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

What is Agarose Gel Electrophoresis?

Agarose gel electrophoresis is a method used in biochemistry, molecular biology, genetics, and clinical chemistry to separate a mixed population of macromolecules, such as DNA, RNA, or proteins, in an agarose matrix.

Agarose is a natural linear polymer extracted from seaweed that forms a gel matrix via hydrogen bonding when heated in a buffer and allowed to cool. These gels are the most popular medium for separating moderate to large-sized nucleic acids due to their wide range of separation.

How Gel Electrophoresis Works

Gel electrophoresis separates DNA fragments by size in a solid support medium. The process involves:

• Sample Loading: DNA samples are pipetted into sample wells.
• Electrophoresis: An electric current

Nerve Histology

• Epineurium: Protects the entire nerve
• Perineurium
• Fascicle
• Axon: Conducts impulses
• Node of Ranvier: Speeds conduction

Spinal Cord Anatomy

Meninges and Spaces

• Epidural space
• Dura mater: Protects the spinal cord
• Subdural space
• Arachnoid mater: Protective membrane
• Subarachnoid space: Contains Cerebrospinal Fluid (CSF)
• Pia mater: Covers the spinal cord

Roots and Nerves

• Posterior root (dorsal root): Sensory input
• Spinal ganglion (dorsal root ganglion)
• Anterior root (ventral root): Motor output
• Spinal nerve: Mixed nerve
• Posterior ramus: Back muscles and skin
• Anterior ramus: Limbs and anterior trunk

Spinal Cord Structures

• Central canal: Contains CSF
• White matter: Conducting tracts
  • Posterior white column
  • Lateral white column
  • Anterior white column
• Gray matter
  • Posterior

DNA Replication: The Biological Mechanism

DNA replication is the essential process by which a cell creates an exact copy of its DNA prior to cell division (mitosis or meiosis). This critical event occurs during the S phase of the cell cycle.

Initiation: Unwinding the DNA

• Helicase: An enzyme that unwinds and separates the double helix by breaking the hydrogen bonds between nitrogenous bases, creating a "replication fork."
• Single-strand binding proteins (SSBs): Bind to single strands of DNA to keep them separated and prevent the helix from re-forming.
• Primase: Adds short RNA primers to the single-stranded DNA template. These primers are necessary for DNA polymerase to begin adding nucleotides.

Elongation and Synthesis

• DNA Polymerase III: Adds complementary

Perineum Anatomy

Perineum Structures

The perineum is a diamond-shaped space between the pubic symphysis (anteriorly), the coccyx (posteriorly), and the ischial tuberosities (laterally), lying just inferior to the pelvic diaphragm (levator ani and coccygeus).

It is divided transversely into two triangles:

• The anterior is the urogenital triangle, which includes the external genitals.
• The posterior is the anal triangle, which contains the anus.

The perineum is also divided into superficial and deep layers, with some muscles common to men and women.

Muscles of the Perineum and Pelvic Floor

Muscles making up the Urogenital and Anal (Pelvic) triangles/diaphragms include:

• Urogenital diaphragm: Superficial and intermediate planes
• Sphincters: Internal and external

Mitosis and Meiosis Comparison

Similarities Between Mitosis and Meiosis

• The sequence of changes in the nucleus and cytoplasm.
• The presence of the stages of prophase, metaphase, anaphase, and telophase.
• The spindle formation and the cycle of condensation of chromosomes.

Key Differences Between Mitosis and Meiosis

• Mitosis occurs in somatic cells, while meiosis is restricted to germ cells.
• In mitosis, each cycle of DNA replication is followed by one division. The resulting daughter cells are diploid (2n) and have the same amount of DNA as the parent cell.
• In meiosis, one DNA replication cycle is followed by two divisions, resulting in four haploid (n) daughter cells, which contain half the DNA of the parent cell.
• In mitosis, each chromosome behaves independently.

The Human Digestive System: An Introduction

The digestive system transfers organic nutrients, vitamins, minerals, and water from the foods we eat to the internal environment. Upon entering the body, food moves through the gastrointestinal (GI) tract, and the nutrients are absorbed and transported to the circulatory system where they are utilized.

Net Gain to the Body

Food and air are the primary sources of net gain to the body.

Distribution within the Body

Nutrients and substances are distributed throughout the body via the GI tract, lungs, storage deposits, and metabolism.

Net Loss from the Body

Excretion from the body occurs via the lungs, GI tract, kidneys, and skin.

Epithelial Cells

Epithelial cells separate compartments and are crucial in the digestive... Continue reading "Human Digestion and Metabolic Regulation" »

Pulmonary Ventilation and Gas Exchange

Pulmonary ventilation: This is the mechanism through which the air in the lungs and the respiratory tract is renewed. It allows air to flow in and out of the lungs. Ventilation is carried out through two respiratory movements: inhalation and exhalation. The diaphragm and the intercostal muscles mainly participate in these movements. By contracting and relaxing, these muscles produce changes in the volume of the lungs.

Inhalation

This is the movement that allows air to enter the lungs.

1. The diaphragm contracts, increasing the vertical diameter of the thoracic cavity.
2. The external intercostal muscles contract. The diameters of the thoracic cavity increase.
3. The lungs, which are elastic, expand.

Exhalation

This is... Continue reading "Human Physiology: Respiratory and Renal System Functions" »

Introduction to Biomolecules

Living organisms are made up of thousands of biomolecules—molecules produced by living systems with distinct properties and functions favored through evolution. Small, simple molecules called micromolecules (or monomers), such as water, minerals, simple sugars, and nucleotides, serve as building blocks for larger macromolecules (or polymers) like proteins, lipids, carbohydrates, and nucleic acids. Biomolecules are classified into inorganic types (e.g., water, minerals, gases) and organic types (e.g., lipids, carbohydrates, proteins, nucleic acids). While biomolecules alone do not exhibit life, they organize into cells and are continuously synthesized and broken down to maintain and perpetuate life.

Water: The Essential

HISTORICAL INTRODUCTION:Intro:Microbiology is the science of living organisms that are only visible under the microscope*Medical microbiology deals with the causative agents of infectious diseases of man his reaction to such infections the ways in which they produce disease and the methods for their diagnosis*The disease is transmitted by contact from man was known since biblical time. Varo and columella (First century BC)*The credit for observation and description of bacterial goes a Antony-Van Leeuwersback (1632-1723)*Father of microbiology (Antony Van Leeuwen hoek (1632-1723) and Logis pastoor (1822-1895)**Scientific development of microbiology*SDM was us by Louis pasteure*perfection ion microbiological studies by robert koch*The Intro of... Continue reading "Laboratory parasitology" »

c) Antigen Processing and Presentation

• Engulf protein antigens, partially digest them, and display polypeptide fragments on the surface for T cells to "see."
• Fragments are associated on the surface with Major Histocompatibility Antigens (MHC II), which are necessary to activate T cells.

d) Dendritic Cell Migration

To increase the chance of interacting with the correct T cells, dendritic cells migrate to secondary lymphoid organs (chemokines are secreted to attract T cells).

VII. Extracellular Killing by the Immune System

A. Natural Killer (NK) Cells

NK cells lyse virus-infected cells, tumor cells, and parasites. They kill cells that do not express MHC class I antigens.

B. Antibody-Dependent Cell-Mediated Cytotoxicity (ADCC)

1. In ADCC, NK cells and macrophages