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

DNA and Chromosomes

DNA (deoxyribonucleic acid) is the biomolecule containing the genetic instructions for building proteins. Proteins, especially enzymes, regulate all life processes, including growth, tissue repair, and reproduction. DNA resides in the nucleus of eukaryotic cells as part of the chromosomes.

Chromosomes are composed of chromatin, a complex of DNA and proteins. When a cell is at rest, chromatin is dispersed within the nucleus, making chromosomes invisible. Before cell division, DNA replicates, and chromatin condenses into shorter, thicker fibers, forming visible chromosomes. Due to DNA replication, each chromosome comprises two identical arms called chromatids, joined by a centromere.

Karyotype

The number, shape, and size of chromosomes... Continue reading "DNA, Chromosomes, Genes, and Cell Division" »

Nutrition Basics

Nutrition involves how our bodies obtain, process, and utilize essential nutrients from food. These nutrients, vital for cell function and survival, include:

Types of Nutrients

• Carbohydrates: The primary energy source. Glucose provides quick energy, while complex carbohydrates (starch, glycogen) require longer digestion. Cellulose, a plant fiber, aids digestion.
• Lipids (Fats): Store energy and form reserves in adipose tissue. Phospholipids are crucial components of cell membranes.
• Proteins: Essential for cell structure and regulatory functions.
• Water: The most abundant component, vital for cooling, transporting substances, waste elimination, and facilitating chemical reactions.
• Minerals: Play structural and regulatory roles in various

Arteriosclerosis vs. Atherosclerosis

These terms are similar, but distinct. Arteriosclerosis is a general term for hardening and loss of arterial elasticity. Atherosclerosis is hardening specifically caused by atherosclerotic plaques.

Heart Conditions

Heart Murmurs

Heart murmurs are pathological noises heard during auscultation, caused by increased flow through normal valves, valve alterations, intracardiac abnormalities, or extracardiac issues. They can be systolic, diastolic, or continuous.

Tachycardia

Tachycardia is an increased heart rate, specifically above one hundred beats per minute at rest.

Leukemia

Leukemia is a group of malignant bone marrow diseases causing an uncontrolled increase in white blood cells (WBC), often appearing in peripheral... Continue reading "Understanding Cardiovascular Diseases and Related Conditions" »

Gregor Mendel's Contributions to Genetics

Note: This section details the scientific method applied to the study of inheritance.

Mendel's Scientific Method in Inheritance

Formulation of the Problem:

How are characteristics passed down from parents to offspring?

Hypothesis:

Sex cells contain structures responsible for the transmission of characters.

Experiment (Proof):

Crosses were made with purebred pea plants. In Cross 1, one character varied while six others remained constant.

Results and Conclusions:

Cross 1: All F1 generation individuals expressed the dominant character. In the F2 generation, the phenotypic ratio was 3:1.

Conclusions: Gametes contain factors responsible for character transmission, and each character is determined by two factors.

Key

Meiosis: Cell Division for Genetic Diversity

Meiosis is a specialized process of cell division that reduces the amount of DNA to maintain a constant number of chromosomes across generations. In advanced organisms, specialized tissues called gonads are responsible for reproduction, producing reproductive cells or gametes.

Therefore, gametes must contain half the number of chromosomes as their parent cells. Without this reduction, the amount of DNA would double with each successive generation. Meiosis ensures that the four resulting haploid cells are genetically distinct from one another and from the parent cell.

Meiotic First Division (Meiosis I)

Prophase I: Homologous Chromosome Pairing

Chromosomes pair together to form homologous pairs. This is... Continue reading "Meiosis Explained: Cell Division for Genetic Diversity" »

Endocrine Glands and Hormones

What are Exocrine Glands?

Exocrine glands are specialized structures with specific functions, releasing chemicals to regulate life processes.

Types of Exocrine Glands

Major exocrine glands in the human body include the pituitary, thyroid, parathyroid, adrenals, testes, and ovaries.

What are Hormones?

Hormones are complex substances produced by endocrine glands, released directly into the bloodstream to regulate various cells and organs.

The Pituitary Gland

The pituitary gland is a small mass of cells located at the base of the brain, in the sella turcica of the sphenoid bone.

The Sex Glands

• Testes: The male sex glands, located in the scrotum beneath the penis.
• Ovaries: The female sex glands, located in the lower abdomen.

The

The Microscopic World of Cells

The Universe Hidden from Our View

The seventeenth-century (17th) invention of the microscope revolutionized our understanding of life.

• In 1674, Anton van Leeuwenhoek invented a powerful microscope.
• He observed a drop of water and what he saw were tiny living creatures, which he called animalcules.

Living Cells: The Building Blocks of Life

We are all formed by living cells.

The Discovery of Cells

• In 1665, Robert Hooke discovered cells while observing cork.

Types of Organisms

• Single-celled organisms:
  • Their size is very variable but they are always microscopic.
  • A single cell is able to perform all the functions of a living organism.
• Multicellular organisms:
  • Can often be seen with the naked eye; they are macroscopic.
  • Their cells

The Central Dogma: From DNA to Protein

DNA Transcription: Creating RNA

The process of transcription converts genetic information from DNA into an RNA molecule. This crucial step involves:

1. The double helix of DNA unwinds, exposing the nucleotide bases.
2. Complementary RNA nucleotides pair with the exposed bases on one of the two DNA strands, known as the template strand.
3. Only one of the two DNA strands is copied during this process.
4. A strand of RNA is synthesized, possessing a base sequence complementary to the DNA template (with uracil replacing thymine).

RNA Translation: Building Proteins

Translation is the process where the genetic message carried by mRNA is used to synthesize proteins. It involves several key steps:

1. The messenger RNA (mRNA) molecule,

Key Terms in Phonetics

Accent: This is the way a language is pronounced, varying according to geographical location, social class, age, and other factors.

Dialect: A variety of a language that differs from others not only in pronunciation but also in vocabulary, grammar, and word order.

Allophone: A predictable phonetic variant of a phoneme.

RP (Received Pronunciation): The standard form of pronunciation, often used as a reference point.

Vowels

Vowels are produced with no obstruction to the airflow; the air passes freely through the vocal tract from the larynx (voiced).

Types of Diphthongs

• Falling Diphthongs: The first element is more prominent.
• Rising Diphthongs: The second element is more prominent.
• Closing Diphthongs: Characterized by a reduced aperture

Body Tissues and Their Specialized Roles

Cells within the human body are specialized to carry out specific processes. In a simplified view, based on their function, we can distinguish the following essential tissues:

• Integumentary Tissue: Covers the outside of the body, providing protection.
• Mucosa: Protects internal cavities, such as those in the digestive and respiratory tracts.
• Adipose (Fat) Tissue: Its cells accumulate fat, serving as a vital food reserve and insulation.

Understanding Nutrition: Fueling the Body

Nutrition encompasses the processes that allow us to use and transform the substances we need to stay alive and maintain bodily functions.

Infectious Disease Transmission: How Pathogens Spread

Infectious diseases are contagious because... Continue reading "Human Body Essentials: Tissues, Immunity, Digestion & Nutrition" »