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

Research on Alcohol and Fertility

Research supported by the National Institute of Child Health suggests that alcohol consumption may affect women's fertility.

• Infertility Risks: According to the passage, women who are infertile may consume more than seven cans of beer per week.
• Heavy Drinking: The passage indicates that women who drink heavily face an increased risk of infertility.

Cellular Structure and Function

Plasma Membrane and Organelles

• Selectively Permeable Membrane: Its function is to control what enters and leaves the cell.
• Phospholipid Bilayer: Contains polar and nonpolar ends, forming the plasma membrane.
• Endoplasmic Reticulum: Its structure facilitates the breakdown of chemical bonds.
• Golgi Apparatus: Producing proteins is not a function

The Electron Transport Chain: ATP Production

Inside the inner membrane of the mitochondria, there is a chain of electron carriers known as the electron transport chain (ETC). Electrons generated from oxidative reactions in earlier stages of cellular respiration pass along this chain.

NADH donates two electrons to the first carrier. As these electrons pass along the chain, they release energy from one carrier to the next. At three specific locations along the chain, sufficient energy is released to synthesize ATP via ATP synthase, an enzyme also located in the inner mitochondrial membrane.

FADH₂ also donates electrons, but at a later stage than NADH. Electrons from FADH₂ release enough energy at only two locations along the chain. This ATP production,...

75% of the world's population carries genetic variations inherited from Neanderthals, which may have resulted in improved brain function.

Approximately 40,000 years ago, hybridization between Neanderthals and modern humans allowed for the transfer of genes that enhanced our cognitive capabilities.

II.3. Evolution and Language

Our ability to generate language is rooted in brain structure. Studies of individuals with brain injuries provide essential information for locating the areas engaged in processing linguistic information.

The cortical areas that control speech are located in the left hemisphere. The two main language processing centers are:

• Broca's area: Responsible for speech coding and production.
• Wernicke's area: Dedicated to speech understanding.

Cell Differentiation and Diversity

Many are unicellular eukaryotic organisms, but the evolution of eukaryotic cells also led to the first multicellular organisms. The development of a multicellular organism is determined by the division, growth, and differentiation of cells.

Every cell in a multicellular organism comes from the splitting of a single initial cell and, therefore, all have the same genetic content. However, despite being genetically identical, not all proteins are equal. All body cells share many proteins, but others are specific to each cell type. This is because the control of protein synthesis is managed by regulating gene expression, which is influenced by various factors, including the modulation exerted by the cellular microenvironment....

The Internal Environment

The internal environment refers to the extracellular fluid within an organism. In simple invertebrates, the interstitial fluid acts as the plasma that bathes all cells. More complex invertebrates possess a transportation system—comprising the circulatory system and haemolymph—that delivers nutrients and oxygen to cells while removing waste products. In some invertebrates and all vertebrates, both interstitial fluid and blood plasma are present, alongside lymph circulating through the lymphatic system.

Circulatory System Functions

In simpler animals, nutrients and oxygen are absorbed directly from the interstitial plasma. In more complex animals, a specialized circulatory system transports these substances. In vertebrates,...

Fertilization

Fertilization is the fusion of male and female gametes, initiating the process of reproduction. It's important to note that fertilization of the egg is not immediate upon contact.

Human Fertilization

In humans, fertilization occurs when a sperm and egg unite in the fallopian tubes after sexual intercourse. Humans develop from the union of these two tiny cells. Mature eggs measure approximately 0.135 mm in diameter, while sperm are even smaller. Each ejaculation can contain between 120 and 600 million sperm. The union of these cells has the potential to create a new human being with extraordinary abilities.

Zygote

In biology, a zygote is the cell formed by the union of male and female gametes during sexual reproduction in organisms...

Allergies

An allergy is an altered and abnormal reaction of the organism to certain antigens, called allergens. Exaggerated reactions occur, which prove to be harmful upon repeated contact with the antigen; these are known as hypersensitivity or anaphylactic reactions.

Hypersensitivity reactions may occur immediately or be delayed. An animal subjected to an antigen of this type is called hypersensitive or allergic, while the antigen is known as an allergen or sensitizing agent.

Immediate Hypersensitivity Reactions

The first contact induces the formation of IgE-type immunoglobulins. Histamine and other mediators cause dilation and increased vascular permeability, resulting in edema. It also causes the contraction of smooth muscles in the bronchi....

Mutations

The genetic material of both cells (DNA) and viruses (DNA or RNA) may be altered at random. Typically, these disorders involve deficiencies that can become lethal. Changes in genetic material are called mutations.

Mutations are a source of variation within a population, meaning differences exist between individuals. Thus, when environmental conditions change, individuals with a particular mutation may be favored and have a greater chance of survival under new conditions compared to others. This is the basis of Natural Selection.

Mutations allow for the evolution of species and, therefore, the continuity of life over millions of years.

Classification of Mutations

Mutations may be classified according to two criteria: the type of cells involved...

Biological Life Cycle: Different Stages in a Living Being

Any biological life cycle can be divided into three parts:

• Early Stage: In most organisms, this begins with a single-cell stage.
• Development: This is the stage at which changes in size occur, as well as the differentiation of internal structures. Development ends when the new body has reached the characteristics of an adult.
• Reproduction: This is the phase in which organisms produce "breeding units" that will give rise to new individuals with the characteristics of the parent.

Cell Cycle

A set of phenomena of variable duration that occurs in the period that begins after cell division:

• Interphase: The period between two consecutive divisions.
• Division Phase: In which cell multiplication occurs,

Cellular Immune Response

The cellular immune response occurs against: microorganisms with intracellular growth and development (bacteria, fungi, viruses, protozoa); cells that are foreign to an organism from another individual (e.g., transplanted organs); and tumor cells. This response involves cytotoxic T cells and helper T cells, which collaborate with antigen-presenting macrophages.

Activation Process

Recognition of Antigen: T lymphocytes recognize antigens only when they are bound to MHC molecules on cell surfaces. When a macrophage detects an extracellular antigen, it activates, phagocytoses the antigen, and processes its proteins into linear peptides. These peptides bind to MHC class II molecules, which are then transported to the macrophage...