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

The Human Respiratory System

By Marco Rios

Ventilation: Air Movement in the Lungs

Pulmonary Ventilation

The total volume of air breathed in and out per minute.

Alveolar Ventilation

The volume of air exchanged between the atmosphere and the alveoli per minute.

The Lungs: Core Organs of Respiration

A pair of organs consisting of the lower part of the respiratory airways, pulmonary circulation, and connective tissue.

Pleural Sacs and Cavity

Thin, fluid-filled membranes that enclose the lungs. The space between the pair is known as the pleural cavity.

Alveolar Cell Types

Type I Cells

Form the walls of the alveoli, facilitating gas exchange.

Type II Cells

Secrete pulmonary surfactant.

Pulmonary Surfactant

A substance that reduces the surface tension of water inside... Continue reading "Human Respiratory System Functions" »

Carbohydrates: Structure and Classification

Classification

• Monosaccharides: Single sugar unit (e.g., glucose, fructose).
• Disaccharides: Two sugar units joined (e.g., sucrose = glucose + fructose).
• Polysaccharides: Many sugar units linked (e.g., starch, glycogen).

Aldose vs. Ketose

• Aldose: Contains an aldehyde (-CHO) group (e.g., glucose).
• Ketose: Contains a ketone (>C=O) group (e.g., fructose).
• Number of Carbons: Triose (3C), Tetrose (4C), Pentose (5C), Hexose (6C).

Structural vs. Stereoisomers

• Structural Isomers: Same molecular formula, different bonding patterns or structure.
• Stereoisomers: Same connectivity, different spatial arrangement of atoms.

Chiral Carbons

• Chiral Carbon: A carbon atom bonded to four different groups, creating an asymmetric center.

Most living things obtain their energy either directly or indirectly from the energy of sunlight captured through photosynthesis.

Photosynthesis in 2 Stages

1. Pigments in the leaves' cells (chlorophyll) capture or absorb the sun's energy, which is used to power the second stage. The leaf cells also need water (absorbed through roots) and carbon dioxide (that enters through small openings on the undersides of leaves called stomata).
2. Inside the chloroplasts, water and carbon dioxide are transformed into glucose and oxygen. Plants use glucose for food and store what they don't need as starch (energy for later use) and cellulose (that makes up the cell walls). Oxygen and water exit the leaf through the stomata.

Stomata

Carbon dioxide enters the plant... Continue reading "Photosynthesis and Cellular Respiration in Plants" »

Understanding DNA Analysis Techniques

Restriction Enzymes: Cutting DNA with Precision

Role: Restriction enzymes cut foreign DNA into pieces to prevent infection.

Mechanism: Special proteins recognize specific DNA sequences (restriction sites) and cut at those locations. Bacteria protect their own DNA from self-cleavage using methylation.

Example: EcoRI

EcoRI recognizes the sequence GAATTC and cuts between G and A. This creates "sticky ends" (overhangs) like G- and AATT, which help join DNA fragments.

DNA Fragmentation and Gel Electrophoresis

DNA is cut into fragments using restriction enzymes. These fragments are then sorted by size using gel electrophoresis.

• Shorter fragments travel farther and faster in the gel.
• DNA fragments are stained for visibility,

Echinoderms

Phylum: Echinodermata

• Sea stars (starfish)
• Sea urchins
• Sand dollars
• Sea cucumbers
• Brittle stars

Key Features:

• Symmetry: Larvae: Bilateral; Adults: Pentaradial
• Body Covering: Spiny skin, endoskeleton made of calcium carbonate
• Movement: Tube feet powered by water vascular system
• Nervous System: No brain; nerve ring with radial nerves
• Circulation: Water vascular system (no true circulatory system)
• Respiration: Diffusion via tube feet or skin gills
• Reproduction: Mostly external fertilization; can regenerate lost parts
• Habitat: Marine only (no freshwater/terrestrial species)

Water Vascular System

A hydraulic system for movement, feeding, and respiration.

Frequently Asked Questions

1. What type of symmetry do adult echinoderms have? Pentaradial symmetry
2. Which

Frog Embryology: Developmental Stages

Frogs reproduce through external fertilization, where the female lays eggs in water, and the male releases sperm over them. Fertilization occurs in the animal hemisphere of the egg. This process forms a diploid zygote. The point of sperm entry determines the gray crescent, which helps in the later development of the body axis.

1. Cleavage: Early Cell Division

The zygote undergoes holoblastic, unequal, and radial cleavage. The first two cleavages are vertical, forming four equal blastomeres. The third cleavage is horizontal but displaced towards the animal pole, resulting in smaller cells (micromeres) in the animal pole and larger cells (macromeres) in the vegetal pole. These divisions continue to form a morula,... Continue reading "Key Biological Systems & Mechanisms Explained" »

Human Nutrition: The Digestive System

Human nutrition involves several key systems: digestive, respiratory, circulatory, and excretory.

Preparation for Digestion

This phase consists of three main parts:

Insalivation

Insalivation involves saliva, a watery substance containing amylase enzymes that break down simple carbohydrates. Saliva is produced in three salivary glands: sublingual, submandibular, and parotid. The tongue, a muscular organ covered in taste buds, helps mix food with saliva, allowing us to taste food.

Mastication

Mastication consists of breaking down food into smaller pieces to ease digestion. Types of teeth include incisors, canines, molars, and premolars. Humans have 20 milk teeth and 32 adult teeth.

Swallowing

Swallowing involves two... Continue reading "Understanding Human Nutrition: Digestive System Essentials" »

Atrial Natriuretic Hormone (ANH)

Atrial natriuretic hormone (ANH) is released by the atria of the heart in response to elevated blood pressure or volume. It lowers blood pressure by encouraging salt excretion in the urine (natriuresis). It also lowers systemic vascular resistance by widening blood vessels.

ANH decreases the kidneys' ability to reabsorb water and salt by blocking the release of renin and aldosterone. To further lessen water retention, it also inhibits the release of antidiuretic hormone (ADH). This combined action reduces blood pressure and volume. By opposing the renin-angiotensin-aldosterone system, ANH preserves fluid equilibrium. It is essential for kidney and heart health. Atrial stretch is what causes the release of ANH.... Continue reading "Atrial Natriuretic Hormone, Urinalysis & Ovary Function" »

Hormones Controlling the Male Reproductive System

There are several important hormones that control the male reproductive system. The main male sex hormone, testosterone, is generated by the testes' Leydig cells. Testosterone is responsible for promoting spermatogenesis and the development of masculine traits.

The regulation of these hormones is crucial:

• Luteinizing Hormone (LH): Stimulates Leydig cells to produce testosterone.
• Follicle-Stimulating Hormone (FSH): Stimulates the generation of sperm by acting on Sertoli cells.
• Inhibin: Secreted by Sertoli cells, it uses negative feedback to control FSH levels.

Furthermore, testosterone and its metabolites support bone density, muscle mass, and libido. Together, these hormones regulate sexual function,... Continue reading "Male Reproductive Hormones, Spermatogenesis, and Meiosis" »