Notes, summaries, assignments, exams, and exercises for Biology for Secondary education

The Fundamental Unit of Life: The Cell

The cell is the basic unit of organization for all living things and is composed of essential biomolecules. Every cell is capable of performing vital life functions.

Key Cellular Structures

• Plasma Membrane: A thin, protective barrier that separates the cell from its environment and regulates the entry and exit of substances.
• Cytoplasm: A viscous liquid medium that houses various cellular structures.
• Nucleus: The organelle that stores and maintains genetic material, isolated from the cytoplasm by the nuclear membrane.

Types of Cells

• Prokaryotic Cells: These cells lack a defined nucleus; their genetic material is dispersed throughout the cytoplasm. Bacteria are examples of unicellular prokaryotic organisms.
• Eukaryotic

The Human Nutritional System: Components and Functions

1. Devices Involved in Nutrition and Their Functions

The human nutritional process involves the coordinated action of four major organ systems:

• The Digestive System: Responsible for digesting food and converting it into simpler substances (nutrients), which enter the bloodstream and are assimilated by our cells.
• The Respiratory System: Deals with gas exchange, providing oxygen ($ ext{O}_2$) and removing carbon dioxide ($ ext{CO}_2$).
• The Circulatory System: Transports oxygen and usable food substances (nutrients) via the blood to the various cells of the body. It also collects and transports carbon dioxide and metabolic waste products produced by our cells.
• The Excretory System: Responsible for

The Human Circulatory and Lymphatic Systems

The human body contains two primary transport circuits: the cardiovascular system, which circulates blood, and the lymphatic system, which circulates lymph.

The Cardiovascular System

The cardiovascular system consists of the heart, which acts as a pump, and blood vessels, which serve as the pathways for blood flow. These vessels are categorized into three types:

• Arteries
• Veins
• Capillaries

Blood Composition

Blood is a vital red liquid composed of two main parts: plasma and solid components.

Plasma (55%–60% of blood)

Plasma consists of 90% water and various dissolved substances, including:

• Gases: Oxygen, CO₂, and nitrogen.
• Minerals: Calcium, sodium, potassium, and chloride.
• Nutrients: Glucose (0.08%–0.12%)

Interplay of Body Systems

Sensory organs capture information as a stimulus and transmit it to the nervous system, which receives, processes, and develops a response. This response is then transmitted to effector organs, which carry out the action.

The Musculoskeletal System

This system controls the movement of the body.

The Endocrine System

This system produces hormones that regulate various body functions.

The Nervous System

Neurons: The Building Blocks

Neurons are specialized cells designed to receive, integrate, and transmit information.

Nerve Impulse

A nerve impulse is a slight electrical current produced by the arrival of information.

Types of Neurons

• Sensory Neurons: Located in sensory organs; they capture stimuli.
• Effector Neurons: Stimulate muscles

The Central Nervous System

The central nervous system consists of the brain and spinal cord. It is responsible for receiving and processing information to control body functions.

The Encephalon

Housed in the cranium, the encephalon comprises the brain, cerebellum, and medulla.

• Brain: The outermost part is formed by gray matter. The cerebral cortex receives information from sense organs and develops response orders. The innermost zone consists of white matter.
• Cerebellum: Coordinates movements, such as walking or manipulating instruments, and allows us to maintain balance.
• Medulla: Controls important body functions automatically.

The Spinal Cord

The outermost part consists of white matter, while the innermost part is gray matter. It serves as a neural...

The Human Digestive System: Anatomy and Function

The digestive system is responsible for breaking down food into simpler substances that can be absorbed and utilized by cells, while removing undigested waste and debris.

The system consists of two primary types of elements:

• The Alimentary Canal: A conduit approximately ten meters long, consisting of the mouth, pharynx, esophagus, stomach, small intestine, and large intestine.
• The Digestive Glands: A set of glands that secrete substances necessary for the chemical breakdown of food, including the salivary glands, liver, and pancreas.

Key Organs and Their Functions

• Mouth: The entry cavity for food. It contains the tongue, a muscular organ that moves food and mixes it with saliva, and teeth used for

Biological Levels of Organization

All living things are composed of cells that can be grouped, giving rise to complex structures such as tissues and organs. However, cells are made up of smaller components. These, in turn, consist of even smaller units. Levels of organization refer to the different degrees of complexity in which matter is organized.

In this organization, the elements of each level are grouped to form other more complex levels, with new features and properties that go beyond the mere grouping of elements from the previous level.

Subatomic Level

This level corresponds to the particles of atoms: protons, neutrons, and electrons.

Atomic Level

Formed by atoms, which are the smallest constituents of matter that maintain their properties....

Food Chains and Trophic Networks

Food chains: A food chain is formed by a number of organisms linearly ordered, so that each of them is the food for the organism that follows in the sequence. For instance, algae are producers that create organic matter from inorganic substances.

Trophic relationships in an ecosystem are rarely as simple as a single food chain. Instead, connections between different chains form a complex structure called a food web. A food web is the set of interconnected food chains within an ecosystem.

Energy Dynamics in the Food Chain

Energy in the food chain: Producers capture only a portion of the light energy from the Sun that reaches the Earth's surface. This energy is utilized for photosynthesis to produce organic compounds...

Cell Biology Fundamentals

Cell: The structural and functional unit of living organisms; all cells originate from pre-existing cells through cell division.

Microscope: Uses a beam of electrons that collides with the preparation to produce high-resolution black and white images, allowing us to observe the internal structure of the cell.

Virus: Acellular entities containing RNA or DNA and protein. They lack their own metabolism, require a host cell to replicate, act as parasites, and alter the host cell.

Animal Cell Components

• Plasma Membrane: Selective and semi-permeable; composed of lipids, proteins, and carbohydrates.
• Smooth Endoplasmic Reticulum (SER): Connected tubes that manufacture lipids and metabolize alcohol.
• Ribosomes: Two sub-units that synthesize

Cellular Metabolism and Aerobic Respiration ATP Yield

The metabolism includes all chemical transformations and energy changes that occur in living beings. Each of these transformations requires the participation of an enzyme; enzymes themselves may be modified as products of other reactions, including protein synthesis.

Enzymes biological catalysts

Enzyme classes include:

• Hydrolases
• Lyases
• Transferases
• Isomerases
• Oxidoreductases
• Synthetases

Vitamins essential for metabolism

Vitamins are essential biomolecules for metabolism. They include:

• Water-soluble: complex B and vitamin C
• Fat-soluble: vitamins A, D, E, K

Aerobic respiration: stages

Stage 1: Glucose to acetyl-CoA

Glucose to acetyl-CoA. Glucose is converted to pyruvate and then to acetyl-CoA.

Stage 2: Krebs