Explanation

• The nucleus is the control center of the cell.
• It regulates all vital activities like growth, reproduction, and metabolism.
• It contains genetic material (DNA).
• Ribosomes make proteins, and cytoplasm supports cell structure.

Last verified on 04-05-2026

Explanation

• Mitochondria are called the powerhouse of the cell.
• Because they produce Adenosine Triphosphate (ATP).
• ATP is the energy currency of the cell.
• ATP provides energy for different cellular activities such as movement, growth, and transport.
• Energy is produced through aerobic cellular respiration using oxygen and الغذائی molecules.
• They are found in the cytoplasm of most eukaryotic cells.
• Richard Altmann first described mitochondria in 1890.

Main Parts of a Cell:

1. Cell membrane → Outer protective layer
2. Nucleus → Controls cell activities
3. Cytoplasm → Jelly-like material between membrane and nucleus

Last verified on 09-05-2026

Explanation

• Cell biology  is a branch of biology that studies the structure, function, and behavior of cells.
• All living organisms are made of cells.
• Also cellular biology or cytology
  

Explanation

• WBCs survive for about 13–20 days, depending on the type.
• WBCs are also called Leukocytes.
• They protect the body against infections.
• They are produced in the bone marrow.

Important Note: The 13–20 days lifespan is not applicable to all WBCs; their lifespan varies according to type.

Explanation

• O⁻ (O Negative) is the universal donor blood group.
• It can be transfused to A, B, AB, and O blood groups.
• O⁻ blood lacks A, B, and Rh (D) antigens.

Additional information:

• Universal Recipient: AB⁺ (AB Positive)
• ABO Blood Groups: A, B, AB, O
• Rh Types: Positive (+) and Negative (−)
• Total Common Blood Groups: 8 (A⁺, A⁻, B⁺, B⁻, AB⁺, AB⁻, O⁺, O⁻)

Last verified on 14-07-2026

Explanation

• Blood is red because of a protein called hemoglobin inside our red blood cells,
• Which contains iron that changes color when it binds to oxygen

Last updated by NS on 5-09-2026

Explanation

• The ovum (egg cell) is generally considered the largest cell in the human body.
• It is the female reproductive cell and can be seen with the naked eye as a tiny dot.
• The ovum is approximately 0.1 mm (100 micrometers) in diameter.
• In contrast, the sperm cell is one of the smallest human cells.

Last verified on 03-09-2026

Explanation

• The longest cell in the human body is the nerve cell (neuron).
• Some neurons can extend up to 1 meter in length.
• They transmit impulses throughout the body.

Additional information:

• The smallest cell in the human body is the sperm cell (spermatozoon).
• It is measures approximately 4–5 micrometers (µm) in length.
• It is mainly consisting of a nucleus and a tail.

Last verified on 23-04-2026

Explanation

Chromosomes are made up of:

• Nucleic acid (DNA or RNA)
• Proteins (histones and non-histone proteins)

A chromosome is made up of proteins and DNA organized into genes.

Each cell normally contains 23 pairs of chromosomes.

Explanation

An atom consists of three subatomic particles:

1. Protons (positively charged)
2. Neutrons (neutral)
3. Electrons (negatively charged)

Additional Information:

A neutral atom has equal protons and electrons; imbalance creates ions.

Discovered by John Dalton in 1808 (Atomic Theory).

Cation = positive ion,
Anion = negative ion,
Isotopes = same element with different neutrons,