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

Cell Wall

Cell wall: A secreted outer layer on the external surface of the plasma membrane. Its functions include providing shape and rigidity to the cell (especially in plant cells), maintaining osmotic balance, uniting adjacent cells to allow fluid exchange and cellular communication, and serving as a barrier against pathogens.

Plasma Membrane

Plasma membrane: A thin shell that surrounds and separates the cytoplasm from the external environment. The cell contents therefore have a different composition than the outside environment. The plasma membrane regulates exchange with the exterior and is primarily formed by lipids and proteins.

Cytoplasm

Cytoplasm: Found in both prokaryotes and eukaryotes. It occupies the space between the nucleus (in eukaryotes)...

Bacteria

Bacteria possess a capsule composed of glucidic substances (uronic acid) or D-glutamine. This structure protects against leukocyte phagocytosis, regulates substance exchange, and facilitates adhesion to specific host tissues.

Cell Wall

The cell wall is composed of peptidoglycan (murein), specifically N-acetylmuramic acid (NAM) and N-acetylglucosamine (NAGA) linked by B(1-4) bonds. It protects against osmotic pressure, lysozyme, and penicillin antibiotics.

• Gram-positive: Thick, lipid-rich wall containing 90% peptidoglycan and teichoic acid.
• Gram-negative: Thin-walled, complex structure with 10% peptidoglycan and an outer membrane containing lipoproteins.

Plasma Membrane and Mesosomes

The plasma membrane limits and shapes the cell while regulating...

Cellular Digestion: Lysosomes and Phagocytosis

Lysosomes and Enzymatic Degradation

Lysosomes function by merging their enzymes with digestive molecules, pouring out their protein-based contents to degrade complex molecules.

Phagocytosis and Macrophage Activity

Macrophages, derived from monocytes in the blood, enter tissues to perform phagocytosis. The plasma membrane encloses a bacterium, coated in a protein called clathrin, forming a phagosome or endocytic vesicle.

• Once the bacterium is captured, the macrophage's lysosomes fuse with the phagocytic vesicle.
• Digestive and proteolytic enzymes, along with bactericidal substances, are released into the phagolysosome.
• The phagocytized organic material is broken down into usable molecules for the cell,

The Molecular Basis of Heredity

DNA as the Carrier Molecule of Genetic Information

DNA is the molecule that carries the genetic information determining the biological characteristics of living beings.

Requirements for Genetic Material

1. Stable: Must maintain its structure.
2. Capable of Replication: Must be able to replicate and produce accurate copies.
3. Transmissible: Must be transmitted from one generation to another.
4. Susceptible to Change: Must be able to undergo changes (mutations) to allow for genetic variety.

Historical Discoveries

• DNA was first discovered by Miescher.
• The study involving bacteria that cause pneumonia (two strains: R and S) showed that the S strain causes death, the R strain is non-offensive, and the R strain can mutate into the S strain.

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Recovering Endangered Species Through Cloning

It is said that through techniques related to cloning, endangered species could be recovered. How? The method to recover endangered species involves a technique called nuclear transfer. The process is as follows:

• 1. Obtain a differentiated cell from the animal you want to clone.
• 2. Extract an egg from a female donor.
• 3. Remove the egg nucleus.
• 4. Transfer the differentiated cell nucleus into the enucleated egg.
• 5. Grow the cell in a laboratory.
• 6. Once it reaches the morula stage, transfer it to the uterus.
• 7. After the gestation period, a new individual is born that is a clone of the donor that provided the nucleus.

Bioethics and Human Dignity

Bioethics is the branch of ethics that seeks to provide guiding...

Blastocyst Structure and Development

The blastocyst consists of the trophoblast (membrane), the blastocoel (cavity), and the embryoblast (inner cell mass), all in relation to the endometrium.

6. Causes of Multiple Births in Assisted Reproduction

In assisted reproduction, two to four embryos are often transferred to ensure better development. While it is expected that only one will implant, in approximately 30% of cases, more than one embryo implants, resulting in multiple pregnancies.

7. Cellular Differentiation and Specialization

Differentiation is the process that defines the structure and function of a specific cell, giving rise to specialized cells. While every cell contains the same genetic information, their potential narrows as development...

Plant Responses: Tropisms

Tropisms are directional growth responses by plants to external stimuli (anything that induces a response).

Types of Tropisms

• Phototropism: Response to a light stimulus. Can be positive (+) (towards light) or negative (-) (away from light).
• Geotropism: Response to the stimulus of gravity. Can be positive (+) (towards gravity) or negative (-) (away from gravity).
• Chemotropism: Response to a chemical substance stimulus.

Photosynthesis: The Process

Photosynthesis is a biochemical process unique to chlorophyll-containing organisms that requires light and occurs in chloroplasts. It releases O2 (oxygen) to the environment and consumes CO2 (carbon dioxide) from the environment (gas exchange with the atmosphere).

Nutrient Transport

Nucleic Acids and Nucleotide Components

Nucleic acids: macromolecules responsible for storing, transmitting, and expressing genetic information. Examples include DNA and RNA.

Nucleotides and Nucleosides

Nucleotides: composed of a phosphate group, a pentose sugar, and a nitrogenous base.

Nucleoside: the combination of a nitrogenous base and a pentose sugar; the glycosidic bond is between C1' of the sugar and the nitrogen atom of the base: N1 for pyrimidines and N9 for purines.

Nucleotide: a nucleoside with one or more phosphate groups (nucleoside phosphate esters).

Nitrogenous Bases

Nitrogenous base: two major types:

• Pyrimidines: C, T, U — single six-membered ring (Cytosine, Thymine, Uracil).
• Purines: A, G — fused six- and five-membered rings (Adenine,

Kingdom Protoctista: Eukaryotic Organisms

Protoctists are eukaryotic organisms with a nucleus containing genetic material and cytoplasmic organelles. They live in aquatic environments, humid areas, or internal liquids.

Protozoa: Heterotrophic Organisms

Protozoa are mobile, heterotrophic organisms. They primarily use asexual reproduction, although sexual phenomena exist for the exchange of genetic information between members. Some present forms of resistance, such as cysts and spores, to survive. They are classified into four phyla according to their locomotion and lifestyle:

• Sarcodina: They use pseudopods and are mostly free-living, such as amoebae.
• Flagellates: They use flagella; some are photosynthetic. An example is Trypanosoma gambiense.
• Ciliates: