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

The Small Intestine

The small intestine is about 6 meters long. In the duodenum, two liquids are added to continue digestion: pancreatic juice and bile. Pancreatic juice contains enzymes such as lipases, proteases, and carbohydrase (e.g., amylase).

Enzyme Breakdown

Each enzyme breaks down food in the following way:

• Protein -> protease -> amino acids
• Lipid -> lipase -> fatty acids and glycerol
• Carbohydrate -> carbohydrase -> sugar

Bile's Role in Digestion

Bile is made in the liver, stored in the gallbladder, and delivered to the small intestine via the bile duct. Bile neutralizes the acid which was added to the food in the stomach because it is alkaline. This provides the optimal pH for enzymes in the small intestine to work. Bile...

Primary Meristem

Located at the tips of juvenile plant organs such as roots, shoots, and buds, the primary meristem is responsible for the plant's growth in length.

Root

The root has several distinct parts: the suberized zone, the zone of absorption, the growth area, and the root cap.

The growth zone, located near the root tip, contains meristematic tissue. This tissue can have one, two, or three meristematic cells. If there is one cell, it gives rise to all other cells. If there are three cells, they multiply and differentiate into the root cap and epidermis (lower cells), the cortex (middle cells), and the vascular cylinder (upper cells).

Shoot

Shoots do not grow in the opposite direction of roots. Shoots have nodes, internodes, and buds.

Buds...

Cell Structure and Function

Key Components of the Cell

The cell is the basic unit of life, and it is composed of several essential components:

• Cell Membrane: A thin layer surrounding the cell, forming the boundary between the cell and its surrounding environment, the extracellular medium.
• Cytoplasm: The substance of the cell, excluding the nucleus. It is formed by a water-rich solution in which a variety of structures, called organelles, are dispersed. These organelles are responsible for carrying out the different functions of the cell.
• Cellular Nucleus: A structure that is usually spherical and located in the center of the cell. It contains the genetic material with the necessary information to direct and control cellular functions.
• Mitochondria:

DNA Deoxyribonucleic Acid Forming Chromosomes

Stores genetic info DNA wounded to histones which becomes nucleosome loops onto chromatin

Codes for protein twisted into chromatid looped and packed into chromosome

Nucleotide Chromatin fibers are coiled and condensed to form chromosomes

consisting of a nitrogen-containing base Histones are proteins that help package and organize DNA in the nucleus of

(a, g, t, c.) or uracil in RNA eukaryotic cells by forming nucleosomes around which DNA is wrapped.

- phosphate group nucleosome is a basic unit of DNA packaging in eukaryotic cells

- sugar chromatid is one of the two identical copies of a replicated chromosome

Homologous Chromosomes chromosome is a long, coiled-up strand of DNA that contains genetic information

chromosomes...

Endocrine System

The endocrine system coordinates body processes using chemical messengers called hormones.

Functions of Hormones:

• Control cell metabolism
• Maintain the body's internal stability (homeostasis)
• Regulate growth, sexual development, and reproduction

Endocrine Glands

Endocrine glands produce and release hormones, which the bloodstream distributes throughout the body to all cells.

Hormone Regulation

The endocrine glands and circulatory system work together to regulate hormones. For example, the pancreas secretes insulin when it detects excess glucose in the blood. Insulin causes muscle cells and liver cells to absorb glucose from the bloodstream.

Nervous System Coordination

The nervous system coordinates the activity of endocrine glands through...

Chemical Evolution

Chemical evolution refers to the processes that created the biomolecules, and then formed structures called protocells. According to Oparin, the first biomolecules were synthesized when the components of Earth’s primitive atmosphere reacted on contact with each other.

Biological Evolution

Biological evolution refers to the processes that led protocells to become different types of cells, and resulted in all the different organisms ever to have inhabited the Earth. Different types of prokaryotic cells were created from primitive cells: heterotrophic cells, photosynthetic cells, aerobic cells, long and very mobile cells.

Fixist Theories

Fixist theories uphold the idea that the species that currently exist on Earth were created...

DNA Mutations

Mutations are alterations to a DNA sequence that occur when a gene is damaged or changed, altering the genetic message. These mutations can have varying effects on health, depending on their location and whether they alter essential protein functions.

Mutations can occur at three levels:

1. Molecular (Gene or Point)
   • These mutations affect the chemical constitution of genes, specifically the DNA bases.
2. Chromosomal
   • These mutations affect a segment of a chromosome, altering its structure through deletions, duplications, or rearrangements.
3. Genomic
   • These mutations affect the entire genome, altering the number of chromosome sets (polyploidy or haploidy) or individual chromosomes (e.g., trisomy 21).

Mutations can be of different types:

1. Gene Mutations:

DNA-RNA: Chemical Composition

Formed by deoxyribonucleotides made up of phosphate, deoxyribose, and nitrogenous bases (adenine, guanine, cytosine, thymine), and by ribonucleotides made up of phosphate, ribose, and uracil.

Molecular Structure

Double-stranded structure and single.

Types

1. Nuclear DNA found in chromatin, mitochondrial DNA in mitochondria, plastid DNA in chloroplasts.
2. Messenger (mRNA), transfer, ribosomal.

Cell Location

1. Chloroplast, mitochondria, nucleus.
2. Cytoplasm, free or associated with ribosomes.

Function

1. Contains the organism's genetic info.
2. Synthesizes proteins according to genetic info in DNA.

Replication

Molecule of DNA replicates in the nucleus.

1. The double helix of DNA opens and the strands separate.
2. Free nucleotides attach to the separated

Understanding Key Human Muscles and Their Functions

Temporalis

• Origin: Along temporal lines of the skull.
• Insertion: Coronoid process of the mandible.
• Action: Elevates the mandible.

Masseter

• Origin: Zygomatic arch.
• Insertion: Ramus of the mandible.
• Action: Elevates the mandible and closes the jaw.

Sternocleidomastoid

• Origin: Attaches to the sternal end of the clavicle and manubrium.
• Insertion: Mastoid region and lateral nuchal line of the skull.
• Action: Flexes the neck.

Pectoralis major

• Origin: Cartilage of ribs 2-6, sternal body, and medial clavicle.
• Insertion: Greater tubercle and intertubercular groove of the humerus.
• Action: Flexion, adduction, and medial rotation at the shoulder.

Biceps brachii

• Origin: Coracoid process of the scapula.
• Insertion: Tuberosity