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

Passive Transport Mechanisms

Diffusion: Movement Down the Concentration Gradient

Diffusion is the passive movement of particles from a region of high concentration to a region of low concentration, aiming to equalize solute concentration. Diffusion occurs naturally because more particles move from the region of higher concentration toward the region of lower concentration.

Simple Diffusion

Simple diffusion enables substances to passively cross cell membranes from a region of higher concentration to a region of lower concentration without using metabolic energy (ATP). Once the concentration of the substance is equal on both sides of the cell membrane, a state of equilibrium is reached.

Facilitated Diffusion

Large, charged, hydrophilic, and polar substances... Continue reading "Cell Transport Mechanisms: Passive vs. Active Movement" »

Essential Medical Concepts

Key Definitions in Health and Immunity

What is Health?

Health is a combination of physical, mental, and social well-being, indicating a state where an individual is not suffering from a disease.

Understanding Antigens

An antigen is a substance that is perceived by lymphocytes and triggers a specific immune response.

Phagocytes: Immune System Defenders

A phagocyte is a specific type of white blood cell that activates when a pathogen crosses the first line of defense.

The Body's Defense Mechanisms

Understanding Immunity and Protection

Non-Specific Immune Response

When a pathogen crosses the first line of defense, the second line of defense is activated. This non-specific response is carried out by specific white blood cells, such... Continue reading "Human Body Defenses and Therapeutic Interventions" »

Characteristics of Living Organisms

Movement

A change of position or place.

Respiration

A chemical process in which oxygen is used to release energy from sugar molecules. Most of it happens in the mitochondrion.

Sensitivity

The ability to detect or sense changes in the environment (stimuli) and to make responses.

Growth

A permanent increase in size by increasing cell number, cell size, or both.

Reproduction

The process that makes more of the same kind of organism.

Excretion

The removal of toxic materials, waste products, and excess substances from an organism.

Nutrition

The process in which nutrients are taken into the body and converted into simpler substances used for energy, growth, and tissue repair.

Cell Structure and Organization

Cells can be classified... Continue reading "Fundamental Concepts of Biology: Cells & Life Processes" »

Nutritional Requirements and Metabolism

Nutrition Defined

Nutrition: Food intake in relation to the dietary needs of the organism.

Autotrophic Nutrition

Autotrophic: The body's ability to synthesize essential substances for metabolism from inorganic substances. Autotrophs have no need for nourishment from other living beings.

Heterotrophic Processes and Transport

Heterotrophic: Done through movements of molecules and ions via the diffusion process. The cell controls its internal chemical composition to regulate the traffic of substances across the membrane. This occurs through two mechanisms:

• Active Transport: Moves against concentration gradients.
• Passive Transport: Moves toward concentration gradients.

Cell Reproduction and Division Cycles

Cell Reproduction

Pharmacology 2

Dependence: physical response, addiction: behavioral.

Pharmacodynamic principle Placebo effect: patient experiencing relief of symptoms or effect that cannot be attributed to medication. Receptor theory; receptor site, binding site for drug molecule, lock & key. Responses agonist(enhances support encourages response) antagonist( inhibits response drug fits receptor but fails to initiate) neutral(no response). Dose response relationship: inc drug concentration =inc potential receptor site=inc biological effect. Steady state: maintaining blood levels within therapeutic range.

Anti-inflammatories: Steroids: end in -one. NSAIDS: selective(COX2 inhibit celebrex) non selective: upset stomach (salicylates, propionic acid, enolic acid,... Continue reading "Pharmacology 2: Pharmacodynamics, Anti-inflammatories, and Homeostasis" »

The Digestive System

The digestive system transforms food into nutrients that are the right size to reach body cells and be absorbed. To carry out this function, the digestive system consists of a group of organs and structures: the digestive tract and the accessory glands.

The Digestive Tract

The digestive tract, in order from top to bottom, includes:

• Mouth: The entry point of the digestive tract. It contains:
  • Teeth to bite and break food into small pieces.
  • A tongue to mix and swallow food, and enable the sense of taste.
  • Salivary glands.
• Pharynx: A cavity shared by the digestive and respiratory systems. Food passes towards the esophagus. The epiglottis, a small, flexible cartilage, prevents food from reaching the respiratory tract.
• Esophagus: A tube

What is VSG and why is it important in pathogenesis caused by Trypanosoma?

VSG stands for Variant Surface Glycoprotein, and it plays a crucial role in the pathogenesis caused by Trypanosoma, the parasitic protozoa responsible for diseases like African trypanosomiasis.

The importance of VSG lies in its ability to undergo antigenic variation. Trypanosomes have a dense coat of VSG on their cell surface, providing a protective barrier against the host's immune system. The parasite, however, can continually switch between different VSG variants, making it challenging for the host's immune system to mount an effective and lasting defense.

This antigenic variation is a key survival strategy for Trypanosoma during the course of infection. As the immune... Continue reading "VSG and Winterbottom's Sign in Trypanosoma Pathogenesis" »

The Endocrine System

The endocrine system is comprised of glands that produce protein substances called hormones. These hormones act as chemical messengers, speeding up or slowing down various activities within the body's cells.

Types of Glands

Exocrine Glands

Exocrine glands release substances through ducts to specific locations. These substances include enzymes, oil, and sweat. Examples include:

• Salivary glands
• Sweat glands
• Oil glands
• Gastric glands
• Intestinal glands

Endocrine Glands

Endocrine glands produce and secrete hormones directly into the bloodstream, acting on target cells throughout the body. Examples include:

• Pituitary gland
• Thyroid gland
• Adrenal glands
• Ovaries
• Testes

Hormones: Action and Functions

Hormones act on specific target cells by binding... Continue reading "The Endocrine System: Glands, Hormones, and Their Vital Functions" »

Gene Pool

The gene pool is the sum of all genetic information carried by all the individuals of a population.

Mutations

Mutations are the ultimate source of all genetic variation, and are the result of random changes in DNA sequences.

Gene Flow

Gene flow is the movement of genes from one population to another. It occurs when individuals migrate from one population to another, thus bringing their genes with them.

Genetic Drift

Genetic drift is a random process where certain alleles are removed from the population by accidental events. It is more likely to affect small populations than larger ones.

Founder Effect

The Founder Effect occurs when a small group of individuals establishes a new population far from existing populations. Because this group is... Continue reading "Evolution and Genetics: A Comprehensive Guide" »

Oral Diseases Associated with HIV

Group 3: Lesions Associated with HIV

• Bacterial infections (e.g., Actinomyces israelii, Escherichia coli pneumonia)
• Cat-scratch disease
• Drug reactions (ulcerative, toxic epidermal necrolysis)
• Fungal infections (e.g., Cryptococcus neoformans, Geotrichum candidum)
• Neurological disturbances (e.g., facial palsy, trigeminal neuralgia)
• Viral infections (e.g., cytomegalovirus)

Kaposi's Sarcoma

Multifocal, vascular neoplasm.

• Decreased immunocompetence activates the latent virus.
• Palate and gingiva are the most common sites.
• Painless red macules progress to nodular lesions.

Differential Diagnosis

• Hemangioma
• Varicosity
• Bacillary angiomatosis
• Pyogenic granuloma

Treatment

• Intralesional injections of vinblastine 0.1 mg/cm² or 0.2 mg/mL saline.