Notes, abstracts, papers, exams and problems of Biology

Methods for Studying Cellular Composition and Function

Biochemical Methods: To understand the composition and function of cellular structures.

• Cell Fractionation: Homogenization and deep freezing.
• Chromatography and Electrophoresis: Used to separate macromolecules.

Isotopic Methods: Incorporating radioactive isotopes into molecules to track their evolution within the cell, followed by autoradiography. Fluorescent markers are also used.

Cytosol and Cytoplasmic Inclusions

Cytosol: The internal liquid medium composed of water, salts, organic molecules, and macromolecules.

Cytoplasmic Inclusions: Accumulations of substances in eukaryotic and prokaryotic cells. Functions include reserve storage (e.g., glycogen and fat in animal cells, vegetable oils and... Continue reading "Cellular Structures: Composition, Function, and Methods" »

Apoptosis: Cellular Suicide

Apoptosis, or programmed cell death, is a crucial mechanism in multicellular organisms. It plays a vital role in development, removing unnecessary cells during embryonic stages (e.g., interdigital tissue), and in adulthood, eliminating damaged or potentially harmful cells. This process involves a series of changes leading to cell death. The cell shrinks, loses water, and forms bubble-like protrusions. The nucleus fragments, and the resulting apoptotic bodies are ingested by neighboring cells. Apoptosis is triggered by signals that activate endonucleases, which in turn produce lethal proteins, hydrolases, and proteases.

The Interphase Nucleus

The interphase nucleus houses the genetic material and controls all cellular... Continue reading "Apoptosis: Cellular Suicide Mechanisms and Nuclear Components" »

Molecular Level: Chemical Composition of Living Beings

1.1. Bioelements

Bioelements are all chemical elements that, in greater or lesser proportions, form living matter. There are six that qualify as the primary bioelements: C (Carbon), H (Hydrogen), O (Oxygen), N (Nitrogen), P (Phosphorus), and S (Sulfur). These make up most of living matter.

Others are involved in smaller quantities but are still essential for cellular metabolism. These are called secondary bioelements, which include Mg (Magnesium), Ca (Calcium), K (Potassium), Na (Sodium), and Cl (Chlorine).

Even smaller quantities of other elements are essential for living beings. These are called trace elements, and their lack causes serious illness and even death. Examples include Fe (Iron)... Continue reading "Chemical Composition of Living Beings: Bioelements and Biomolecules" »

Nutrient Transport

Ascent of Sap

Gross: The movement of water and minerals from the roots to the leaves via the stem's xylem. Water flows upward due to two factors:

• Transpiration Pull: Water loss during photosynthesis and transpiration creates negative pressure.
• Root Pressure: The lower osmotic concentration in the soil compared to the root interior drives water flow.

Gas Exchange

Plants have a lower respiratory rate than animals and require less oxygen. Gas exchange occurs through stomata, facilitated by the enzyme carbonic anhydrase:

H₂O + CO₂ ↔ H₂CO₃ ↔ H⁺ + HCO₃^-

Increased H⁺ concentration lowers pH, activating an enzyme that breaks down starch into glucose.

Photosynthesis

Photosynthesis occurs in chloroplasts, where chlorophyll and carotenoids... Continue reading "Plant Biology: Nutrition, Growth & Reproduction" »

Infectious Diseases

Bacteria: Single-celled organisms that can cause diseases through toxins.

Mushrooms: Unicellular or multicellular organisms causing fungal infections, thriving in moist environments.

Protozoa: Single-celled parasites found in aquatic environments.

Viruses: Non-cellular entities requiring a host cell to reproduce.

Modes of Transmission

Direct contact, inanimate objects, contaminated water or food, airborne pathogens, animal transmitters.

Internal Defenses

Nonspecific: Phagocytes acting against any microorganism.

Specific: Lymphocytes producing antibodies against specific microorganisms.

Noninfectious Diseases

Body System Dysfunctions

Respiratory: Asthma, chronic bronchitis.

Bones and Joints: Osteoarthritis, osteoporosis, cancer.

Deficiencies

Caused... Continue reading "Understanding Human Health: Infections and Body Functions" »

Cell: Basic Unit of Life

1_Celula: The fundamental unit of structure and function in living organisms, forming the lower portion of the material that meets the functional vitales.

2_Difference: Variations arise from differing degrees of specialization. While all cells share a similar chemical composition and structure, some remain undifferentiated, specializing for specific functions.

3_Structures: All cells possess a plasma membrane, a cytoplasmic matrix, and genetic material, enabling self-replication and transmission of species characteristics.

Cell Types: Eukaryotic and Prokaryotic

4_Eukaryotic: Cells with a true nucleus and various organelles enclosed by a plasma membrane. Prokaryotic: Cells lacking a nucleus, with the plasma membrane as the... Continue reading "Cell Structure and Function: Eukaryotes vs. Prokaryotes" »

Cell Cycle and Division

The cell cycle includes the period from when a cell is formed until it divides, resulting in new cells. It has two main stages: Interphase (initial, long duration) and Division (final, short, resulting in two daughter cells).

1. Interphase: This stage includes DNA duplication and consists of three phases: G1, S, and G2. During interphase, the cell nucleus is called the interphase nucleus.

• G1 Phase: mRNA and protein synthesis occurs. The cell has one diplosome (two centrioles). At the end of G1, there is a restriction point (R point), after which the cell is committed to completing S, G2, and M phases.
• S Phase: DNA replication occurs once the cell has reached sufficient size, synthesized essential proteins, and has enough

Internal Environment

The internal environment is the set of surrounding cells and liquids of an organism. Cells extract the nutrients and oxygen they need from it, and discharge waste and carbon dioxide produced during metabolism. The interstitial fluid originates from blood that has been filtered through the thin walls of blood capillaries.

Homeostasis

Homeostasis is a set of mechanisms whose mission is to maintain a constant internal environment, meaning that its properties do not vary. The maintenance of these properties is called homeostasis, and the task is performed by different devices and systems of the organism.

Veins and Arteries

Arteries and veins differ in that arteries carry blood from the heart to the various organs of the body, and... Continue reading "Understanding the Human Body: Internal Environment and Blood Circulation" »

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

Protein Structure, Properties, and Functions

Quaternary structure: The association of multiple polypeptide chains, resulting in a cluster of subunits. Only some proteins have this level. Formed by several polypeptide chains, each unit is called a protomer.

Properties of proteins:

1. Solubility: Proteins have high dispersion and form colloidal solutions.
2. Denaturation: Increased temperature or pH changes alter the links that stabilize the protein structure, causing it to lose its biological activity.
3. Specificity: Each species has its own unique set of proteins, and there is even individual specificity, which can lead to transplant rejections and allergies.
4. Buffer capacity: Proteins, being amphoteric, can help neutralize pH variations.

Classification of