Notes, summaries, assignments, exams, and exercises for Biology for Baccalaureate

The Building Blocks of Life: DNA and Nucleic Acids

DNA (Deoxyribonucleic Acid) is the main component of genetic material in most organisms. Together with RNA (Ribonucleic Acid), it forms the genetic material for some viruses. Both DNA and RNA belong to a group of molecules called nucleic acids.

Nucleotides: The Basic Units

Nucleotides are the smaller molecules that, when linked together in a repeating pattern, form the structure of nucleic acids like DNA.

The Structure of DNA

DNA has a super-compact, coiled form that allows it to fit inside cells. This coiled structure is organized into bodies called chromosomes.

Location of DNA in Cells

• Prokaryotes: The DNA is located in the cytoplasm.
• Eukaryotes: The DNA is found within the cell nucleus.

The Core

The Eukaryotic Cell Nucleus

General Characteristics

The cell nucleus is a membranous organelle that allows for the compartmentalization of DNA. It contains proteins called histones and acts as the cell's control center.

Number, Shape, Location, and Size

• Number: Most cells have a single nucleus. Some, like liver cells, can exceptionally have two. Multinucleated cells formed by cell fusion are called syncytia, while those formed by mitosis without cell division are called plasmodia.
• Shape, Location, and Size: The nucleus is typically located in the center of an animal cell. In plant cells, it is often pushed to one side by the large central vacuole.

Structure and Composition of the Nucleus

The nucleus can be observed in two main states: the interphase...

8.LA cell membrane: a structural unit
1.LA plasma membrane as a structural unit: the plasma membrane is a selective barrier, has the same structure in every cell, so q is called the unit membrane, lipid bilayer membranes as a unit. 2 composition of the plasma membrane: lipid and proteins. 2. Membrane Lipids 1: 1. Phospholipids: polar head and apolar tail, 2. Glycolipids: Only found in the outer face of the plasma membrane, 3.Esteroides: derivatives of cholesterol in animal cells. . 2.2 Membrane Proteins: 1. Integrals associated with the membrane bound x the van der Waals bond, 2. Perifericas: weak links. The membranes are asymmetric, q inner and outer faces have a different composition. 3 Models Membranes: fluid mosaic model. membrane fluidity...

Understanding Genetic Mutations

Random mutations are alterations of the genetic material (DNA in cells and DNA or RNA in viruses). They usually involve deficiencies and can sometimes become mortal. They are typically recessive and remain hidden. Mutations can occur in somatic cells (somatic mutations) or in the reproductive cells (germ mutations).

Mutations can occur spontaneously (natural mutation) or can be induced artificially (induced mutations).

Classification of Mutation Types

Based on the extent of the genetic material concerned, there are three main types of mutations:

• Gene mutations: Alterations of the nucleotide sequence of a gene.
• Chromosomal mutations: Alterations of the gene sequence within a chromosome.
• Genomic mutations: Alterations

Catalan Vowel Sounds

• [i] High front vowel (cim, i, i, i)
• [u] High back vowel (fum, u, u, u)
• [e] Mid-high front vowel (Fuster, e, e)
• [o] Mid-high back vowel (camí, o, o, o)
• [ɛ] Mid-low front vowel (palla, e, e)
• [ɔ] Mid-low back vowel (donut, o, o)
• [a] Low central vowel (pal, a, a)

Catalan Consonant Sounds

Bilabial and Dental Consonants

• [p] Voiceless bilabial plosive (stop, p, b in dissabte)
• [b] Voiced bilabial plosive (ball, b, v)
• [β] Voiced bilabial approximant (esbart, between vowels or specific consonants)
• [t] Voiceless dental plosive (tancar, t, d in quiet)
• [d] Voiced dental plosive (dau, d)
• [ð] Voiced dental approximant (ajudar, between vowels or specific consonants)

Velar and Nasal Consonants

• [k] Voiceless velar plosive (cama, c, g, qu)
• [g] Voiced

Eukaryotic Cell Reproduction:

Mitosis Phases:

1) Prophase:

Key occurrences:

• Disappearance of the nucleolus. The genes that synthesize 45S ribosomal RNA (rRNA) are located on chromosomes 13, 14, 15, 21, and 22 (in humans).
• The nuclear envelope disappears due to water entering the cytosol.
• The mitotic spindle forms from the centriolar microtubule organizing center.
• Duplication of the centrosome.

2) Metaphase:

Key occurrences:

• The spindle is completely formed.
• Chromosomes, which appeared as filaments in prophase, are now fully compacted and consist of two chromatids (each containing a DNA molecule).
• Kinetochore microtubules form and push the kinetochores on the chromosomes to align them in the equatorial plane of the cell.

3) Anaphase:

Key occurrences:

• Shortening

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

Major Theories of Biological Evolution

Lamarckism: Inheritance of Acquired Characteristics

Lamarckism is a theory of evolution proposing that species are the result of a long process of gradual change, progressing from simple to complex forms. Its key principles include:

• Tendency toward Improvement: All organisms strive for improvement through an inherent vital impulse.
• Law of Use and Disuse of Organs: Environmental changes necessitate an increase or a diminution in the use of certain organs. These organs develop more or less depending on their use.
• Function Creates the Organ: Environmental changes give rise to new needs, which can develop an organ shaped in response to that function.
• Inheritance of Acquired Characteristics: Changes acquired by an

Enzymatic Reactions: Fundamentals

Chemical reactions begin with the breaking of bonds between atoms in reactant molecules, followed by the formation of new links that yield product molecules.

Transition State

This state occurs when the bonds in the reactants are weakened or broken, but new bonds have not yet fully formed.

Activation Energy (Ea)

The energy required for reactants to reach the transition state, allowing the chemical reaction to proceed.

Spontaneous Reactions (Low Ea)

Reactions where the activation energy is very low, often obtained from the kinetic energy of molecules or incident light.

Non-Spontaneous Reactions (High Ea)

Reactions where the activation energy is so high that they require external heat to proceed.

The catalytic action lowers

Nervous Tissue

Nervous tissue cells produce responses sent to muscles and glands, leading to movements and secretions, respectively. These functions are performed through nerve impulses, which are common electrochemical signals. Nerve endings reach all body parts. Except for the simplest invertebrates, whose nervous tissue consists only of neurons, in other animals, it is also composed of a very different set of glial cells.

Neurons: Structure and Function

Neurons are the structural and functional units of the nervous system. They receive information from both the internal and external environments of an organism. Neurons have a high degree of specialization. Once mature, they cannot divide, and their numbers are definitively established from...