a chromosome, which prevents

• Many carbon-based molecules are made of many small subunits bonded together.
• Monomers are the individual subunits.
• Polymers are made of many monomers.
• Four main types of carbon-based molecules are found in living things.
• Carbohydrates are made of carbon, hydrogen, and oxygen. Include sugars and starches. Carbohydrates can be broken down to provide energy for cells. Some carbohydrates are part of cell structure.
• Monosaccharides are simple sugars.
• Polysaccharides include starches, cellulose, and glycogen.
• Polymer (starch)
• Starch is a polymer of glucose monomers that often has a branched structure.
• Polymer (cellulose)
• Cellulose is a polymer of glucose monomers that has a straight, rigid structure
• Many contain carbon chains called fatty acids.
• Fats and oils

Gene and Alleles

• A gene is a unit of heredity that occupies a specific locus on a chromosome.
• A locus is a specific location on a chromosome where a gene is located.
• Alleles are different forms of a gene that occupy the same locus on homologous chromosomes.

Hardy-Weinberg Equilibrium

• The Hardy-Weinberg equilibrium is a population genetics model that describes the frequencies of alleles and genotypes in a population that is not evolving.
• The five conditions for Hardy-Weinberg equilibrium are:
  1. No mutation
  2. No gene flow
  3. No genetic drift
  4. Random mating
  5. No natural selection

Population Genetics

• Population genetics is the study of the genetic variation within populations.
• Genetic variation is the presence of different alleles in a population.
• The gene pool is the