Notes, summaries, assignments, exams, and problems for Biology

Essential Health Concepts

Public health encompasses the activities and services aimed at promoting, protecting, and restoring the health of populations.

The Immune System

The immune system is a complex network of organs, cells, and molecules that defends the body against infectious agents and abnormal cells, including cancerous cells.

Diagnosis

Diagnosis is the process of identifying a disease and determining its primary cause.

Chemotherapy

Chemotherapy involves the use of chemical drugs to combat disease.

Disinfectants and Antiseptics

• Disinfectants: Substances used to destroy microorganisms on objects.
• Antiseptics: Substances used to eliminate microorganisms that colonize tissues, such as skin.

Antibiotics

Antibiotics are chemicals that destroy or inhibit... Continue reading "Essential Health Concepts: Public Health, Immunity, and Treatments" »

Thin Filament Structure

The thin filament is composed of three types of proteins:

• Actin: Forms helical rolls.
• Troponin: Binds to actin and tropomyosin. It is formed by three subunits:
  • C: Calcium-binding unit.
  • I: Calcium-inhibiting unit.
  • T: Troponin-tropomyosin union unit.
• Tropomyosin: Covers the active binding sites on actin for myosin.

Muscle Adaptation Mechanisms

Hypertrophy

An increase in the size of muscle fibers, therefore increasing muscle size.

Hyperplasia

An increase in the number of muscle fibers, not their size. This has been observed in animals like cats.

Atrophy

A reduction in the size of the muscle. It is typically caused by lack of muscle use and protein loss.

Autogenic Inhibition Explained

Autogenic inhibition is a reflex that causes muscles... Continue reading "Muscle Function, Adaptation & Energy Systems" »

Understanding Living Organisms: Core Concepts

Origin and Development of Life

• Animals born from eggs are called oviparous.
• Those that arise from the mother's body are called viviparous.
• Plants may arise from seeds or spores.
• Fungi are always born from spores.

Nutrition: How Organisms Obtain Energy

Plants are living beings that possess chlorophyll, which enables them to make simple substances like water, carbon dioxide, and some minerals. This process is called photosynthesis and is performed using solar light.

Organisms obtain food in various ways:

• Herbivores eat plants.
• Carnivores eat animals.
• Omnivores eat both plants and animals.

Respiration

All living organisms breathe to sustain life processes.

Reproduction Strategies

The primary form of reproduction... Continue reading "Understanding Living Organisms: From Cells to Kingdoms" »

The environment is everything that surrounds us. It can therefore be an urban environment or, more broadly, a natural environment. It is generated by the natural world and influenced by humans. This applies to both transformed and non-transformed environments.

What is Ecology?

The science that studies ecosystems is **ecology** (from Greek: *oikos* 'house' + *logos* 'study'), meaning the study of the 'living house' or ecosystems. Ecologists seek to explain phenomena that occur in the environment.

Earth's Spheres and Ecosystems

On Earth, there are several layers: the atmosphere, hydrosphere, and lithosphere. There are broader terms that encompass the Earth as a whole: the biosphere, ecosphere, and ecosystem.

• Biosphere

  The part of the planet that contains

The Relations Function

Living beings perceive information from the external environment and their body. This information consists of stimuli that can be positive or negative. This process occurs in three steps:

• Reception of the stimulus: By specialized structures or bodies.
• Integration of information: Information is processed, and a response is generated through the nervous system.
• Execution of the answer: This is carried out through muscle movements and physiological changes caused by hormones.

Function of Reproduction

• Asexual: Requires only one individual to produce more descendants.
• Sexual: Needs the intervention of two individuals, called germ cells, which are specialized.

Diversity and Classification of Living Things

The variety of creatures inhabiting... Continue reading "Living Organisms: Functions, Diversity, and Classification" »

Mendel's Experiments with Pea Plants

Mendelian genetics refers to the laws of inheritance discovered by Gregor Mendel through his work with pea plants. He studied specific characters, including:

• Seed color (Yellow vs. Green)
• Seed surface (Smooth vs. Wrinkled - implied, though not explicitly stated in the original text)

In his first cross, Mendel bred purebred yellow-seeded plants with purebred green-seeded plants. The resulting first filial generation (F1) consisted of 100% plants with yellow seeds.

Conclusions from Initial Crosses

• Each individual carries two hereditary factors (now called alleles) for each character, one inherited from each parent.
• In an individual carrying alleles for both yellow and green seeds, the yellow allele dominates over

1. Inorganic Chemical Compounds in Cellular Reactions

Electrolytes are inorganic chemical compounds necessary for cellular reactions.

2. Collecting Tube Reabsorption

Chloride reabsorption in the collecting tube: 1%

3. Urinary Potassium Excretion

Urinary excretion of potassium: 15%

4. Medullary Osmotic Gradient

The countercurrent multiplier mechanism in the loop of Henle creates the medullary osmotic gradient.

5. Urine Acidification

Urine acidification occurs in the collecting tube.

6. Hormonal Control of Blood Pressure

Renin converts angiotensin I in the hormonal control of blood pressure.

7. Glomerular Filtration

Capillary hydrostatic and colloid osmotic pressures determine glomerular filtration volume.

8. Smooth Muscle in Digestive Tract

Longitudinal and... Continue reading "Renal and Digestive Physiology: Cellular Processes and Regulation" »

Nucleic Acid Building Blocks

Nucleoside Structure

The nucleoside core is formed by a pentose sugar joined to a nucleobase via an N-glycosidic link. This bond occurs between carbon 1 (C1) of the pentose and nitrogen 1 (N1) of pyrimidine bases or nitrogen 9 (N9) of purine bases, with the loss of a water molecule.

Nucleotide Structure

A nucleotide is a nucleoside with one or more phosphate groups attached.

Phosphate Ester Bond

The phosphate ester bond links the C5 of the pentose sugar to a phosphate group (PO₄^3-).

Nucleotide Linkage: The Phosphodiester Bond

The phosphodiester bond is an esterification located between the phosphate group at position 5' of one nucleotide and the hydroxyl group on carbon 3' of another nucleotide. This forms the backbone... Continue reading "Nucleic Acids: DNA and RNA Molecular Structure and Roles" »

Main Characteristics of DNA Replication

• Semiconservative: Each new DNA molecule is formed by an original DNA strand and one newly synthesized strand. Synthesis occurs by the addition of mononucleotides in the 5' to 3' direction.
• Bidirectional: From a single origin, two replication forks move in opposite directions. In bacterial viruses, there is a single starting point, while in eukaryotes, there are several called replicons. Each DNA fragment is replicated from a single origin.
• Semi-discontinuous: In one strand (the leading strand), fragments are synthesized continuously. In the other strand (the lagging strand), synthesis is discontinuous, meaning small fragments are synthesized separately and then joined together. These are known as Okazaki

DNA Replication: A Detailed Explanation

DNA replication is a fundamental process in all living organisms. It ensures the accurate duplication of the genome before cell division. This process involves several key steps and enzymes.

1. Unwinding the DNA Helix

The first step involves unwinding and opening the DNA helix. This process, also known as DNA despiralization, separates the two DNA strands. Specific enzymes, including helicases, attach to the DNA strands and unwind them. Topoisomerases prevent the formation of knots during this unwinding process.

Replication begins at specific points of origin. In prokaryotes, there is typically one point of origin, while eukaryotes have multiple origins due to their larger DNA content. Helicases break the... Continue reading "Understanding DNA Replication: A Comprehensive Look" »