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

Photosynthesis: Energy from Sunlight

Photosynthesis is the process by which organisms, typically plants, create energy-rich organic substances from inorganic substances, using sunlight as an energy source.

Photosynthesis Reaction and Phases

It is an anabolic process that takes place in chloroplasts. In this process, water, carbon dioxide, and minerals are transformed into organic compounds (glucose).

For photosynthesis to occur, it requires an energy source from sunlight. This light energy is captured by a pigment present in chloroplasts, called chlorophyll. The general equation is:

CO₂ + H₂O + Light Energy + Minerals → Glucose + O₂

Photosynthesis has two main phases:

• Light-dependent phase: Energy captured from the sun is converted into chemical

Meiosis

2-step cellular division of primitive germ cells (46, diploid)  mature germ cells (23, haploid)

Lyon Hypothesis

genetic activity of 1 of the X chromo in each cell of a female embryo; when X chromo in female is inactivated = Barr body forms; X chrome dispersed into nucleus; gross abnormalities

Trisomy 21

Down Syndrome; 3 identical chromo at the same allele; most frequent; fissured tongue; macroglossia, slanted eyes, low IQ, hypodontia

Trisomy 13

poor prognosis; 3 chrom on 13; bilateral cleft lip/palate, microphthalmia/anopthalmia

Karyotype

a photographic representation of of a person’s chromosomal make-up; gross abnormalities

Turner Syndrome

lack X chromosome from father; no Barr bodies on smear; webbed neck, short statue

Klinefelter

extra X chrom... Continue reading "Oral Pathology and Systemic Conditions" »

Simple and Composite Foods: Essential Nutrients

Understanding Simple and Composite Foods

Simple foods consist of a single component. Examples include salt and olive oil. Composite foods (which make up the majority of foods) contain water, minerals (inorganic substances), and organic substances such as glucides, lipids, proteins, and vitamins.

Water and Mineral Salts

Water is an inorganic substance crucial for life processes. Our body is approximately 65% water. Organs and tissues with high metabolic activity, like the heart and brain, have the highest water content. Organs and tissues with lower metabolic activity, such as bone and adipose tissue, have a lower water proportion.

Intake: We obtain water through water-rich foods and beverages. Properties:

Energy and Matter in Ecosystems

How Does Energy Flow?

Ecosystems maintain an open flow of energy because producers, like plants, transform solar energy into chemical energy through photosynthesis. This energy is then used and degraded as it passes through the trophic levels of consumers (herbivores, carnivores) and decomposers (bacteria, fungi). Ultimately, the activities of all living organisms in the ecosystem generate thermal energy as heat, which dissipates into the environment.

This energy flow is unidirectional because the solar energy entering the ecosystem is transformed into chemical energy within living organisms and eventually lost as heat.

Key Points:

• Typically, no more than 10% of the energy from one trophic level is transferred to

Cellular Components and Their Functions

Lysosome

Features: Lysosomes are vesicles containing substances that digest nutrients.

Function: They break down more complex substances into simpler ones.

Centrosomes

Features: Centrosomes are located near the nucleus and consist of two perpendicular cylinders formed by proteins.

Function: They are involved in cell division and the formation of cilia and flagella.

Understanding Health and Disease

Disease

Definition: A disease occurs when a part of the body is altered and can no longer perform its function properly, leading to dysfunction.

Health

Definition: The World Health Organization (WHO) defines health as a state of complete physical, mental, and social well-being, not merely the absence of disease.

Symptoms

When... Continue reading "Cellular Biology and Human Health: Diseases and Prevention" »

Cell Structure and Function

Key Components of the Cell

The cell is the basic unit of life, and it is composed of several essential components:

• Cell Membrane: A thin layer surrounding the cell, forming the boundary between the cell and its surrounding environment, the extracellular medium.
• Cytoplasm: The substance of the cell, excluding the nucleus. It is formed by a water-rich solution in which a variety of structures, called organelles, are dispersed. These organelles are responsible for carrying out the different functions of the cell.
• Cellular Nucleus: A structure that is usually spherical and located in the center of the cell. It contains the genetic material with the necessary information to direct and control cellular functions.
• Mitochondria:

Organism Response to Stimuli

Organisms have systems that allow them to collect information from within and outside their bodies and respond to changes that occur.

Key Concepts

• Stimulus: Any factor capable of triggering a response in an organism. This can be physical or chemical.
• Response: The action an organism performs as a reaction to the stimulus received.
• Sensation: The ability to receive stimuli (e.g., sight, hearing, touch, smell, and taste).
• Perception: A function that requires the interpretation of a stimulus by the brain and the elaboration of complex responses.

Sense Organs and Receptors

Sense organs are responsible for receiving environmental stimuli. Receptors are cells within these organs that capture and transmit the stimulus to the brain... Continue reading "Organism Response to Stimuli & Coordination" »

Basic Concepts of Genetics

Genetics studies the transmission of hereditary traits.

• Gene: A fragment of DNA containing the information needed to make proteins or to determine a specific characteristic.
• Genome: The complete set of genes from an organism.
• Genotype: The genetic makeup of an organism (e.g., represented by letters like AA, Aa, aa).
• Phenotype: The observable traits or characteristics resulting from the genotype and its interaction with the environment.

Mendelian Genetics Principles

Mendelian genetics applies the methodology practiced by Gregor Mendel, which involves making crosses between individuals with known phenotypes to infer their genotypes.

Mendel's Laws of Inheritance

Mendel formulated three fundamental laws governing the transmission... Continue reading "Genetics Fundamentals: Mendelian Laws & Human Conditions" »

1. Functions of the Digestive System

Digestion and absorption of nutrients.

2. Elements Forming the Small Intestine

Duodenum, jejunum, and ileum.

3. Valves of the Stomach

The stomach has the pyloric valve, and the duodenum connects with the esophagus via the cardia.

4. Portions of the Large Intestine

The large intestine is divided into the following parts:

• The first portion consists of a blind sac.
• The second part is called the ascending colon.
• The third portion is the transverse colon.
• The fourth part is the descending colon.
• Finally, the sigmoid colon, rectum, and anus.

5. Intestinal Loops

Intestinal loops are folds that form the small intestine to adapt to the available space in the abdomen.

6. Gastrointestinal Annexes

These include the parotid salivary... Continue reading "Digestive System: Functions, Organs, and Common Conditions" »

Vertebrate Circulatory Systems

Simple Closed Circulation (Single Circuit)

Fishes

The heart in fishes has one atrium and one ventricle. From the ventricle, deoxygenated blood is pumped to the branchial artery, which branches into arteries supplying the gill lamellae. In the gills, blood becomes oxygenated. This oxygenated blood is then collected by efferent gill arteries that converge into the aortic root and then the dorsal aorta, which distributes it to the body tissues. This is a single-circuit system.

Closed Double Incomplete Circulation

Amphibians

The heart is composed of two atria and one ventricle. The two atria are separated by an interatrial septum. The right atrium receives deoxygenated blood from the body, and the left atrium receives oxygenated... Continue reading "Animal Circulatory Systems: Vertebrates & Invertebrates" »