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

The Circulatory System

The circulatory system is the anatomical structure that includes both the cardiovascular system (which carries and circulates blood) and the lymphatic system (which carries lymph).

Its main function is to transport nutrients, gases, hormones, and blood cells to the body's cells. It also helps fight disease, stabilize body temperature and pH, and maintain homeostasis.

Basic Structures of the Circulatory System

• Arteries
• Veins
• Blood
• Heart
• Capillaries

The Nervous System

The nervous system is a network of ectodermal tissues found in animals. Its basic unit is the neuron. Its main function is to quickly capture and process signals, exerting control and coordination over other body systems to achieve timely and effective interaction with... Continue reading "Understanding Human Body Systems: Circulatory, Nervous, Locomotor, and Digestive" »

Enzymatic Reactions: Fundamentals

Chemical reactions begin with the breaking of bonds between atoms in reactant molecules, followed by the formation of new links that yield product molecules.

Transition State

This state occurs when the bonds in the reactants are weakened or broken, but new bonds have not yet fully formed.

Activation Energy (Ea)

The energy required for reactants to reach the transition state, allowing the chemical reaction to proceed.

Spontaneous Reactions (Low Ea)

Reactions where the activation energy is very low, often obtained from the kinetic energy of molecules or incident light.

Non-Spontaneous Reactions (High Ea)

Reactions where the activation energy is so high that they require external heat to proceed.

The catalytic action lowers

... Continue reading "Enzyme Reaction Mechanisms and Kinetic Regulation" »

Food Composition and Nutrients

Simple and Compound Foods

• Simple: These consist of a single type of substance. Examples include oil and table sugar.
• Compounds: These are composed of different substances. Examples include bread and milk.

Inorganic Substances

These are not unique to living matter.

• Water: The most abundant compound in living things and the medium in which life develops within cells.
• Minerals: Chlorides, carbonates, and phosphates, along with sodium, potassium, and calcium, are found in bones and teeth, providing hardness. They are also dissolved in all body fluids, such as blood, tears, and sweat.

Organic Substances

Carbohydrates

The simplest carbohydrates, such as glucose and maltose, have a sweet taste. Glucose is a sugar that cannot be... Continue reading "Nutrients in Food and How the Digestive System Works" »

Sperm and Egg Characteristics

Sperm are male gametes, representing highly specialized cells. These cells are small and mobile and consist of three parts:

• Head: The most voluminous part of the sperm. It contains the nucleus, with 23 chromosomes, and the acrosome, a cellular organelle that secretes substances that participate in the fertilization of the egg.
• Tail: Consists of a flagellum, a protein structure that allows the movement of the sperm.
• Neck: Lies between the head and tail. It contains numerous mitochondria around the base of the flagellum; these cellular organelles provide the energy needed to travel to the egg. It also contains a centriole, an organelle responsible for controlling movement.

Eggs have 23 chromosomes and have a very different... Continue reading "Sperm, Egg, Ovaries, and Spermatogenesis" »

How New Species Originate: The Speciation Process

All living things descend from a common ancestor. Evolution explains how a single species can diverge into two or more, leading to the current biodiversity. This process, known as speciation, typically occurs as follows:

• Geographic Isolation: Two populations of the same species become separated by a geographical barrier, such as a sea or a high mountain range.
• Independent Evolution: Both populations then undergo independent evolutionary paths. Mutations occur randomly in each, and since the number of genes is very high, these mutations will differ between the two populations.
• Accumulation of Differences: The accumulation of these genetic differences, combined with the pressures of natural selection,

... Continue reading "Speciation & Evolutionary Evidence: Unpacking Biological Change" »

Part II: The Endocrine System

Endocrine System Function

The endocrine, or hormonal, system is another system of coordination within the body. This system is closely related to the nervous system, and they are dependent on each other. In some cases, the nervous system stimulates or inhibits the secretion of hormones, and in others, the hormones stimulate or inhibit the action of the nervous system.

The endocrine system consists of a series of glands located throughout the body. These glands, called endocrine glands, are not anatomically connected to each other. They pour their secretions directly into the bloodstream.

Endocrine glands are formed by specialized secretory cells that synthesize chemicals called hormones. Once produced, hormones are... Continue reading "Endocrine System: Function, Hormones, and Diseases" »

Mitosis: is a dynamic, continuous and very complex whereby the nuclear material is duplicated and then divided and shared equally between the daughter cells.
Phases of mitosis: interphase, prophase, prometaphase, metaphase, anaphase, telophase.
Chromatic chromosome is a newly formed, still attached by the centromere.
Equatorial plate: the formation is taken as linear chromosomes in the center of the spindle in the metaphase stage of mitosis and meiosis.
Spindle fibers: attract the respective chromosomes toward the centrioles.
Meiosis is a type of reduction division and multiple it is performed by two successive divisions during which four daughter cells are formed, the chromosomes are duplicated so that the number of chromosomes that appear... Continue reading "Mitosis and Meiosis" »

Cell Structures and Their Functions

The cell is composed of various structures, each with specific functions vital to its survival and operation. Here's a breakdown of key cell components:

Cell Membrane

The cell membrane is a lipid bilayer that protects the cell, regulates the passage of materials, and helps maintain cell shape.

Endoplasmic Reticulum (ER)

The endoplasmic reticulum is a network of internal membranes forming tubes and vesicles that transport materials. There are two types:

• Smooth ER: Lacks ribosomes; produces steroids and aids impulse conduction in muscle cells.
• Rough ER: Contains ribosomes; synthesizes and transports proteins.

Ribosomes

Ribosomes are granules made of RNA and proteins (not membrane-bound). They synthesize proteins.

Golgi

... Continue reading "Cell Structures and Their Functions: A Comprehensive Look" »

The Human Digestive System

The digestive system is responsible for processing food and transforming it so nutrients can be absorbed and distributed to every cell in the body.

The Respiratory System

The respiratory system captures the oxygen needed by cells and removes the carbon dioxide (CO2) produced during cellular metabolism.

The Circulatory System

The circulatory system transports nutrients and oxygen to cells and removes waste substances.

The Urinary System

The urinary system handles debris and waste products ejected from cell metabolism, which are carried by the circulatory system to be filtered and expelled.

Key Components of the Digestive System

• Digestive Tract: Measures about 8 meters and varies in diameter along its length. It begins in the

... Continue reading "Human Digestive System Explained: Processes & Organs" »

Water Properties

• Water behaves like a dipole: OH bonds shift to oxygen, creating partial charges.
• Hydrogen bonds form between water molecules.
• Water is a great solvent due to hydration atmospheres.

Osmotic Pressure

• Hypertonic: Increased osmotic pressure, higher concentration.
• Hypotonic: Lower osmotic pressure, lower concentration.

Disaccharide Characteristics

1. Hydrolyzable into subunits.
2. Sweet taste.
3. Crystallizable.
4. Water-soluble.
5. No reducing power loss.

Hemiacetal Linkage

Cellulose

Cellulose consists of parallel chains joined by hydrogen bonds, forming microfibrils and fibers. This structure makes cellulose water-insoluble and rigid, providing structural support in plants. Humans and animals lack enzymes to break down cellulose, but some organisms (e.g.,... Continue reading "Water, Lipids, and Carbohydrates: Essential Biochemicals" »