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

Blood Tissue

Blood is a tissue fluid that flows through the veins and arteries of all vertebrates. Its characteristic red color is due to the presence of the pigment hemoglobin in red blood cells.

Blood has a solid phase and a liquid phase, represented by the plasma. Its main function is the logistics of distribution and systematic integration.

Blood consists of formed elements and blood plasma.

Platelets

Platelets are small cell fragments (2-3 um in diameter), oval and without nuclei. They are produced in the bone marrow from the fragmentation of the cytoplasm of megakaryocytes. Their normal quantitative value is between 150,000 and 450,000 platelets per mm3.

They serve to plug injuries that could affect blood vessels. Platelets contribute to clot... Continue reading "Understanding Blood, Cartilage, Muscle, and Nervous Tissue" »

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.

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

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" »

Kinds of Amino Acids

Amino acids can be classified into several categories:

• Nonpolar:
  • Aliphatic
  • Aromatic
• Polar Uncharged
• Charged:
  • Acidic (Anionic)
  • Basic (Cationic)

Proteins: Building Blocks of Life

Proteins are biopolymers formed by molecular chains of 20 different amino acids, each with its own characteristics.

Protein Structures

Primary Structure

The primary structure is characterized by the specific composition of amino acids and their sequential order within the polypeptide chain.

Secondary Structure

The secondary structure refers to the folding of the primary structure due to the formation of hydrogen bonds between the -C=O group of one peptide bond and the -NH group of another. This results in the side chains (R groups) adopting specific spatial arrangements... Continue reading "Amino Acids and Protein Structures: A Comprehensive Look" »