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

The Golgi Apparatus: Structure and Function

The Golgi Apparatus (GA) is found in all eukaryotic cells, essential in the transfer and packaging of products from the Endoplasmic Reticulum (ER), and involved in the synthesis of glycoproteins and mucopolysaccharides.

Distribution and Morphology

Its distribution depends on microtubules and motor proteins in secreting cells. In protein-secreting cells, the GA is located between the nucleus and the apical pole. In ganglion nerve cells, it is located around the nucleus with expansions to the cell surface. In Leydig cells, it is an ovoid mass located at one pole of the nucleus. In hepatocytes, it is distributed throughout the cytoplasm.

Its form differs from one cell to another and also within the same... Continue reading "Golgi Apparatus: Structure, Function, and Cellular Roles" »

Sensory Receptors

Sensory receptors are structures formed by nerve cells specialized to capture and transform stimuli into nerve impulses. The receptors are classified as:

• Chemoreceptors: Sensitive to chemicals.
• Mechanoreceptors: Sensitive to mechanical stimuli such as touch, pressure, sound, or gravity.
• Photoreceptors: Sensitive to light.
• Thermoreceptors: Sensitive to changes in temperature.
• Nociceptors: Sensitive to heavy pressure and responsible for pain.

Receptors can also be classified according to their location:

• Internal receptors: Located inside the body, particularly in the viscera. Responsible for collecting information from internal organs.
• External receptors: Located on the surface of the body. Responsible for collecting external stimuli

Milk and Dairy

Provides protein, vitamins, and calcium. Recommended serving: 250 mL of milk and 80g of dairy products.

Meat, Fish, and Eggs

Excellent sources of protein, vitamins, and iron. Recommended serving: 100g of meat and 150g of fish.

Legumes and Potatoes

Offer carbohydrates and protein. Recommended serving: 80g of pulses and 180g of potatoes.

Vegetables

Rich in vitamins, minerals, and fiber. Recommended serving: 125g.

Fruits

Packed with vitamins, fiber, minerals, and carbohydrates. Recommended serving: 125g.

Cereals and Grains

Provide carbohydrates. Recommended serving: 80g of pasta or rice, 50g of bread.

Fats, Oils, and Butter

Sources of lipids.

Carbohydrates

Nutrients that provide energy. Simple sugars, like glucose, are the primary source of cellular... Continue reading "Nutrition Essentials: Building a Balanced Diet" »

Cell Membrane Differentiations: Junctions

Some areas of the cell membrane may have specific adaptations, such as invaginations (e.g., microvilli) to increase surface area, or structures that form unions between cells. These junctions are essential for stabilizing tissues and providing mechanical adhesion. They are particularly prevalent in tissues under heavy strain, like epithelial tissues or heart muscle, where their primary function is to provide mechanical strength to the union. These junctions are classified into:

Adherens Junctions (Bands of Adhesion)

• These junctions are formed by transmembrane proteins that bind cells together.
• On the intracellular side, these proteins are associated with actin filaments, which are part of the cytoskeleton.

The Vital Role of Algae in Aquatic Life

Algae are a very large group of photosynthetic protoctists dependent on the aquatic environment. They all possess chlorophyll pigments, which give them their coloration, and their cells have a cell wall composed of cellulose. Algae colonize all aquatic habitats.

Ecological Importance and Reproduction

Through photosynthesis, algae form the first link in the food chain in ecosystems, discharging large amounts of O₂ into the atmosphere.

Reproduction is typically:

• Asexual: By binary fission or fragmentation.
• Sexual: Involving the interference of gametes and meiospores.

Most algae are microscopic, unicellular, or colonial, forming phytoplankton that floats in the upper, illuminated layers of the oceans and is of... Continue reading "Algae Classification: Types, Pigments, and Aquatic Role" »

Active Transport Across Cell Membranes

Active transport enables certain types of proteins within the cell membrane to move substances. This process consumes energy, typically provided by ATP molecules, allowing transport against a concentration gradient.

The Sodium-Potassium Pump

The sodium-potassium pump is a transmembrane protein that actively transports sodium ions (Na+) out of the cell and potassium ions (K+) into the cell. This counter-gradient transport exhibits ATPase activity, meaning it breaks down ATP to power the movement. For every three Na+ ions pumped out, two K+ ions are pumped in, consuming one ATP molecule. This action generates potential differences across the membrane, contributing to the membrane potential. This potential is... Continue reading "Cellular Membrane Transport and Nerve Signal Transmission" »

English Vowels

Short Vowels

• /ɪ/ (as in: sit): Front, unrounded, between close and half-close.
• /ɛ/ (as in: dead): Front, unrounded, between half-close and half-open.
• /æ/ (as in: cat): Front, unrounded, between half-open and open.
• /ʌ/ (as in: does): Between front and central, unrounded, half-open.
• /ɒ/ (as in: dog): Back, rounded, between half-open and open.
• /ʊ/ (as in: good): Between back and central, rounded, near-close.

Long Vowels

• /i:/ (as in: sweet): Unrounded, almost fully closed.
• /ɜ:/ (as in: bird): Central, unrounded, between half-close and half-open.
• /ɑ:/ (as in: fast): Almost fully back, unrounded, fully open.
• /ɔ:/ (as in: hawk): Back, rounded, between half-close and half-open.
• /u:/ (as in: shoe): Almost fully back, rounded, almost fully

Gene

A gene is an organized, linear sequence of nucleotides in a DNA molecule that contains the information necessary for the synthesis of a macromolecule with a specific cellular function.

Genome

The genome is the entire set of genes of an individual or species, contained in a haploid set of chromosomes.

Genotype

The genotype is the sum total of the genetic information contained in an organism's chromosomes.

Karyotype

A karyotype is a schematic, photograph, or drawing of the metaphase chromosomes of a cell, arranged according to their morphology and size. The karyotype is characteristic of each species, as is the number of chromosomes, and it represents all individuals of that species.

Natural Selection

Natural selection is the process by which species... Continue reading "Fundamental Genetics Terminology Explained" »

The Organization of the Human Body

Cellular and Tissue Hierarchy

A Cell is the basic structural and functional unit of living things.

• All human cells originate from a single initial cell called the Zygote.
• Although we originate from one cell, we develop several types of specialized cells.
• A group of specialized cells results in a Tissue.

From Tissue to Organism

A Tissue is a set of cells of the same type performing a specific function.

• The combination of various tissues forms an Organ.
• A combination of organs results in an Organ System or Apparatus.

We use the term System when there is only one predominant tissue type (e.g., Nervous System).

The union of all systems and apparatuses results in a Multicellular Organism.

Specific Roles of Human Tissues

Tissues... Continue reading "Human Body Structure and Function: Cells, Tissues, and Organ Systems" »

The Biosphere

The biosphere is the set of all living things on Earth.

Understanding Ecosystems

An ecosystem consists of interconnected components:

• Biotic Components: Living things that inhabit a particular place and interrelate.
• Abiotic Components: All the physical environmental conditions or non-living elements within the dwelling of living beings.

Relations Between Components: Living organisms in a specific location are adapted to certain conditions of their physical environment and, in turn, modify it.

Ecological Relationships

There are relationships between individuals of the same species and between different species, such as predation, parasitism, symbiosis, and commensalism.

Photosynthesis

Photosynthesis is the process of converting light energy... Continue reading "Understanding Earth's Living Systems" »