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

Blood: Functions and Composition

Blood is a type of connective tissue. It is a thick red liquid made up of specialized cells suspended in a watery solution of molecules and ions. Blood transports nutrients and oxygen to the cells and carries waste residues to where they can be eliminated. Besides that, it regulates body temperature, pH and water volume, transports hormones, and defends our body from infections or from excessive blood loss when we get wounded. Blood is the only liquid tissue in our body because the matrix in which blood cells are immersed is liquid. The liquid component of blood is called plasma and it represents about 55% of blood volume.

Plasma: Composition and Role

Plasma is a pale yellow liquid. About 90% of it is water. The...

Excretion

Elimination of waste substances from blood is performed by the urinary system and other organs.

Urinary System

• Kidneys: bean-shaped organs behind the abdomen, filtering blood to form urine.
• Ureter: thin tubes transporting urine to the bladder.
• Urinary bladder: elastic bag storing urine.
• Urethra: duct transporting urine outside.

Other organs involved in excretion are lungs, liver, and sweat glands.

The Circulatory System

Function: Transporting O2, nutrients, and collecting CO2 and waste substances.

Blood

• Blood Plasma: 55% of blood, transporting nutrients, waste substances, and CO2.
• Blood Cells: red blood cells, white blood cells, and platelets.

Blood Vessels

Arteries, veins, and blood capillaries carry blood around the body.

Heart

Hollow muscular...

Unit 8. Endocrine System

The endocrine system is made up of the endocrine glands and the hormones they produce. Those glands produce hormones, chemical messengers that affect many cell processes (accelerating, delaying, starting, or stopping them). Hormones are transported by blood to all the cells in the body, but they only affect very specific target cells, which have specific receptors for that hormone. The hormone causes changes inside those cells.

Glands release only small quantities of hormones, and once the hormone has carried out its function, it is eliminated from the body.

The hypothalamus, a gland located in the brain, connects the nervous system and the endocrine system. It is one of the most important glands because it controls many...

Protein Synthesis and Protein Structure

Definition of Proteins

Proteins are large molecules formed by the union of amino acids. There are 20 unique amino acids, of which 8 are considered essential because they cannot be synthesized by living organisms. Proteins differ from each other based on the specific order (sequence) of these amino acids.

Functions of Proteins

• They form part of cellular structures.
• They are involved in cellular metabolism.

The Synthesis Process (Gene Expression)

Protein synthesis occurs in two main phases:

1. Transcription: Information transfer from DNA to mRNA (occurs in the nucleus).
2. Translation: Information transfer from mRNA to Protein (occurs in the cytoplasm, involving ribosomes).

Transcription: DNA to mRNA

Genetic information...

Nervous System Coordination

Nervous coordination is carried out by the nervous system. Neurons are divided into three parts: the cell body, the dendrites, and the axon.

• The cell body contains the nucleus and other organelles.
• Dendrites are short, branch-like projections.
• The axon is a longer projection. It ends in a series of slender branches which widen slightly at the tip and are called axon terminals.

In general, axons are protected by a white substance called myelin. The axons of various neurons sometimes group together to form nerve fibers, and these in turn can group together to form nerves.

Neuron Connection: The Synapse

Neurons are connected to each other. The place where one neuron connects to another is called a synapse. A nerve impulse...

Still the Eye

Homeostasis

Thermoregulation

The Nervous System: Communication Network

Neurons: The Building Blocks of the Nervous System

• Neurons: Specialized cells that conduct electrical impulses throughout the body. They are elongated cells with a cell body and a thin axon.
• Dendrites: Thin projections that extend from the cell body and connect with other neurons to allow electrical impulses to pass through.
• Myelin Sheath: An insulating lipid layer that surrounds some axons, speeding up impulse transmission.
• Nerve: A bundle of nerve fibers enclosed within a protective sheath.
• Nerve Fibers: Long axons of neurons together with any associated tissue.

Types of Neurons

The nervous system is comprised of three specialized types of neurons:

• Sensory Neurons: Transmit messages from receptors (e.g., eyes,

Biotic and Abiotic Factors

An ecosystem consists of all the living and nonliving parts of an environment. Biotic factors are the living parts of an ecosystem, while abiotic factors are the nonliving parts.

Living things need nonliving things to survive. Without food, water, and air, living things die. Other essential elements for living things include:

• Sunlight: It provides energy that plants and certain bacteria absorb to make their own food.
• Shelter
• Soil

Trees are biotic elements which need water, an abiotic element. Without water, a tree would not produce oxygen; conversely, without trees, water would not complete the water cycle.

Changes in abiotic factors can result in extreme problems for some organisms. For example, if a plant is adapted to...

Deoxyribonucleic Acid (DNA)

Composition and Structure

• Name: Deoxyribonucleic Acid
• Composition: Deoxyribonucleotides (nucleotides with deoxyribose: Adenine (A), Guanine (G), Cytosine (C), Thymine (T))
• Structure: Outer skeleton with pentose and phosphate, bonded by complementary bases.

Location and Functions

• Location: In the nuclei of eukaryotic cells and the cytoplasm of prokaryotic cells.
• Functions: Controls cell activities and carries genetic information.

Ribonucleic Acid (RNA)

Composition and Structure

• Name: Ribonucleic Acid
• Composition: Ribonucleotides (nucleotides with ribose: Adenine (A), Guanine (G), Cytosine (C), Uracil (U))
• Structure: Single chain of ribonucleotides.

Location and Functions

• Location: In the nucleus and cytoplasm of cells.
• Functions:

Enzyme Function and Segregation

1. What is the function of amylase? What is the function of pepsin? Why are they segregated?

• Amylase: Amylase begins the digestive process by breaking down starch when you chew your food, converting it into a smaller carbohydrate.
• Pepsin: Pepsin helps digest the proteins in food.

They are segregated because amylase functions primarily in the mouth (saliva), while pepsin functions in the highly acidic environment of the stomach.

Essential Digestive Terminology

2. Definitions:

• Chyme: Is the semi-fluid mass of partly digested food that is expelled by the stomach.
• Intestinal Flora: Is the symbiotic bacteria occurring naturally in the gut.
• Defecation: Is the final action of digestion, by which organisms eliminate solid, semi-