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

Cell Theory Fundamentals

1. All living things are composed of one or more cells.
2. The cell is the basic unit of life.
3. All cells originate from pre-existing cells.

Types of Cells

Prokaryotic Cells

Simple structure, lack a nucleus, and contain no membrane-bound organelles (e.g., bacteria).

Eukaryotic Cells

Complex structure, possess a nucleus and various organelles (e.g., plant and animal cells).

Cell Organelles: Structure and Function

Organelles Common to Plant and Animal Cells

Cell Membrane

Controls the entry and exit of substances.

Cytoplasm

Jelly-like substance that holds organelles; site of many cellular reactions.

Nucleus

Controls cell activities and holds the cell's DNA.

Nucleolus

Responsible for making ribosomes.

Ribosomes

Sites of protein synthesis (make proteins)

Anatomy, Pathology, and Lab Essentials

Bones: Rigid organs that make up the skeletal system of vertebrates, providing support and protection for the body’s organs.

Cranium: The part of the skull that protects the brain.

Backbone: Also known as the spine or vertebral column, a flexible and strong structure running along the center of the back, made up of small bones called vertebrae.

Skull: A bony framework enclosing the brain of a vertebrate.

Joints: The points where two or more bones, or a bone and cartilage, are attached in the body.

Ligaments: Short bands of tough, flexible fibrous connective tissues that connect two bones or cartilages, or hold joints together.

Cartilage: Firm, flexible connective tissue found in various forms, from which the... Continue reading "Anatomy, Pathology, and Lab Essentials: A Comprehensive Glossary" »

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.

Common Pulmonary Pathologies

• Bronchiectasis: Permanent, abnormal dilation of bronchi.
• Cystic Fibrosis: Genetic disease causing thick, sticky mucus buildup in the lungs and digestive tract.
• Emphysema: Alveolar distention; trapped air.
• Pleural Effusion: Excess fluid accumulation between the two pleural layers surrounding the lungs.
• Pneumonia: Inflammation of the lung; most frequent.
• Pulmonary Edema: Abnormal buildup of fluid in the air sacs of the lungs.
• Pulmonary Embolism: Blood clot in the main pulmonary artery or its branches, originating elsewhere in the body.
• ARDS (Acute Respiratory Distress Syndrome): Severe lung syndrome caused by direct or indirect issues, characterized by inflammation, impaired gas exchange, and potential organ failure.
• Hyaline

Proteins: Structure, Function, and Classification

Proteins are complex molecules made up of amino acids. They perform various essential functions in the body, such as:

• Structural Support (e.g., collagen)
• Enzymatic Activity (e.g., lactase)
• Transport (e.g., hemoglobin)
• Defense (e.g., antibodies)

Classification of Proteins

Proteins are classified based on their structure and function.

Classification Based on Structure

• Fibrous Proteins: (e.g., collagen)
• Globular Proteins: (e.g., enzymes, antibodies)

Classification Based on Function

• Enzymes
• Hormones
• Structural Proteins
• Transport Proteins
• Defense Proteins

The Urea Cycle and Ammonia Removal

The urea cycle is a series of biochemical reactions that occur in the liver to remove excess ammonia from the body. This process... Continue reading "Essential Biochemistry: Proteins, Lipids, and Metabolic Pathways" »

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

The Role of Autotrophs

Autotrophs are crucial because they create their own food from sunlight through a process called photosynthesis. They form the base of all food chains by producing energy-rich compounds, such as glucose, and releasing oxygen, which is essential for other organisms to survive.

Chloroplast Structure

A chloroplast is enclosed by two outer membranes. Its interior contains a fluid-filled space called the stroma, where the Calvin Cycle occurs. Within the stroma are stacks of flat, disc-like structures called thylakoids. Each stack is known as a granum (plural: grana). The thylakoid membranes contain chlorophyll, the site of the light-dependent reactions.

Function of Chlorophyll

Chlorophyll is the green pigment found in chloroplasts.... Continue reading "The Process of Photosynthesis: From Sunlight to Sugar" »