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

Main Reasons Why Cell Divides

• Larger cell demands more place for the DNA.
• Larger cells result in less moving nutrients and waste materials across the cell membrane.

Information Overload

Cell grows, information is used to build the molecules needed for cell growth. DNA doesn't increase.

Exchanging Materials

Food, oxygen, water enter by the cell membrane, waste products also go out like that.

Division of the Cell

Forms 2 daughter cells. Cell division: process in which a cell divides into 2 daughter cells.

Asexual Reproduction

1 parent, cell divides by fission, little chances of genetic variation, found in bacteria, 2 offspring.

Sexual Reproduction

2 parents, cell divides by meiosis, genetic variation, found in mammals, 1 offspring.

Both

Forms of reproduction,...

Protein Synthesis: From DNA to Protein

1. Transcription: Copying the Genetic Message

Transcription is the process of copying part of the genetic message from DNA to RNA so that it can be used to synthesize a specific protein.

Stages of Transcription:

• The double helix of DNA unwinds.
• Complementary nucleotides position themselves opposite one of the two strands.
• Only one of the DNA strands is copied.
• An RNA strand is produced with a sequence of bases that is complementary to the DNA bases.

2. Translation: Building the Protein

Stages of Translation:

• The message copied as RNA is identical to the message in the DNA (except it contains uracil instead of thymine).
• This RNA, known as messenger RNA (mRNA), is a single-chain molecule that can leave the nucleus.

Work of the Cell: Metabolism and Disease

Metabolism: The set of biochemical transformations that occur in living cells. It has two parts: anabolism and catabolism.

Anabolism

Anabolism is the part of metabolism dedicated to the production of molecules that comprise cells from nutrients.

Catabolism

Catabolism is the part of metabolism involved in the production of energy that the cell constantly needs to perform its functions. It uses organic nutrients.

Nutrients are essential substances that cells need but are unable to synthesize; therefore, they must be obtained through diet.

Healthy Lifestyles

Healthy lifestyles include:

• Personal hygiene
• Domestic hygiene
• Occupational hygiene
• Proper eating habits
• Adequate sleep
• Regular exercise
• Avoiding drugs
• Avoiding a sedentary

Enzymes: Biological Catalysts

Enzymes are globular proteins that act as catalysts for biochemical reactions occurring inside or outside the cell.

Enzyme Composition

There are two main types of enzymes based on composition:

• Holoproteins: Consist solely of an amino acid chain (e.g., ribonuclease, lysozyme).
• Heteroproteins: Composed of two components: an apoenzyme (the protein part) and a cofactor (a non-protein part, which can be a coenzyme or a prosthetic group).

Factors Affecting Enzyme Activity

Enzyme activity is influenced by factors such as temperature (T°) and the concentration of the substrate.

Enzyme Inhibitors

Enzyme activity can be reduced or stopped by inhibitors, which can be:

• Competitive Inhibitors
• Noncompetitive Inhibitors

Enzyme Classification

Enzymes...

Mendel's First Law: The Law of Uniformity

Mendel started his experiments by crossing two individuals homozygous for a particular trait. The first law, or the law of uniformity, states that if you cross two pure individuals differing in one character, the offspring is uniform, all showing the dominant character.

Mendel's Second Law: The Law of Segregation

For the F2 generation, Mendel allowed plants with the Aa genotype from the F1 generation to self-fertilize. The second law, the law of segregation, states that the recessive traits that do not occur in the first generation reappear in the second generation in the proportion of three dominant to one recessive.

Mendel's Third Law: The Law of Independent Assortment

The third law, the principle of independent

Interaction

Interaction is the set of processes through which a living being obtains information from the environment, takes decisions, controls its actions, and coordinates the functioning of the body itself.

Obtaining Information

There are various mechanisms responsible for obtaining information from the exterior and the interior of the body. These mechanisms are called receptors.

Analysis of the Information and Elaboration of a Response

This process is carried out by the nervous system and the endocrine system. The elaborated response is an order that is transmitted to the organs via different procedures.

Execution of a Response

The effectors, which are the organs responsible for carrying out a response, are as varied as the possible responses...

Cell Structure and Function

A cell is the smallest structural and functional unit of life that can carry out the three vital functions: nutrition, reproduction, and interaction.

• Nutrition: obtaining energy, renewing the cellular structure, and obtaining biomolecules.
• Interaction: cells can adapt to changes in their environment and continue performing the activities they need to live.
• Reproduction: formation of new cells.

Types of Cells

Prokaryotic Cells

Prokaryotic cells do not have membrane-bound structures, are relatively small, have a single circular chromosome, have isolated ribosomes in their cytoplasm, and have cavities in their cytoplasm that function as mitochondria. Organisms belonging to the Monera kingdom have prokaryotic cells.

Eukaryotic

Gas Exchange

Blood is circulated to the lungs to obtain oxygen. This happens in the alveoli. Air entering the lungs has a higher concentration of oxygen and a lower concentration of carbon dioxide than the air that the lungs release. The blood exiting the lungs has a higher oxygen concentration and a lower carbon dioxide concentration than when it enters. The amount of nitrogen remains constant. Oxygen passes through the alveolar wall. These gases traverse the membrane of the cells by diffusion.

What Happens Inside the Alveoli?

The total surface area of the lungs' alveoli is enormous. Each alveolus is surrounded by many tiny blood vessels called capillaries, and the wall is extremely thin.

Microorganisms in the Air

Upper respiratory illnesses like...

These are energetic and structural substances found in many foods that we eat daily. There are two groups:

Simple Carbohydrates

• Monosaccharides: They are the simplest ones.
• Disaccharides: They are formed by two monosaccharides joined together.

Complex Carbohydrates (Polysaccharides)

They are neither sweet nor crystalline and they are not soluble in water. They include:

• Starch: It is made up of glucose molecules.
• Cellulose: It makes up vegetal fibre and forms the plant cellular wall. It is also made up of glucose molecules.

Inorganic Substances

These are small inorganic substances with variable composition. In solid state, they are structural. In dissolution, they are regulatory and allow our organs to function correctly and intervene in the regulation....

Human Digestive and Circulatory Systems

Nutrition is the process by which a living being obtains the matter and energy needed to sustain life.

Components of Digestive Function:

• Taste: Involves eating food, breaking it down, and transporting it.
• Reduce: Food is broken down into simple molecules that cells can use.
• Absorb: Simple molecules are absorbed and passed into the bloodstream for circulation to all body tissues.
• Remove: Undigestible remains are eliminated.

Digestive Tract Components:

The Pharynx

A short part of the digestive tract, also part of the respiratory system, extending from the oral cavity to the top of the esophagus.

The Esophagus

The conduit between the pharynx and the stomach.

The Stomach

An enlarged, bag-shaped part of the digestive tube,...